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R/E/P => R/E/P Archives => Brad Blackwood => Topic started by: bblackwood on July 10, 2004, 03:05:12 pm

Title: Any DIY EQ interest?
Post by: bblackwood on July 10, 2004, 03:05:12 pm
I've been toying with the idea of building a very simple passive (LC) broadband peaking EQ and am wondering if this would be something you guys would be interested in doing online as a collaboration. I'm contemplating a boost only EQ that's fixed bandwidth (pretty broad bandwidth) and having only two bands (perhaps three), low (possibly mid) and hi. Probably only have two or three freqs per band and would utilize switches throughout.

This kind of project is relatively simple, and while many of us have several EQs in our rack, would be a nice chance to get your hands a little dirty, so to speak, while making something that sounds good and can be used everyday.

What do you think? Is this something in which you'd be interested in participating? If there is enough positive response, we'll do it online together, otherwise, I'll simply post what I do and you guys can do whatever you wish...
Title: Re: Any DIY EQ interest?
Post by: Viitalahde on July 10, 2004, 03:35:56 pm
No need now for this kind of an EQ.. Got the passive EQ done and Sontec clone in a few months - next year I'm going for a Klein&Hummel UE-100 tubed eq.

But if you want, I could still hop in the project and offer some ideas..? What are yer plans for the gain make-up? I suggest something discrete.. Joe Malone at JLM audio has a new op-amp (JLM99v) that some at TheLab have tested and reported to sound exteremely beautiful with tight low end and silky mid range. The sucker can take over +/-30v rail voltages too..

I also have the switching thing in my passive eq I like - and I could share that with you if you want. Basically, it allows you to use each band in either stereo (left controls only) or dual mono (L&R controls) mode. Simple to do with rotary switches, requires a lot of wiring though. But I think it does a great thing to the workflow.
Title: Re: Any DIY EQ interest?
Post by: OatBran on July 10, 2004, 04:56:58 pm
  Definitely keep us updated on the forum, please.  I'd love to see some schematics, pictures, and parts lists as well.  This is something I would consider doing myself.  What kind of price range are we talking when all is said and done?  Will this EQ you make be something you will use in your process?  Are you making this out of a need that you have to fill?  Thanks.
Title: Re: Any DIY EQ interest?
Post by: Gold on July 10, 2004, 05:13:37 pm
Viitalahde wrote on Sat, 10 July 2004 15:35

next year I'm going for a Klein&Hummel UE-100 tubed eq.



A friend of mine has a pair of those. They sound very very good. I think each channel is five or six rack spaces. Impressive. They are very clean sounding. It ain't no Massive Passive. That sounds like a very worthwhile project for a mastering studio.

Brad,
I don't really need an EQ like that and I have a number of other things I'm working on.
Title: Re: Any DIY EQ interest?
Post by: doughiggins on July 10, 2004, 07:35:29 pm
yes
Title: Re: Any DIY EQ interest?
Post by: mcsnare on July 10, 2004, 09:18:54 pm
I'd be very interested, especially if you could find a schematic for a Universal Audio 550. Then couple it with a transformerless tube make up stage. Whadda ya say?
Dave
Title: Re: Any DIY EQ interest?
Post by: Viitalahde on July 11, 2004, 05:05:44 am
Gold wrote on Sat, 10 July 2004 22:13

Viitalahde wrote on Sat, 10 July 2004 15:35

next year I'm going for a Klein&Hummel UE-100 tubed eq.

A friend of mine has a pair of those. They sound very very good. I think each channel is five or six rack spaces. Impressive. They are very clean sounding. It ain't no Massive Passive. That sounds like a very worthwhile project for a mastering studio.


Yeah, they look really worthy - and complicated. That huge Fairman EQ is based on these. But this is a future project, first I need the basic devices..

More about the passive EQ project

I once tried those AC line filter blocks - on audio. They're building blocks that have a low pass filter composed of inductors and capacitors, and they come in different values. Normally ment to filter all the crap out of incoming AC.

I honestly think that these could be very well used in a passive eq design with carefully calculated impedances and a lot of testing. I remember I tried them in hi-pass configuration too. They sounded pretty good. The great thing here would be that they're readily-available, shielded and easy to use if a good design came up for them.

Different frequencies might be problematic though.. But as an idea I think it's worth checking out.
Title: Re: Any DIY EQ interest?
Post by: malice on July 11, 2004, 05:15:50 am
I'm game with that brad, should be interesting and we could learn from this

malice
Title: Re: Any DIY EQ interest?
Post by: TomW on July 11, 2004, 09:09:44 am
Hi Brad and all!!!

Been a long time lurker, great forum here - I'm learning a lot but still just a novice with a keen interest in mastering...and DIY Audio.

I find this topic very interesting - I was planning a passive Pultec styled-eq similar to Viitalahde's, Class-A make-up etc, more frequencies than the original but then...

I read Fred Forssell's paper on a passive EQ topology and evolution. Maybe it gets a little more complicated than the thing you're thinking about Brad but its worth a read.

http://www.forsselltech.com/schematics/EQ1A.PDF

The paper with this provides some interesting ideas.

http://www.forsselltech.com/Evolution%20of%20an%20EQ%20Desig n2.pdf

I would be interested in developing this topology to make a 4-band EQ with passive low and high bands with some discrete opamp gyrators for the 2 mid bands.

http://www.forsselltech.com/schematics/Gyrator1.htm

What do people think?? There would be many options for discrete opamps, although its not really a totally passive eq.

Cheers Tom
Title: Re: Any DIY EQ interest?
Post by: bblackwood on July 11, 2004, 10:55:26 am
Well, I'm still deciding on the details, but do know that it will be:



I'm going to start hammering out some of the details and will be posting a little more soon enough, starting with a general block diagram in the next few days...

Anyone else interested?
Title: Re: Any DIY EQ interest?
Post by: D Harris on July 11, 2004, 11:01:32 am
Sounds like fun, sign me up.
Title: Re: Any DIY EQ interest?
Post by: bobkatz on July 11, 2004, 11:07:52 am
bblackwood wrote on Sun, 11 July 2004 10:55

Well, I'm still deciding on the details, but do know that it will be:

  • two band, 'boost' only





I'm interested in this, too, Brad. But why boost only when it is so easy to design a cut into the circuit? In fact, in passive EQ, cut is real easy to design.

Make up gain....  I vote for a 990 style footprint, since there are so many discrete amps that can be plugged into the socket. There's an issue of output coupling cap, though most following devices are far less susceptible to DC offset problems than people think.
Title: Re: Any DIY EQ interest?
Post by: bblackwood on July 11, 2004, 11:12:08 am
Bob, the thinking is to keep it as simple as possible. Cut may be implemented, but I want this to a fun and easy project to get people's DIY feet wet. I'm flexible, but I don't want this to grow into the passive EQ design I did a few years ago that was going to require a 4Ru box, custom inductors, etc.

Also, I haven't even asked them yet, but I imagine I'll be bouncing some of these designs off some of my more astute designer buddies who do this stuff in their sleep (and who's names are easily recognizable in the pro audio design world)...

990 footprint idea is golden, Bob. Good idea.
Title: Re: Any DIY EQ interest?
Post by: Viitalahde on July 11, 2004, 11:52:41 am
bblackwood wrote on Sun, 11 July 2004 16:12

990 footprint idea is golden, Bob. Good idea.


It's actually easy to design a layout that can take both normal 8-pin IC's and 990 footprint. My Sontec PCB's designed by Fabio Bauman are like this..
Title: Re: Any DIY EQ interest?
Post by: grock5 on July 11, 2004, 12:06:09 pm
Something based off the early cinema/langevin stuff would be cool.

Make-up gain could be provided externally.

Title: Re: Any DIY EQ interest?
Post by: JPRisus on July 11, 2004, 10:53:34 pm
I'm very interested in this, for learning purposes mainly... been looking to get into the DIY thing for a while now but haven't taken the plunge yet. Great idea Brad!
Title: Re: Any DIY EQ interest?
Post by: OTR-jkl on July 12, 2004, 12:16:48 pm
Sounds like lots of fun - and I sure could use the EQ...

Any rough guesses about the cost?
Title: Re: Any DIY EQ interest?
Post by: Kris on July 12, 2004, 03:09:15 pm
Useful and great sounding?  Sounds like fun!
Title: Re: Any DIY EQ interest?
Post by: bblackwood on July 13, 2004, 10:24:35 am
Real quick - brutal week so little will happen this week on the EQ.

Frist, it looks like there is enough interest to do this online.

As for cost - that depends on how deep you want to go. You can build your own PSU or spend anywhere from $50 to several hundred to buy one. Every part will have multiple choices that may affect the sound or perhaps reliability. I'm guessing here, but I imagine you can build something like this for anywhere from $200 to $as-much-as-you-want-to-spend...

More to come soon.
Title: Re: Any DIY EQ interest?
Post by: malice on July 13, 2004, 11:28:25 am
I had this address of fair designed PSU, every voltage, several different powers, quite cheap ...

I'll try to find the link


malice
Title: Re: Any DIY EQ interest?
Post by: doughiggins on July 13, 2004, 02:24:38 pm
malice wrote on Tue, 13 July 2004 08:28

I had this address of fair designed PSU, every voltage, several different powers, quite cheap ...

I'll try to find the link


malice


cool


Brad, if we can contribute in any way, let us know...maybe some of the bulk resistors/caps  or something may be advantgeous to pair up with others, and especially the chasis and screening will be good to spread custom costs across?!
Title: Re: Any DIY EQ interest?
Post by: valvetone on July 13, 2004, 11:40:52 pm
Count me in!  This sounds like a great project, I've been looking for something to get my feet wet with DIY.

Damon
Title: Re: Any DIY EQ interest?
Post by: archtop on July 14, 2004, 01:40:17 pm
Me too, Me too.


I've never built anything. but I made all the snakes, and soldered 'em
to to my 4 TT patchbays (twice Sad ).
Title: Re: Any DIY EQ interest?
Post by: saxist on July 14, 2004, 10:56:40 pm
Yeah, I'm in.  Probably in lurk mode, since I doubt strongly that I'll be able to add anything to design decisions, but I'd love to follow along.

Eric H.
Title: Re: Any DIY EQ interest?
Post by: dcollins on July 15, 2004, 02:26:09 am
TomW wrote on Sun, 11 July 2004 06:09

Quote:


I would be interested in developing this topology to make a 4-band EQ with passive low and high bands with some discrete opamp gyrators for the 2 mid bands.



Could be too complicated for this sort of DIY project.  Unless the discrete opamp only has 3 transistors!

http://www.forsselltech.com/schematics/Gyrator1.htm

Probably better to use a real inductor for this project, as everyone knows they have more "vibe."

I discussed with B-rad two ideas for something like this.  First, is a three band Baxandall with either IC or 990 size opamps.  Probably too clean for the audience.  Second, was just the old bog-standard buffer to passive 600 Ohm LCR network to make-up amp, probably fixed Q, but doesn't have to be.  Tube construction is a little more painful, but at least they can be seen with the naked eye.  PSU also costs more than with opamps.

In thinking about this, I was reminded of the old "saturable inductor" where you have in effect another input to the system.  Used in ancient de-essers. Distortion is probably off the map. Can you cobb your own from existing parts, is the question.

This might actually be unique today, so you didn't hear it from me.

We can recycle those old Western Electric circuits untill the bovine return......

DC

Title: Re: Any DIY EQ interest?
Post by: lucey on July 15, 2004, 01:48:51 pm
im interested but too busy to commit for sure.

the tech talk is over my head but a simple unit is best IMO, one notch and 2 boosts would be cool
Title: Re: Any DIY EQ interest?
Post by: jlapointe on July 15, 2004, 02:47:49 pm
dcollins wrote on Thu, 15 July 2004 03:26



In thinking about this, I was reminded of the old "saturable inductor" where you have in effect another input to the system.  Used in ancient de-essers. Distortion is probably off the map. Can you cobb your own from existing parts, is the question.



Please tell more! What's the premise here? A DC bias on the inductor to put it into saturation earlier?  How was it implemented as a de-esser?      
Title: Re: Any DIY EQ interest?
Post by: TomW on July 19, 2004, 05:32:23 pm
Hi DC!

I think you're right - it may be too complicated. I just figured the gyrators might make it a little more flexible and good inductors for mid ranges are hard to find as far as I know. Still gyrators would no longer be passive..........

From searching the web I only know of the pultec HF inductors from sowter and cinemag. There are cheap ones from a variety of other sources though. IIRC big inductors are needed for midrange stuff and they seem harder to find in the right values.

I think the baxandall sounds interesting - they seem very common with hifi manufacturers.

What do people think to the single amp forssell topology?

Cheers Tom  Smile
Title: Re: Any DIY EQ interest?
Post by: Doug Van Sloun on July 19, 2004, 10:27:42 pm
Count me in too!!  Baxandall filters with 990's sounds very tasty!
Title: Re: Any DIY EQ interest?
Post by: theo mack on July 19, 2004, 11:36:48 pm
I'm in.

My wish list:

2 boost bands, 1 cut

balanced in and out.

something nice for make up gain like john hardys 24V 990
It would be nice to concentrate on the passive eq part of the circuit and have the easy plug in JH 990 24V on the back end.
Title: Re: Any DIY EQ interest?
Post by: dcollins on July 20, 2004, 01:52:12 am
JLaPointe wrote on Thu, 15 July 2004 11:47
Quote:


Please tell more! What's the premise here? A DC bias on the inductor to put it into saturation earlier?  How was it implemented as a de-esser?      



Yes, an external bias is applied.  That's about all I know of it!  Why doesn't someone research this and get back to us?  I still like the idea, but if was that great, why so rare?

An Ortophon de-esser worked like this but the I've never seen the actual guts, just the schema.

DC
Title: Re: Any DIY EQ interest?
Post by: bblackwood on July 23, 2004, 03:33:37 pm
Still trying to keep yup here, so little has been done, though I am bouncing ideas off of our own DC (and I'm dragging Dave Hill into it...).

Updates as available.
Title: Re: Any DIY EQ interest?
Post by: dcollins on July 24, 2004, 01:39:04 am
bblackwood wrote on Fri, 23 July 2004 12:33

Still trying to keep yup here, so little has been done, though I am bouncing ideas off of our own DC (and I'm dragging Dave Hill into it...).

Updates as available.


Ooh, I've got it!  Baxandall with a "color" knob.  Or should that be "colour?"

Google "three band baxandall schematic"  Or?

DC
Title: Re: Any DIY EQ interest?
Post by: malice on July 24, 2004, 08:19:10 am
bblackwood wrote on Fri, 23 July 2004 21:33

Still trying to keep yup here, so little has been done, though I am bouncing ideas off of our own DC (and I'm dragging Dave Hill into it...).



Dave who ?

kidding

If Dave Hill is in, all I can say is : wow !

this is getting better and better

As an STC-8 user, I take this opportunity to state that Dave has made my life considerably more comfortable Wink

malice
Title: Re: Any DIY EQ interest?
Post by: moogus on July 24, 2004, 10:20:23 am
I cant help myself from responding here.  

We just finished 2 mastering pultecs the other week, that are pretty darn close to what youre describing.

2 bands, with sepperate freqs (12) for cut and boost, in 0.5db steps to 5.5db.

Switched bandwidth on high boost (inductive) from, well, fairly narrow to very very wide.

Using the JLM instrument opamp from the mastering console to give fully balanced i/o and provide the makeup gain, which runs on +/-24V, has +36 headroom, bandwidth from DC to above 10meg and plenty of zeros in the THD%.

Theyre certainly useful little beasts, and we found the matching between the two units to be extremely close, just with normal 1% resistors.

This version also drives 6db more level thru the inductors than the old version, and reports suggest this has improved the eq's utility on program material.

It would certainly be worth experimenting with making the gain up before the eq, based on these results.

Good luck with it.


M
Title: Re: Any DIY EQ interest?
Post by: bobkatz on July 24, 2004, 11:28:56 am
moogus wrote on Sat, 24 July 2004 10:20



This version also drives 6db more level thru the inductors than the old version, and reports suggest this has improved the eq's utility on program material.




The drive to the inductors can be an interesting form of distortion generator. I'd make it variable.

BK
Title: Re: Any DIY EQ interest?
Post by: lucey on July 24, 2004, 01:51:30 pm
moogus wrote on Sat, 24 July 2004 09:20

I cant help myself from responding here.  

We just finished 2 mastering pultecs the other week, that are pretty darn close to what youre describing.

2 bands, with sepperate freqs (12) for cut and boost, in 0.5db steps to 5.5db.

Switched bandwidth on high boost (inductive) from, well, fairly narrow to very very wide.




sounds good, is this something you can help us DIY or are you a manufacturer?
Title: Re: Any DIY EQ interest?
Post by: malice on July 24, 2004, 01:56:26 pm
lucey wrote on Sat, 24 July 2004 19:51

moogus wrote on Sat, 24 July 2004 09:20

I cant help myself from responding here.  

We just finished 2 mastering pultecs the other week, that are pretty darn close to what youre describing.

2 bands, with sepperate freqs (12) for cut and boost, in 0.5db steps to 5.5db.

Switched bandwidth on high boost (inductive) from, well, fairly narrow to very very wide.




sounds good, is this something you can help us DIY or are you a manufacturer?


Moogus works with a nice manufacturer in OZ, but maybe he is willing to participate ...

Moogus ?

malice
Title: Re: Any DIY EQ interest?
Post by: dcollins on July 24, 2004, 08:03:44 pm
moogus wrote on Sat, 24 July 2004 07:20

I cant help myself from responding here.  



Quote:


We just finished 2 mastering pultecs the other week, that are pretty darn close to what youre describing.



What are you using for input, interstage and output transformers?

Iow, just cause it has an inductor, does _not_ make it a Pultec!

Quote:


Using the JLM instrument opamp from the mastering console to give fully balanced i/o and provide the makeup gain, which runs on +/-24V, has +36 headroom, bandwidth from DC to above 10meg and plenty of zeros in the THD%.



That sounds interesting.  I'm a little scared about the >10MHz response though.  I tend to go for something around -3 at 300kHz just because there is so much RF noise out there today.  Arguably the recordings I have that sound the most "open" were done on gear that was positively struggling to be flat at 20k!  But that's a story for another day...


DC

Title: Re: Any DIY EQ interest?
Post by: bobkatz on July 24, 2004, 08:15:03 pm
dcollins wrote on Sat, 24 July 2004 20:03



Quote:


Using the JLM instrument opamp from the mastering console to give fully balanced i/o and provide the makeup gain, which runs on +/-24V, has +36 headroom, bandwidth from DC to above 10meg and plenty of zeros in the THD%.



That sounds interesting.  I'm a little scared about the >10MHz response though.  I tend to go for something around -3 at 300kHz just because there is so much RF noise out there today.  Arguably the recordings I have that sound the most "open" were done on gear that was positively struggling to be flat at 20k!  But that's a story for another day...


DC




DC, I don't know the JLM, but would you be satisfied with an opamp with feedback compensation so resulting frequency response was around -3 dB at 300 kHz?
Title: Re: Any DIY EQ interest?
Post by: dcollins on July 24, 2004, 08:34:06 pm
bobkatz wrote on Sat, 24 July 2004 17:15

Quote:


DC, I don't know the JLM, but would you be satisfied with an opamp with feedback compensation so resulting frequency response was around -3 dB at 300 kHz?


That's a good place to start the rolloff. When I'm calculating the feedback R/C it's always something from say 150k to 300k.  For audio that is.

That JLM stuff looks interesting, but I don't know how anyone can use that kind of output level.  90% of stuff is on +/- 15V rails so if your opamp is really swinging +/- 60 Volts, there's gonna be padding somewhere. The A/D converter chip wants to see like 2 Volts....

Since low noise is so easy to achieve nowdays, why not just run your system at low levels and get the headroom that way?

DC
Title: Re: Any DIY EQ interest?
Post by: moogus on July 25, 2004, 12:16:32 am
[quote title=malice wrote on Sun, 25 July 2004 03:56]
lucey wrote on Sat, 24 July 2004 19:51



Moogus works with a nice manufacturer in OZ, but maybe he is willing to participate ...

Moogus ?

malice



Id love to help as much as I can, although you already have some real designers on board.

If youd like me to I can foward some questions on to Joe.


M
Title: Re: Any DIY EQ interest?
Post by: moogus on July 25, 2004, 12:22:14 am
dcollins wrote on Sun, 25 July 2004 10:03



What are you using for input, interstage and output transformers?

Iow, just cause it has an inductor, does _not_ make it a Pultec!

Quote:


Using the JLM instrument opamp from the mastering console to give fully balanced i/o and provide the makeup gain, which runs on +/-24V, has +36 headroom, bandwidth from DC to above 10meg and plenty of zeros in the THD%.



That sounds interesting.  I'm a little scared about the >10MHz response though.  I tend to go for something around -3 at 300kHz just because there is so much RF noise out there today.  Arguably the recordings I have that sound the most "open" were done on gear that was positively struggling to be flat at 20k!  But that's a story for another day...


DC





No xformers, Its not a Pultec copy, just a passive EQ.  I use that term rather loosely.  

The ones we just built have something like that bandwidth, because we havnt limited them yet.  Of course you can limit it to whatever you like.


M
Title: Re: Any DIY EQ interest?
Post by: moogus on July 25, 2004, 12:31:27 am
dcollins wrote on Sun, 25 July 2004 10:34

bobkatz wrote on Sat, 24 July 2004 17:15

Quote:


DC, I don't know the JLM, but would you be satisfied with an opamp with feedback compensation so resulting frequency response was around -3 dB at 300 kHz?


That's a good place to start the rolloff. When I'm calculating the feedback R/C it's always something from say 150k to 300k.  For audio that is.

That JLM stuff looks interesting, but I don't know how anyone can use that kind of output level.  90% of stuff is on +/- 15V rails so if your opamp is really swinging +/- 60 Volts, there's gonna be padding somewhere. The A/D converter chip wants to see like 2 Volts....

Since low noise is so easy to achieve nowdays, why not just run your system at low levels and get the headroom that way?

DC



That particular device is designed to be as transperant as possible, hence the massive headroom, and it was designed for the mastering console, not the EQs.  It just happened to provide an elegant solution in that situation.

High output headroom is a feature of a lot of Joe's designs (as is low noise).  I guess you could say its one of his 'trademarks' as a designer.

Best of luck to yall with this,


M
Title: Re: Any DIY EQ interest?
Post by: Terry Demol on July 26, 2004, 05:37:27 am
moogus wrote on Sat, 24 July 2004 15:20

I cant help myself from responding here.  

We just finished 2 mastering pultecs the other week, that are pretty darn close to what youre describing.

snipped

Using the JLM instrument opamp from the mastering console to give fully balanced i/o and provide the makeup gain, which runs on +/-24V, has +36 headroom, bandwidth from DC to above 10meg and plenty of zeros in the THD%.

M


Hi Moogus,

Is this with the JLM99V or as your instrument opamp description
suggests, a fully balanced instrumentation amplifier Bal IP ->
SE OP, or just the front end of an instrumentation amp ie;
CM gain = x1 bal in bal out, or lastly, a fully balanced VG
(current) IP such as Nelson Pass's "Supersymmetry"?
 
There are a few issues which may be relevant WRT BK's and DC's
comments of BW limiting but they don't aply to all topologies
and designs, lets make sure we are all talking the same
language first.

Some of the topologies are in effect current feedback, ie
feedback to the IP emitters and as such you need to be careful
using FB BW compensation (as BK suggested). However there are
ways around all this.

You mention BW of 10meg, just for the record, with devices these
days having Ft's in the 100's of megs that is pretty common.
Joe seems to favour very simple topologies (which I like too)
and high voltage rails (which I also like), as such the high
BW will certainly be a given.  

There were valid questions of the necessity of such high rails
(DC). I think one big advantage is that simple circuits can
be more linear without the need for cascoding to linearise
capacitances and early effect etc. The headroom issue as DC
suggests is a red herring IMO the benefits are elsewhere.
Check some BJT data sheets and look where the miller C gets
very linear WRT voltage across the device. You can really
measure this especially on simple low FB circuits and at higher
frequencies.

Another related issue is if the given stage is fed from a
higher impedance such as a passive vol control. In this case
there will be increased distortion due to IP device modulated
miller C and as stated before it will manifest itself at higher
freq.

Cheers,

Terry
Title: Re: Any DIY EQ interest?
Post by: bblackwood on July 27, 2004, 07:18:00 pm
OK, I'm starting to like DC's three band Baxandall (with either IC or 990 size opamps) idea. I dunno, probably just as easy to implement, especially with PCBs (which we will have made - already have a great source).

Thoughts?
Title: Re: Any DIY EQ interest?
Post by: theo mack on July 27, 2004, 09:55:28 pm
I'm In !
990 size opps please.
How about a face plate order too.

Title: Re: Any DIY EQ interest?
Post by: moogus on July 28, 2004, 05:43:59 am
Terry Demol wrote on Mon, 26 July 2004 19:37


Hi Moogus,

Is this with the JLM99V or as your instrument opamp description
suggests, a fully balanced instrumentation amplifier Bal IP ->
SE OP, or just the front end of an instrumentation amp ie;
CM gain = x1 bal in bal out, or lastly, a fully balanced VG
(current) IP such as Nelson Pass's "Supersymmetry"?


Cheers,

Terry





Hi Terry

The inst. amp I speak of is not the 99V.  Its the one Joe designed for the mastering console and it has balanced input and output and an unbalanced 'insert' point in between.  We dont sell it as a sepperate 'product' at the moment, as it was really just made for the console, but were working on a new pure 990 style opamp called the 99S (S for symetrical).



M
Title: Re: Any DIY EQ interest?
Post by: jfrigo on July 28, 2004, 02:52:26 pm
bblackwood wrote on Tue, 27 July 2004 16:18

OK, I'm starting to like DC's three band Baxandall (with either IC or 990 size opamps) idea. I dunno, probably just as easy to implement, especially with PCBs (which we will have made - already have a great source).

Thoughts?


Forgive a non-designer's question, but I thought the Baxandall circuit was a shelving filter, and three shelves would be a bit odd. Is there a peaking filter that is close enough in circuit design to still be called Baxandall? As I just use the things and don't design them, I'm in the dark here. Who can help?

I'd think three broad peaking filters would be preferable for this particular project, but I guess two shelves and a mid peak would be OK too. This is starting to get interesting, so maybe I'll hop on board for this project. 990 size seems like a good idea as I'm interested in trying some Forssells in there.

Title: Re: Any DIY EQ interest?
Post by: bblackwood on July 28, 2004, 03:04:51 pm
jfrigo wrote on Wed, 28 July 2004 13:52


Forgive a non-designer's question, but I thought the Baxandall circuit was a shelving filter, and three shelves would be a bit odd. Is there a peaking filter that is close enough in circuit design to still be called Baxandall?

His original designs were shelves, but seems like just about anything that has the filters in the negative feedback loop is considered a Baxandall anymore...
Title: Re: Any DIY EQ interest?
Post by: Terry Demol on July 28, 2004, 11:19:00 pm
jfrigo wrote on Wed, 28 July 2004 19:52

bblackwood wrote on Tue, 27 July 2004 16:18

OK, I'm starting to like DC's three band Baxandall (with either IC or 990 size opamps) idea. I dunno, probably just as easy to implement, especially with PCBs (which we will have made - already have a great source).

Thoughts?


Forgive a non-designer's question, but I thought the Baxandall circuit was a shelving filter, and three shelves would be a bit odd. Is there a peaking filter that is close enough in circuit design to still be called Baxandall? As I just use the things and don't design them, I'm in the dark here. Who can help?

I'd think three broad peaking filters would be preferable for this particular project, but I guess two shelves and a mid peak would be OK too. This is starting to get interesting, so maybe I'll hop on board for this project. 990 size seems like a good idea as I'm interested in trying some Forssells in there.




Yes, there are 3 band Banxandall peaking EQ circuits
that work in NF loop of an inverting OPA.
I'll dig one up and send a link tonight.

My guess a FET IP might be better than BJT. You can keep
R's high and C's low and use HQ film types also no offset
problems so can be direct coupled. Should be nice.

Also a thought, you might want to include a mid
shift switch, which should be pretty easy to
do.

Cheers,

Terry



Title: Re: Any DIY EQ interest?
Post by: Bob Olhsson on July 29, 2004, 10:07:43 am
My understanding has always been that a Baxandall eq. uses very broad peaks set up so that the first frequency affected moves closer to the midrange as you increase the amount of boost or cut.
Title: Re: Any DIY EQ interest?
Post by: bblackwood on July 31, 2004, 09:58:01 am
Only 10 votes? Come on, weigh in with what you'd prefer...
Title: Re: Any DIY EQ interest?
Post by: theo mack on August 01, 2004, 03:50:55 am
hey are we doing a stereo unit?
I'd like stereo. Shared psw, and controls.

Title: Re: Any DIY EQ interest?
Post by: bblackwood on August 01, 2004, 07:57:45 am
Stereo, yes.
Title: Re: Any DIY EQ interest?
Post by: JPRisus on August 01, 2004, 09:07:40 pm
what about stereo/dual mono? i'd like two independent sets of controls personally.
Title: Re: Any DIY EQ interest?
Post by: bblackwood on August 01, 2004, 11:15:53 pm
That's what I meant, JP (sorry if I didn't make it clear). Two mono channels in one box...
Title: Re: Any DIY EQ interest?
Post by: Kris on August 04, 2004, 11:37:10 am
You can put me down for 'either'... or 'both' . Very Happy
Title: Re: Any DIY EQ interest?
Post by: Techne on August 04, 2004, 02:10:52 pm
My question may be a bit premature for this project, but i was wondering what opinions you DIY'ers have about chassis selection.  Anyone have good/bad experience with any of the prefab boxes out there?  Sorry if this is a bit OT.
Title: Re: Any DIY EQ interest?
Post by: JPRisus on August 04, 2004, 02:36:44 pm
Techne wrote on Wed, 04 August 2004 14:10

My question may be a bit premature for this project, but i was wondering what opinions you DIY'ers have about chassis selection.  Anyone have good/bad experience with any of the prefab boxes out there?  Sorry if this is a bit OT.



Just got a Hammond half-rack enclosure for my monitoring unit... seems like a solid piece, although i haven't drilled into it yet. I've used small Hammond enclosures for homemade guitar pedals in the past, good stuff, never a problem. Hope the same for the rack units!
Title: Re: Any DIY EQ interest?
Post by: bblackwood on August 04, 2004, 02:39:37 pm
Par-Metal is my chassis of choice.
Title: Re: Any DIY EQ interest?
Post by: theo mack on August 05, 2004, 09:26:31 pm
How much $$ are we guessing for parts?
Are we trying to stay under $300/ ch + PS and Case?
Or do you think it will be more.

Title: Re: Any DIY EQ interest?
Post by: bblackwood on August 05, 2004, 09:48:00 pm
I honestly have no idea. I don't really care about the cost, but I'd guess that excluding chassis and PSU, $300/ch would probably  be more than enough...
Title: Re: Any DIY EQ interest?
Post by: jfrigo on August 05, 2004, 09:53:12 pm
Terry Demol wrote on Wed, 28 July 2004 20:19


Yes, there are 3 band Banxandall peaking EQ circuits
that work in NF loop of an inverting OPA.
I'll dig one up and send a link tonight.



Terry,

Did you come accross that link? I'd be interested in taking a look if possible. Thanks.


Brad,

What's your preference? Apart from "whatever the group decides," which of those bar graphs contains your vote?
Title: Re: Any DIY EQ interest?
Post by: bblackwood on August 05, 2004, 10:02:24 pm
jfrigo wrote on Thu, 05 August 2004 20:53

Brad,

What's your preference? Apart from "whatever the group decides," which of those bar graphs contains your vote?

LCR. There's something in me that's wanted to build a modern 'passive' EQ for years...
Title: Re: Any DIY EQ interest?
Post by: Fabio Bauman on August 09, 2004, 04:02:25 pm
Hi Brad, Jaakko, everybody.

I'm new around here, hope to learn some mastering trick from you guys Surprised  As the subject is DIY EQ, I though you might be interested on  my Sontec DIY page. Lots of people are building it right now, I should have news there soon. On meantime, you can find some directions and layouts and schematics and experiences and docs...

http://www.thediypill.phx.com.br/diy_sontec.htm

cheers!
Fabio
Title: Re: Any DIY EQ interest?
Post by: bblackwood on August 09, 2004, 05:40:02 pm
I've looked at that before and have a couple of thoughts:
1 - too complicated for what I'm trying to do here
2 - not sure it will sound like a Sontec without the HS-1000s
3 - I'm not sure I'd even feel right about it as Sontec is still in business (though that would be called debatable by some). I don't think it's kewl to build a clone of something one can actually go out and buy.

Maybe some day, but for now I want to build something simpler and more original (or at least not in production, even in theory).
Title: Re: Any DIY EQ interest?
Post by: JPRisus on August 10, 2004, 11:56:58 am
I think this was mentioned earlier in the thread, but any chance if including a cut band in the midrange? say, 220, 330, 470, 680? I don't know about anyone else, but that would increase this unit's usefullness tenfold IMHO. too complicated? maybe we could make this optional?

BTW, my simple monitor is coming out great, thanks for the help Brad and everyone!
Title: Re: Any DIY EQ interest?
Post by: bobkatz on August 11, 2004, 06:53:11 pm
I vote for a midrange cut, too. How about something like the old Pultec where you could select boost or cut? And be sure to use a big toggle like one of those old vacuum cleaner switches.  Anyone have Pultec blue paint  Smile
Title: Re: Any DIY EQ interest?
Post by: JPRisus on August 11, 2004, 07:31:39 pm
bobkatz wrote on Wed, 11 August 2004 18:53

I vote for a midrange cut, too. How about something like the old Pultec where you could select boost or cut? And be sure to use a big toggle like one of those old vacuum cleaner switches.  Anyone have Pultec blue paint  Smile


Don't forget bakelite knobs!

Seriously though, i'd be up for going the extra mile on a mid-cut circuit... that would change this project from a fun DIY novelty item that would get limited use, to something I could use every day in a much more useful manner (something more akin to tracking and mixing. Yeah yeah, this is a mastering forum, i know...). After thinking of the Hz I mentioned earlier, i'm still pretty hell-bent on 220, 330, and 470 for the cut bands (fixed Q, something musical). Aside from that, it would be nice to see a HF boost around 10-12k, which wasn't listed by DC on the other thread/post.

The prospects of this EQ are very exciting!

Brad, you mentioned you already had a PCB source lined up... any chance it's these guys?
pcbexpress.com
They look cool, priced them out for a DIY SSL comp I thought about trying a while back.

BTW, I think I gave props to Hammond chassis recently on here... i'm offically taking that back, not digging it AT ALL. Useable for the time being, but i'll need to find a better 1/2 rack unit in the future for my monitor. On the other hand, Hammonds rule for guitar pedals.
Title: Re: Any DIY EQ interest?
Post by: hollywood_steve on August 11, 2004, 08:03:50 pm
BTW, I think I gave props to Hammond chassis recently on here... i'm offically taking that back, not digging it AT ALL

Curious what the problem is?  I have used their 2RU & 3RU chassis without any problems.  What happened?
Title: Re: Any DIY EQ interest?
Post by: JPRisus on August 11, 2004, 08:52:23 pm
hollywood_steve wrote on Wed, 11 August 2004 20:03

BTW, I think I gave props to Hammond chassis recently on here... i'm offically taking that back, not digging it AT ALL

Curious what the problem is?  I have used their 2RU & 3RU chassis without any problems.  What happened?


Steve... perhaps my problem was due specifically to their 1/2 rack 1U model, but the front panel design doesn't make it compatible for the engraving that I planned and designed (which followed standard measure and design), it's slightly higher than 1 RU, only some of the edges were finished, a couple of the self-tapping screws ended up stripping themselves on the way in, and the corner brackets (which were not mentioned in the product description or measurements) made it impossible to include the amount of connectors I originally spec'd it for. I've had to cut a few corners that i'm not so happy about, but in the end I do have a killer passive monitor that was a dramatic step up from my previous situation. The enclosure is the only aspect of this project i'm not 100% satisfied with.

FWIW, I went a much more simple approach to my monitor than some of the mastering guys, since i'm working in a tracking/mixing DAW room... Grayhill 6-pos rotary and DPDT center-off toggle, TKD 10k stereo pot (as suggested by John Klett for someone else's desk), 18awg stranded copper wire throughout, unbalanced, all neutrik connectors (RCA, TRS, XLR for options), Kilo aluminum knobs (very similar to Manley's). Will post pics of inside and out once I'm happy with the aesthetics...  front panel is blank right now. Man I love those knobs!!!

Thanks to everyone who helped/suggested/warned or whom I flat-out bothered, 'specially B-rad!
Title: Re: Any DIY EQ interest?
Post by: dcollins on August 12, 2004, 03:30:42 am
hollywood_steve wrote on Wed, 11 August 2004 17:03

BTW, I think I gave props to Hammond chassis recently on here... i'm offically taking that back, not digging it AT ALL

Curious what the problem is?  I have used their 2RU & 3RU chassis without any problems.  What happened?



They are cheap and have bad tolerances.  I like Lansings, and use plenty of LMB's, as well.

DC
Title: Re: Any DIY EQ interest?
Post by: bblackwood on August 12, 2004, 09:53:33 am
JPRisus wrote on Wed, 11 August 2004 18:31

Brad, you mentioned you already had a PCB source lined up... any chance it's these guys?
pcbexpress.com
They look cool, priced them out for a DIY SSL comp I thought about trying a while back.

No, I have a friend who's father owns a PCB manufacturing facility in Europe. They will manufacture to our specs and are very reasonable (if friends can't take advantage of a little nepotism, what god its it?).

I might have said it earlier, but I'm really happy with the options and build quality of the cases from Par-Metal. A little more expensive, but I'm thrilled with the way my console turned out..
Title: Re: Any DIY EQ interest?
Post by: bblackwood on August 12, 2004, 09:56:20 am
OK, the consensus seems to be passive filter sections, 'boost' and cut on 2 bands (hi and lo freqs) with a midband cut, 990-style opamp factor.

Again, I'll start crunching numbers ASAP and after everything is checked in Spice, somebody will do the board layout for us...
Title: Re: Any DIY EQ interest? Name?
Post by: theo mack on August 12, 2004, 11:04:48 am
How about a group buy of a cool blue engraved face plate.

Oh, and What will be the name of this EQ ?

How about the Blackwood 1? Are you too bashful for that brad?

How about the EQ-BW-2 ?
Title: Re: Any DIY EQ interest? Name?
Post by: bblackwood on August 12, 2004, 11:12:10 am
theom wrote on Thu, 12 August 2004 10:04

How about a group buy of a cool blue engraved face plate.

We could do a group buy of the faceplate, sure. But for a few dollars more, everyone could customize it as they wish...

Quote:

Oh, and What will be the name of this EQ ?

Whatever you want...

Quote:

How about the Blackwood 1? Are you too bashful for that brad?

How about the EQ-BW-2 ?

Oh, no way. Forget that, not a chance. I'm not doing anything worthy of putting my name on the front panel, just lifting designs out of the Audio Cyclopedia...
Title: Re: Any DIY EQ interest?
Post by: JPRisus on August 12, 2004, 12:39:20 pm
bblackwood wrote on Thu, 12 August 2004 09:56

OK, the consensus seems to be passive filter sections, 'boost' and cut on 2 bands (hi and lo freqs) with a midband cut, 990-style opamp factor.

Again, I'll start crunching numbers ASAP and after everything is checked in Spice, somebody will do the board layout for us...


sounds killer, can't wait!
Title: Re: Any DIY EQ interest?
Post by: chrisj on August 12, 2004, 01:22:30 pm
Brad, it wouldn't be happening the way it is happening if not for you. Someone's gotta row the boat, you know? Go ahead and let your name be used. If you don't like that we could use a diminutive, like 'The Bradlet' Smile
I'm following this thread very closely as I'm expecting to eventually make a modular digital/analog hybrid console that sums the outputs of some DACs through discrete Pultec-esque circuits to analog outs, but I haven't the slightest desire to clone anything, just to make a decent passive EQ that does what I want. As such, this project is going to be terribly useful to me for study Smile
Title: Re: Any DIY EQ interest?
Post by: JPRisus on August 12, 2004, 03:43:19 pm
chrisj wrote on Thu, 12 August 2004 13:22


I'm following this thread very closely as I'm expecting to eventually make a modular digital/analog hybrid console that sums the outputs of some DACs through discrete Pultec-esque circuits to analog outs, but I haven't the slightest desire to clone anything, just to make a decent passive EQ that does what I want. As such, this project is going to be terribly useful to me for study Smile



Funny you should mention that Chris... I'm thinking of a similar thing, probably an 8-into-2 (or pair of 4-1) summing bus with Jensens (or Sowters) on the inputs, running into my DRS-2 for makeup. Tranny stage for tone, maybe attenuators on the inputs (maybe not).


As for our EQ names, how about EQphonic , or Euphonic-Q? I'm all for a tribute to the skipper on this one, even if he's too damn humble to want his own name on it!
Title: Re: Any DIY EQ interest?
Post by: OTR-jkl on August 12, 2004, 04:21:06 pm
REPhonic EQ-1
Title: Re: Any DIY EQ interest?
Post by: bblackwood on August 12, 2004, 04:30:10 pm
Seriously guys, we're not naming it after me or my company. I'm designing nothing here, just copying others' work.

Why not name it something like 'LCREQ' or 'PPEQ' or name it after your company - you guys are the ones building them...
Title: Re: Any DIY EQ interest?
Post by: theo mack on August 12, 2004, 08:17:45 pm
how about:

 the

                 R/E/P-EQ


I still think it will be known as the Blackwood EQ, but naming it after this board might be cool.
Title: Re: Any DIY EQ interest?
Post by: mcsnare on August 13, 2004, 07:06:08 pm
B Rad-E-Que
Title: Re: Any DIY EQ interest?
Post by: JPRisus on August 13, 2004, 07:21:23 pm
or just B-B-EQ, hehe
Title: Re: Any DIY EQ interest?
Post by: theo mack on August 13, 2004, 10:15:21 pm
or:

 BARB-EQ
Title: Re: Any DIY EQ interest?
Post by: JLM Audio on August 13, 2004, 11:12:20 pm
Just thought this might be of interest here

http://www.jlmaudio.com/JLM99XMB%20as%20Channel%20Strip.gif

The drawing just shows how a opto compressor and/or passive EQ with no makeup amp can be inserted in our JLM99xMB Mic Pre PCB.

http://www.jlmaudio.com/PEQ1%20Mastering%20800.jpg

It is not to hard to make a switchable passive eq that can be switched by center off toggle from cut / off / boast like the massive passive. Summit Audio actually did this in there EQF-100 years before the massive passive arrived. But the EQ bands have to be laid out in a different way to the normal PEQ-1A to get the cut/boast on each EQ band. The simple Pultec PEQ-1A passive EQ with good balanced input amp and makeup amp is pretty unbeatable for all applications. Photo of two custom JLM mastering PEQ1 fully 0.5dB switched and bypass relays can be interlocked. All parts have to hand matched so left and right track each other perfectly for mastering. We use fft to trim both sides to less than 0.1dB difference.
Title: Re: Any DIY EQ interest?
Post by: mcsnare on August 14, 2004, 05:00:30 pm
Brad, can you get Dave Hill to design a "flavor" circuit for the B-B-EQ. Two positions "wet" or "dry" or alternately "Memphis" or "Texas"....
Dave
Title: Re: Any DIY EQ interest?
Post by: JackJohnston on October 23, 2004, 05:43:02 pm


If this is moving forward, I would love to be part of it.

Jack Johnston
jackjohnston99@hotmail.com
Title: Re: Any DIY EQ interest?
Post by: malice on October 24, 2004, 02:03:00 am
Yeah, is this still a project or what ?


malice
Title: Re: Any DIY EQ interest?
Post by: bblackwood on October 24, 2004, 11:29:27 am
Yah, at some point...

Had a wild hair, have no idea where I thought I'd get the time. At some point I'm sure I'll have a down day or three...
Title: Re: Any DIY EQ interest?
Post by: ammitsboel on October 24, 2004, 05:52:43 pm
Why not make it as simple as possible, and do a passive design with no gain makeup?
Just a very simple passive design with 2 shelves so we can "shelve" the sound gently into brighter or darker...?
And sent the audio level through as few as possible components!
Then we use our other gear for gain make up(if needed).
Title: Re: Any DIY EQ interest?
Post by: bblackwood on October 25, 2004, 03:54:06 pm
ammitsboel wrote on Sun, 24 October 2004 16:52

Why not make it as simple as possible, and do a passive design with no gain makeup?

Well, the gain makeup is kinda 'free' when you take into account the buffering amps...

Quote:

Just a very simple passive design with 2 shelves so we can "shelve" the sound gently into brighter or darker...?
And sent the audio level through as few as possible components!
Then we use our other gear for gain make up(if needed).

Would be cool, but I think the values of the EQ would change according to the load. Someone correct me if I'm wrong here...
Title: Re: Any DIY EQ interest?
Post by: ammitsboel on October 25, 2004, 05:28:21 pm
bblackwood wrote on Mon, 25 October 2004 20:54


Would be cool, but I think the values of the EQ would change according to the load. Someone correct me if I'm wrong here...



Yes, but that's the funny part... or should i say funky part!  Very Happy
...ok, we better go for the line amps.
Title: Re: Any DIY EQ interest?
Post by: judah on October 25, 2004, 09:34:22 pm
Hey! Has it all gone in vapor? I found it oit only now. I'd love to build something having some help from a DIY group. Any news about the EQ?

R.
Title: Re: Any DIY EQ interest?
Post by: Bill B on October 26, 2004, 12:42:48 am
yes, what's the status of this project? i just found out about it and would love to build one, or two....
Title: Re: Any DIY EQ interest?
Post by: Level on October 26, 2004, 01:19:20 am
Just built a new "repair, refurbish and rebuild" room. new solder station and even a solder vat with test instuments abound.

MY diy hat is on for the Winter.

Two words:

Klark T.

I do use them and can improve in ways. I also have my old MCI modules that toggle that were recapped that were the "drum eq to die for" modules in my day 10 years ago.

WTF..Whats hot, what is not?

The analog EQ's on a FOH large scale Ramsa were also Smile Smile Smile.


Look at what can be sweetness in 0.5 dB swings up to 18dB for us hard corers.


I like DC to 70hz @ 6dB +/- 18dB
Vari/para 45-650hz ]
Main 800hz
Vari/para 370hz to 3.8K
Ditto for 1.5 to 17K

And a fully 6dB/oct centered at 14.5K

HPF at 23hz and 70
LPF at 19K @ 12dB/oct and 38Khz (for DSD filter)


+24dbFs @ 0.01THD is fine.

Title: Re: Any DIY EQ interest?
Post by: judah on October 26, 2004, 02:55:33 am
It seems it just disappeared. Gone. Bum. Sayonara. Adios.

R.
Title: Re: Any DIY EQ interest?
Post by: ammitsboel on October 26, 2004, 03:52:35 am
Level wrote on Tue, 26 October 2004 06:19


Look at what can be sweetness in 0.5 dB swings up to 18dB for us hard corers.


I like DC to 70hz @ 6dB +/- 18dB
Vari/para 45-650hz ]
Main 800hz
Vari/para 370hz to 3.8K
Ditto for 1.5 to 17K

And a fully 6dB/oct centered at 14.5K

HPF at 23hz and 70
LPF at 19K @ 12dB/oct and 38Khz (for DSD filter)


+24dbFs @ 0.01THD is fine.




AAArh... a 19k LPF!! 12db/oct!!!
I will trust my converters on that. Was it a joke?

I have a passive eq that can do the acrobatic things already.
I just want a simple unit with 2 bands very broard bands.

best regards
Title: Re: Any DIY EQ interest?
Post by: bblackwood on October 26, 2004, 09:00:04 pm
Way too complicated for this Bill, but thanks.

I hope to get to this at some point soon enough, but finding time is difficult lately (like tonight, still here cutting parts after 11 hours).

Why not do it as a true group DIY and have some of you guys help crunch some numbers?
Title: Re: Any DIY EQ interest?
Post by: OTR-jkl on October 26, 2004, 10:46:23 pm
bblackwood wrote on Tue, 26 October 2004 20:00

Why not do it as a true group DIY and have some of you guys help crunch some numbers?

Let me know what you need...
Title: Re: Any DIY EQ interest?
Post by: bblackwood on December 21, 2007, 12:44:14 pm
*bump* (it's only been three years...)

I think I'm going to make this happen soon, if anyone is still interested. Here's what I'm currently thinking:

Seem interesting enough? I'm going to have my tech mull over this in a few weeks when my new (active) EQ arrives...

(* = it's been some time since I even looked at a passive EQ, we might have to have an active buffer so the slopes/freqs don't shift)
Title: Re: Any DIY EQ interest?
Post by: Gold on December 21, 2007, 01:38:27 pm
This would be a good option for input buffering and makeup gain. http://www.jlmaudio.com/dINgO.htm
Title: Re: Any DIY EQ interest?
Post by: bblackwood on December 21, 2007, 02:04:56 pm
Yah, good call, Paul.

Just chatted with my tech, he's gonna think over it and see what he can come up with.
Title: Re: Any DIY EQ interest?
Post by: djwaudio on December 22, 2007, 11:39:46 am
bblackwood wrote on Fri, 21 December 2007 09:44



I think I'm going to make this happen soon, if anyone is still interested.


I'll build one of these too. I could use a simple LCR EQ. How can I help?
Title: Re: Any DIY EQ interest?
Post by: bblackwood on December 22, 2007, 11:53:03 am
djwaudio wrote on Sat, 22 December 2007 10:39

bblackwood wrote on Fri, 21 December 2007 09:44



I think I'm going to make this happen soon, if anyone is still interested.


I'll build one of these too. I could use a simple LCR EQ. How can I help?

For now, I'm waiting to hear back from my tech, likely be a week or so. Looks like he's going to draw in simple buffer and line amps with it to keep everything shifting with different loads. I have to wait to see if this is really simple enough for the average studio guy to do, but worse case scenario someone can have their tech wire it up...

Anyone else interested/have any ideas regarding this?
Title: Re: Any DIY EQ interest?
Post by: Gold on December 22, 2007, 09:16:43 pm
If the object is a group build sort of thing I think it will have to be a kit. Design and make some PCB's and put together a Bill of Materials. If it's a schematic without layout I think it will be beyond the capabilities of most.
Title: Re: Any DIY EQ interest?
Post by: bblackwood on December 22, 2007, 09:19:11 pm
Gold wrote on Sat, 22 December 2007 20:16

If the object is a group build sort of thing I think it will have to be a kit. Design and make some PCB's and put together a Bill of Materials. If it's a schematic without layout I think it will be beyond the capabilities of most.

Yah, a kit is the plan (well, PCB's with BoM). Even then, some are less adventurous than others...
Title: Re: Any DIY EQ interest?
Post by: Gold on December 22, 2007, 11:39:28 pm
Sounds like fun. I'm in for two channels.

Title: Re: Any DIY EQ interest?
Post by: jdg on December 23, 2007, 12:16:28 am
totally in
Title: Re: Any DIY EQ interest?
Post by: bigaudioblowhard on December 23, 2007, 02:35:34 am

whats LCR?

bab
Title: Re: Any DIY EQ interest?
Post by: djwaudio on December 23, 2007, 02:46:29 am
bigaudioblowhard wrote on Sat, 22 December 2007 23:35


whats LCR?




L = inductor
C= capacitor
R= resistor

The basic circuit concept for a passive filter. Others who know what they are talking about can elaborate.
Title: Re: Any DIY EQ interest?
Post by: bigaudioblowhard on December 23, 2007, 12:56:17 pm

I recently bought a pair of UTC 3A Passive EQ's from, I think, 1949. I have no idea what I'm gonna do with em, but they're at a tech right now getting cleaned up, so haven't listened to em yet.

I got em on ebay, and the seller said they sound "amazing", but everything on ebay is listed as "amazing".

Anybody heard these "amazing" EQ's?

bab
Title: Re: Any DIY EQ interest?
Post by: Allen Corneau on December 23, 2007, 11:42:15 pm
djwaudio wrote on Sun, 23 December 2007 01:46

bigaudioblowhard wrote on Sat, 22 December 2007 23:35


whats LCR?




L = inductor
C= capacitor
R= resistor



Aww... I thought it would be a 3-channel unit for left-center-right! Laughing
Title: Re: Any DIY EQ interest?
Post by: hnewman on December 24, 2007, 11:57:31 am
If it is a full kit I'd be interested as well.
Title: Re: Any DIY EQ interest?
Post by: mbruce333 on December 28, 2007, 12:58:56 am
I'm in as well!  I've had EQ on the brain lately so this will be a very cool learning experience.

Mike Bruce
Auricle Audio Mastering
www.auricleaudiomagic.com
myspace.com/auricleaudiomastering
Title: Re: Any DIY EQ interest?
Post by: gbacklin on December 28, 2007, 08:05:40 pm
Hmmmm, this does sound interesting. The last thing I built, was a 40meter tuna-tin  Laughing

Take Care,
Gene
Title: Re: Any DIY EQ interest?
Post by: J.J. Blair on December 29, 2007, 06:58:37 pm
Sounds fun.  Count me in.
Title: Re: Any DIY EQ interest?
Post by: Larrchild on December 29, 2007, 07:04:28 pm
*looks around*

Wow, plenty of compressors.

Not so much, EQ's.

I'm in.
Title: Re: Any DIY EQ interest?
Post by: David Glasser on December 29, 2007, 07:06:10 pm
I'm in.

But only if it has blue LEDs.

Title: Re: Any DIY EQ interest?
Post by: compasspnt on December 29, 2007, 07:22:02 pm
Will be watching with interest.

Title: Re: Any DIY EQ interest?
Post by: Gold on December 29, 2007, 07:49:10 pm
David Glasser wrote on Sat, 29 December 2007 19:06

But only if it has blue LEDs.



I agree. There should be a blue LED on/off switch. Perhaps we should install a meter to monitor the LED current.
Title: Re: Any DIY EQ interest?
Post by: Larrchild on December 29, 2007, 08:08:21 pm
To get a basic idea of how a resistor, coil and capacitor make an EQ, go here and fiddle with the "f=" slider.
http://www.ngsir.netfirms.com/englishhtm/RLC.htm
Then change some other part values and watch the curves change.
Notice the "Q" change when you adjust "R".
You may notice both "C" and "L" change the frequency of the filter.
It's the phase shift that's important. Where it says; "I leads V" and "V leads I".
For identical curves, one phase shift will usually sound better than the other.
Title: Re: Any DIY EQ interest?
Post by: present on December 30, 2007, 05:17:11 am
I really need to catch up on the technical side of things but I'm very interested.
Now, it will have a switch that goes 'ping' right?
Title: Re: Any DIY EQ interest?
Post by: Viitalahde on December 30, 2007, 05:42:44 am
I have new L/C EQ plans of my own, but I had my coils custom wound by an Austrian guy.. Very HQ Ni-Fe cores, good stereo matching. Maybe he could help you with the coil needs if that isn't sorted.
Title: Re: Any DIY EQ interest?
Post by: Greg Reierson on December 30, 2007, 10:39:30 am
David Glasser wrote on Sat, 29 December 2007 18:06

I'm in.

But only if it has blue LEDs.




Is that why Brad doesn't have a Great River EQ?


GR
Title: Re: Any DIY EQ interest?
Post by: mastertone on December 30, 2007, 12:46:22 pm
this sounds like fun Cool
count me in!
Title: Re: Any DIY EQ interest?
Post by: Peter Beckmann on January 07, 2008, 04:54:35 am
A little late to the thread, but sounds like fun.

PB
Title: Re: Any DIY EQ interest?
Post by: RMoore on January 07, 2008, 06:43:04 am
DIY passive mastering EQ that will bring joy into the user's lives?

Watching with interest - good luck people!
Title: Re: Any DIY EQ interest?
Post by: jason goz on January 07, 2008, 08:46:34 am
If this eq can have stepped cut and boost controls then i'm in
Jason
Title: Re: Any DIY EQ interest?
Post by: mastertone on April 01, 2008, 04:12:45 pm
So, any news on this one?

/Jonas
Title: Re: Any DIY EQ interest?
Post by: bblackwood on April 03, 2008, 03:14:09 pm
Well, I'm still trying to figure out how to do this in such a way as to make it DIY-able. Not really very easy as my tech most certainly does NOT want to be a hand-holder through the process...
Title: Re: Any DIY EQ interest?
Post by: bblackwood on April 03, 2008, 03:14:10 pm
Well, I'm still trying to figure out how to do this in such a way as to make it DIY-able. Not really very easy as my tech most certainly does NOT want to be a hand-holder through the process...
Title: Re: Any DIY EQ interest?
Post by: bblackwood on April 09, 2008, 01:47:04 pm
Ok, this is cool - I had two guys volunteer to bang on the design a bit and also support those who need it during the build process, so I met with my tech today and we went over the basics. to keep this simple (and keep it as affordable as possible), we decided to skip the inductors, so it's shelf only, will allow for boost and cut at variable frequencies. Will have a solid state buffer and makeup amp, so interfacing won't be an issue. This should result in a very clean and transparent EQ that's good for overall shaping.

Obviously if you want something more complex, it's up to you, but this will be the basic design. We can have a mod thread if people want to...

More to come...
Title: Re: Any DIY EQ interest?
Post by: David Glasser on April 09, 2008, 01:57:25 pm
Brad,

See if you can configure it so the gain stage can be a 2520/990/Forsell form factor.
Title: Re: Any DIY EQ interest?
Post by: Noah Mintz on April 09, 2008, 02:31:34 pm
bblackwood wrote on Wed, 09 April 2008 13:47

Ok, this is cool - I had two guys volunteer to bang on the design a bit and also support those who need it during the build process, so I met with my tech today and we went over the basics. to keep this simple (and keep it as affordable as possible), we decided to skip the inductors, so it's shelf only, will allow for boost and cut at variable frequencies. Will have a solid state buffer and makeup amp, so interfacing won't be an issue. This should result in a very clean and transparent EQ that's good for overall shaping.

Obviously if you want something more complex, it's up to you, but this will be the basic design. We can have a mod thread if people want to...

More to come...


Sorry if this is a repeat comment because I don't have time to read the entire thread, but...

the idea of an 'open source' DIY EQ seems like a great idea. Good EQ design is not a simple thing and I can see it as greatly beneficial to have a bunch of minds/ideas on a hardware design.  
Title: Re: Any DIY EQ interest?
Post by: bblackwood on April 09, 2008, 02:38:09 pm
David Glasser wrote on Wed, 09 April 2008 12:57

See if you can configure it so the gain stage can be a 2520/990/Forsell form factor.

Yep, that's included - thanks!
Title: Re: Any DIY EQ interest?
Post by: Jeff Baggett on August 27, 2008, 08:18:36 am
any progress on this?
Title: Re: Any DIY EQ interest?
Post by: bblackwood on August 27, 2008, 09:51:08 am
Jeff Baggett wrote on Wed, 27 August 2008 07:18

any progress on this?

No, my tech has been buried and hasn't had the chance to do anything with it.
Title: Re: Any DIY EQ interest?
Post by: OLDTUBEY on January 29, 2009, 01:45:00 am
Yeah, Yeah, Yeah, I'm interested in participating! Yes, I know this is sort of late and is in response to a post submitted in 2004:)..... I have a little bit of experience with the building of both passive and active EQ's as well as other high end audio from the ground up. 'Been doing it since about 1974. The last company I worked with off and on since about '92 made some very good equipment. Their EQ's were considered by many to be the very best in the world and definitely regarded as the industry standard. Unfortunately my 'Boss' man as I call him Cool started losing his mind several months ago and then one day just stopped communicating. There must be some sort of curse on that old school. Now I think that he/they may have dropped off the face of the Earth suddenly and left me holdin one of the bags:).....I was also a procurement agent for them for a number of years.....got about 30,000 pounds of the stuff in the basement....along with a whole bunch of extraordinarily hard to find three legged semiconductors.... that go into some little modules... I refer to them as the 'Motorola Diamonds'.... The 'Boss' keeps his dwindling inventory of em locked up in a Safe I think......have a few schematics too:)..... But I'm not gonna be around much longer.I was thinking that maybe I should sell this stuff while I'm still alive and give the money to a children's research hospital or something.
But I'd really like to make sure that they've actually closed down, outta business and aren't just hiding from me, before I go and let the cat outta the bag. Otherwise they might come gunnin for me. Anybody know anything? Any ideas?

Kind Regards,

Gruntboy Alf from hillbilly heaven
Title: Re: Any DIY EQ interest?
Post by: dcollins on January 29, 2009, 06:31:53 am
OLDTUBEY wrote on Wed, 28 January 2009 22:45

Yeah, Yeah, Yeah, I'm interested in participating! Yes, I know this is sort of late and is in response to a post submitted in 2004:)..... I have a little bit of experience with the building of both passive and active EQ's as well as other high end audio from the ground up. 'Been doing it since about 1974. The last company I worked with off and on since about '92 made some very good equipment. Their EQ's were considered by many to be the very best in the world and definitely regarded as the industry standard. Unfortunately my 'Boss' man as I call him Cool started losing his mind several months ago and then one day just stopped communicating. There must be some sort of curse on that old school. Now I think that he/they may have dropped off the face of the Earth suddenly and left me holdin one of the bags:).....I was also a procurement agent for them for a number of years.....got about 30,000 pounds of the stuff in the basement....along with a whole bunch of extraordinarily hard to find three legged semiconductors.... that go into some little modules... I refer to them as the 'Motorola Diamonds'.... The 'Boss' keeps his dwindling inventory of em locked up in a Safe I think......have a few schematics too:)..... But I'm not gonna be around much longer.I was thinking that maybe I should sell this stuff while I'm still alive and give the money to a children's research hospital or something.
But I'd really like to make sure that they've actually closed down, outta business and aren't just hiding from me, before I go and let the cat outta the bag. Otherwise they might come gunnin for me. Anybody know anything? Any ideas?

Kind Regards,

Gruntboy Alf from hillbilly heaven



I think it's a terrific first post.


DC
Title: Re: Any DIY EQ interest?
Post by: Matt_G on January 29, 2009, 08:42:58 am
Especially considering that he registered in September 2008 & it's taken him almost 6 months to do this first post. So I guess we're talking about a British EQ? Would be nice to know what company you used to work for Smile
Title: Re: Any DIY EQ interest?
Post by: Ben F on January 29, 2009, 05:54:35 pm
OLDTUBEY wrote on Thu, 29 January 2009 17:15

The last company I worked with off and on since about '92 made some very good equipment. Their EQ's were considered by many to be the very best in the world and definitely regarded as the industry standard. Unfortunately my 'Boss' man as I call him Cool started losing his mind several months ago and then one day just stopped communicating. There must be some sort of curse on that old school. Now I think that he/they may have dropped off the face of the Earth suddenly and left me holdin one of the bags:).....


Hey man, was that company Sontec by any chance?
Title: Re: Any DIY EQ interest?
Post by: Steffen on March 30, 2009, 07:16:09 am
 I just came over this thread lately and got inspired  Embarassed
4 bands, boost only, broad fixed bandwidth, covering the entire frequency range (and above, the upper band goes up to 27k to add air).
the absolutely cool thing about it is, since we work with switches here, all taps can be made from the same restorstring so it acts like a pot with 4 wipers. it can´t get more minmalistic I think   Very Happy

here are a few shots:


http://www.diygallery.de/forum/EQP4/EPQ4A.jpg


http://www.diygallery.de/forum/EQP4/EPQ4B.jpg

matched filterboards and resistorladder

http://www.diygallery.de/forum/EQP4/filterboards.jpg

Elmas  Cool

http://www.diygallery.de/forum/EQP4/elmas.jpg

http://www.diygallery.de/forum/EQP4/EPQ4inside.jpg
Title: Re: Any DIY EQ interest?
Post by: Gold on March 30, 2009, 07:28:57 am
Very nice! The single resistor string for all bands is clever. The styling is excellent as always.
Title: Re: Any DIY EQ interest?
Post by: bblackwood on March 30, 2009, 08:14:42 am
Steffen wrote on Mon, 30 March 2009 06:16

 I just came over this thread lately and got inspired

Wow, Steffen - amazing as usual!
Title: Re: Any DIY EQ interest?
Post by: Steffen on March 30, 2009, 09:29:02 am
thanx guys!

btw...an interesting observation (hope this isn´t old news)

I already suspected (real) parallel passive to be much different in therms of band interaction
from the "usual" aktive (summing) eqs. last friday I used my new toy for a few trax
and I was amazed with how much boost you can get away without messing it all up.
if you feather a little it keeps sounding natural even with 3dB/band boost or more.

so I did some measurements (which actually proved what I suspected)

an active eq and my parallel passive one band set to 500Hz/10dB boost ,another
band to 2kHz/10dB boost. active Qs matched to the passive so it looks
quite similar when the bands are soloed. but the fun starts when both
band are activated. the passive still looks like 2 10dB boosts (the center frequencies seem to
shift a little due to the interaction) but the active looks like a big broad 15dB boost
at around 1K

index.php/fa/11797/0/

def a different kind of eq ....but I absolutely love it after one day of use Smile

btw: I have no chance to compare but I´d expect the manley MP or the gyraf in between these
two extremes of interaction. if somebody is interested to evaluate let me know..




Title: Re: Any DIY EQ interest?
Post by: Andrew Hamilton on March 31, 2009, 10:14:34 am
Steffen wrote on Mon, 30 March 2009 09:29

thanx guys!

btw...an interesting observation (hope this isn´t old news)


Wow.  How about 1/3 dB steps?  Gorgeous build.  

Steffen wrote on Mon, 30 March 2009 09:29


index.php/fa/11797/0/



O.K., but the 2k and 500 Hz colors are backwards, right?  Rolling Eyes

[sorry.  The graph really is gorgeous.  When I first read the post I hadn't followed all the leader and thought your new toy was an AP or dScope, rather than the eq.  What is that graph generated with?]


Steffen wrote on Mon, 30 March 2009 09:29

...
I´d expect the manley MP or the gyraf in between these
two extremes of interaction. if somebody is interested to evaluate let me know..



The Manley can be a little narrow or very wide, but I think the most telling part of its "parallel reality" is what the manual mentions - that when two switches are set to the same general frequency, the respective power of each is less than when either switch is soloed (as it were), so that extreme-looking settings aren't necessarily all that extreme.  Plus, one is encouraged to combine a boost with a nearby cut in order to achieve custom transforms that cure [anomalies of] both space (f) and time (
Title: Re: Any DIY EQ interest?
Post by: Steffen on March 31, 2009, 11:02:46 am
Quote:

Wow. How about 1/3 dB steps? Gorgeous build.


thanx Andrew, the 1/2 steps feel just right...but I miss a 5th band centered@1k
it was ment to be "helper eq" but it´s turning out to be the primary workhorse haha Smile


Quote:

O.K., but the 2k and 500 Hz colors are backwards, right?


ups, yeah you are right..typo
the plots are made with fuzzmeasure  
http://supermegaultragroovy.com/products/FuzzMeasure/

btw...the rise at 40k seem to come from  parasitic capacitance in the lomid inductor

ah, and good idea..have to check what happens with 2 band more narrow or equal frequency.
Title: Re: Any DIY EQ interest?
Post by: Viitalahde on March 31, 2009, 11:12:53 am
Nice work Steff. Reminds me of my new EQ that I use every day. Dual mono in construction, +/-3dB, three bands, six frequencies per band. I have a proper front panel sitting right here, I only need to install it. Then I'll dare to take pics of it. I've been using mine for some 3-4 months now, and it has came invaluable in shaping the tone without really adding anything.

But I say the sound is in the caps, and in this case paper in oil rules for the filters. Mundorf Supreme for the output. 7193+6SN7 in the amp, and a regulated 300v B+. I used polypropylene motor run caps in the PSU, they're cheap, good and will never wear out. Bloody huge, though.

Mine also has the filters in parallel, and you most certainly can bend the sound without hurting it. Something very nice happens when I cut from 350Hz and 75Hz at the same time, for example. Very broad bands that interact.

My new EQ is so nice in cutting things that I use it more often like that. It does not punch a hole in anything, things just open up where I want them to.