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[bblackwood]

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?

[theo mack]

I'm In !
990 size opps please.
How about a face plate order too.

[moogus]

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

[jfrigo]

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.

[bblackwood]

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...

[Terry Demol]

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

[Bob Olhsson]

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.

[bblackwood]

Only 10 votes? Come on, weigh in with what you'd prefer...

[theo mack]

hey are we doing a stereo unit?
I'd like stereo. Shared psw, and controls.

[bblackwood]

Stereo, yes.

[JPRisus]

what about stereo/dual mono? i'd like two independent sets of controls personally.

[bblackwood]

That's what I meant, JP (sorry if I didn't make it clear). Two mono channels in one box...

[Kris]

You can put me down for 'either'... or 'both' .

[Techne]

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.

[JPRisus]

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!