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[moogus]

Hey John and all,

Im looking for circuity info on the Yamaha PM2000 console from the late 70s.  I know its mostly A class with xformer i/o, but I dont know anything about the eq.

Any info about this console would be greatly appreciated.



M

[Bo Hansén]

Hi M,

First of all, the PM-2000 are a very nice sounding console.

The electronics are not in true class-A like old Neve circuits, this console are build with a discrete amps module NE80100 and NE80200 in simular pakage like API 2520 or Hardy 990, and this is a differential amplifier "OP-amp" there NE80100 are use as output amplifiers and have a complementary output circuit that work in class A/B.
But normally in this type of amps there are high current through the output transistors, so we can say that is work in "small signal class-A"
Unlike the NE80100 are the NE80200 use as a main op-amp in different places and can have a class-a output or maybe a input circuit that are suit for high gain application.

The equalizer are designed like older "L and C circuits, (L=inductor, C=capacitor) but they have a "gyrator" (electronic inductor) instead for the passive inductors.

If I not remember wrong, they use transformers from Tamura.

[moogus]

Hey thanks Bo.

Do you know if they use the discrete opamp exclusively thoughout the console, inlcuding the EQ?  Or are there IC opamps in it aswell?


Cheers,


M

[Bo Hansén]

Hi Moogus,

This discrete op-amp are used in the main audio chain, and what I remember, they use ordinary IC/OP-amps in other not so important circuits like talk back/communications, oscillator, AUX and some other things.

[jason spartz]

I know that Yamaha has a basic owners manual on the website.  It might be helpful if you are looking for the fixed frequencies that eq section offers.  If you are looking for more info on the design structure of the Eq circuits then you will want to get a copy of the schematics.  I think that they are a nice sounding board.  Eq is a bit limited.

Jason

[moogus]

Thanks all for you help.

It looks like Im going to be buying one, which comes with a full service manual.  I might post up some more info/pics/schematics for reference once It arrives.

Once again, thanks!



M

[josh]

You can download the entire manual (including schematics and other service info) from the yamaha web site.

The PM2000 is not discrete Class A, the PM1000 is.  The PM2000 is *not* simply a more full-featured version of the PM1000...  Different design altogether.  Just FYI...  this is a common piece of confusion.

[Bo Hansén]

Hi Josh,

I will only do a small comment regarding the PM-1000 "class-A"

Unfortunately I must say that even this console have not a real class-A design, also this console have class-A/B amp circuits in the microphone input amp, channel routing/output amp and the line output amps.
But as I wrote in my first post, if there are enough with quiescent current trough the complementary output transistor, they will work in "small signal class-A" (this is not same class-A philosophy as in old Neve consoles)

It is not a bad thing to have class-A/B amps, it was used in mostely of the equipments that we like from the 1970`s as API, Quad-Eight, Triad, Urei, Ampex, 3M, MCI, Studer and a lot of others gears.

[moogus]

Well I bought it!

24ch version in timewarp condition (dont think it was ever toured) with a spare PSU and roadcase.

So far Ive only done a few test recordings to try out the pres and eq, and have been very happy with the results.  The pre sounds like an incredibly smooth verion of an API and is surprisingly quiet (I used my Beyer ribbons and had no noise problems).  The HF eq band is actually passive and sounds great, even with the full 15db of boost.

The mid and low bands are active gyrator type circuits that use HA1457 SIL package ICs, running on +/-24V.  However the Q of the mid bands is 2.5 which is much too narrow (at least for my taste) so were going to change 2 channels to 0.6 and see what they sound like.  These bands also use tant caps, which we will probably change to MKT and NP electros.

The mic pre and output drive circuits use Yamaha descrete opamps (NE80100 for pre and NE80200 for output).  Much to my delight, they have the standard 990 opamp pinout and run on +/-24V rails, so we will definitely try substituting our JLM 99V and 99S opamps at some stage to see how they sound.

All inputs and outputs(24) are transformer balanced, with the exception of the inserts, which are unbalanced, although on sepperate TRS jacks for in and out.  Were also considing trying different loads on the input xformers, as Yamaha have not loaded them much.

The whole desk is really designed for easy servicing, and comes appart quickly and precisely, when you want it to.  The faders are great too - P&G knock offs that are smooth as the proverbial.

So overall Im pretty happy with it, so far.

Were going to document all the mods we do, with schematics and simulations of the new eq curves, and hopefully some recording examples aswell, and put them up somewhere on www.jlmaudio.com for any other PM2000 owners who are interested, as this desk is a real 'sleeper'.  

Ill post the url of this page when its up.

Thanks again to those who helped me out with info in this thread.


M  

[violindave]

curious about the mods to that board. I have some modules from a PM1000 that are being turned into preamps and wonder if your mods would work on that board also?

[moogus]

No, the 1000 is very different, at least as far as the EQ goes, to the 2000.  From what I know about it you might want to change the mid band freqs to something more useful, but this is not as easy to do as it is on the 2000.

BTW weve decided to make the mid bands of my 2000 fully inductive and also spread the freqs out, aswell as lowering the Q.  So far its working well.



M

[moogus]

Update:


Weve made the mid bands of one channel fully inductive, moved the freqs (spread them out) and widened the Q, and the result sounds fantastic.  Ive only done some preliminary testing, running line sources thru the channel (both single instruments and mixes) and all I can think is that I cant wait to mix on this thing.  

Inductors are definitely the way to go in the mid bands, no question.  Its just a matter of fine tuning the values now, and then modding all the channels.  Its great that none of the original caps need to be removed from the eq switch PCB, just 5 resistors which are easy to pull.

The little LCR blobs are all together in a tube of heat shrink (one for each band) and sit nicely in a conveniently free space near the top of the channel.  Its all rather neat!

Stay tuned for more progress reports, and some recordings to have a listen to.



M

[trexrox]

Just FYI, I have seen PM2000's come loaded with Jensen Transformers (not as a mod, but from the factory)...  IF there's a JE-XXXX Part number on there, then you can be sure it's a Jensen.

These are great sounding boards... I used to mix FOH on one in a 1000+ Venue that had tube amps on the horns of the PA!!!  It was sweet!

[jason spartz]

The PM-2000's that I have run across have the Tamara transformers all over them.  I have yet to see Jensens myself.  I wonder if maybe this was a change that happened later in the production of the board?  

Moogus,  I am very interested in your mods on the EQ section.  Keep posting with updates.  When you get it fine tuned I would love to try your mod on my board!  

I think they are a great sounding board myself.  If the EQ can be developed into a better function it would be great.  I swapped two of the matrix output opamps with a pair of John Hardy 990c opamps.  I like it!  The Yamaha opamps have character but can get a little muddy in the low mids.  The JH's keep close to the character but it is a bit cleaner and it does not get as muddy.  I tried a pair of Fred Forssell 992's as well but that made the sound thinner.  It really changed the character of the board sound.  

Jason

[t(h)ik]

Thank you for the information you are putting out.  I am a newbie with a PM2000.  I love the sound of my board, I mean I really love it...I bought it used from a very wonderful man in my host nation but alas, there is noise that shows up on mixdown and the matrix works 90 percent of the time, it usually craps out during the most intense part of someone's session and there are lights blown and maybe some meters on the fritz.

I can only say that I am giddy and thrilled that I have access to this medium and the possibility to maintain my board myself for many future years of enjoyment.

Can't wait for your future posts...