Yamaha PM1000 Recapping/Upgrade

Hello,

I'm recapping a Yamaha PM1000 16 channel mixer and would like to upgrade the input transformers to Lundahl or Jensen on 4 of the channels to start and see how it sounds.

I have a schematic I can't read for the board. Can anyone help me figure out what kind of transformer to order? Lundahl is very friendly on the phone but the guy who knows the parts well is impossible to get a hold of.

Here's a link to the manual/schematic:

http://www2.yamaha.co.jp/manual/english/download.php?div=pa&lang=english

Enter: pm1000

Thanks and nice to be here when it all began.
Bob

The part no. on the schemo is GA80071 for the input trafo, I guess this is a SONY??
There is a 4k7 resistor accross the secondary (followed by.47 cap and a 470R into the transistors).
I guess that an ordinary 1:7 mic transformer like the LL1538 would be fine in this spot and give you the flexibility of two secondaries.

I would only buy one or a pair though (you dont get much bulk discount) and see, it may not make much difference to the overall soung once it has been through the whole desk.

Good luck!

Which Wilco are you a fan of - wilco Johnson I assume.

Jonathan,

You are correct on the GA80071 part#. How do you guess the transformers are Sony? Do you know anything specifically about their work back then if they were in fact Sony?

Here's some photos of the modules:
http://www.bobbymcalister.com/DIY%20Photos/pm1000.html

I assume the UTC looking ones on the master modules are outputs but why two of them? They have part# GA80080 so same manufacturer. What would be a replacement for those? Would Lundahl or Jensen have some too?

Thanks,
Bob

Hei Bob,

I took a look at the schematic for the Master & monitor module. Why two GA 80020's there both line outs. One is A and the other B outs.

A is T2 GA 80020 B is T3 GA80020 and T4 is your monitor out using the GA80020 there to!

Luhndals would be fine there, you could put the luhndal on the T4 and A/B the differents with the line outs T2/T3

I don't have a Pm1000 desk just a few modules I will rack up soon

Chris ... Oppdal

Wilco, the manufacturer was an absolute guess,

the transformers are more likely to be Japanese rather than UTC no?

I'm just thinking of my old Otari deck - has japanese transformers on the output.

Some say the line out transformer has a greater effect on the overall colour. But I'm shooting from the hip (with a glue gun).

If you look at the pdf2/page9: "system headroom" block circuit, it seems that the input transformer is a 1:1 / 0dB device.

Wierd - but I've seen this before in some 1975-vintage pro boards. It seems that the transformer's only function is to balance and do ground insulation.

Jakob E.

According to Scott Dorsey, the transformers used on all the Yamaha mixers throughout the 1970's and 80's were made by Tamura. He said the larger ones are quite good (as used in PM1000 and 2000), but that the littler ones (like in my rack-mount PM180) don't sound as good.

I have an old rack-mount PM180 in which the input transformers are 600/3000 ohm units. I personally like the color of these smaller ones.... they saturate in a pleasant way which is useful for many things.

BTW, does anyone know anything about the little SIP Toshiba op-amps that all the post-PM1000 stuff used? These little buggers ride on +/- 24v rails, and I actually think they sound good, in an old school kind of way. I cannot, for the life of me, find any data sheets on these things.

I was thinking of modifying the PM180 with something like OPA604's that can handle the higher supply voltage just to see the difference (at least in the line-level stages) , though that probably won't be for awhile.

JC

Really diminishing returns to buy better transformers than are stock in the PM-1000. For the cost of really redoing it, all I could forsee is a bit cleaner of a sound, and some of the appeal is a bit of an iron injection. And, yes, I do believe they are Tamuras.

See if someone can snag text from the old PM recapping thread, as there was some good component level wisdom which escapes me. IIRC, the main signal path on the PM-1000 is discrete tranistors and their discrete opamps. The discrete opamps in PM's get as much as 24v, so if you're intent on upgrading, make sure you have something that can take the heat. The stock discrete opamps are not 990 clean, but no one really complains about them. The 7 pin SIP opamps in the other PM's are a bit of a mystery - no one seems to know a sub for them or anything like that - and I might be attributing a sound to them that's elsewhere in the circuit, but yeah, there is a bit of a sound to the channels that use them that is cool in its way. I would like to be able to try something else just to see, though.

If anything needs fixing on the PM desks, it's probably the headphone amp. It seems pretty bad, and in mine the opamp is a bizarre mutant critter. That might be a canidate for dropping in a new board with a modern circuit.

tf

I'm in the process of racking two pm1000 moduals. Does anybody know why the phantom power 48V buss goes to the center tap of the input transformer?

Just for kicks I'm going to try using some those $8.24 Edcor 600:600 transformers for the output. http://www.edcorusa.com/transformers/audio/wsm/wsm600-600.htm If they suck I'll spring for some Cinemags.

Cheers,

elco
:guinness: :shock: :sam:

Elco,

In the good old days when 0.1% resistors were hard to find, it was common practice to connect phantom like this.

But please don't connect an unbalanced source with the phantom power on. This will saturate the input transformer core - not good at all if decent-grade input-transformer core-material was used..

Jakob E.

So should I just omit the 48V on the center tap and use 1%'s on the XLR's?

Cheers,

elco
:shock:

No, just use it as is..

Thanks Jakob! :thumb:

[quote author="gyraf"]If you look at the pdf2/page9: "system headroom" block circuit, it seems that the input transformer is a 1:1 / 0dB device.

Wierd - but I've seen this before in some 1975-vintage pro boards. It seems that the transformer's only function is to balance and do ground insulation.

Jakob E.[/quote]

Does this mean the transformers might lend less to the tone? Are the Lundahl 1538's still a replacement? Sorry but I can solder but me no read funny symbol on techy paper. What about the output transformer, can someone describe the Lundahl replacement? Would that be the 1539?

Also, would someone please mention the Jensen equivalent of both the input and output?

Really diminishing returns to buy better transformers than are stock in the PM-1000. For the cost of really redoing it, all I could forsee is a bit cleaner of a sound, and some of the appeal is a bit of an iron injection.

Click to expand...

I'm definitely not going to dump much into transformers until I hear the A/B of a couple of channels. The Lundahl 1538's won't go to waste around here anyways if it turns out to be a negligible upgrade.

See if someone can snag text from the old PM recapping thread, as there was some good component level wisdom which escapes me.

Click to expand...

Bump. Yes please.

The discrete opamps in PM's get as much as 24v, so if you're intent on upgrading, make sure you have something that can take the heat. The stock discrete opamps are not 990 clean, but no one really complains about them. The 7 pin SIP opamps in the other PM's are a bit of a mystery - no one seems to know a sub for them

Click to expand...

Hmm, where are the opamp(s) on the input module? Are they the six toy tires bunched together there in the middle of the input PCB? I'd be curious if anyone has thoughts about the opamps. What does the PM1000's design put it beside's compared to an API or Neve?

Thanks (whew),
Bob

[quote author="trenchfickler"]
IIRC, the main signal path on the PM-1000 is discrete tranistors and their discrete opamps.

If anything needs fixing on the PM desks, it's probably the headphone amp. It seems pretty bad, and in mine the opamp is a bizarre mutant critter. That might be a canidate for dropping in a new board with a modern circuit.
tf[/quote]

The PM1000 doesn't use any of those discrete op amp modules at all. It uses a simple discrete amplifier circuit that's not modular, and this one amplifier is repeated throughout the desk. There is one other, even simpler amplifier that's used in a few places too. The only op amps in the whole board are those horrible little cannisters in the headphone amp.

Although you can't easily swap out the input or output amplifiers like you can on the PM700 and other versions that had the 2520-compatible modules, you CAN master the gain stage that's used repeatedly, and once you decide how you'd like to mess with it, it's a simple matter of repeating your work across the channels and output modules. I haven't messed with any changes besides capacitor replacement, and adding a direct output on the end of the channel amplifier (right before the pan knob).

Nice to see you here Ulysses! I lost all of my info on how I was going to add direct outs to my PM1000 when TT was removed. Would you be so kind as to tell me how you did it again?? Did you use a couple 33K resistors or something before the pan??

The 3MB PDF of the schematic is here:

http://home.new.rr.com/lordjimbo/PM1000E_2.pdf

ulysses,

Thanks, that helps. I've seen your blurb on your website about the PM1000 you were messing with.

Can you give advice on the capacitor replacements? Especially the ones in the amplifier circuit? BTW, is it just simply time to replace caps after 30 years?

Oh, man, direct outs! I was just thinking about this on at least 3 channels...

Any info please!

Wilcofan, I replaced my caps with Panasonic FC caps, with the exception of the tantalum caps, which I replaced mainly with Panasonic tantalums. It made the board quieter, and sound nicer as well. If we get access to the archives at the old forum, there's some great threads on this topic over there...

I've been using my PM1000 lately, and it sound WONDERFUL. The preamps are killer.

[quote author="ulysses"]
The PM1000 doesn't use any of those discrete op amp modules at all.[/quote]

I guess that's the PM-700 and PM-2000 then, maybe the PM-430(?), too. Had know idea the PM-1000 didn't have them.

tf