Yamaha PM700 direct outs

[atavacron]

Before anyone disses this mixer, I'll say that it was free, and I liked the sound of the pres before I tucked it away in a closet two years ago and forgot about it. But now...hey...why not? I can solder. I can spend $12 on 12 jacks. As I recall, all channels worked pretty much fine.

Has anyone modded one of these guys to have direct outs? Screw the inserts; just I/O would be dandy.

Would the direct outs be balanced or unbalanced? -10 or +4?

Further down the rabbit hole, I'm looking for the main Left card for mine - left main and secondary outs no worky.

I'd be entertained to hear about how you've used this mixer, too.

Thanks!

[floydisbest]

bump

[Tomer1]

Its not as simple as spliting the connection between a direct out and summing bus im afrid.
I suggest you look for advice
http://www.gearslutz.com/board/geekslutz-forum/
and in prodigy pro, I bet someone has already done this.

[floydisbest]

Thanks but I've already looked on all of gearslutz.com, including the geekstlutz area, to no avail.

Never heard of prodigy pro but will check out

[travisinhell]

hey, i'm in the same boat. i just picked one up for nearly free, figured i could try some mods or blow something up - at the very least i have some parts for possibly building some preamps. everything on it works so i figured why not, but....considering the amount of hiss that i'm hearing on mine, i'm not sure if it's worth the trouble of adding direct outs, even if it were only a matter of tapping in with jacks - from what i understand it's more involved than that. i also considered racking a couple of the preamps, but i'm not sure if the hiss is coming from the mic channels, or further down the line.

as far as finding that card...i saw some pm700 channels on fleabay not long ago. you might do a completed auction search there and hit the seller up about the main card.

any way, like i said, i more or less got this thing as a learning project, and i have a couple of bucks to throw at it in the name of learning something. i'm still at a pretty elementary level with all the electronics stuff, but i'm gaining some ground here and there. i think i also found a full service schematic for it.

[Radiorockstar]

I have one of these that I modded a couple years ago.
Although I dont claim to know much of anything about electronics, I did manage to replace all of the IC opamps on each channel with Burr Browns, and I replaced the two master bus opamps with John Hardy 990c (if I recall correctly.) It worked and sounded way cleaner and punchier. Whether or not I took all the proper electronic steps...i dont know...but I am interested in how to wire a direct out on each channel as well. I would also be interested in the possibility of wiring a bypass switch for the eq on each channel. I would be curious if anyone has any thoughts or suggestions.

[illacov]

I have a pair of these racked in my studio with a 5 Fish Power Supply.

I absolutely adore these preamps!

If making the cards into stand alone pres is the same as direct outs, then my tech should be able to help you.

I also have a schematic of the PM700 if anyone needs it.

Peace
Illumination

[travisinhell]

i have the service manual (including schematic) of the pm700 if anyone wants it. i wired up a direct out (unbalanced) on one of the channels for testing (with the advice of a member here), but it's been a while now, and the details are fuzzy. if i remember correctly, i soldered it at the pan pot. fwiw, i liked the sound over the other cheap preamps that i had on hand to compare it to, although it doesn't have a lot of gain - should be fine for recording any source that's at least moderately loud. according to what i've read, these preamps are crap, so i guess that makes the modern entry level preamps diarrhea.

radiorockstar, if you can share any details of your mods, that would be awesome.

[Radiorockstar]

It would be great to get whatever manuals you have. I think I have the basic product manual and the basic schematic, but maybe I don't have the full service manual? Thanks

[Radiorockstar]

I will take some photos and upload the opamps I used asap.

[Radiorockstar]

I replaced the orignal TA7136P inline style IC opamps with the Burr Brown(Texas Instruments now I think) OPA604AP IC opamps which are not an inline package. The TA7136P have 7 legs, and the Burr Brown have 8 (1 is not used) There are 3 of these on each preamp card (see schematic) 1 is the preamp, 1 the MON 1 Echo send, and 1 the MON 2 Send (if I recall correctly) I had to wire jumpers with shrink on each Burr Brown in order to fit these to the inline circuit board (like 504 solder points on the 12 channels by the time you solder both ends of the jumpers...)

I replaced the original Yamaha NE-80100 Program Bus Opamps with John Hardy 990c Opamps. The 990c's create an incredible amount of heat. (which Im not sure if this is normal or not) The 990c/NE-80100 are both the standard pinout like an API 2520, however the 990c is the only opamp I found that has a wide enough voltage range to work with the odd voltage on the PM700 (See schematics) I think a standard 2520 would fry itself, but not sure about that as well.

Although I dont use this board much, it has been, and still is a fun project for me. I took it out to use for sound on a live gig one night for grins and was blown away! I was able to compare it to an Allen & Heath Mix Wizard 16 channel that night.....The PM700 had a thunderous kick drum and snare, rich all around. Im sure the transformers coupled with my mods helped a ton. The Allen & Heath was pitiful in comparison to the fullness of the PM700 especially in the Sub. Funny thing is I have about $400 less invested in the PM700....oh yah and a lot of hours soldering.

[travisinhell]

thanks for sharing, radiorockstar. did you upgrade the preamp or bus opamps first? i'm wondering if you did any before/after listening and what your impressions were.

i took a look at my pm700, and this is how i wired the unbalanced direct out (solder points marked in red). also, check your pm's.

http://stashbox.org/930886/pm700_direct_out.png

oh and btw, using the direct out is less noisy than going through the bus.

[Radiorockstar]

Thanks for the service manual Travis, thats the one i did not have.

Before I modded, I did do some listening comparisons. I also recorded some program audio through the console for comparison as well. However I probably dont have proper comparison samples due to the fact when I first got the unit I only had an m-audio interface to use for conversion, which I no longer have and also do not have modded samples of audio through the m-audio device. I will look through my old sessions and see what I can find however.

I hope to post some comparisons with the current mods through my lavry converters with some control audio for comparison in the next couple weeks.

From what I recall....the biggest difference was the burr brown mods, however the John Hardys made a large difference as well.

With the original opamps and no mods the PM700 sounded muddy, cloudy, and not very punchy. It sounded like a live console from the 70's. The high end was somewhat lost. The low end was a giant pile of mud...you get my point.

The Burr Brown mods changed this drastically. They tightened the low end, with mid warmth, and I had a nice high end as well. They gave the console punch.

The John Hardy mods added an extended tightness, punch, and clarity(esp in high end, though it is not hyped high end) and almost opened up the console even more. With the BB mods and the Yamaha opamps still on the master bus, the sound still had a "rounded off" feel to it. It was still a bit cloudy, and unclear. The Hardys changed all of that.

One question I have, and I still need to do further tests, but I think the next big difference and reason for mods may be in the power supply. I recall getting a slight hum/bump around 117Hz in the noise floor, which I think may be a doubling of 60cycle? I may consider removing the power supply to a separate box, and potentially modding it to be "cleaner." Any thoughts you guys have on this would be much appreciated.

[chameleoned]

I know this is an old thread- but Rockstar- if you're still listening...do I need to replace all the op-amps on the pre card? I saw you replaced all 24 of them...but I'm not using the sends for anything. Just the direct outs...so can I just replace the preamp TA7136P with the OPA604AP? It would mean only 8 replacements!

thanks,
Ed

[BrandonOleksik]

hey illacov, could you send me that schematic by chance man? that would be awesome.

[Radiorockstar]

Originally Posted by chameleoned

I know this is an old thread- but Rockstar- if you're still listening...do I need to replace all the op-amps on the pre card? I saw you replaced all 24 of them...but I'm not using the sends for anything. Just the direct outs...so can I just replace the preamp TA7136P with the OPA604AP? It would mean only 8 replacements!

thanks,
Ed

You most likely could only replace those opamps. There may be some additional ones on the master channels as well, but not having it in front of me I don't remember.

[chameleoned]

@Rockstar- ok, thanks very much. So, I'm ordering up some of the opa604ap but it looks like the pinouts don't correspond between the opamps either...on the Ta7136P - pin 1="Freq. comp" and pin 5= "voltage comp". While the replacement lists pin 1 and pin 5="offset trim". Are these essentially the same thing? I'm confused by the terms!

thanks!

[Radiorockstar]

Here is a link to the Burr Brown OPA604 Manual
www.uib.es/depart/dfs/GTE/staff/jfont/InstrETT/OPA604.pdf

Keep in mind that the TA7136P is in single in line package and the new parts come in DIP or even surface mount. So you will need to build a little pin-to-pin mapping or conversion.

Below is the conversion I used....but then again I don't claim to be an expert at this stuff, so you could ask a professional who may have a different opinion and may know more.

Also a couple of the opamps I ordered were either defective or were overheated by me in the process of doing all this, so I would suggest ordering a couple of extra.

TA7136P pins:
1. frequency comp
2. non-inverting input (+ input)
3. inverting input (- input)
4. V-
5. voltage comp
6. outout
7. V+

OPA604 TA7136P
1. Offset Trim 1. frequency comp
2. - In 3. inverting input (- input)
3. +In 2. non-inverting input (+ input)
4. -Vs 4. V-
5. Offset Trim 5. voltage comp
6. Output 6. outout
7. +Vs 7. V+
8. No Internal Connection

[chameleoned]

Beautiful! That is exactly what I was looking for. I'll plan on upgrading 4 channels- I bought 8 chips. That should get me through.

ON a side note, I love these preamps. I've added phantom power to 2 of the channels and upgraded the caps on all the input cards and made direct outs where the ribbon connects to the card. The recap made the channels sound much better and I really think they sound really good on drums. My only complaint I've found is the noise level I find at high gain when using condensers...I'm hoping the opamp upgrade will solve some of that. If not, then I'll still have a slightly different flavor in the arsenal.

Next step is pulling these out of the mixer and a proper rack job...

thanks!!

[Radiorockstar]

Let me know your results. I think the opamp will have a large impact on your noise floor in addition to punch and clarity, good luck and please post results as you finish the work.

[MikeC1980]

I found some Schematics in my schematics folder, I hope these are useful to someone:

[kstackm]

Originally Posted by Radiorockstar

Here is a link to the Burr Brown OPA604 Manual
www.uib.es/depart/dfs/GTE/staff/jfont/InstrETT/OPA604.pdf

Keep in mind that the TA7136P is in single in line package and the new parts come in DIP or even surface mount. So you will need to build a little pin-to-pin mapping or conversion.

Below is the conversion I used....but then again I don't claim to be an expert at this stuff, so you could ask a professional who may have a different opinion and may know more.

Also a couple of the opamps I ordered were either defective or were overheated by me in the process of doing all this, so I would suggest ordering a couple of extra.

TA7136P pins:
1. frequency comp
2. non-inverting input (+ input)
3. inverting input (- input)
4. V-
5. voltage comp
6. outout
7. V+

OPA604 TA7136P
1. Offset Trim 1. frequency comp
2. - In 3. inverting input (- input)
3. +In 2. non-inverting input (+ input)
4. -Vs 4. V-
5. Offset Trim 5. voltage comp
6. Output 6. outout
7. +Vs 7. V+
8. No Internal Connection

Thanks for that info Radiorockstar. I'm just chiming in, but that PM Amp info is golden. I don't have a PM 170 but I do have the PM 180 and I think I'm going to get under the hood soon. Curios to see what moving out that power supply does for the overall sound for sure.

- KS

[chameleoned]

So just a followup to the op-amp conversion project suggested by Rockstar. This turned into a rather involved (and worthwhile) project. Ultimately I chose 4 strips out of a pm430 and removed them to rack up into a single unit. However, to start with- I'd like to offer my opinion on the opa604 mods. First off, as suggested by rockstar, it's easy to fry the components so you need to work slowly and carefully. My workaround was to purchase some inexpensive IC socket holders from Radio Shack. This way I never had to apply any heat to the delicate op-amps. Worked a charm and cost about 2$ in parts. The sound: There is a noticeable improvement. The sound is "tighter" and slightly more defined. It's not night and day, but it is an audible improvement. However, I am taping directly off of the channel strips, so I bypass the output transformers later in the path anyways- so I can't comment on the other op-amps he upgraded. I will say that, the biggest aid to the sound of these channels was tapping into them upstream of the "master output" section. It seemed like a lot of the murk in this mixer was in that section.

Ok, so my final setup and modifications are as follows. I had 4 channels rackmounted. Channels #1 and #2 contain the op-amp upgrade, a phantom power supply, and a recap. Channels #3 and #4 have only a re-cap. On those channels, I chose to leave the opamps stock- only because I kinda like the loose flop on these for certain vintage drum sounds. Next, I made some more important mods by swapping out the 3 stage gain adjustment switches with a fully sweepable 2k linear taper dual gang pot for better control. Also, I swapped the volume faders with 500k audio taper pots that I had on hand. It compacts things a bit and leads to a slightly better gain control.

BTW: I come in with a balanced xlr and exit out 1/4" unbablanced jacks. It's an unbalanced signal I am taking off of the channel strips. (taped off the ribbon cable)

Soundwise, I love these for drums. They have a very 70's feel to them. They are definietely character preamps. Dark, thick and wooly. They are not Neve or API BUT...they are an interesting piece, I do alot of electronic music recording, so these sound GREAT on a drum machine.

If you can find one of these cheap, you may enjoy the project. Ultimately, it probably cost me 400-500 in parts? Maybe less, it's been going on for a couple years now, so I don't remember. If you do it my way, you'll end up with a ton of extra parts for other projects down the road.

Psssttt....the (uneeded) output trans are really nice for a transformer mojo box. Those tamuras have gotten a lot of use in my mojo box- way more then some of the "better" and much more expensive transformers in there. I'm jus' sayin.

Ed

[Radiorockstar]

Originally Posted by chameleoned

I will say that, the biggest aid to the sound of these channels was tapping into them upstream of the "master output" section. It seemed like a lot of the murk in this mixer was in that section

I would definitely agree....the stock NE-80100 amps in the master section that i replaced were definitely "murky"

Sounds like you went above and beyond! Lots of great ideas as well. Would love to check out some pics if you've got em?

[glencho]

Originally Posted by chameleoned

So just a followup to the op-amp conversion project suggested by Rockstar. This turned into a rather involved (and worthwhile) project. Ultimately I chose 4 strips out of a pm430 and removed them to rack up into a single unit. However, to start with- I'd like to offer my opinion on the opa604 mods. First off, as suggested by rockstar, it's easy to fry the components so you need to work slowly and carefully. My workaround was to purchase some inexpensive IC socket holders from Radio Shack. This way I never had to apply any heat to the delicate op-amps. Worked a charm and cost about 2$ in parts. The sound: There is a noticeable improvement. The sound is "tighter" and slightly more defined. It's not night and day, but it is an audible improvement. However, I am taping directly off of the channel strips, so I bypass the output transformers later in the path anyways- so I can't comment on the other op-amps he upgraded. I will say that, the biggest aid to the sound of these channels was tapping into them upstream of the "master output" section. It seemed like a lot of the murk in this mixer was in that section.

Ok, so my final setup and modifications are as follows. I had 4 channels rackmounted. Channels #1 and #2 contain the op-amp upgrade, a phantom power supply, and a recap. Channels #3 and #4 have only a re-cap. On those channels, I chose to leave the opamps stock- only because I kinda like the loose flop on these for certain vintage drum sounds. Next, I made some more important mods by swapping out the 3 stage gain adjustment switches with a fully sweepable 2k linear taper dual gang pot for better control. Also, I swapped the volume faders with 500k audio taper pots that I had on hand. It compacts things a bit and leads to a slightly better gain control.

BTW: I come in with a balanced xlr and exit out 1/4" unbablanced jacks. It's an unbalanced signal I am taking off of the channel strips. (taped off the ribbon cable)

Soundwise, I love these for drums. They have a very 70's feel to them. They are definietely character preamps. Dark, thick and wooly. They are not Neve or API BUT...they are an interesting piece, I do alot of electronic music recording, so these sound GREAT on a drum machine.

If you can find one of these cheap, you may enjoy the project. Ultimately, it probably cost me 400-500 in parts? Maybe less, it's been going on for a couple years now, so I don't remember. If you do it my way, you'll end up with a ton of extra parts for other projects down the road.

Psssttt....the (uneeded) output trans are really nice for a transformer mojo box. Those tamuras have gotten a lot of use in my mojo box- way more then some of the "better" and much more expensive transformers in there. I'm jus' sayin.

Ed

Hi There Chamaleoned..Could please explain how did you ended up adding the direct outs...

Are they balanced? what is the ouput impedance?

Thanks

[GREENFENDR]

I've got a PM430 that I've wanting to toy around with, I'm glad I found this thread.

Does anyone have any audio samples? I'd love to hear some

[bibleboy3]

Originally Posted by chameleoned

So just a followup to the op-amp conversion project suggested by Rockstar. This turned into a rather involved (and worthwhile) project. Ultimately I chose 4 strips out of a pm430 and removed them to rack up into a single unit. However, to start with- I'd like to offer my opinion on the opa604 mods. First off, as suggested by rockstar, it's easy to fry the components so you need to work slowly and carefully. My workaround was to purchase some inexpensive IC socket holders from Radio Shack. This way I never had to apply any heat to the delicate op-amps. Worked a charm and cost about 2$ in parts. The sound: There is a noticeable improvement. The sound is "tighter" and slightly more defined. It's not night and day, but it is an audible improvement. However, I am taping directly off of the channel strips, so I bypass the output transformers later in the path anyways- so I can't comment on the other op-amps he upgraded. I will say that, the biggest aid to the sound of these channels was tapping into them upstream of the "master output" section. It seemed like a lot of the murk in this mixer was in that section.

Ok, so my final setup and modifications are as follows. I had 4 channels rackmounted. Channels #1 and #2 contain the op-amp upgrade, a phantom power supply, and a recap. Channels #3 and #4 have only a re-cap. On those channels, I chose to leave the opamps stock- only because I kinda like the loose flop on these for certain vintage drum sounds. Next, I made some more important mods by swapping out the 3 stage gain adjustment switches with a fully sweepable 2k linear taper dual gang pot for better control. Also, I swapped the volume faders with 500k audio taper pots that I had on hand. It compacts things a bit and leads to a slightly better gain control.

BTW: I come in with a balanced xlr and exit out 1/4" unbablanced jacks. It's an unbalanced signal I am taking off of the channel strips. (taped off the ribbon cable)

Soundwise, I love these for drums. They have a very 70's feel to them. They are definietely character preamps. Dark, thick and wooly. They are not Neve or API BUT...they are an interesting piece, I do alot of electronic music recording, so these sound GREAT on a drum machine.

If you can find one of these cheap, you may enjoy the project. Ultimately, it probably cost me 400-500 in parts? Maybe less, it's been going on for a couple years now, so I don't remember. If you do it my way, you'll end up with a ton of extra parts for other projects down the road.

Psssttt....the (uneeded) output trans are really nice for a transformer mojo box. Those tamuras have gotten a lot of use in my mojo box- way more then some of the "better" and much more expensive transformers in there. I'm jus' sayin.

Ed

what difference between a PM 100 and a PM 700 ??? are eq circuits the same??? transformers etc etc


Bill

[GREENFENDR]

Never Heard of a PM 100, do you mean PM1000? if so, then they're related, but not the same, the 430 and 700 uses an IC Op-amp on the input channels, the PM1000 has discrete op amps. I know that the PM1000 works on a higher voltage then the 430 and 700 as well.

I'm sure there are other differences, but those are the ones I've come across.

[spaceludwig]

Greetings, fellow enthusiasts, new poster here.

I was delighted to happen upon this thread. I undertook a PM700 project myself almost 10 years ago and stopped due to the lack of feedback (no pun intended) I was getting on another DIY pro-audio forum at the time, most likely due to the nature of the board I had chosen to work on. So I find myself pleasantly surprised to read that others have done so as well and that some have actually racked a few channels of this unit successfully.

What I did accomplish at the time was to change the input IC's by making some adapters as seen here (not too elegant, but functional)



and replacing the copper ribbon cable (those cables do not age well, a lot of problems with the console can be narrowed down to its deterioration ) connecting all the channels



Having read and heard much in the last years about summing boxes I have decided to pull the console out of the closet and use it to sum my mixes. The reason I'm writing about it here is to share my ideas/progress and to ask questions as I move along since I'm far from having any expertise on electronics.

My most immediate goals are:

1-Change the input opamps. Since I will be using the console as a summing mixer, which means inputs will be line level, I suspect 5534's will be fine since at unity gain the IC has no opportunity to impart its "character" on the sound. Why waste a good chip if it'll never be heard?

2-Swap the potted opamps at the output with current chips that have enjoyed some favorable reviews. I'd like to try the OPA604 & 627 since I have them on hand. Also, I've heard that at operating voltges of 18V and above the 604's sound very musical (whatever that means) and would like to hear this for myslef

Opinion and question: The Monitor 1 pots just under the orange pan knobs



seem like a total waste of real estate on this board in a summing context. I would like to pull them out and replace them with a switch allowing me to bypass the EQ entirely, i.e. on/off. Given the schematics in one of the posts above, where would I take the signal from and where would I insert back it into the circuit to bypass the EQ? Would taking from pin 6 of IC 1 be correct? Any help/advice would be appreciated.

Lastly, I would like to track these changes sonically. What I'm thinking is perhaps someone could make 8 tracks of a simple song available for download which I could mix and sum on my DAW then do the same on the yamaha as I make the changes (EQ bypass, swap output opamps, change input tranny, change output tranny, etc). This would allow everyone interested to have somewhat of an objective measure of how the mods are impacting the audio. The files should cover the frequency spectrum, i.e.: Kick, snare, overheads, vocals, guitar, bass, horn.

Anyhow, my apologies for the long post, I look forward to reading your comments.

Cheers

[audiopete]

Hi everyone. First thanks to the peeps here who contributed to this thread - it was a nice help to get started. Hopefully I can return the favour if someone needs it. Please feel free to contact me.

I have restored and modded one of these (1979) for a client and it turned out spectacular.

Mods include:

8 true balanced direct outs that go to a 8 channel Mogami snake of TRS 1/4" - these channels are no longer routed to the main buss
8 illuminated EQ bypass switches
8 phase reverse switches
Mic opamps upgaded to BurrBrown OPA134
Mon send opamps repurposed to allow a BurrBrown balanced output driver that feeds the snake for true balanced outs
Aux In 1 & 2 redesigned to be balanced stereo ins feeding the Monitor buss EQs making them a stereo stand alone EQ with balanced ins and outs
Completely recapped
All balanced wiring is Mogami console cable

The remaining 4 channels were recapped but I left the original 7136P opamps for some variety. These 4 also still go through the main buss.

BTW. those old Toshiba 7136Ps are the same opamps BOSS used in the original Japanese DS-1 Distortion pedals and BOSS has since moved on to another opamp and the circuit is different. These are great for building original DS1 clones. I can help you with that if you are interested....

There was a lot of engineering put into this project beyond what has been mentioned here in this thread. I recommend Brown Dog DIP to SIP adapter boards for the modern opamps, rather than soldering tails on and potentially frying your chip, but they still need to be reconfigured to make the differing pinouts work. Cimarron Technology, Inc. It's not that hard to do if you are experienced with the soldering iron and Dremel.

I will probably be replacing the 80100 buss opamps in the standalone EQ (the former Mon 1 & 2 opamps) with John Hardy 990Cs at my client's request.

Oh yeah, this board was missing 3 black plastic cue caps and I was able to score the last 7 NOS caps Yamaha had in stock, and these might be the last ones in the world.

You can see the whole project here at my facebook diary (no facebook account required) Vintage Restorations & Upgrades - 1979 Yamaha PM700 | Facebook

Cheers and thanks again to everyone who contributed. These are cool old boards but they aren't cheap or easy to upgrade like this, that's for sure.