Troubleshooting and Fixing a Quantum Board

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Troubleshooting and Fixing a Quantum Board

Post by littlesongs » Sat Mar 24, 2007 2:48 pm

I just acquired a Quantum QM-8P from a fellow Tape Op'er -- thanks Kelly!

Like most new owners of old gear, I have been searching high and low for information on Quantum consoles, anecdotes, schematics, history, and of course, other owners. I started this thread in the hope that I can find out more about these beasties, and I promise that pictures of my mixer will follow in upcoming posts.

As a kind of introduction, and hopefully, to make this thread helpful to others, here are some of the more relevant bits of what I have found so far in my sojourns. Some of these links have unanswered questions that experienced folks might be able to answer, so perhaps this will verge on a META before long. Starting with Tape Op, of course, here goes:

"Quantum QM-168 Console Repairs"
http://swan.he.net/~tapeop/viewtopic.php?t=28475

"Vintage Quantum 20 Channel Console RARE (updated w/Pics)"
http://swan.he.net/~tapeop/viewtopic.php?t=40661

"Early R.E.M. drum sound?"
http://swan.he.net/~tapeop/viewtopic.php?t=40550

"Quantum Audio Labs"
http://swan.he.net/~tapeop/viewtopic.php?t=35920

"75101A input transformer"
http://www.prodigy-pro.com/forum/viewtopic.php?t=6236

"Quantum Audio QM 22/20 Questions"
http://www.prodigy-pro.com/forum/viewtopic.php?t=17991

"Quantum Audio Labs?"
http://www.prodigy-pro.com/forum/viewtopic.php?t=3593

"Quantum Broadcast Board"
http://www.prodigy-pro.com/forum/viewtopic.php?t=2398

"Quantum Audio Labs?"
http://recforums.prosoundweb.com/index.php/m/9448/0

"Quantum QM-22/20 power supply et al"
http://recforums.prosoundweb.com/index.php/m/184718/0

"Quantum Audio Labs QM3000 channel strips?"
http://recforums.prosoundweb.com/index.php/m/117621/0

"QUANTUM GAMMA console"
http://recforums.prosoundweb.com/index.php/m/4732/0/

"Quantum Audio Labs"
http://recforums.prosoundweb.com/index.php/m/36408/0

"Quantum Audio Labs - history, info, experiences?"
http://gearslutz.com/board/showthread.php?p=540841

"Quantum Audio Labs"
http://www.gearslutz.com/board/showthread.php?t=76268

"quantum audio labs series 22"
http://www.gearslutz.com/board/showthre ... ht=quantum

"good tech in denver, colorado area?"
http://www.gearslutz.com/board/showthread.php?t=110331

Tiny Telephone featured in Mix Magazine -- before the Neve
http://www.tinytelephone.com/html/mixmag.html

Seismic Seance has a Quantum
http://www.iamspoonbender.com/seismic/index.html

AES obituary for John Pritchett
http://www.aes.org/aeshc/docs/jaes.obit ... _PG573.pdf

Early Quantum QM-8 for sale
http://www.soundbroker.com/CONSOLE/?listingid=15728

I would love to hear from anyone else with a Quantum or experiences using or repairing these consoles.
Last edited by littlesongs on Thu Mar 29, 2007 1:18 pm, edited 1 time in total.
"Keep singing, keep writing, keep playing, keep recording. Stay humble, follow your heart, and it'll all lead to a good place."
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jacobehrmann
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Post by jacobehrmann » Tue Mar 27, 2007 8:13 am

I think quantum is fantastic. i got a qm-168 that has recently gone through a recapping and ic work. i never heard the board before the changes. the board sounds cool. what i love the most- the eq section. simple, nice choices- that make me look good. its just a pleasure to eq.

after that- i got a qm-8a that has not been through a clean up. the eq choices are more limited, but still sound fantastic. the really, really big deal, however, is the mic pre. i just love it. really could not be happier.

i would love to lean what records have been made on quantum boards. ive see here and there that some James Brown was recorded on Quantum- but no reference to what records. Also, Ive read that the Dead Kennedys were recorded on quantum.

really- i just think quantum is the shit, and like you, I would love to know more.

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Post by littlesongs » Thu Mar 29, 2007 12:33 pm

Thanks a bunch for the reply. According to Mitch Easter, "The really old stuff was done on a Quantum console with limited EQ... 414s on BD and SN, probably EV CS-15P on toms, and SM7s overhead. Then, white noise derived from a radio was keyed to the snare to generate brightness! No room mic. these sessions were done in a tiny garage with hard walls." So, for the list, the first R.E.M. EP, "Chronic Town" was tracked at Drive-In on an early Quantum. The full thread is linked in my first post. I like that one of my all-time favorite releases, by one of my all-time favorite engineers/producers was cooked up on one of these consoles.

Jacob, since your board was recapped and rechipped, did they do any mods or swap op amps out? Or was it brought to original spec? I am very curious, since I have read and reread all the threads concerning care and feeding, but I still do not have a definitive answer. After a few weeks of research, pms and e-mail, here are a few conclusions:

No surprise, virtually everyone seems to agree that the electrolytics ought to be combed through and changed out, or at the very least, the ones that bias the preamps. Consensus also seems to dictate that the tantalums -- other than the ones that are dedicated to power -- can stay put if they are happy. The power supply for my board is pretty quiet and in good shape, but it was not set up for phantom power. If I read the advice correctly, eventually, I should replace it with +16V/-16V linear supply and figure out an LED solution for metering.

To this point, the opinions wildly differ when it comes to the op amps. Thankfully, everything is socketed, so there is room to experiment, but I do not have the budget or time to try every suggestion I have seen. I have to echo a few concerns, from Brian Roth and others, about substitutions that change the nature of the entire circuit. I would rather make it perform to the top parameters of the original design, rather than build a mixer from scratch.

From what I have gathered, many folks think that finding a cache of TL075s for the 4136s in the EQ should be a priority. Does anyone have a suggestion of where to find them? Since they have been out of production for a while, all the usual places, and a few unusual places, have not had them in stock.

There is also a school of thought that recommends an upgrade of LM301s, but only in the summing and output section. There was also a simple mod to make the output run in class A, with "a 2.21k resistor across pins 4 and 6 of the 3140." I like the idea of a little color on the front end, but better slew and gain after that, so these angles intrigue me. Who has tried these ideas? The debate was mixed about whether it sounds good as-is or ought to have further modifications.

The positives seemed pretty consistent. The preamps can sound very very good. The transformers they chose for these boards are fantastic. The equalizer -- especially the six band -- is better than merely useful and is close to the league of other top models. For a short ten years, it seems like QAL came close to the best of the recording studio boards and far surpassed virtually anything in broadcasting.

It is obviously the 21st century if we are waxing poetic about IC based boards, but hindsight being what it is, there were a few gems. According to a short and casual conversation with my tech guru -- a fellow who spent 25 years maintaining and modifying broadcast gear and now concentrates fully on recording studios -- our boards can get in the league of "that era of Trident and Neve" with a realistic amount of work. He said that they were designed and built very well, but engineered to embrace a few lesser bits that would bring the price point in line with the competition.

RTFM is very important, and schematics are mandatory, so here are some docs to keep this thread compliant. Here is the lowdown on the QM-168, from fellow TOMB member, Danielson:

http://bolstad.net/quantum/Quantum%20QM ... Manual.pdf
http://bolstad.net/quantum/QM-168%20sch ... 20card.jpg
http://bolstad.net/quantum/QM-168%20sch ... utputs.jpg
http://bolstad.net/quantum/QM-168%20sch ... busses.jpg
http://bolstad.net/quantum/QM-168%20sch ... 0input.jpg
http://bolstad.net/quantum/QM-168%20sch ... 20card.jpg
http://bolstad.net/quantum/QM-168%20sch ... 0panel.jpg
http://bolstad.net/quantum/QM-168%20sch ... supply.jpg

My deepest gratitude to Dan for the schematic! My board is a 4X4, but it is almost identical. So far, I have been pretty impressed. Even though it needs some work to get a bit more headroom, it is warm, and so far, even without too much attention to the innards, pretty clean. I am starting to understand why people have embraced these consoles. I also guess I ought to shut up before the prices get stupid. I would really love to find out what other folks have done with success to these boards, and if anyone disagrees, agrees or has more to add to what I have found, please holler. A big thanks to everyone who has weighed in on Quantum.
Last edited by littlesongs on Sat Dec 29, 2007 12:50 am, edited 2 times in total.
"Keep singing, keep writing, keep playing, keep recording. Stay humble, follow your heart, and it'll all lead to a good place."
-- F.M. Cornog

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Post by littlesongs » Wed Apr 04, 2007 1:23 am

Here is an excerpt from a 1998 Tape Op interview Todd Costanza did with John Vanderslice of Tiny Telephone. This conversation happened right after he acquired the Quantum that was discussed three years later in Mix.

"Todd: You're getting a new board...

John: Yeah. It's a Quantum Audio Arts board from 1976. It was hand built. It's a 31 x 8 board. It's actually a quadraphonic board. It was made for quadraphonic recordings. It came from Studio 55 in Los Angeles. A big mainstream studio. At the time it was a primo boutique board, it's discrete mic pre's, very good Neve style usable EQs, four band parametric, all the way up to 20,000 cycles. I mean, you gotta love that.

Todd: Who advised you on this board?

John: Well, I actually talked to a number of people about the board. The first thing I did after find out it was for sale was I got the number of the engineer that worked at Studio 55 on the board for 12 years. His name is Gabe Veltree. And he had no financial interest in talking to me about the board. He has no financial interest in whether the board is sold or not, so I knew he was a totally disinterested third party. So I just called him and said, "This board you used to work on is for sale through a third person and what do you think of the board? You worked on it for 12 years." He's a big name guy.

Todd: You just rang him up?

John: I just called him up. On a Sunday. That's pretty ballsy. Anyway, he was incredibly nice to me, and he vouched for the board. He said, "$7,000 is a steal, you should grab that thing. It's a great board. We did so many records on that thing." Twelve years he worked on that thing. He did the first Tom Petty record, he did Pointer Sisters, like "He's So Shy," "I'm So Excited," Barbara Streisand, a bunch of stuff.

Todd: There'll be ghosts in that board.

John: There are going to be ghosts in that board. Barbara's going to be fucking screaming in that board: "Get me my coffee!" So, that's the idea. What you want to do is call up like a 50 or 60-year-old engineer whose been working for forty years, you know, maybe he's mastered records at CBS, maybe he's worked at Ocean Way. Find out the pros and just say, "Hey, I'm a young guy and I need some advice." They will keep you on the phone longer than you want to stay on the phone, because they are just impressed that anyone cares anymore and that you respect them. So that's what I did."

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Post by littlesongs » Wed Apr 04, 2007 6:22 am

I got a nice e-mail back from Analog Devices and they had these substitutions:

LM301AN -- ADI equivalent OP07
CA3140E -- ADI equivalent AD711

While rooting around for additional information, I found these two threads as well, from the first of several helpful Quantum owners to contact me here on TOMB, fazeka. Thanks Chris! Though similarly titled, some conclusions and opinions differ between the two.

"709 IC substitute for older consoles?"
http://www.epanorama.net/phpBB2/viewtop ... 69879ef62d

"709 IC substitute for older consoles?"
http://www.audiobanter.com/showthread.php?t=82275

There is also a picture of his Quantum console and 3M deck here:
http://messageboard.tapeop.com/viewtopi ... c&&start=0

The chip questions still remain, but with other pressing needs, I may just recap first and see if I like it. Has anyone had exceptionally good luck with a particular type, brand or supplier of replacement capacitors?

I really appreciate all the help from the "Quantum Qult" -- both in the past by asking smart questions and sharing good answers, and in the present with your answers here and in my box.

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Post by fazeka » Wed Apr 04, 2007 6:53 pm

I have recapped the board and replaced the 4136s in the EQ with the impossible-to-find TL075 (I got lucky and found what I needed, 1981 NOS). Those links are copies/references of the original rec.audio.pro newsgroup thread started by me with none other than Paul Stamler contributing...

I'd be interested in anyone else who does the mod to run the 3140 in class A...
Last edited by fazeka on Thu May 31, 2012 2:56 am, edited 1 time in total.

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qunatum audio labs series 22

Post by garbagelarge » Fri Apr 06, 2007 11:52 am

hey - i have a quantum audio labs series 22 with 3 mic modules - i posted about it on gearslutz. i think i have decided to keep it and try to work on it myself. i am mostly interested in it for the preamps. i compared them to my mackie onyx board and they seemed to have no low end - but an interesting character. i replaced the large electrolytics in the power supply - i think this helped out the low end, but i haven't done too much testing. i would like to put direct outs on this board, and phantom power. im wondering what my first step should be - should i replace ALL the electrolytics in the modules and power supply. i dont know much about audio electronics yet - im really excited to learn. i am planning on getting the seventh circle kits to get me started. i hear a lot about opamps and changing/exchanging them. do the get old, like caps? or different ones just have different/better performance?

thanks gals and guys, ben

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Post by fazeka » Fri Apr 06, 2007 1:02 pm

I thought the series 22 was more of a radio production/broadcast console?

Caps get old and dry up. Opamps usually last longer - if it ain't broke don't fix it. Most times, people are changing out opamps to get better performance out of the board. However, you really should know what you are doing as many times, upgrading with more modern/faster chips means more strain on the power supply and stability issues. I think it's better to have a pro or a tech take care of any upgrades, especially chip upgrades, if you've never done them before or have little to know experience in electronics.

Where are the pictures of all these Quantums? 8)

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Post by garbagelarge » Fri Apr 06, 2007 1:29 pm

thanks fazeka - your propbably right about trying to change chips myself - im just really excited to learn about this stuff. this board was donated to our non-profit studio - so it would be a good one to learn on. should i just go ahead and change all the electrolytics? it is a broadcast console - it was donated by a radio station. - ben

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Post by fazeka » Fri Apr 06, 2007 3:42 pm

Well, Quantums are nice boards for the $ nowadays as they can be had rather cheaply... though that may change in the future as more peeps get hip to the Quantum jive.

Welcome!

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Post by littlesongs » Sat Apr 07, 2007 5:04 am

Image

As promised, here is a photograph of the board. This is what I saw when the two of us first met on Craigslist. Not exactly audio porn, but a mysterious allure nonetheless, and certainly seemed worth an e-mail. Since this picture was taken, through divine providence, most of the bits have been found. When we went to pick up the Scully a week ago, Alan handed me all the missing buttons and the two prodigal op amps in a ziploc bag. I love this tiny town. I am still looking for nine fader knobs and would like to match the original round ones. I will post more pictures soon. Really. 8)

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Post by littlesongs » Sat Dec 29, 2007 12:34 am

Thanks again to all the great folks who have made this thread a goldmine and helped me along the way. At long last, here is a batch of photographs of the QM-8P. This board was configured for broadcasting and production -- with triggers for carts, etc. It has many features not found in most radio consoles, so I believe it would been right at home in a production booth, or a film/video editing suite. These days, it would probably fit in well at a swanky LPFM or netcast station.

Image

Image

Image

Image

Image

Image

Image

Image

Image

Image

Image

After almost a year, I still lack the time, space and skills to fully restore and appreciate this board. In my world -- with three other small desks -- it has become a once in a while mic pre option with a Sasquatch sized footprint. This Quantum came to me from a great member of our TOMB and I would love to pass along that tradition. I am open to reasonable offers and imaginative trades. Please pm me if you have a hankering for this project.
"Keep singing, keep writing, keep playing, keep recording. Stay humble, follow your heart, and it'll all lead to a good place."
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Post by inverseroom » Sat Dec 29, 2007 7:52 am

I like those individually bypassable EQ bands.

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Post by littlesongs » Sun Dec 30, 2007 11:37 am

My understanding is that the eq is inductor based as well. It really is a unique board. I bet the folks who used it professionally liked it a great deal. I enjoyed many of the industry quirks including the built in mono amp. In the broadcast spirit, I hooked it up to a dinky little Quam monitor. Every fader can be pulled further into cue and it essentially functioned like a solo button.

My initial reasoning behind getting this board was to have something to pair with my Scully 4-track. It has four outputs, four line inputs, four mic inputs and an effects loop. It also has four more input channels -- for tape machines, carts, and turntables -- that could be used with other sources. Not a ton to work with, but not bad either. If this board were 100% happy -- or I was a better braver tech -- I might be writing something really glowing in this space. However, in the interest of getting musical things done, I found an old reliable Soundcraft 200 for most of the chores.

I dearly wish it were modular, and frankly, that was the dealbreaker on the project for me. Like a good number of folks here I suspect, I've soldered this and that, made cables, and done troubleshooting. However, this one seemed a bit daunting. Sure, the five caps you need to change are right there in plain sight. Unfortunately, the clearance is such that only magical elfin creatures could fit in there. It is more than just a little complex to get apart. I believe a fearless frugal Weller wieldin' solder suckin' multimeterin' messiah is what this project deserves.
"Keep singing, keep writing, keep playing, keep recording. Stay humble, follow your heart, and it'll all lead to a good place."
-- F.M. Cornog

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Post by inverseroom » Sun Jan 06, 2008 7:14 am

OK so...I bough this board from David, with the intention of turning it into an ULTRA PRIMO DRUM KIT MIXER. Yowza!

Got a question for you, David, and figured I should put it here. Those bus outs there in the back...I assume you could set things up so that they function more or less as direct outs for the first four channels...that is, by just selecting the outputs on the channels?

And you know what, after ten minutes of careful study, I think I can recap those channels without taking them out of the case. I don't quite think that's an insane assumption...there's about twice as much space between cards as in my Hill.

Watch this space, to watch me fall on my face. :D

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