T*R*E*E AUDIO 500 Op Amp

[boji]

http://www.treeaudio500.com/diagram1.html

Block diagrams makes use of a "SPA690" throughout. Is this a black box low gain discrete or something anyone is famalliar with?

Might anyone know where they are getting their inspiration? OPA690?
 

 

[boji]

http://www.inwardconnections.com/products.htm
Inward Connection's Op-Amp was designed by John Hall, that's all I've been able to find out.

 

[analogical]

[email protected]:

The SPA690 is an all discrete amp block designed by legendary audio designer John Hall. These are proprietary and Inward does not sell these. We also use cinemag transformers.

-Ian Gardiner
Boutique Audio

Anyone want to take a guess at the mystery amp? I mean what can this thing do that 990 can't?

 

[QUEEF BAG]

part 1
I think it is an upgraded replacement for the twenty five twenty.
the way i heard it (that was a qualification there, this is third hand),
John was hired to improve the sound of a Legacy that was not quite
transparent and open as the owner wanted, as his previous console
excelled in that quality.
His solution was to replace twenty five twenties with something better and
cleaner, so he designed a replacement op amp that installed in their place(s).
I am assuming this is also that device.
Just a guess from third hand info, so a big grain of salt may be in order.

part 2
from the stupid question and slightly off topic department:

So i was lookin' at an old REP magazine from the early 80's the other day...
and i see an ad for the hardy 990 op amps, and one line in the ad says
you can stick 'em in place of a 2520, no prob.
I believe if one were to ask him about that now, he would say he doesn't make
those anymore.
Did anything change? I didn't think so...I thought they have been the same
the whole time. Other than a couple small tweaks.
Can you just drop in a 990 in place of a 2520?
seems to simple.
sorry if this is a dumb question, but is looks like a good thread to ask in,
and i know many lurkers will be interested in the info.

 

[John Hardy]

So i was lookin' at an old REP magazine from the early 80's the other day...
and i see an ad for the hardy 990 op amps, and one line in the ad says
you can stick 'em in place of a 2520, no prob.
I believe if one were to ask him about that now, he would say he doesn't make
those anymore.
Did anything change? I didn't think so...I thought they have been the same
the whole time. Other than a couple small tweaks.
Can you just drop in a 990 in place of a 2520?
seems to simple.

I still make the 990, but not the clear epoxy package anymore. The current version of the 990 is the 990C. You can see the data package for the 990 here:

http://www.johnhardyco.com/pdf/990-2007.pdf

Generally the 990C can be used as a direct replacement for a 2520. However, whenever one type of op-amp is replaced with another, it is always important to look at the surrounding circuitry for that op-amp to see if there are any issues that need to be addressed. For example, the 990 is optimized for low source impedances, so it is better to use a low-ratio input transformer rather than a high-ratio input transformer in a mic preamp that is based on the 990.

Thank you.

John Hardy

 

[Tubemooley]

As already mentioned, the SPA-690 is Inward's discrete opamp. I believe it is the same footprint as 2520 and 990. John Hall designed it (also already mentioned). Like John Hardie said, it is pretty much a drop-in replacement for any 2520. Inward does not sell these (again, already mentioned). They used to sell a few of them but not anymore. I just e-mailed with Inward in early January of this year. I have tried to trace John Hall's career. I believe he worked for Quad Eight for a while (not certain on that). But he also worked for Sphere (more certain on that). One of the Sphere line amp circuits is the SPA-50. It's a fairly small circuit board, maybe 3" x 3" with gold edge card fingers. So it plugged into an edge card connector. There are maybe 5 transistors on an SPA-50. There is a schematic floating around on the internet. I have it saved somewhere. I can dig it out and post it. Go to the Orphan Audio website and take a look - http://cms.orphanaudio.com/index.php?id=89,0,0,1,0,0      See those two incandescent light bulbs on the card? Those are "fuses". If the card draws too much current, the bulbs will blow out and hopefully save the card from fatal damage. The Sphere gear is truly sick from what I have heard. There are probably less than 100 Sphere consoles left in the world. That's my guess. I could be wrong. They weren't in business for that long. So here is what I have hypothesized.... The SPA-50 (and possibly other circuits) evolved into the SPA-690. All these guys worked together out in LA in the 70's and into the 80's. Deane Jensen, John Hall, Ed Reichenbach and several other guys. They didn't all work together at one place at one time. But they knew each other. And yes, at various times they were competing against each other for business. But they still all knew each other. Anyways, I believe the SPA-690 was one of John's last designs. He's an old man now and he lives in Tennessee. He is not in the best of health. I have tried to contact him but got no response. The guys out in Cali (Ken Hirsch at Orphan, Ian and Steve at Inward) know how John is doing and try to help him out. Inward is licensed to use the SPA-690 and no one else is. It's their product and their design (now). Inward used to do various mod jobs and upgrades for people as contract work. They aren't doing that anymore because they are making and selling their own products. There are a number of mixers which show up on the **** periodically which have had the master section reworked by Steve using SPA-690's and Cinemag iron. I've seen this on a Toft ATB just recently. The Inward stuff looks really, really killer and I wish I had some money to try it. Their 500-series modules are relatively affordable but still not cheap. I bet they are sick. I would really like to hear the discrete VCA compressor against the opto compressor. And the Inward EQ's..... That's some sick **** from what I have read (mostly on the ****). Any questions? DANA.

 

[Tubemooley]

I should have mentioned this.... The SPA-690's are supposed to sound really, really good. Very clean and transparent but very even across the audio bandwidth. Clean highs and full bottom. No mid-range bump as with some of the 2520's. This is the magic of the SPA-690. Again, we may never know how they do this. It's the circuit and the transistors in there. It doesn't matter how they do it. They sound really, really good. I have read this many, many times from the guys that have them. That's why I want to hear these things. I was out in LA in August 2009 and I made arrangements to see the 12-channel Tree mixer which vintage king has (or had) on demo. I saw the mixer. It's like part of the cockpit from an F-22 Raptor fighter. The sides are friggin' thick alumimum which has been hand-polished. It weighs 300 pounds. It wasn't plugged in and running when I saw it unfortunately. It was in the garage of the vintage king duder out there (Jeff something........). Should I stop now? DW.

 

[Tubemooley]

I have issues..... The Inward DEQ-1 equalizer has 18 to 20 SPA-690's in it. It's a 3U rack box. It's not being made anymore. There are probably 50 of them out there. Pete Min out in LA was just selling his on the ****. The Inward Mix690 has 20 SPA-690's in it. It's a 2U rack box. It's still being made. Sonic Circus just had a just one on the bay for like 3500. I think they sold it. You can still buy these new for like 4500 I think. Who wants to help pay for my prescriptions? DW.

 

[boji]

Hugs not drugs man.  Thanks so much for the history lesson! seriously!

 

[PRR]

> I believe it is the same footprint as 2520 and 990

Bit-o-history: after tube op-amps came Burr-Brown's discrete transistor opamps. B-B defined the module and footprint that many-many people used. B-B usually kept the five/six basic pins (V+, V-, In+, In-, Out, and often Ground) in the same place, but there are exceptions (hardwired followers), and the "other" pins could be most anything the module needed.

> Generally ... a direct replacement

Recall the whole point of opamp design. Instead of making many different amps (hi-gain, buffer, mixer, differencer, integrator/hi-cut), you make one too-super-good amp and add a few passive parts to define what it should do in a specific socket. So at some level "all opamps work the same".

But there's no "Universal Opamp". Tubes need +/-300V and flow 1mA, transistors are far easier at +/15V and can flow 10mA. The early B-B opamps eventually settled to good precision, but schmeared fast signals and made hiss current. Audio-heads demanded good speed with high Pro levels which imply +/-24V and 40mA. The resulting 48V max is a bit past the customary 40V rating of many transistors, so that's a Cost. Someone adds up the cost over 3 yards of desk, and decides to build mostly +/-15Vmax opamps with a few heroic ones at key external interfaces. While you can build a circuit to eat 10V to 60V without change, if you are "told" it will only be used at one specific voltage you may be able to save a buck, which adds up on a big desk. Likewise a resistor long-tail is clean and cheap, works fine for hi-gain amps, summers, and Baxandalls, but won't be happy in a low-gain follower. Also that resistor is sized to the supply: some came with a chart for 12V 15V 18V and 24V use.

And of course a basic audio issue: noise impedance. A transistor can give very low noise, but only over maybe 10:1 of impedances. Low noise around 5K is easy with very early Silicon devices; why the 2N5086 blurb says "low noise". Low noise near 500 would be a better zone for a lot of audio but had to wait for another generation of devices.

The nice thing about the 990 and family is that, in low-Z networks, it is nearly "universal". It eats many different supplies, has gobs of drive, has to have muscle because its noise impedance is low, and the sonics are very excellent, miles ahead of some cruder old modules or most ICs (which didn't have muscle either). If you have 1:2 mike-iron or a lot of 10K mix-resistors, it's real happy. If you have 1:10 iron or a few 100K mix resistors, other op-amps may be a better choice.

And the thing about audio is that if you define THE important-to-you parameters, you can sometimes whomp-up a specific device which nudges-out any "universal" device.

It Depends.

 

[emrr]

More History:

John Hall worked for Langevin, and headed the design on the tube 5116-B and SS AM-16.  He moved almost immediately (probably with Art Davis) to Altec, where he was responsible for the 9470A/9475A packages.  I've not heard of anything definitive before the Langevin employment, but it might stand to reason that he could have worked on projects at Cinema Engineering as well. 

 

[PRR]

.

 

[Tubemooley]

Beautiful. Excellent additional info PRR and EMRR. I didn't know that John worked at Langevin and Altec too. Ya' learn something every day. DW.

 

[djgout]

Yes the SPA-690 is John Halls design. John lives around nashville and is still very active. He did in fact work for Electrodyne and sphere and a few others. He's a great guy, almost 81 and still messing with gear. (i actually just bought an old scope from him). According to John the residual noise of the distortion analyzers he used to test the 690 was actually noisier than the amps.  He did design the Sphere SPA-60 and the amps used in the electrodyne 710/711 modules and alot of other things.  It's great to go visit with him, he'll talk your ear off in a great way.

He's also still designing transformers.  Inward is the only place making the 690s and you've gotta talk to them to get your hands on them.

-justin

 

[Samuel Groner]

According to John the residual noise of the distortion analyzers he used to test the 690 was actually noisier than the amps.

It would be a very bad sign if it weren't that way--even with todays distortion analysers, and even more so with what's been available back then...

Samuel

 

[boji]

I love you guys and this forum. /sniff