learn from recording consoles?

[zenmasterbrian]

I've always felt that we could learn much about high performance audio design from the design of recording studio consoles.

One of my audio heros, Douglas Self, has been involved in the design of such.

I am hoping that there will be people reading this who have experience with recording consoles.

Let me give some examples of the things that I believe could be
informative.

1. Grounding scheme. This is complex, and must be well done.

2. Power supplies and voltages. Such consoles have outboard power supplies? I like this. I have read that they can go up to as much as 2KW. Are they linear or SMPS? What frequency of SMPS?

What voltages? Just two, plus and minus? Another for digital? The 48v fantom voltate. I have often thought that there could be slight design performance advantages for having two pairs of plus and minus voltages. The lower one would be for outputs of op amp circuits. The higer pair could be for the inputs. I believe there could be distortion improvements for line level. I also believe that you could maximize noise performance for some low level circuits be eliminating active current sources on the inputs.

I have not fully checked any of these out. But how do these consoles do it?

3. Overall architecture. How do you get the functionality without too many opamp stages?

4. Discrete vs monolithic? Jensen makes a discrete opamp module which runs on +/- 24 volts. The design of monolithic opamps really is an art. They have all sorts of proprietery distortion correction circuitry.

5. Inverting mode. Of course using inverting mode is a way to get low distortion. But where you have a level control, it usually has to feed a non-inverting mode opamp. Look at how they architect these consoles.

6. JFET inputs. These can be lower noise for high impedance. Are they used? Are they used anywhere else, like for their distortion characteristics?

7. Diffpair mirroring, meaning use two, one NPN and one PNP, to get even order distortion?

8. Circuits without diffpair inputs? These could lower noise for
single ended source. It could work when you don't have to have response to DC, and so you could have an op-amp with low freq gain in the feedback path, to give you your good DC offset, feeding back into a common emitter.

9. Moving magnet and moving coil phono inputs.

10. All the types of tone controls and dynamics management, and microphone preamp limiting.

11. Then all the new ADC issues too.

12. Thermal, heat sinks, LM394, biased how high? How much low z drive on outputs?

Anyone have knowledge of such consoles? Any good links?

cross posted at Audio Explortions, 10 groups. Come join in
http://groups.google.com/group/audio...p_source?hl=en
http://groups.google.com/group/audio...on_links?hl=en

[zenmasterbrian]

PS,

If anyone wants to talk about the compatibility of SMPS with linear audio, or about the option of JFETs instead of BJT, this is a great place.

[myhrrhleine]

All good of you're designing a new console.
If your audio application is different, so will your design criteria be different.

[zenmasterbrian]

<<
If your audio application is different, so will your design criteria be different.
>>


Yes


Mostly what I want to look at are how to get the lowest noise, how to get the lowest distortion, and the best architecture for utility.

I also want to look at power supply issues.

[Nrik]

Originally posted by zenmasterbrian

Mostly what I want to look at are how to get the lowest noise, how to get the lowest distortion...

Without knowing anything about mixers etc. I think big headroom and large voltage signals is important here.

[zenmasterbrian]

The lowest distortions are obtained from OPamp like circuits. So it works out that it is mainly the distortion of the input diff pair.

But this is determined by many things, including loading and gain of the second stage.


The noise of such circuits is also very low, but there may be ways to go a bit lower.


Modern opamps have very very good specs, but not necessarily the best possible.

Still I wonder if some people are going discrete, thinking they are doing better, maybe based on simulations, but not really being better.


There are quite a number of circuit issues to consider.

I'm hoping there are some who have experience with analog recording consoles, maybe even schematics.

[myhrrhleine]

There is also the consideration that what can be done with chips won't necessarily apply to discretes, or designs at different voltage/current levels.

[pinkmouse]

Out of, I would guess, two dozen consoles I've had open, only one had anything other than opamps all the way down the line, and that had Jfets on the input only, and 741s everywhere else.

[zenmasterbrian]

<<
There is also the consideration that what can be done with chips won't necessarily apply to discretes, or designs at different voltage/current levels.
>>

Totally true. But it also cuts the other way. When is it best to use chips vs discretes, and at what voltage/current levels.

When you are willing to go to great expense, and to disipate lots of power, what will give you the lowest noise and lowest distortion.

I'm hoping someone might have links to web sites, or even manuals or schematics.

I have read of high performance recording consoles taking 2kVA for 32 channels.

Douglas Self has been involved in recording console design, and has engaged in this quest to get the best SNR and lowest distortion in the final product.


<<
Out of, I would guess, two dozen consoles I've had open, only one had anything other than opamps all the way down the line, and that had Jfets on the input only, and 741s everywhere else.
>>

I am surprised about the 741s.

I would wonder the date.

Jensen still offers discrete OP AMP modules which they say perform better than monolithics. I don't know if they still beat the newest monolithics.

Underlying my interest in this thread is, when can discretes still beat monolithics. It can't just be simulation results either.

JFETS? Do you mean monolithic opamps, or discretes? On what inputs? Usually it would only be for high impedance that you would bet better noise. Like High Z microphones, moving magnet phono, or elect. guitars.

Where these JFETs diff pairs, or single ended.


Using JFETs at line level for square law distortion is a controversial idea that many writters, like Doug Self, dismiss.

[myhrrhleine]

Originally posted by zenmasterbrian
Jensen still offers discrete OP AMP modules which they say perform better than monolithics. I don't know if they still beat the newest monolithics.

Same old op-amps from about 20 years ago?

You could rebias their output for class A if you like them.

Using JFETs at line level for square law distortion is a controversial idea that many writters, like Doug Self, dismiss.

There are other reasons to use JFETs than square law distortion.