Re: Uli Behringer of The Music Group Q&A
The current ADA8000 does not use the type of circuit you mention. That's the problem.
While that opamp is a bit beefier, you still can drive its output into current limiting with only a 100 ohm resistor. I would suggest raise this value to 470 ohms. That would give you a theoretical 32ma max current draw on a full rail swing.
That should fix it.
Please advise on how I can contact you personally (via a PM)
Bob
Dear Bob,
thank you too for your comment.
Output stages.
I would have to check what circuitry has been applied for in the ADA8000. In general we use servo-balanced output stages which provide for a 6 dB gain adjustment if pin 2 or 3 are tied to ground. It is possible that the ADA8000 uses a simple inverter for the balanced output stage due to the fact that the unit does not have (shorting) TRS outputs.
The current ADA8000 does not use the type of circuit you mention. That's the problem.
However in contrast to the TL072, the 4580 which we're now using in the new ADA8200 can drive loads up to 50 mA which should resolve any issues you might have encountered.
All our designs feature current-limiting output resistors of around 100 Ohms.
While that opamp is a bit beefier, you still can drive its output into current limiting with only a 100 ohm resistor. I would suggest raise this value to 470 ohms. That would give you a theoretical 32ma max current draw on a full rail swing.
Gain VR linearity.
This (common) problem has been resolved with a Midas-designed preamp which uses a stereo VR with laser-trimmed carbon tracks.
That should fix it.
Clocking issue.
I am not familiar with any clocking problem but I am happy to feed this information back to our R&D department in Germany. Perhaps you could drop me an personal note here so we can better understand how to replicate this issue.
Thank you for your valuable input!
Please advise on how I can contact you personally (via a PM)
Bob