Hi all-
First of all, I pecked that last emil out to quickly and didn't realize my gaff. You tie the audio to the power suppl not the gaff as some one noted. The the resistor value was about 3k?. Doing this largely depends on whta load the IC sees after it but yes, tie the audio output to one of the power supply rails depending on which transistor(s) you want to hear, NPN or PNP. We like the sound of NPN better for OPA 2604, 604, AD797, OPA 627. The 627 was a toss up really, we ab'd everything we did and with the NPN/PNP issue for the 627 it was tough to call.
Hi Gyraf.... yeah for all of these test that he have done, we have ab'd stereo pairs of modules in the board against the modded version so I have been fortunate enough to hear the change in real time. All of these tests were done with an ABX box in case some of the changes were subtle enough that we wanted to pick blindly. Almost none of them were that subtle.... like being able to pick after one flip from unmodded to modded or vice versa.
Testing was made much easier with John Chester's Audio Precision device. John is the formidable brains behind all of the mods we have done. He is very, very sharp, an intellect you would all be glad to know.... cool dude too.
So no Gyraf, there is absolutely no placebo effect going on here. I have heard the changes, some pretty profound all along the way and while it often was obvious, we went about choosing things blindly. This has been an incredibly invaluable experience, a very rare opportunity to hear first hand many of the things people talk about practiced in front of me to experience first hand.
The console started out as an Allen & Heath Saber. Soul II Sould mixed a muli-platinum album on one, but I can tell you, this thing is an order of magnitude better than when I got it. We have performed three modification sets to it and each time is was, "Wow!".
This might have been the most profound of them all though.
Oliver Archut is making some transformers for the inputs of the console right now that we liked and those should go in in August. We are also going to make some various discrete amplifiers to A/B to see what we like the most and possibly replace the input amplifiers with one of Johns designs.
Gotta run....
j