The additional trimmer is for adjusting the meter tracking, in other words 'the dance'. Set you meter to zero GR, apply a test signal and compress some 5-7 dB (read at external meter).
Adjust R X26 until the meter reads correct GR.
Mute signal, readjust 0 GR, reapeat procedure until your meter reads the proper amount of GR.
Does anyone know if this has enough gain in the makeup stage to act as a mic pre? I have always wanted to hear an Akido mic pre... I would put a 1:10 input just before r103, maybe with a lower value. If I could get 40db plus the 20db from the tx, I would do it.
Hi... I just got my D-AOC working and I have a few questions about the power supply.
My Edcors are in the mail so I set it up without transformers. It sounds REALLY great. Frequency response is nearly flat to 20Khz. There is distortion but I like it. I think it might be worth keeping it this way as a "color" box.
I'm using half of a 250-0-250 toroid. It is actually giving me 270vac. I have 325vdc before R1 and 302vdc after R1. I have 258vdc after the vreg and end up with 248vdc after Rx28.
The vreg heats up to around 120F (49C) but R1 is 170F (77C) or more. I guess it's all within the specs, but I'm worried about R1 (470R 2W). Should I replace it with a 3W or even 5W resistor? Should I use 500R or higher to bring down the voltage into the vreg?
The voltage spikes up to around 295vdc before settling down to 248v. Is that normal?
Also, I'm using AC for the heaters, which seems to work fine (self noise is -82db). The transformer is rated for 2A, so I wonder if I am leaving enough overhead if I'm using 1.8A for the heaters? I'm running the lights off the 5v winding.
I'm looking forward to hearing the difference the transformers make. But for a budget build, doing this with AC heaters and no transformers still makes a pretty great box.
I found that the capacitance of the wire i used (20-30cm, ~120pF/m) to the output pot gives a rolloff about -1dB @ 20kHz. When replacing the out pot with fixed resistors at the pcb i got a boost of +1dB @ 20kHz, probably due to some transformer resonance or something.
Finally had time to finish the late Christmas present i made myself, wanted to make it look fancy for my first Tube project, i think that's mission acomplished, but don't know if i'll do on my next build tough :. Had some tiny issues but all is good.
I got to thank Volker and Analag for the project, Franck @NRG for all the panel work Danke Schoën to you guys i'll have an Augustiner on this one, PROST!
Also like to thank Mad.Ax for his help and clarifications (merci monsieur) and all of you guys here for the inspiration and help also, without the forum i wouldn't even have tought about all this.
On quick sound check, i was pleased by the sound and compression, i'll use it as is for some time and tweak on taste, i just have a low HT when all tubes are in 188V at R128 ???, but all works as expected, all matched as possible etc....