Sun King said:I have +18.1V & - 18.1V (after adjusting the bourns pots). I have 44.1V (is this enough, was hoping it would be 48V) on the phantom rail, and I have 2.5V on the SW rail (shouldn't this be 5V?).
Sun King said:I have wired up to the preamps and tested with a rode NT2A condenser mic.
Sun King said:I have tried both gar2520s in both preamps, same result in both.
Sun King said:When I switch on the phantom, the LED lights up, but if I then enable the the pad and/or polarity switches, they do not all light up (like the power gets drained) and causes the 48V LED to go off. I have also tried the DI and no sound.
Sun King said:I haven't hooked the chasssis ground yet, would this stop it from operating properly while testing?
Sun King said:Also, I have used the same solid core copper hook up wire for the mic in and line out connections (does this matter? Should it be stranded?), making sure pin 2 goes to pin 2 of the XLR connectors, and pin 3 goes to pin 3 of the XLR connectors
lower the positive and negative rails from 18V to 16V for now, there is not a lot of improvement in terms of headroom in having them at 18V but I guess the Opamps will run a bit hot in temperature, dont need that now for testing purposes, put them at 16v and decide in the future if you want higher voltage.
For the Phantom power rail 44V is completely fine, most mics work with a much smaller voltage and I never seen you condenser that didn't work at 44V phantom power supply.
Anyway you should be able to set it to 48V, but leave it at 44V for now.
have you done this?
"Lastly......Harpo mentioned something about leaving out the voltage doubler caps C11 and C12 on the PSU.
Also, Harpo said "better use a TL783 or at least a LM317HT instead of a LM317 for REG48 and for +48VDC out instead of +44VDC out use 220R instead of 240R for R7". "
Anyway with phantom power on, measure DC voltages in input XLR pins, Pin1 to pin2 and pin1 to pin3
Sun King said:Could it just be that without the grounding to PIN 1 of the XLR that it's not working with a condenser mic?
Sun King said:
I had an LM7805C in REG_SW, but have now put an LM7824C which now gives me 21.9VDC on the SW rail.
Sun King said:I did not swap R7 (yet........)
Sun King said:I will change that resistor, but i don't have one handy at the moment.
as for the LM7824, it was another thing that Harpo mentioned. If I recall, it was taking into account the voltage draw that both preamps would need for the relays. Do you think this is wrong?