e-licktronic Forum

The main out on my and a friends unit sounds quite distorted and noisy. Single outs are fine. Especially audible with kick and toms.

the master section is just a few components... check the opamp or transistors for noise?

Heard the same from another finished unit. Noisy main outs.
Hope this can be solved

it does sound like overdriven, but the strange thing is it is not dependent on the instrument volume.
BD has the same distortion, even if I set the volume really low.

I don't have the time currently to thorougly analyse the output stage.
So maybe someone else can chime in and report how their output behaves?

I also noticed a difference to the original 909 schematic.
The trace to R472 is after D195 in the 909 service manual. In the nave it is before the diode.
But I have no Idea what all the transistors are for in the output mixer anyways. so it might be unrelated...

comboy wrote:I also noticed a difference to the original 909 schematic.
The trace to R472 is after D195 in the 909 service manual. In the nave it is before the diode.
But I have no Idea what all the transistors are for in the output mixer anyways. so it might be unrelated...

Q82 and Q83 act like a mute circuit when power on or off the Nava. It prevents "plok" in your speakers.
Unsold both transistors to know if issue come from Mute circuit or Amp circuit.

Best regards,
e-licktronic

yep - I tested it by removing the two 22k resistors and the mix out immediately gets clean.

hmmm it is something else. but has to do with the muting circuit.
I cut the traces to place take the signal after d195, but the mix out is still distorted.
for now I will remove the 22k resistors again to get a clean mix out.
maybe the designer of the kit may find the time to fix this hardware bug?

comboy wrote:hmmm it is something else. but has to do with the muting circuit.
I cut the traces to place take the signal after d195, but the mix out is still distorted.
for now I will remove the 22k resistors again to get a clean mix out.
maybe the designer of the kit may find the time to fix this hardware bug?

What 22k is this?
In the master out there are two 2.2k.

r470 and r469 on the big main pcb, not the small jack IO pcb

comboy wrote:hmmm it is something else. but has to do with the muting circuit.
I cut the traces to place take the signal after d195, but the mix out is still distorted.
for now I will remove the 22k resistors again to get a clean mix out.
maybe the designer of the kit may find the time to fix this hardware bug?

Are both channel L and R distorted ? You should measure 0v to Q79 collector
Try to replace Q79.

Best regards,
e-licktronic