HUM when inverting phase on my green pre

[flaheu]

I've setup my green V14, everything ok, very clear sound,but...
When i switch on the DPDT phase switch, i get a audible hum ???
The 0v of the input and output are connected together, the pre is not in the box yet, and my ground (from AC) is not connected.

Anyone ever had the case ?

Please help

 

[peterc]

Flaheu

Check the continuity on the Phase switch.

Try it with the AC gnd connected. What are you listening on, amp or mixer etc.

Does the signal level change when flipping the phase i.e. does it go one legged? Do you have a dual chan scope to check out the + and - outputs simultaneously?

Some switches can be sensitive to heat on the pins, & this can cause problems with the signal.

Peter

 

[flaheu]

i'm listening mike, have tried different one, nothing changed.
the level doesn't seem to change when on.
i don't have dual scope.
If AC connected and no result, do you think, i should change this DPDT switch with another ? what do you mean by "does it go one legged"
:green: :green: thank you very for yor help

 

[peterc]

What is your playback system? Mixer or amp?

One legged means only one side of the balanced signal is connected, which would happen if one side of the switch is faulty.

Try it into a balanced input & see if it still happens.

Peter

 

[flaheu]

my green output is connected into the balanced input of my R*M*E FIREFACE soundcard.

OK, i'll try to change the switch.

I've still 3 green to build, so i'll build them and see if my problem appears on the other channels.
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To set up the led meter, i've injected a signal into the pre , but this was 19.6 V peak to peak (The max i could reach with my signal generator).
So what would be the output voltage required if i want to calibrate with the yellow led (because of the lack of power with my generator).
Maybe i have to build a signal generator myself, with sufficient power ?

Thank you very much for help, exept this hum when polarity switched, the green is really a top class preamp !!