9k high noise floor problem.

[TheGuitarist]

I've got a quad 9k preamp going and one of the channels has a high hiss noise floor compared to all the other channels.
I've tried swapping out every ic and cant see anything wrong.

Anyone have any ideas?

 

[ruffrecords]

Does the noise level alter as you change the gain?

Cheers

Ian

 

[TheGuitarist]

sure does! And its there with or without mics plugged in.

 

[ruffrecords]

sure does! And its there with or without mics plugged in.

OK, that means it is the front end circuit is the source of the noise. I don't have a circuit to hand but I would suggest you try disconnecting the phantom power and see if that makes any difference.

Cheers

Ian

 

[gemini86]

In this circuit one half of the gain pot ties in further down the stream, worth mentioning.

 

[ruffrecords]

In this circuit one half of the gain pot ties in further down the stream, worth mentioning.

Yes, I just found a schematic. Bloody complicated it is too. Don't have my head around it just yet. Give me nice simple tubes any day.

Cheers

Ian

 

[s2udio]

Double check resistor values and connections.....especially around that dual gang gain stage !
If 3 are ok....should'nt be that hard to find .

 

[ruffrecords]

Double check resistor values and connections.....especially around that dual gang gain stage !
If 3 are ok....should'nt be that hard to find .

You could also measure the gain and check it ties up with what is expected - that often reveals a lot about what is wrong.

Cheers

Ian

 

[envelope]

Have you made any discoveries, based on the recommendations yet? 

I've got a quad 9k preamp going and one of the channels has a high hiss noise floor compared to all the other channels.
I've tried swapping out every ic and cant see anything wrong.

Anyone have any ideas?