Sound Skulptor forums

Build help and troubleshooting => CP5176 FET compressor => Topic started by: yjmira on December 11, 2023, 01:22:40 PM

Title: noisy/hiss output
Post by: yjmira on December 11, 2023, 01:22:40 PM

hello , 

im having lots of noise/static hiss if the output is turned up after 5 .

all other tests and measurements are good
and audio passing trough the unit is also working fine 
and sounds good..

ive read somewhere it could be due too malfuntioning of a voltage regulator?

can someone help me out ?
thanks a lot

Title: Re: noisy/hiss output
Post by: JPK on December 11, 2023, 05:06:22 PM

There is no voltage regulator on this unit.
Can you measure the AC voltage of the noise at the output, with input xlr unplugged and the input and output gain at max?

Title: Re: noisy/hiss output
Post by: yjmira on December 11, 2023, 06:31:32 PM

18mv between pin 2 and 3




 

Title: Re: noisy/hiss output
Post by: JPK on December 12, 2023, 09:54:19 AM

It could be caused by a high frequency oscillation somewhere in the circuit.
Check the value and solder joints of C3, C4, C10, C17, C26.

im having lots of noise/static hiss if the output is turned up after 5 .
Does it come gradually or suddenly after 5?

Title: Re: noisy/hiss output
Post by: yjmira on December 12, 2023, 01:55:42 PM

it comes gradually not suddenly but now its only hearable around 8 on out.

so after reflowing those solder points and some others i checked
i now only measure 2-3mv between pin 2 and 3 on output

i guess that is in the normal range or should it be totally zero?

thanks 

Title: Re: noisy/hiss output
Post by: JPK on December 13, 2023, 10:54:23 AM

This looks much more normal. It cannot be 0, there is always some noise.

Title: Re: noisy/hiss output
Post by: yjmira on December 13, 2023, 12:43:34 PM

yes :) all good now !

its an amazing sounding compressor 

thanks a lot for the help JPK