Sound Skulptor forums

Build help and troubleshooting => MP566 Tube microphone preamplifier => Topic started by: pristudio on December 28, 2021, 11:59:57 AM

Title: Noise when switching form MID to HIGH gain
Post by: pristudio on December 28, 2021, 11:59:57 AM

Hello!

As a long time user of SoundSkulptor products, I just added to my collection two nice MP 5.66 and I just finished to assembly.
They both sounds good so far, I have only a loud click noise when changing from MID to HIGH gain settings on both units.
They're both inside an 8 units API lunchbox, with separate power supply.
Other than that it seems all good. Any suggestions on what it could be?

Thanks!!
Roberto

Title: Re: Noise when switching form MID to HIGH gain
Post by: JPK on January 09, 2022, 08:49:20 AM

Check the direction of capacitor C5 and the solder joints on R15.

Title: Re: Noise when switching form MID to HIGH gain
Post by: pristudio on January 17, 2022, 04:05:59 PM

Quote from: JPK on January 09, 2022, 08:49:20 AM

Check the direction of capacitor C5 and the solder joints on R15.

Thanks for your reply!
On both units, C5 direction and solder joints on R15 appears to be ok.
It's strange I have the same problem with both units, could it be the API lunchbox?
 
Roberto

Title: Re: Noise when switching form MID to HIGH gain
Post by: JPK on January 17, 2022, 04:50:17 PM

Do you get the click with no input signal?
Some clicking is normal here.
You could try to reduce it by using a higher voltage cap in C5 (watch out the size).
Also reducing the value of R15 (by 1/2 or 1/3) might reduce the clicking.
(not tested).