DIY amp - high noise floor - how best to troubleshoot?

Che_Guitarra

Tele-Holic
Joined
Mar 23, 2012
Posts
766
Location
Perth, Australia
I recently built a Deluxe style amp. Mostly based off a 6G3, but elements of DR and tweed exist in the circuit too. Prior to this build, I built the exact same circuit with a spare 15W trafo set I had and it turned out great. So I decided to build again at 20W for the times I need more oomph.

Anyway, the noise floor on the 20W version is really high in comparison. Hmmm.

Trying to troubleshoot:
All tubes have been swapped with confirmed working backups. Not an iota of difference.
I've installed a copped bus wire that runs the length of the chassis and directly collects all circuitboard grounds. No difference.
I've run the filter cap grounding directly to the IEC pin. No difference.
I've installed shielded cable on any V1 wire that passes under the circuitboard. No difference.
I've re-heated every single solder incase one of them was cold. No difference.
I've poked every wire with a chopstick out of curiosity. Once again - no real difference.

I'm running out of ideas.

The only real difference between this amp and my 15 watter is the use of orange drop caps. I've also used axial electrolytics (board mounted), as opposed to a cap can. Maybe this is where I need to turn my attention?

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Any suggestions? I'm all ears.
 

Tonewolf_Amps

TDPRI Member
Joined
Mar 3, 2018
Posts
14
Location
Port Hueneme, CA
Is that chassis painted? Make sure those input / output jacks and pots have a good clean connection to chassis. Scrape off the paint to bare metal and use star washers.
 

gusfinley

Tele-Afflicted
Joined
Jun 11, 2014
Posts
1,640
Location
SLC, UT
Look into an artificial heater center tap on the heater circuit. I would highly recommend using 1% resistors in the circuit as an imbalance can present itself as hum. Some say 1% is not needed. I got tired of reinstalling 1% resistors into my amps and always use 1% resistors now.
 




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