Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Tapsnap on February 07, 2019, 08:20:10 pm

Title: "Stout" gain hiss and hum.
Post by: Tapsnap on February 07, 2019, 08:20:10 pm

So, I have built an amp that is very close to the Stout circuit shown on this website. When I turn up the gain, I am getting a lot of hiss and hum. If I keep the gain low around 1 or 2, I can raise the volume to max without introducing any of this hiss and hum, but as soon as the gain gets above 2, the hiss and hum becomes really annoying. Is this normal or should I be doing some troubleshooting. By the way, even with the gain on low the amp overdrives nicely at full volume so maybe I need to change the pot. Any suggestions?

Title: Re: "Stout" gain hiss and hum.
Post by: Tapsnap on February 07, 2019, 09:24:46 pm

I'm sorry I was mistaken, the "Stout" circuit is quite different. I must have been thinking of something different. Essentially it's a push pull amp with 12AX7s and 6V6s. Its paraphase inversion and there is a 500K pot just before the phase inverter that is the gain. The volume is between first and second stage of the preamp.