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Hi all hope I can get some help, this is my first built and went very well until now.

I completed the build a few days ago and everything went fine, no fire, smoke etc.. amp turned on and sounded great. Now when I take the amp off standby and onto On there is a static sound kind that kind of sounds like when you have an amp on and a cable plugged into the amp and then plug the cable into the guitar. I hope that description makes sense.

When I switch it from On to Standby there is a sound that I can only discrete as a wurbble (is that even a word) that is not very loud and gets quiet and goes off really quickly, not really sure how to word it any other way. At times when I turn the amp from Standby to On there is a loud static type noise and then clears and works perfectly while I use it but again the wurbble when I turn it off.

Any ideas of what this can be? Hope you guys can help, let me know if pics would help.

Thanks in advance!

Hi davesin - welcome to the forum!

I'm not quite sure what this is. I've built a lot of amps and I also repair a lot of amps. Older/vintage amps with crudely designed standby switches like the brit45 sometimes do make some weird noises when take them in and out of standby. What the standby switch in the brit45 does is disconnect the rectified high DC voltage between the rectifier and the standby switch. So when you take the amp out of standby, you are connecting the high voltage tap to the main filter caps, which then charge up and begin to provide the high voltage to the tube plates. The plates need the high voltage to bias correctly and amplify signal. So what you are hearing could be DC voltage leaking into the signal path somewhere.

If you did not hear this sound when you first built the amp, but you now hear every time you use the standby switch, you could have a solder joint that has gone cold/intermittent. Going back and reflowing solder joints is usually a good a idea.

If the amp makes this sound every time you operate the standby switch, you can try removing tubes one at a time until the sound goes away, to see if you can isolate a certain portion of the circuit. Start with the 12AX7 closest to the input, then move toward the power tubes, one by one. You don't need to remove the power tubes, because removing them will kill all sound anyway. Also swapping each tube one at a time with a known good tube (perhaps from a different amp) is always a good thing to do.

Also, if you are able, take voltage readings at each of the main filter caps (C15-C17) and compare them to the voltages listed on the schematic to see if anything is way off.

http://byocelectronics.com/board/viewtopic.php?f=49&t=52194

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MasterDelayer/Reverbrador/Ampaholic/TopJacker

Thanks Morgan, good to finally be building!!

The static is gone today when I turn the switch to ON but wurbbles and wurbbles from ON to Standby but no static so you may be right about a cold solder joint somewhere.

I'll try the tube trick you mentioned and see if I can figure out where the bad joint is instead of just redoing solder on everything which would be a major pain. I'll also try and poke around with a chop stick and see if any obvious noises come up anywhere.

I'll post back tomorrow afternoon when I get off work and have time to get in there.

Thanks again Morgan