Tube Amp Archive

Hi guys,

thanks for all your help. I solved all issues. It was mainly a problem with ground wiring. I re-wired whole amp and put together grounds as suggested (low current together, high current together...) Now it's working perfectly.

Thanks again.

Just to add some observations.... I think something is wrong with grounding scheme I used. I tried to connect 360V CT directly to negative pin of electrolytic capacitor. The effect of squeal of 100Hz seems to decrease. I will go through whole design again and check grounding scheme.

Just to add some observations.... I think something is wrong with grounding scheme I used. I tried to connect 360V CT directly to negative pin of electrolytic capacitor. The effect of squeal of 100Hz seems to decrease. I will go through whole design again and check grounding scheme.

I am from EU where we have 230V @ 50Hz. Yes I have two builds. Head is 100W with EL34 power valves and this one which is combo with 6L6 power valves.

Here are some screenshots of signal measured at speaker jack. That error occurs when switching stdby switch. The frequency of oscillation is 100Hz which is double of 50Hz. I tried to replace PI decoupling cap but without any good results. I also added 100nF/630V cap at choke side but no changes at a...

Here are pictures. Because this is combo version PCB inside must be turned around which makes this amp harder to debug. But I had to make it so because I wanted to keep all controls at same position as in head version. My head version is working OK, but this one has errors.

Thanks for your comprehensive debug hints and tips. I'll go through list and check all that. I attached schematics of how I've done power supply. In my design it's basically done the same way. Except that now I replaced choke with resistor (for test purpose - to test for voltage flyback). I did some...

Hi, I made a SLO based clone and I am facing two problems. 1. When I flip standby switch I can hear low frequency squeal for 2-3 seconds. I tried several things such as replacing inductor with resistor (just for test purpose to see if I am getting flyback voltage in power supply), I replaced electro...