Good as can be expected. I ripped apart an old tube radio to convert to a guitar amp but it has a buzz... I've implemented a distributed star ground, replaced all tubes, twisted on the primaries of the output transformer, bypassed the cathode resistors on the preamp and bumped up the filter caps.
Less hum, but still buzz. 120hz. Unacceptable.
I may need an isolation transformer.
i'll ask a O friend, but damn micah/impressive*/*
We do what we can before we leave this rock.
https://video.nostr.build/e1981f7a84f46379dafb4c2fb246641d0e0821980aa9724c3aa2bf601174c30b.mp4
Future*/* fuckYES*'*
These things are very cool... but they lack low end.
Finding a proper output transformer for these oddball output tubes is expensive.
The one's that come with the radio typically work fine, but they drop off frequencies rapidly sub 200hz.
Anyway. Back to the bench.
i know an audio guy & will hit him uP*/*
You're always very positive and supportive. Glad we're frens. 😇
is there a hum with no imput?
Hum is greatly reduced. Buzz is my game. Yes, even with no input... when I'm back at it I'll update more, but from memory, when tone is dimed, buzz is reduced.. when I back off of tone, buzz is back.
This is class A, so some noise is ok. There is just too much.
It's almost 100% due to dc voltage entering into the signal.
Where is the question. It is likely somewhere in the preamp stage.
No isolation transformer... so full wall voltage across the tube heaters. So there's that.
Biggest suspect IMHO is the power switch being connected to the back of the volume pot.
Tests tests and more tests.
Heath a co. in the 60s had an amp with betr output AA100 i think, Ebay 4 partz
Funny thing about output transformers is they have to match up with the output tubes being used. Mine is a single ended output using a 50l6gt.
I think this would work a charm... but $80 is killing me.
https://edcorusa.com/products/gxse10-1-7k-10w-1-7k-ohms-single-ended-tube-output-transformer
he did say 60 or 120 hum but not sure if that helps with this scenario
120hz is what I'm dealing with. My suspects I mentioned are likely 60hz issues, so I think I can safely eliminate tube heaters and switch as sources.
I may have to just suck it up and be ok with some extra buzzzzz.
he might of said buzz/& about ground'n out to check for source if i'm rem. correctly _close enuf i hope 2 help
It sounds like there is a tip in here for me... I'd love a clearer explanation of how he would check for the source.
I use the term buzz in reference to 120hz. Hum = 60hz.
gotcha
Ok. Last word on the subject for now (ty for entertaining me):
I found that the ground for the tone knob is on an eyelet that connects directly to the chassis. I have also run a ground wire from this eyelet to the preamp ground section (which includes grounds for the input, 1st tube and volume knob).
I probably created a ground loop this way. I will remove the grounds from this eyelet so the tone knob is only grounded alongside the rest of the preamp section and report back later when I have time... 🤞
I was suspecting the tone knobs ground already because with no input signal, the buzz strengthens when the tone knob is adjusted.
Oddly, the buzz disappears when the tone is all the way up and strengthens when reducing the tone downward.
I'm excited to have a lead to investigate. Ty again for your support.
soundz feasible/let me know
Embarrassing to admit... My tone circuit was configured incorrectly. Oof. The potentiometer wasn't properly grounded. Super lame.
I did fix the othrt potential ground issue I mentioned before.
Works a charm now. Buzz free.
nutt'n wrong B*n B*eaRassed/or not-f th@ my friend*/* *_* _____lolz*
It was super cool of you to let me talk through it. It helped focus on a plan of attack.
Tell your friend I said thank you as well.
i'm just thinkn olde solutionz r gettn hardr but he IZ oldeschool
I visited an 88 year old amateur radio (ham) the other day. He asked, over 2 meter, with help fixing up an old radio.
I went to his place and spent 2 hours looking over his rig. By the time I left, I had finally got to the point where I understood why he was asking for help.
That older generation has some serious DIY intelligence.
just talked to my guy "i cut my teeth on tubes" but he's got IT going in othr areaz/need moar info he says and i'm still workn on betr transfer but*/there IZ that
