Hiss/oscillation on the OD channel of an ODS

[CB Amp]

Swapping the OT primaries should result in a big squeal or no squeal.
So it's uncertain what you actually did.

????????????
Forget this OT, pleeaaase... I buid amps for 20 years, so I know this problem of OT leads. Yes it produces a big squeal if it's wired incorrectly with a NFB loop.
What I did is certain, I wrote it again and again, did you read it ? My english is perhaps not clear enough, if so, sorry. It is wired the correct way. And with the OT wired in the correct way, there is a whistle/oscillation/feedback/big hiss on the OD channel. OK ???

[erwin_ve]

Ok clear. If you want us to help you, precise and clear descriptions on things you did or didnt are a must.
For the picture: can you post a complete gutshot and a schematic?
Fe. there is no clear view on the Od/clean wires on the relay.
When having the oscillations, does tapping on wires on the Od tube, with a chopstick, increase oscillations?

[Aaron]

Those heater wires are running parallel with the OD wires. I would try lifting them up and see if that makes any difference, or try shielded wire.

Thanks,
Aaron

[talbany]

So you did an ODS using true point to point ..That took some Ball's.
If you did? it could very well be in your Layout/ lead dress.( I see signal wires running parallel with heaters) Point to point methods work ok in lower gain type applications, however, can be an antenna for all sorts of outside interference! noise and hum, especially in a high gain application given the extra(sometimes longer) wire runs, flying leads and components spread out over a wide area. Lead-dress becomes critical!
Just because you were successful in building 1 amp design using PTP doesn't always guarantee the next will be noise free!. This is generally why most guitar amp builders shy away from true point to point.NOISE and Expence!

What do we have to do around here to get a full shot or shots of the amp.

Btw. Yes Output transformer sec leads reversed on the PI causes positive feedback usually startles most of the dogs on my street
Tony

[bepone]

Cb amps, dissasemble it. Think better. Hiss is about layout and grounding.. Every stage also need to have each own cap.. Hiss and humm are telling you how good you are in seeing what is hidden..every wire is an antenna a you have bunch of receivers..i did SLO 100 p2p without hiss.. Reconstruction is the fastest method
p.s. here is my example, on the beggining of the video you can find some pics..
https://www.youtube.com/watch?v=kyi_vo1MTOs
i didnt use shielded wire too much, only gave space between the stages and DC heating for first two tubes..., signal is going from right to the left, and then to the stages at back, 4xECC83 with p2p+1xECC83 for PI , a lot of gain ..

[Reeltarded]

para heat and signal as stated above but..

I had an amp SCREAM on me and drive me insane. Rewired signal 50 times. Rebuilt stages 50 times...

I was using same components and starting over.

I redressed shielded signal wires. One has three hairs sticking in a microscopic break in the inner jacket.

Turn your amp up just below the volume where it starts the squealing and take a stick to those signal wires. If one of those wires is microphonic..

[mojotom]

I did build my last ODSs and ODSR point to point without any noise issue but, especially for the gain stages of the OD you need to either put your heater wires (twisted) flat against the chassis then try to run the signal and PS wire on a different plane as the heaters, or at least cross them at 90 degrees.

I usually put the heaters down then run B+ and signal wire flat against the chassis but crossing the heaters at an angle then run a bus bar on top of the tube to run Ck/Rk at 90 degrees from the chassis plate.

From what I’ve seen on your pictures everything is layed out on a linear fashion so could be a mess noise wise. I would rotate the terminal stripes 90 degrees in order to cross heather wires at an angle.

That was a quick lunch break answer

[CB Amp]

Thank you all for your replies and advices.

Those heater wires are running parallel with the OD wires. I would try lifting them up and see if that makes any difference, or try shielded wire.

Thanks Aaron, the wires next to the heaters are not signal but B+ wires. But it could also cause some noise, yes...

So you did an ODS using true point to point ..That took some Ball's.
Just because you were successful in building 1 amp design using PTP doesn't always guarantee the next will be noise free!. This is generally why most guitar amp builders shy away from true point to point.NOISE and Expence!
What do we have to do around here to get a full shot or shots of the amp.

Thanks Tony. Yes, I like challenges...
I use real PTP on my amps for 5/6 years and they are dead quiet. But it's the first time I put a high gain OD section. This is clearly a problem.
I have disassembled parts at that time, so everything is too messy to take some pics...

i did SLO 100 p2p without hiss.. Reconstruction is the fastest method
p.s. here is my example, on the beggining of the video you can find some pics..
https://www.youtube.com/watch?v=kyi_vo1MTOs
i didnt use shielded wire too much, only gave space between the stages and DC heating for first two tubes..., signal is going from right to the left, and then to the stages at back, 4xECC83 with p2p+1xECC83 for PI , a lot of gain ..

Great build, thanks. Yes, I will rebuilt mine.

para heat and signal as stated above but..
I had an amp SCREAM on me and drive me insane. Rewired signal 50 times. Rebuilt stages 50 times...
I was using same components and starting over.
I redressed shielded signal wires. One has three hairs sticking in a microscopic break in the inner jacket.
Turn your amp up just below the volume where it starts the squealing and take a stick to those signal wires. If one of those wires is microphonic..

I don't have signal wires, except to the pots where they are shielded. But I have microphonics on the second signal cap (here on the picture).
So I have to rebuilt it, perhaps at 90°, I'll check it...

I did build my last ODSs and ODSR point to point without any noise issue but, especially for the gain stages of the OD you need to either put your heater wires (twisted) flat against the chassis then try to run the signal and PS wire on a different plane as the heaters, or at least cross them at 90 degrees.
I usually put the heaters down then run B+ and signal wire flat against the chassis but crossing the heaters at an angle then run a bus bar on top of the tube to run Ck/Rk at 90 degrees from the chassis plate.
From what I’ve seen on your pictures everything is layed out on a linear fashion so could be a mess noise wise. I would rotate the terminal stripes 90 degrees in order to cross heather wires at an angle.
That was a quick lunch break answer

Thanks a lot mojotom. I also have the heaters and B+ flat on the chassis, but I think you're right, everything is much too linear (especially with this cap on the picture). I will follow your advice.

Thank you all for your time.
Cyril.