Naylor SD 60 problem

[passfan]

So I builds me an SD 60 and spent a little time debugging the presence circuit and also an annoying oscillation anytime the master was turned up all the way. Now it plays alright except I've noticed now that, any picking other than light , produces a constant overtone of around 12k or higher. It does not change in pitch and it rings out with the chord or note when its held. It's not that loud that you'd hear it but for the fact that it's a high enough frequency that it annoying and causes ear fatigue. I've been through one end of the circuit to the other. I swore it was in the first preamp tube but then I plugged a different preamp into the effects return and got it through the return triode, PI, and output section. It's driving me buggy. Anybody run across anything like this

[cbass]

I noticed on the pictures of an original the lead going to the input of the PI is shielded with the shield attached to the cathode I dirent do it on mine but it maybe something to try .they had to have done it for a reason .

[passfan]

Im starting to wonder if its something with my hearing. I just played the amp again , through the low first and then the high. I noticed that sitting here now I can somewhat hear the frequency like maybe its tinitis. Through the low it's barely noticeable and when I stop playing I can still hear it. When I go to high it gets more prominent but I wonder if the Ice pickeyness of the amp is fooling my hearing into making it worse. Perhaps I need to go to the ear doctor. I swear its in the 14 to 15 K range. I spent the afternoon swapping components out to no avail. Perhaps it's official. I'm crazy

[cbass]

Crazy happens sometimes I can think an amp sounds like shit and nthen plug it in a few days latter and think well this sounds pretty damn good and vice versa

[passfan]

Well sometimes I think my problems are compounded by older cabinets that sit out in the shop that goes from hot to cold and dry to humid. I've had to do repairs to cabinets before. I need a dedicated cabinet kept indoors with great drivers.

[Leo_Gnardo]

Now it plays alright except I've noticed now that, any picking other than light , produces a constant overtone of around 12k or higher. It does not change in pitch and it rings out with the chord or note when its held. It's not that loud that you'd hear it but for the fact that it's a high enough frequency that it annoying and causes ear fatigue.

Are you watching the output with an 'scope? Might be setting off an oscillation at audible frequencies you hear as a "chirp." You would see it right away with a scope. Lead dress can help some. Prodding wires with the mighty chopstick while watching and listening, you might find an optimal placement where the chirp quits and you have aaahhh finally, satisfying audio. Failing that a disc cap across the plates of the drive tube may calm it down. I've had to use values from 47 to 1000 pF depending on the amp.

[passfan]

Are you referring to a snubber on the plate resistor on the overdrive triode Leo ?

[cbass]

I believe Leo is talkin bout a cap cross them PI plates. Like seen in some marshalls and fenders. Well I guess some fenders have snubbers across the plate resistor but I think he means across the Pi plates .its a known band aid to fix oscillation

[Leo_Gnardo]

I believe Leo is talkin bout a cap cross then PI plates. Like seen in some marshalls and fenders. Well I guess some fenders have snubbers across the plate resistor but I think he means across the Pi plates .its a known band aid to fix oscillation

What cbass said.

[V2]

Are you sure it's not 'pick chirp'? I built an amp with a 4-stage preamp from Kevin O'Connor's TUT book (also used in the Rocca HG100) and was bothered by an overtone. It took me a while that it was from my heavy pick attack.

Jake E Lee could get some mad pick chirping, likely on purpose. Check out the first 10 seconds of Heaven's train, for example:

https://www.youtube.com/watch?v=PBUsGZJdpJQ

[passfan]

Thanks but no , it's not a pick chirp. It's a steady tone much like someone turned on a signal generator at 14K. Constant and unrelenting it drives your brain mad until you mute the strings again

[passfan]

Well I guess I am crazy. Shot a 1K tone through the amp and all the scope shots were clean. Nothing riding on the sine wave. I got a lot of hash on one side of the pi from the probe for some reason. I reflowed the joints there and put a 100pf across the plates for good measure. Couldnt get the probe to come clean there for some reason

[stephenl]

Are you plugging your guitar directly into the amp? I had an issue very similar to what you are describing and it turned out to be coming from the switching power supply that was powering my effects.

[passfan]

No pedals, just straight cable. Used different tubes , different cable , different guitat and different cabinet.
The amp sounds good so it might be time to get my hearing checked. I have a constant background noise in my hearing of 8 to 10 K and pretty much well tone deaf above 10 K. Perhaps this high gain amp
is aggravating it.

[Leo_Gnardo]

I have a constant background noise in my hearing of 8 to 10 K and pretty much well tone deaf above 10 K. Perhaps this high gain amp
is aggravating it.

Tinnitus + presbycusis. One of the features of presbycusis (aka natural hearing loss with age) is that turning up the treble annoys the listener. That's why our parents & grandparents could take only so much of our bashing pots & pans, later drums & cymbals, as kids. Not much practical can be done about it except give your ears lots of quiet rest, & protect what hearing you have with muffs or plugs when using power equipment & in other noisy activities. Getting used to a mellower tone for your guitar & stereo is part of the program too.