JTM50 Build

[Marcomel79]

That looks... noisy. If the intention of the heat shrink was to reduce interference (which seems marginal), tucking the NFB in like that is counter-productive

I used the heat shrink for a cleaner look, it was too busy with the leads exposed.
Maybe ill go in the if the issue arises again. Like i said, it only happened twice, after 9 on the dial. I usually have the presence between 0-4

Maybe we should call this technique "the European's variac"!

The transformers were donors so i cant do anything about that unfortunately

 

[Pete Farrington]

So after doubling up the mains filtering from 32uF to 64uF, the amp is still ghosting. Not as bad as before, but especially if using the neck pickup around the 12th fret.

The transformers were donors

Have you confirmed the OT ratio / primary impedance?
Some speakers might make intermodulation more noticeable. Alternatively, from that description, the issue maybe cone cry. In which case a different speaker cab would definitely help.

A higher inductance choke may also help

That’s a possibility.

As I understand it, the greater the draw, the more HT ripple (and hence ghosting).

Bias is most significant at idle and low to medium power outputs.
Ghosting shouldn’t be apparent until the power amp is being overdriven, so I’m not sure cooling the bias will help much here.

But this is based on text descriptions of the issue, whereas it’s possible that a soundclip demonstrating it might lead things in another direction.

 

[Marcomel79]

Have you confirmed the OT ratio / primary impedance?
Some speakers might intermodulation. Alternatively, from that description, the issue maybe cone cry. In which case a different speaker cab would definitely help.

@Pete Farrington Yes, the OT has 4, 8 and 16ohm taps with a primary of 1.8K. Therefore im using an 8Ohm cab on the 4Ohm tap, ad 16Ohm on the 8Ohm tap. The 16 Ohm tap is isolated. The prolem is not there when i use my other amps with the same cab...

The choke is 3H 250mA.... i tried to record the sound with my phone but it didnt capture it...