Traynor YBA (JMP type) Recapping

[Mick Bailey]

My own view on this is the original designer probably left them that way for a reason - maybe it added another step in manufacturing that wasn't necessary. It's a low-gain amp and not critical. when working on an amp I always bear in mind that the job in hand is to fix it and get it working, rather than redesign it.

[Guitarist]

Well I tightly twisted those speaker wires. Would also shielding them help?
Also, I looked up the PT and it for a 100W with a 2KΩ primary. I see 50 Watters have almost twice that. There is no impedance selector that I can see. So are el34s still the best tube complement and what might be the best cab Ωs?

[Mick Bailey]

Would also shielding them help?

I can't ever recall seeing an amp with shielded leads to the OT. Be careful you're not trying to fix a problem that doesn't exist. As for the OT impedance - is the transformer original to the amp? It should have a turns ratio of around 21.5:1 giving a primary impedance of 3.68K with an 8 ohm load. If there's any doubt, check your actual transformer ratio.

[Chuck H]

I've never seen shielded OT leads. And, you said "PT" in the above post #17 but I assume you meant OT. Do twist the leads to the speaker jack or impedance selector (I know your amp doesn't have one, but in general) and I also like to twist the leads to the power tube plates as well for at much length as is convenient. Both sets of wires routed away from the preamp. Same for the NFB lead. Route it away from the preamp as much as possible. Though I know the NFB shunt resistor that it connects to is often close to the preamp or at least the panel controls.

If you DO have a 100W OT with a 2k primary intended for an 8 ohm load in the amp being used for a pair of EL34's then you can always use it into a 16 ohm load. Reflecting 4k impedance to the power tubes. Close enough. But DO check the turns ratio for yourself as Mick said. Remember when checking the turns ratio to measure the input signal with the unit under test conditions because OT's can load the signal down. So if you measure .5V from your signal source unloaded you may only have .3V or .4V when it's connected and you'll need to know this for accuracy in the equation.