WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
Building, troubleshooting and testing of these amplifiers should only be
performed by someone who is thoroughly familiar with
the safety precautions around high voltages.
Hard to say with so little info, as valves have no 'sound' of their own (unless dropped on a hard surface).
In a properly designed amp, using valves within the design tolerances, there should be very little difference between brands.
In less strict designs, especially those meant to add colour/warmth/character ie distortion, there can be very perceivable differences.
Long time ago I developed a dislike for the small plate East German ECC82 as it didn't sound well in *my* amp at that time, where the long plate Philips did. Thinking back, I'd like to know why there was a difference, but alas, that amp is no more.
I have no experience with the various JJ versions or La Radiotechnique.
Since the ECC82 is not the most linear type, switching to a 12BH7 or rewiring for a 6FQ7/6CG7 could reduce distortion, if that's what you're after.
I have on loan the Blue Aura v40 but i don't know whether i'll keep it or no
"In a properly designed amp, using valves within the design tolerances, there should be very little difference between brands" this sums it all i guess
I bought the RCAs 5814A black plates and indeed there is a sonic difference compared to the JJs, big one i'd say.
My concern now is:
"the 5814A is equivalent to a 12AU7WA, it is ruggedized and redesigned; the filament current raised to 175ma per section versus 150ma per section for a 12AU7"
"Watford valves suggested the Radio Technique / ECC82/6189/12AU7WA for extra bass and warmth." They would do, they sell valves. Personally I think valve A has more bass or whatever than valve B is c*ap, but the whole valve supply chain is built on the idea that a Mullard sounds better or different to a Brimar so what do I know.
I'd change the caps in the tone control or change a cathode bypass cap to get more/different bass, that or get a pedal, still, horses for courses.