Originally Posted by
Marco
I’m presuming that the type of valve selected dictates the circuit used, so perhaps bigger valves demand bigger and better power supplies. Therefore, it’s the circuit as a whole that’s better, rather than the valves themselves. However, if I’m talking bollocks, just say! Regardless, though, I know what I’m hearing and there’s undoubtedly something in it.
Marco.
You have such a broader experience of listening to different valve types that I can learn from you in that respect.
What you are presuming above is correct, that the circuit conditions and component values are dictated by the valve used, though a 'bigger and better' power supply is not necessarily required.
The fact that there are so many varieties of valve that can perform a 'small signal' role at audio frequencies is at once impressive, but yet frustrating.
You want the best? How to choose?
The variation of a valve characteristic is quite large, so the best designs try to cater for that. Some circuits I have studied I would leave alone but there are many that I would tweak to improve the acceptability of different valve makes and age. The problem of course is that published valve curves are based on the 'average' performance. This can vary by 20% or more depending on the particular manufacturer and their acceptance criteria.
This is I'm sure why generally the special quality SQ or E88CC type of valve will sound better in any given circuit.
There is a broad 'sweet spot' for valve operation but it could be at 1mA for one type but 20mA for another. What is required foremost is that the valve characteristics are as linear as possible, but none are perfectly linear. Do you know that certain valve types are specifically non-linear for applications requiring large operational ranges?
I imagine, but have never tried it, that small circuit tweaks could be made to bias and HT voltage (though they are always interdependent to some extent) to lessen the sound differences between different valve makes in the same circuit.
The 6SN7 valve is particularly good where linearity is concerned. Its sweet spot is in the 2mA area just for information.
Regarding power supplies the 'quality' of the power is of course of paramount importance, as the psu is part of the signal circuit however much it appears not to be.
The use of a wall-wart switch mode is as much to prove that quality performance can be achieved using one, plus also doing it at a specific price point. The Firebottle circuit has additional circuitry that gives a regulated HT, an important factor in achieving good linear performance.
Alan
I love Hendrix for so many reasons. He was so much more than just a blues guitarist - he played damn well any kind of guitar he wanted. In fact I'm not sure if he even played the guitar - he played music. - Stevie Ray Vaughan