B+ voltage effect on tone

[EtherealWidow]

Alright. Tried to find some information on this, but I couldn't seem to find much of anything. I'd like to draw from all of your guys' experience and compile a list of different output tubes functioning at different B+ voltages and their tone operating within that voltage range. Ready? GO!

[JazzGuitarGimp]

If we're talking output tubes, then screen voltage should be considered as well as anode voltage.

[EtherealWidow]

Oh shoot. Adding that other element and then how that's going to interact with anode voltage is going to just be crazy. And that's disregarding so many other factors. You could probably write a book on those two variables alone for common output tubes. Welp... although this isn't going to be the most scientifically astute thread, I guess just general observations would suffice.

[Firestorm]

And then there's impedance...

[EtherealWidow]

ALRIGHT! So having established that the subject is going to be very over-simplified and that there are a near infinite amount of variables, I feel that we can still make this thread a valuable source of information for marrying the power supply and power section.

For example:

At +---V a 6V6 typically sounds like farting on wet fiberglass
At +---V more robust flavors start to emerge and notes of chocolate and maple wood dominate the senses
At +---V the tube arcs over and kills your family pet

[martin manning]

Are you from TGP? ;^)

[ToneMerc]

ALRIGHT! So having established that the subject is going to be very over-simplified and that there are a near infinite amount of variables, I feel that we can still make this thread a valuable source of information for marrying the power supply and power section.

For example:

At +---V a 6V6 typically sounds like farting on wet fiberglass
At +---V more robust flavors start to emerge and notes of chocolate and maple wood dominate the senses
At +---V the tube arcs over and kills your family pet

Ok, pertaining which 6V6 then, a smoked glass top Raytheon from the early 50's, a Tung-Sol reissue or that small big bottle tube that JJ calls a 6V6?

too many variables

TM

[jelle]

The op is asking for effect of B+ on tone, so this means that the B+ can be the only parameter that is varied to obtain a simple list.

In my opinion, this type of information is only meaningful when acquired in person. This is what many if us here have done, myself included.

If you would go this route then you will find out that with different voltages, other parameters are changed by the amps designers. This due to physics, and it is too much of a simplification to just ignore this for the sake of having a simple linear list.


I would suggest downloading RDH4, the radiotron handbook, and you will see what I mean. Good luck, Jelle

[ToneMerc]

In my opinion, this type of information is only meaningful when acquired in person. This is what many if us here have done, myself included.

ditto

TM

[VacuumVoodoo]

We need to divide the subject into two chapters: preamp and power amp as supply voltage magnitude (B+ is an anachronism from the times of battery powered car radios) will have different affect on each part.
Assuming any particular amplifier and only supply voltage the changing parameter, primary most significant effect will be:
1. Preamp: supply voltage governs headroom
2. Power Amp: supply voltage governs output power
There are secondary effects characteristic to peculiarities of the circuit design.

[martin manning]

In a typical guitar amp circuit, the screen voltage is close to the plate voltage, so you could assume that the screen voltage will be proportional to the plate voltage, and that the load impedance is held constant. With proportional voltages, holding constant impedance will keep the load line in more-or-less the same place on the characteristic curves. If you further stipulate that the drive voltage will be adjusted proportionally, this is much like power scaling, which is known to be relatively transparent, tonally speaking. I propose that the answer to this question is:

A 6V6 sounds like a 6V6, and a 6V6 at high voltage is louder than a 6v6 at low voltage.

And one more thing...

Ready? GO!

This rubs me the wrong way.

[Leo_Gnardo]

This may be totally subjective & "my ears only" but I find lower high-voltage supplies to yield a more relaxed tone, and higher voltages to yield a brighter, tighter sounding result.

The term "high tension" as applied to electrical supply sort of carries through to the audio.

Your results may vary...

[EtherealWidow]

Alright. Makes complete sense that it might be one of those things that you have to experiment with in person with each individual build to get a feel for just that variable being adjusted in just that circuit and then draw the similarities from there. Figured it was worth a shot though. Thanks guys.

[Firestorm]

You could build a test bed to experiment with: simple preamp, your choice of PI, two tube output and multitap OT. Add a power scaling circuit set up to scale the whole amp, just the power amp, or individual nodes.

[EtherealWidow]

Absolutely. I've been wanting to build something like in the "naked amp" thread. I have a lot of different circuits that I've been wanting to test first hand. Finally have some money coming in, so as soon as every thing gets settled in I should be able to.