Switch for High Voltage AC

[eschertron]

I'll wire it up with the 330-0-330 taps but do it in a way where changing to the 355-0-355 taps is easy. Play for a while and then decide whether or not to mess with it at all.

So with all the caveats (caveati?) presented, and you being duly advised, I say put a switch in knowing that only you will use it, only for testing purposes, only switching a de-energized line, and that you'll likely choose one or the other voltage and eliminate the switch after testing is done.

[DRH1958]

Why not just get a PT with a 3A rating for the 5v winding and then just pop in a 5U4? That usually gives ~20-25 volts extra on the B+. This seems easier and your PT might be less costly because it will only have the single HV secondary. You could even try a 5AR4 if it won't exceed any voltages you want. Have you already bought the tranny and if so, is it rated for 3A for the 5v winding?

EDIT: They do make stainless plugs for that ground switch hole or you could just put in a cheap switch to plug the hole and don't hook anything to it.

[R.G.]

Or put in a switch that short around the tube rectifier to leave it with the solid state "back up" rectifiers. Should be good for 50-60Vdc.

[trobbins]

Paralleling the 330v switch terminal to switch common with a diode would likely maintain a current path during switching and hence alleviate some of the concerns expressed.

[TheTinMan]

Or put in a switch that short around the tube rectifier to leave it with the solid state "back up" rectifiers. Should be good for 50-60Vdc.

That is a far better approach than switching high voltage PT secondary windings. I was just thinking of some way to use the alternative set of secondaries on this PT.

I have several of those progressive DP3T off-on-on switches and sketched a way to use that for Off/Tube Rectifier/SS Rectifier a while ago. Alternatively, a dedicated DPDT switch would allow me to switch both rectification and the power tube cathode resistor. That way I could adjust the bias for the higher voltage.

Wouldn't the voltage jump be more than 50 volts?

330 * 1.4 = 462 unloaded

I realize that the amp's load will pull down the B+ some. Adding a "sag" resistor or a string of zeners in line with the backup diodes could be used to dial in the higher voltage too.

As I get off track with thoughts like "Gee, that way I could use 6L6s" it's time to remind myself of the primary design goal: a vintage sounding Tweed Deluxe. I seriously doubt that an OT rated for 20 watts would be happy for long being driven by a pair of 6L6s.

Many thanks for brain storming with me. I always learn more this way and there's no telling when something we considered here might be great in a different build. And R.G.'s last idea is well worth considering.

Cheers,
Chip

[Pdavis68]

Or just get a one of these or a different tube rectifier with a different voltage drop. There are a few ways to skin this cat without making it difficult. And as several people have mentioned, it's just not one of those things you're not likely to switch often. You're very likely to find what you like and keep it that way. So spend the $10, buy a SS rectifier and see if you prefer the sound. If you don't stick the tube back in and call it good (and you can probably get at least $8 back for the SS rectifier on Ebay).