Tube to SS rectification switch

[hebaton]

Would like directions, layout on implementing a switch to allow tuibe OR SS rectification in my JTM45.
I would like to have a second bias adjustent pot so that I can switch from one to the other without having to worry about bias...
Don't see any room on the board, suppose I could add a small one somewhere ???

[Stevem]

Are you playing the amp loud enough to experience power supply voltage sag?

You do not need to add a new board to mount the diodes on, they can go right on the rectifier socket.

[neskor]

Check this PDF from Ceriatone

[maxkracht]

https://robrobinette.com/Generic_Tube_A ... ier_Switch

[martin manning]

Fancy solution. Might be able to hang all the parts from the rectifier socket and the DPDT.

[martin manning]

Made a couple of tweaks to get the bias to come in faster, mainly by reducing the input resistor. This will minimize the chance of running under-biased at start-up, especially with SS rectifier..
Some voltages have been added to show the effect of the SS vs. vacuum rectifier at the same output tube plate dissipation (KT66).

[hebaton]

THank yo Martin. I'll have your solution implemented !

[martin manning]

Thank you Martin. I'll have your solution implemented !

Great, I'm interested to hear what you think of the result, meaning if you think there is an appreciable difference in the tone between SS and vacuum.

[hebaton]

Well, I can answer that already because this is not my 1st JTM45 clone. One i previously had and stupidly sold had that option. It did make a significant difference in how the amps responds especially as you push it harder. IT gerts bass a bit tighter and the over all feel of the amp is stiffer and somewaht more agressive...

[martin manning]

One I previously had and stupidly sold had that option. It did make a significant difference in how the amps responds especially as you push it harder.

I'm not surprised that +20V, and more with the lack of sag, would alter the preamp sound quality. Still interested to hear if modifying the one you have now produces a similar result.

I tweaked the drawing above one more time to use pin 7 on the rectifier socket as a tie point for the second pair of 1N4007's, which provides more flexibility in locating the switch. The 50k vacuum bias trimmer can be small in size, and mounted directly on the switch lugs. It only dissipates a few mW.