22/33 D'lite build

[lbradshaw]

I am thinking about building an d'lite 6v6/6L6 amp. But, what I would like to do is have all four tubes mounted in the chassis at all times, and then be able to foot switch between the 6V6s and 6L6s. I assume I can run two bias supply from the same source in parallel. The biggest question I have at this point is what relay/switching to use on the 6v6/6L6 primary? Any thoughts?

[angelodp]

I used a DPDT on/on switch as per Moss's recommend. There are pics of the build over on Brown Note. But mine is a 22/33 Transformer and only 2 power tubes.

cheers Ange

[brownnote]

I am thinking about building an d'lite 6v6/6L6 amp. But, what I would like to do is have all four tubes mounted in the chassis at all times, and then be able to foot switch between the 6V6s and 6L6s. I assume I can run two bias supply from the same source in parallel. The biggest question I have at this point is what relay/switching to use on the 6v6/6L6 primary? Any thoughts?

The big caveat is the foot-switching part...realistically that's not going to work.
It can be done but not easily.
You don't want to switch the primaries when the amp is live....it's risky for your OT, there are safety issues switching high voltage, and there will be a LOUD pop.

[phsyconoodler]

I don't see any advantage at all by doing this.The tonal variations are not as pronounced as you would think.
I would rather use 6L6's and power scale or power dampen the amp to get a wider range.Or 4-6V6's and a half power switch.

[blinddog]

Why not use an amp switcher?
IMHO
Seems easier and more cost effective, and also allows more tonal variation.

Easier to troubleshoot and fix later.

http://www.voodoolab.com/ampselector.htm or Lehle




Good Luck

[jelle]

Budda did a small series of amp that could switch between 4xel84 of 2x6L6. The tubes were cathode bias, each section had it's own phase inverter and the preamp was always conncted to both phase inverters. The plates of he ubes were also always connected to the OT. All they switched was the cathode bias.

Sounded great IHMO, but no dumble style amp.

Maybe you can do someting inspired on this but beware of taking it into production...Mesa has the patent now and apparently forced Budda to stop making these amps.

Anyway, have fun!

Jelle

[blinddog]

That's Right The Mesa Blue Angel could switch between 2-6V6 or 4-EL84 or Both. If I remember correctly that was panel switch only though, no foot switch.

[Tavda3172]

lbradshaw,
What you would do is leave the primary alone at 4k and have all tubes in the circuit at the same time , all running off of the same bias supply. You would just have individual bias adjustments for each pair or you could have one for each tube if you wanted. Then you could use relays to switch the drive lines to each pair of tubes which could easily be done via a footswitch just like any other channel switching in the amp. The tubes that were switched out would simply idle happily but contribute nothing to the output of the amp. All you would need to add is a DC blocking capacitor after each relay that is 10x larger that the coupling cap from the PI to ensure their is no tone change and no DC on the switch. And you only need one bias supply and one phase inverter.
-Kevin

[Luthierwnc]

I second the two amp recommendation. Messing with power systems on the fly is hard to do safely or gracefully. Plus, the half power thing needs a corresponding impedance change. I've never liked the half-power version of any amp I've ever made. All it seems to do is kill the low-end. These "D" amps should have pretty clean output sections anyway.

Mike Fuller has an excellent blurb on the Fulltone site about his two-amp stage set-up. I figure if the king of pedals can't modify one amp to do it all, what chance do I have. You may need to build an active splitter box but there all sorts of plans for those on the net.

Skip

[Luthierwnc]

There is an isolated A/B/Y box on RG Keen's site:

http://www.geofex.com/

Go down to 2004 for the improved schematic. On the rare occasion when I need one, I have a simple passive box but it is only A/B, never both. YMMV, sh