Using 6v6's in a Proluxe?

[rockybottom16]

I've build 4 small amps so far and had great success, but I'm still pretty green in some areas; so please bear with me as I continue to learn. I'm getting ready to build a Proluxe using Weber's layout, except I'll make it cathode biased. But I know a lot of the time I may want to use 6v6's in place of the 6L6's. I'd also use a 5y3 with 6v6's. The OT that the Weber layout calls for has a 4K primary and 2, 4, & 8 ohm taps, whereas the typical 5e3 tranny has a 6.6K primary. Here's my question: What taps are recommended to use with the different tubes? The speaker will be 8 ohm. I guess what I'm really gonna build is a deluxe with a 40w OT, and I'd like to be able to used the 2 different types of tubes. The occasions where I actually will need more than 15 watts will be pretty rare, but I'd like at least one amp that has it when I may need it. Thanks for your help!

Ken

[Chuck H]

It doesn't work exactly like all that. That is, you can't just plug in bigger or smaller power tubes for different output power without other design criteria being changed with the tube swap. The 4k primary is too low for 6V6's. Also, the typical 450Vp for that amp is too high for 6V6's. That amp is supposed to be a 5e3 on steroids. If getting more watts from a 5e3 were just a matter of changing the power tubes there wouldn't be any need for the Proluxe design!?! When using 6v6's plugging in the higher voltage drop rectifier will help. A little. Probably get you down to about 435Vp. Then you could change the impedance selector to the 4 ohm when plugged into your 8 ohm speaker. This would reflect a primary of 8k to the 6V6's. JJ 6V6's should be able to handle this. You sure don't want to plug the 6L6/s back in without changing the rectifier back to the GZ34 or WZ34 and moving the impedance switch back to the 8 ohm tap. But there's still the issue of biasing. Cathode biasing that design will probably allow it to self bias with either tube. I can't say for certain. And the amp would still have an output power of about 20 watts with the 6V6's as compared to 35 watts with the 6L6's (Not 40 watts, remember that you cathode biased it!). And the difference in actual volume between 20 watts and 35 watts isn't much. I would expect you to end up with an amp that sounds a little too tight and loud to emulate a 5e3 and a little too spongy and quiet to be the "Proluxe" with either power tube type in place. When working with simple amp designs like this it might be best to just build an amp that sounds and responds the way you want and then attempt power reduction with something like an attenuator, power scaling or maybe a triode/pentode switch. JM2C