pushpull PT 440VAC 125mA

[surfsup]

Guys I posted this in the technical forum a couple days back but just curious as I'm not familiar with dumbles at all, and been listening to some great blues OD sounds from your guys' dumble clones lately...

is there a dumble design that can be built with a PT 220-0-220 pushing 125mA? I'd like to investigate that before I start moving forward too far...

[David Root]

300VDC is OK for the preamp but too low for the PI and power tubes, using "normal" tubes, that is.

Maybe if you found a PI tube that could use 300V and push enough current to a power tube that could function properly at 300V. Have to look thru www.tubedata.org or RCA RC-30.

Or, you have enough DC mA available to consider a voltage doubler to feed the PI and power tubes, for a pair of 6L6GC or EL34.

[ToneMerc]

is there a dumble design that can be built with a PT 220-0-220 pushing 125mA? I'd like to investigate that before I start moving forward too far...

My short answer is no. Even when configuring it as as voltage doubler in theory could get a about 620V with no load , but the current capacity of the HT would be be negated to only around 60mA.

TM

[David Root]

You're right, I forgot about the DC conversion factor.

[Firestorm]

What you're proposing to do is really no different from power scaling (or VVRing) an entire amp -- along with all the quirks that entails (at lower voltages tube stages will clip with lower input, etc.), so you would have to design the B+ string pretty carefully and redesign the PI (and maybe attentuate signal pre-PI). But the real gating factor will be the 125mA available current. If you limit yourself to EL84s or 6V6s, it's probably do-able, but the question becomes how "Dumble" would it sound?

[surfsup]

Ok. thanks. I will take Dumble off the list for now. I started looking myself and the voltages were all running around 400-430 so I figured. Thx.