Low power push pull ideas?

[Fretts]

[QUOTE=Fretts;6728]

You're probavly thinking of the E.A.R. V20

Look at 12BH7s. They have 3.5 watt anode dissipation per section.

Arthur B., 12BH7 sounds like a candidate, low power by nature, not weird or esoteric, not hard to find. Now if the tone is acceptable, we are off and running.

6CL6 is rated for around a watt. Anyone have experience with this one?

[Arthur B.]

[QUOTE=Fretts;7698]

6CL6 is rated for around a watt. Anyone have experience with this one?

I'm quite sure the 6CL6 as more power than that, but it should work just fine.

[bob p]

it would be a whole lot easier for average guys (me, for example) to find a good tube for this application if push-pull plate loads were published for these amps in the tube data sheets. invariably, it seems that they aren't.

[Tom Phillips]

it would be a whole lot easier for average guys (me, for example) to find a good tube for this application if push-pull plate loads were published for these amps in the tube data sheets. invariably, it seems that they aren't.

I assume that you mean that the data is not in the old RCA receiving tube manual. That's probably because the tube was never intended to be used in push pull. That doesn't mean that it wouldn't work, just that with so many tube types available in the old days, no one was using the particular tube that way.

[bob p]

Yes -- for tubes that were not specifically designed for P-P applications, Ra-a is not published in the tube data sheets. Yes -- that's definitely the case for the old RCA receiving tube manuals. It also seems to be the case for every other data source I've looked at, including every factory tube data sheet that I've ever been able to find. If this is just a case of me just looking for information in the wrong place, please let me know!

Taking a look at the archives at a place like Frank's Electron Tube Pages, there are plenty of tube data sheets from a variety of manufacturers. Invariably, it seems that plate to plate load resistances aren't published for these types of tubes. I could be wrong about this -- there could be a data sheet in a language that I can't read that contains this information -- but I've read every one of them for most of the "common" mini triodes and pentodes and I haven't found good data.

The problem isn't that small triodes or pentodes can't work in P-P applications. The problem is that the load data for that application doesn't seem to be available anywhere. That lack of published information is the biggest impediment toward the creative use of these tubes in new applications. At least that's the biggest impediment for me.

[J Martin]

There is a way to calculate load resistance from plate resistance, or at least come very close, but the formula escapes me at the moment. That is what to search for instead of a published value.

[bob p]

fwiw, i am familair with the 10% rule, which isn't all its cracked up to be.

[Ray Ivers]

Single 12BH7, push-pull, fixed bias, 300V B+, 15K plate-plate load (courtesy of GlassWare's P-P Calculator):



This was just from five minutes dicking around - I really didn't try a whole bunch of different loads, B+ voltages, etc.

Ray

[mooreamps]

I see no reason to even go push-pull for this type of project. I would use the first gain stage of a 12ax7 as the pre-amp, and then the second gain stage into a 10K primary impedance of a small O/T. All can be done with one tube, and have a nice warm SE tone.

-g

[pbreyfogle]

So, what was the verdict?

So, Fretts, what did you finally decide to go with?
Sounds like you're after just the thing I need...

[Rob Mercure]

Hey Guys,

Hate to come in late but I like the 6G6 - an "ST" bottle small output pentode that was used to power the headphones in WWII aircraft, etc. The basing is 7AC so it's "plug and play" with the 6V6, etc. and the plate dissipation is only 2.75 W. An attractive good sounding tube that usually goes for cheap (and I've got a whole box of about 40 WWII - new in box - military surplus tubes).

Rob