Low power push pull ideas?

[Fretts]

The plan is for a complete amp with all the goodies. Volume treble, bass, trem, reverb, phase inverter, push-pull output, the works. No inverse feedback.
The special characteristic is a 5-watt maximum output, with 1 watt being more like it, and an 8-inch speaker.
I don't want to reinvent the wheel, so, at the risk of pounding a topic that may have already been done to death here...
What are some suggestions for a really low-watt but completely true pushpull output section? I still want everything the big amps do when they are sweating, so no class-A and no single-ended configurations will do.
I do know about Zachary Vex's nano amp and it is a monster, just great, but I want to take it to the next level and make a complete amp in a cabinet with a handle.

[MWJB]

Search "utube 1W guitar amp", 6SN7 in push-pull output. This might give you a starting point.

12BH7 could also be a candidate?

[riscado]

glad you decided to include a phase inverter as a feature

[Bruce / Mission Amps]

More shameless promotion...

I have about 10 or 11 smallish combo cabinets (about the size of a Fender Vibrochamp but with a 10" speaker cutout) and some matching chassis' left from our old Starlite project... one of which was a mini amp with a low power, push pull 6SN7 PA.
No reverb in the Starlite series but a multi-spring 9" reverb tank will fit in the cabinet and the chassis is very universal. It has plenty of tube socket holes for stuff like this as it was a chassis design used for small amp experimentation anyhow.

Since we moved, we've found all kinds of stuff we are going to stick it all on Ebay for the do it yourself builders.... but, if a few of you are interested, I'll whip something up, shoot some pictures and list the cabinets and chassis in our "garage sale" page at Mission Amps.

[riscado]

Bruce's sugestion is a good one...

I also saw an amp some time ago, which was around 1w, but I'm not sure wether it was SE or push pull, I'm talking about the emery microbaby amp, you could try and check a schematic for that one (if there is one on the web of course).

[Fretts]

I picked my front end; it will be a variation on my '65 Cambridge Reverb 18 watt.
Now I need to modify the power section. I've seen a very expensive stereo amp that uses ten 12AX7s as the power section, maybe I could investigate a reduced version of that as a possibility. On the other hand, what 9-pin small-bottle power tubes are available? Is there a "baby" version of the EL84? Any shortcuts here before I go on a research mission?

[quayhog]

how low wattage do you want? Look at the 6HU8 (ELL80). It has two power pentodes in one bottle capable of three watts push pull. I've no experience with this tube but the low wattage possibilities may be worth investigationg.

The 12AU7 would make a better low watt power triode than a 12AX7.

[Fretts]

Thanks for the heads-up.
Regarding "12"'s in general, how about the 12AT7? I see it is used as a reverb driver in Fenders, which is essentially a miniature power amp anyway, complete with output transformer. The only catch is that it is not a push-pull pair. My understanding is that the AT7 is intended as a current amplifier more than a voltage amplifier, similar to power tubes.
Power - yes, about two or three watts is about right for this.
Since I am looking to reproduce as much of the familiar sound as possible, I am expecting to look at low power tetrodes or pentodes. I don't know - but I suspect - that simply underpowering an EL84 will not give the same effect as a much smaller tube being pushed to nearly its limits. So it's a suggestion of a low-power output tube that I am looking for, something designed to produce a watt or so each, then I want to drive them hard.

[Tom Phillips]

... how about the 12AT7? I see it is used as a reverb driver in Fenders, which is essentially a miniature power amp anyway...

Jeff,
The 12AT7 would work. In his book TUT2, Kevin O'Connor's talks about converting the single ended Fender 12AT7 reverb driver to PP. He shows a "transformer loaded Schmitt splitter" configuration which is an interesting way to get a PP output section without a separate phase inverter circuit. I don't see any reason that you couldn't design a phase splitter feeding the 12AT7 in PP. There is no mention of the transformer used. maybe he sells them or uses something like a Hammond 125A.
Tom

[markbul]

The Hammond 125A will work - Angela had the 125C for a better price, so that's what I used for my push-pull 12AU7 build.

[Arthur B.]

I picked my front end; it will be a variation on my '65 Cambridge Reverb 18 watt.
Now I need to modify the power section. I've seen a very expensive stereo amp that uses ten 12AX7s as the power section, maybe I could investigate a reduced version of that as a possibility.

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

On the other hand, what 9-pin small-bottle power tubes are available?

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

Is there a "baby" version of the EL84? Any shortcuts here before I go on a research mission?

There are triode/pentode TV tubes that would work. You can try a cascode output stage if you are so inclined.

[Mr. dB]

how low wattage do you want? Look at the 6HU8 (ELL80). It has two power pentodes in one bottle capable of three watts push pull. I've no experience with this tube but the low wattage possibilities may be worth investigationg.

I vote for this solution, if only because I like the harmonic spectrum of tetrode or pentode outputs for guitar. Triodes are a little too "pretty" and just don't seem "interesting" enough when you abuse them.

Triodes are for preamps and hifi.

[Fretts]

I vote for this solution, if only because I like the harmonic spectrum of tetrode or pentode outputs for guitar. Triodes are a little too "pretty" and just don't seem "interesting" enough when you abuse them.

Triodes are for preamps and hifi.

Mr. dB: Exactly, we are on the same page. I am seeking the reverse of the usual. Typically I have said, why can't I have a big amp that does everything my little amp does? Now I am zagging; I want a little amp that does *everything* my big amps do --except vibrate my clothes--.

riscado: For my goals, a phase inverter IS a feature; I want All of it. The nasal honk, all of it.

[Fretts]

[QUOTE=Arthur B.;6718]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.

[doctord02]

Triodes are for preamps and hifi.

I guess you have never played or heard a Moonlight... Uses a 6SN7 in push pull for the power stage.

Nothing pretty or HiFi about it... Do a Google search for Moonlight clips.