1 Watt Single-Ended Output Stage

[nosaj]

Just got off three weeks in Ireland. Never heard anybody say "porridge" anywhere else! :P
Either way, seems kind of "un-American" to me... paging Senator McCarthy...

Justin

It's probably not porridge but turnip greens and juice on top of some fresh honey yellow cornbread make a nice style cereal and not bad for breakfast either.
nosaj

[d95err]

1 Watt will be way too loud to crank at home. You should look at the built-in attenuator used by the Marshall 1 Watt amps, which takes it down to about 0.1W. That attenuation was designed for the "kids-asleep-in-the-next-room" volume level.

In general, I think a push-pull 1W stage with a proper phase inverter will sound better than a single-ended design.

[FalderGuitars]

Porridge? Are you from the UK or Ireland? Or IN the UK or Ireland? If so: you put your location in your profile, it may help to speed things along - not everyone reads whole threads before chiming in, and you don't want someone suggesting 120V primaries or other such stuff, right?

Justin

Nice work, Columbo

Duly noted and updated. I forget the majority of forums are US based, and that your National Grid privides a rather conservative 120V. Must take some of the fun out of getting a shock

Just one more thing...

[FalderGuitars]

There sure are a lot of porridges
https://en.wikipedia.org/wiki/Porridge
jason

I'd think twice before saying that in Scotland

[Enzo]

Well, if you build a 1 watt amp, no matter how loud it is, it will be no challenge to a common $6 L-pad. Dial it down as far as you like.

[Zozobra]

The ecc99 is a good tube to use for this too. Check these builds out by a fellow forumite:
http://music-electronics-forum.com/t43163/
http://music-electronics-forum.com/t43822/

[mozz]

If you've already got an amp you like a less efficient speaker could be an answer. I took a 10inch field coil with some help from here and antiques radios forum built a speaker similar to a fluxtone Where you increase or decrease the speakers efficiency toned down a tweed deluxe from headphone level to pretty damn loud. It's not a master vol at all. Only thing I had to buy was the 50watt rheostat.

nosaj

In series or parallel with the field coil? I've got some rheostats here waiting for a project like that.

[nosaj]

In series or parallel with the field coil? I've got some rheostats here waiting for a project like that.

Here's my thread
http://music-electronics-forum.com/t39353/

nosaj

[Gregg]

Since it's not a mass production amp I would recommend the 6P30B or its military version 6P30B-R. You can get those at ridiculously low prices on ebay and one of them will get you pure class A one Watt without any problems. However note that they draw like around 40mA of anode current so you would need an appropriate OT.

[SoulFetish]

Triodes are bland sounding as power tubes, why not try a small pentode instead?
It will sound much closer to what a typical tube amp does .

Fahey speaks the truth here!! I would rather imagine a Pentode output stage , than play through a triode one.

[Chuck H]

Since Matt has already stated that there isn't much satisfaction from the Valve Junior with an attenuator and would like an amp that can be cranked I will guess that he means 'without an attenuator'.

My first consideration here is that, for me, when considering all the compromises of playing that quietly attenuators work pretty damn well. Perhaps it's not the attenuator or the Valve Junior that is the problem. Perhaps what you're missing in the tone is the particular sound of a push/pull amp. In which case there is no single ended micro amp that will give you what you want regardless of whether it's triode or pentode. But now we're talking about the need for a push/pull pair of pentodes producing less than a watt. That starts to nudge the ridiculous end of the micro amp fad for me. But...

As a personal amp, or Rockman style playing module type thingy, you could do it by building the thing as a headphone amp. Tubes don't care a fig what the speaker load is as long as the transformer ratio mates it properly at the primary. You'll need to identify a transformer that could mate the power tubes to a 600 ohm load and provide an appropriate primary impedance. This might require repurposing a transformer typically used for something else. There is still the matter of power into the headphones, but that could be managed somewhat with a pre headphone load circuit consisting of inductors, caps and resistors to correct for the fact that headphones do not sound like guitar speakers. In the end you have an AB1 pentode amp running into headphones. At what seem to me to be far too much trouble.

Perhaps try any normal push/pull amp into an attenuator that offers infinite control or has a headphone output to see if it's the single ended output clipping that's not ringing your bell. That's what I might try next.

[Mike Sulzer]

Perhaps what you're missing in the tone is the particular sound of a push/pull amp. In which case there is no single ended micro amp that will give you what you want regardless of whether it's triode or pentode. But now we're talking about the need for a push/pull pair of pentodes producing less than a watt. That starts to nudge the ridiculous end of the micro amp fad for me. But...

Why not use a pair of EF86s? You could easily get way under a watt. And the pair would cost you only $36, so expensive, it would have to sound good. Might have to wind your own transformer, but here is another chance to lose some efficiency and get still lower power.

[Chuck H]

There are also some micro tubes. The ones that just have leads for soldering rather than socket pins. You don't see them in use, but they can still be found for sale if you look. You could probably find a 100-500mW power pentode in that style. As to winding a transformer... I still think you could repurpose one typically used for something else just as well as making one. Unless you're Mike, R.G., Pete or Juan (or anyone else capable that I skipped). Surely a rank amateur without all the necessary understanding would kludge a homemade job as bad or worse than using a "not quite ideal" 12V power transformer backwards or something like that.

[Loogie]

Well, if you build a 1 watt amp, no matter how loud it is, it will be no challenge to a common $6 L-pad. Dial it down as far as you like.

Ya, go for the L-pad. A few bucks. You might be surprised.

[Gregg]

There are also some micro tubes. The ones that just have leads for soldering rather than socket pins. You don't see them in use, but they can still be found for sale if you look. You could probably find a 100-500mW power pentode in that style.

Yes, go some of those for example the 5902 pentode (russian 6P25B - harder to find) or the russian ones - 6P30B or 6P30B-R. They are also cheaper.
Here's a complete project with 5902 with power transformer as output transformer:

https://jjs.at/electronic/class_ab_subminiature.html

You can make your own sockets for them or during the experiments just use a DIL-8 socket. Don't worry it will take the voltage and current - it was tested many times