very small desktop tube amp schematics

[Kay Pirinha]

As the goal is an output power of not more than 3 watts per channel, triode-pentode combinations, such as 6BM8/ECL82/PCL82, come to mind. Only two tubes plus the necessary periphery.


Best regards!

 

[rock4016]

Also 6CL6 is cheap and can be used in a 2 tube spud style amp for about 3w as a pentode.
B+300v and screen about 170v or so.

Here is a larger one, than can be made smaller than 6x10.
Custom built Orange Spud( SEP 6cl6/6197) integ. amp.

 

[smoking-amp]

6HZ8 gives you an improved 6CL6 pentode (lower knee voltages, 8 Watt diss) and a Mu 70 triode in the same 9 pin bottle. On the $1 list too. Two tubes makes a complete 8 or 10 Watt P-P amplifier.

Then there are the sub-mini tubes. 6021 and 5902 or 5639 can make a complete 4 Watt P-P amplifier. Some nearly pocket size amplifiers around using these.

 

[mashaffer]

6HZ8 gives you an improved 6CL6 pentode (lower knee voltages, 8 Watt diss) and a Mu 70 triode in the same 9 pin bottle. On the $1 list too. Two tubes makes a complete 8 or 10 Watt P-P amplifier.

Then there are the sub-mini tubes. 6021 and 5902 or 5639 can make a complete 4 Watt P-P amplifier. Some nearly pocket size amplifiers around using these.

Just grabbed a bunch of those for some P-P experiments. Neat looking bottles.

 

[smoking-amp]

Neat looking bottles.

I think they are called neonoval tubes (or Fat-Boy tubes!). Fit a standard noval base, just a bigger bottle. Sylvania seems to have come out with them originally.

Some other neonovals:
7695, 7754, 6GC5, 6GM5, 6HC8, 12HG7 (some), 6LB8, 6KU8, 6HZ8, 6JT8 (some), 6EW7 (some), 6FD7, 10/6FR7

 

[pcan]

Compared to other options, the single ended 6ak6 tube does require lower filament and B+ currents, therefore the transformers are small and you may mount them closer. The two output transformers are at 90 degrees related to the power transformer and choke.
To get down to the 14x14cm size you may substitute the two PC92 with one ECC81 (ECC/PCC92 is exactly one half of ECC81). Point to point wiring will be more difficult but still doable. You may also use a smaller choke, or a LR08 regulator plus a power transistor to avoid the choke.

 

[TheGimp]

I built several SE amps based on 6P1P-EV, and get about 2.5W out:


There is a whole thread on it here:

FireFly Single Ended Tetrode

 

[gideon1990]

Some inspiration.

That is so cute, any info on it? Especially where to get such small transformers

 

[FlaCharlie]

14x14 cm sounds great ��

I found a possibly similar design here:

Micro Champ Amp - monster.party.hat

small guitar amp with around 2w

Obviously, the guitar amp is mono and designed to produce distortion.

I know you're in Europe but if you could pick up one of the little Magnavox SE amps via eBay it might fit your needs.

I just modded one using the existing chassis and transformers to create a true SET. It measures about 5" (13cm) by 8.5" (22cm). Here's the link: Flea Power SET - Magnavox 12BH7 Mod

There's also the relatively famous mod by Dave Gillespie over on AK that is based on the same amp but runs the original 6BQ5s in pentode. Magnavox Flea Power: Getting More Out Of The 8600 Series - A Lot More! | Audiokarma Home Audio Stereo Discussion Forums

His design replaces the OTs however, to allow use of 8 ohm speakers. The 12BH7 version I built allows the use of 8 ohm speakers while still using the original OTs.

You might also consider the Fred Nachbaur Mini-Bloc: A Low-Cost Single-Ended Triode Amplifier

I would guess that a stereo version could be built on a very small chassis.

 

[Sorento]

Have a look at this competition for the smallest amp, best output*size product to be more correct.
Bastel-Wettbewerb 2004 - Teilnehmer
Especially Reinhöfer's ZWERG (dwarf) winner design 2x5W output in a 160x55x55 millimeter box 1p24p in pp.
Zwerg
Although Herr Reinhöfer has passed away some years ago, his opts are still available on Audioröhrentechnik Ausgangstrafo Übertrager Bandfilter Spulen Röhren Audio Fassungen 516201 516228 516236 516260 516686 NF-Übertrager Drossel Trafo Hifi Highend

 

[artosalo]

I have such small SE with ECL85 or soviet made 6F5P. 2.5 W is available as an UL.
Both amplifier and the regulator PCB's are available.

 

[Kay Pirinha]

Which output transformers did you use?


Best regards!

 

[artosalo]

I used a cheap polish, was it TELTO 5k2 SE transformer. These amplifiers have been built quite many.
The best results were achieved with Ogonowski LO-SE15-2/1.
LO-SE15-2/1 Transformator głośnikowy SE - Lampy Elektronowe On-Line. Największy polski sklep z technik

Photo of my OPT's.

 

[cgraf]

Cool !

Hi Artosalo
Cool little amp. And I do not have to do a PCB myself 🙂
I would take an amp and a psu PCB with pleasure...

Best regards
Christoph