How much gain can 2 tubes and 12v get you? Answer inside!

[spongebob]

Here's another link I found on the same topic (it's in german, beware! but nice pics):
http://www.jogis-roehrenbude.de/Roehren-Geschichtliches/Niedrigspannungs-Roehren/Niedrigspannungs-Roehren.htm

These vintage 12V tubes are really hard to find, even on ebay, so I started looking for alternatives, anyone ever tried russian subminiature tubes, for example the 1SH24B? (more here)


This seems to be the datasheet, but it's in russian! :wink:

These tubes (pentodes?) are available from pollin.de for 26 cent, is there anything I could build with them? I have no experience with tubes whatsoever, and that would be an easy (and very inexpensive) start!

[Torchy]

Well thanks, ... you did it.
You have ruined my life with your "toobs".
It was bad enough with "Mr Run-off-to-the-groovy" and his sparkly jfets.
I now have another obsession I didn't have before.

Fetzer.
Professor Tweed.
Matchbox.
Sopht tube amp (12AL8)

And a bunch more stuff, but Im going to start with a Ruby-Tuby.
Hey, life just got fun again  :lol:

[petemoore]

I had some old tube Radios, I turned into guitar amps, and A Westinghouse tube powered extension cabinet...also tube.
 Although these amps didn't distort by themselves heavily at all, they were superb sounding late night/low level jamming amps.
 The reports of the tone from casual passers by, and users of the amps was that they sound very good!!!
 I didn't like the high voltage...and finding a suitable input point with the thing on...ya know the old 'touch' method with an insulated screwdriver...sure did make some fine low level jamming amps.
 I'm still looking for that 'gold bag' of tubes around here....
 12 volt tubes?...yup too cool !!!
 Breadboarding, and modding tube ccts. without the threat of high voltage, that's having the good, Without the bad ! ! !

[slajeune]

Hi Spongebob,

I have a few of these "pencil tubes".  A few things worth pointing out:

- The output is very low (i.e. below 10mW)
- They require 'weird' heater voltages (i.e. 1-1.5V).  This can easily be supplied by a AA battery.

Fred Nachbaur as a 'baby design' built using tiny tubes:

http://www.dogstar.dantimax.dk/tubestuf/gallery4.htm

This site as LOTS of information on pencil tube:

http://pw2.netcom.com/~wa2ise/

Cheers,
Steph.

[slajeune]

Just found 2 more VERY interesting tubes:

- 5797 power pentode
- 5798 dual medium triode

Interesting facts:

heater and plate voltage = 26.5 Volts (again, thinking about single power supply design).  The 5797 is rated at .8w max plate dissipation!!!  Hum, I smell another cool experiment.....

Steph.

[Peter Snowberg]

That 5797 looks wonderful! Too bad the mu is only 24 on the dual triode, but three stages of that should be able to do just fine.

Hmmmm..... an oscillator and one of those little RF/IF pentodes would make for a 12V tube tremolo . I need some of these tubes!

Now there's also the four stage 12V tube overdrive pedal to be made here.

I wonder if Sovtek/NewSensor/EH will ever explore this area?

Take care,
-Peter

[aron]

This seems like a FUN and safe amp to explore. I need to try this. It already sounds great!

[Alpha579]

Are there any tubes designed to work at a mid point to the car battery ones and full blown 330v jobs? Something like a 50-100watt valve? Would you be able to use these(if there are any) for 5-10 watt amps?

And also, are there any valve rectifiers made to be used at these 12v levels?

[slajeune]

Hi,

Are there any tubes designed to work at a mid point to the car battery ones and full blown 330v jobs? Something like a 50-100watt valve? Would you be able to use these(if there are any) for 5-10 watt amps?

Most regular tubes can be operated at roughly 100v.  So, if you want to go to 100v, you can use regular tubes.

And also, are there any valve rectifiers made to be used at these 12v levels?

In this thread, Peter posted a very good list of 12v tubes and characteristics.  A few of them have either 1 or 2 diodes.  This could be usefull as a rectifier.

Thanks,
Steph.

[D Wagner]

Steph,

Who is a good US source for these tubes?  What price can I expect to pay per tube?  This project looks really cool and do-able.    

Thanks!

Derek

[tazwolf]

i just ordered some 12U7s and 12AL8s from Antique electronics
www.tubesandmore.com

they were about 3-5 dollars - the most expensive item was the transformer which was 18 dollars.

Can't wait to get them and start breadboarding - by the way can anybody tell me do these tubes glow when powered?

/Taz

[slajeune]

Hi Tax,

Can't wait to get them and start breadboarding - by the way can anybody tell me do these tubes glow when powered?

/Taz

Yes, they do glow and the 12AL8 gets HOT (hotter than the 12U7).

Cheers,
Steph.

[Alpha579]

Tazwolf, which transformer did you get?

[Alpha579]

In this thread, Peter posted a very good list of 12v tubes and characteristics. A few of them have either 1 or 2 diodes. This could be usefull as a rectifier.

Thanks,
Steph.

Looking at the data sheets, it looks like the cathodes of the two diodes/triode are connected :? . If this is right, how can you use them as rectifiers?

[Peter Snowberg]

There are several 12V tubes with diodes in them, but these are small signal diodes and not power rectifiers. The 12DL8 is a good example... it's a space-charge tetrode with two diodes. The diodes are rated at 5mA MAX (each) and the space-charge grid wants 75mA on top of the 40mA that you can pull from the plate. They're good for detector use, but unuseable for supply.

I was looking at one low(er) voltage diode tube and the forward voltage drop was about 10 volts.

Take care,
-Peter

[slajeune]

Hi Alpha,

Tazwolf, which transformer did you get?

At 18$, I guess he went for the Hammond 119DA which is what I am using for the low voltage tubes.

Cheers,
Steph.

[Alpha579]

Cheers Steph, didnt see that...btw, have you actually built a finished version of the sopht? If so, any picys?

[slajeune]

Hi,

Cheers Steph, didnt see that...btw, have you actually built a finished version of the sopht? If so, any picys?

No, not yet.  It's still on the breadboard.  I might take a picture of my breaboard connected to my gibson cabinet just for fun!!!

Cheers,
Steph.

[tazwolf]

Alpha579: The transformer I bought was the Hammond 119DA.

/Taz

[slajeune]

Hi All,

I had a bit of time to play with the amp tonight and I slightly revised the design.  It is now a bit more balanced in the output (highs versus lows) and the distortion sounds just right.  You can see the latest design at:

http://www.sopht.ca/index.php?s=26

I'll try to post a sound clip and voltage readings this weekend.  I might try to sligthly rebias the output tube as it is a bit below spec'd readings.

Cheers,
Steph.