Tube stuff help...

[gf]

Hi,

I've been checking this forum lately, but this is my first post.

I don't own an amp, and I want to build a good sounding amp, but I want to work only with low voltages (30v or less).

First I wanted to build a solid state amp, but then I found the 12AE7 low voltage tube(it is a dual triode, medium mu, low mu).

I don't know if this idea will will work, but I was thinking on using a 12AX7 with low voltage to get the signal to 12-15v, and then passing this signal to the 12AE7, so it will be clipping the signal, and you will get a tube overdrive. I don't know if a hard overdrive can be produced, but I believe that a nice clean sound for the clean channel can be produced.

Also, I was searching the web and I found this site that have two low voltage tube amplifiers (maybe the owner of this site is a member here) designed to be used with batteries. What do you think of using these designs for a guitar amplifier ?

http://members.aol.com/sbench101/

The last idea is to take the output of a low power amplifier like the one mentioned, and use an op amp to get higher power.

Please reply with your thoughts,

Gabriel

[Paul Marossy]

You could use an LM386 at the end of the circuit to boost the output. That would make your amp probably around 1/2 watt or so, and it should be fairly loud.

[slajeune]

Hi gf,

first off, I don't think that it is possible to have a 12-30V output from a 12AX7 at starved plate voltages.  I have played with low voltage 12AX7 (although the voltage was at 12V) and I could get some distortion when using 2 12AX7.  But even that distortion was fairly tame.

You are running the tube outside of it's linear operating points and therefore, you can achieve the 100 gain figure.

Low voltage tubes do seem very interesting!  Have a look at the 12U7, it's a low voltage medium mu tdouble triode somewhat like a 12AU7 (i.e. gain of 20).

There was some talk on the ax84 forum about a 'working' low voltage all tube amp (i.e. 30V max) using 1 x 12U7 as a preamp and 1 x 12K5 as an output tube.  Although the volume is expected to be low (i.e. in the milliwatts), this could be good enough for bedroom practice.

Cheers,
Stephane.

[gf]

Thanks for the answers