Valvecaster noob

[demym]

Hi,

i have finally built a Valvecaster (but using a 12AX7, tomorrow i'll get a 12AU7, and running it at 9V).

The layout from which i've got it from is here:



I used a 50k trimmer for the gain pot cause i didn't have the pot.

It fires up, the tube (12AX7) glows, and it also sounds crunchy. But when i turn the (GAIN) trimmer, i don't get more or less gain, but it acts more as a jfet biasing trim... you know, that spot come and go kind of thing.

Could it be because i'm using a 12AX7 instead of a 12AU7 ?

Also, will it be more gainy with a 12AU7 ? 12AT7 ?

Thanks in advance

[anchovie]

Could it be because i'm using a 12AX7 instead of a 12AU7 ?

Also, will it be more gainy with a 12AU7 ? 12AT7 ?

Yes, this circuit is really hit-and-miss with a 12AX7, especially at 9 volts.

By "more gainy" do you mean "more loud" or "more distorted"?

[demym]

i mean more distorted.

is it possible to provide more voltage to the (grids?) while operating still at 12V ? Are there some benefits ?

thanks a lot.

[Cardboard Tube Samurai]

Just use a 12AU7 and run it at 12(.6) volts and you'll be very happy

[demym]

Ok, i'll try that tomorrow.

But, for example, the Tube Star of Renegadrian runs at 48V and more... how does the tube get 12.6V from that voltage ? (very noob question i know).

Thanks anyway

[phector2004]

use a voltage multiplier. (MAX1044, but there are better ones I haven't gotten around to buying yet...)

You split your 12V into a) the multiplier and b) the heaters

Multiplier then goes through caps and diodes to double/triple/quadruple/n-tuple the original voltage. The current supply from the multiplier isn't too high though, so you can't power heaters with it. You power them directly from the wall wart.

[demym]

where in the circuit at the beginning on the post do i connect B+ and where do i connect the 12V for the heaters ?