12ax7 on G9 Preamplifier

[Gearsix]

Hi to all, this is my first post on this forum and I'd like to know if there is a way to use 12ax7 tubes instead of 12au7 in the Gyraf G9
I know that these tubes are different, but I have some nos Siemens tubes that I'd like to use in a important preamp project

 

[sam system-d]

Hi and welcome here, there's a ton of information in the meta about this. If I remember right, you should stick to the 12au7... take a look here :
http://www.groupdiy.com/index.php?topic=3514

edit :
even better :
http://www.groupdiy.com/index.php?topic=3586.msg359339;topicseen#msg359339

 

[gemini86]

Ax7 in the output section won't drive a transformer very well. Ax7 in the input will slam a ton of gain into the srpp output, and that topology doesn't sound good overdriven, imo. You can of course drop some gain off the first stage.

 

[Gearsix]

Thank you very much for the quick replies
So I have no chance to use the 12ax7 ... I'll save them for future projects!