Posted: Sun Apr 15, 2007 8:25 pm
Hi Guys,
Long time watcher / first time poster!
Firstly Steve - I reckon you have to be one of the most generous and helpful guys on the planet - the work you do here is invaluable to all us "wannabe" amp techs.....
I have been planning a Jube build for a while now and the SDM layouts are obviously central to this - a couple of questions;
1) Has anyone built and validated Steve's extra gain control layout (2550X) - this does seem like a logical mod and a confirmed lack of pop on switching would be nice... otherwise I'll just give it a try!
2) I have PT iron for a 100W but was originally intending to build the 50W with pentode / triode switch. In the past I have successfully switched the outer two power tubes to ground on a 100W build and I figured this coupled to a triode switch on the inner tubes would provide a flexible 100 / 50 / 25 watt amp. The question I have relates to halving the speaker impedance setting when these lower power modes were running: consensus seems to be this is not critical for master volume builds as there is less stress on the output stage compared to the non-MV models running flat out - but would this also hold for dropping down the extra step to 25W? Alternatively would it make any difference if all four tubes were pentode/triode switched to hit 50W with the switch to ground dropping the outside tubes to hit 25W?
Any and all thoughts welcome before I start buying the extra parts....
Long time watcher / first time poster!
Firstly Steve - I reckon you have to be one of the most generous and helpful guys on the planet - the work you do here is invaluable to all us "wannabe" amp techs.....
I have been planning a Jube build for a while now and the SDM layouts are obviously central to this - a couple of questions;
1) Has anyone built and validated Steve's extra gain control layout (2550X) - this does seem like a logical mod and a confirmed lack of pop on switching would be nice... otherwise I'll just give it a try!
2) I have PT iron for a 100W but was originally intending to build the 50W with pentode / triode switch. In the past I have successfully switched the outer two power tubes to ground on a 100W build and I figured this coupled to a triode switch on the inner tubes would provide a flexible 100 / 50 / 25 watt amp. The question I have relates to halving the speaker impedance setting when these lower power modes were running: consensus seems to be this is not critical for master volume builds as there is less stress on the output stage compared to the non-MV models running flat out - but would this also hold for dropping down the extra step to 25W? Alternatively would it make any difference if all four tubes were pentode/triode switched to hit 50W with the switch to ground dropping the outside tubes to hit 25W?
Any and all thoughts welcome before I start buying the extra parts....