thinking about a 5g9 with 5y3 and princeton eq. how's that?

[pietro_moog]

hi guys.
i have a 5f2a with a 10" speaker, i like it and it's not that loud. a few weeks ago i heard a 5e3 of a friend and that's a really nice amp!
unfortunately that's really too loud for me but i feel i need a push-pull amp, i wanna rely on my 10" speaker inefficiency.

so, i'd much prefer the 5g9 design, i LOVE tremolo and that is said the best.
i don't need 2 channels like the original, i need an EQ, like maybe the princeton reverb (maybe without the cathode cap..)
do you guys think this thing is going to have too much gain to be clean (a nice clean) ?

second, since my PT is the hammond replacement one with 325v primaries, a gz34 would land me in the 400v territory, so i wanna stick with my 5y3. do you guys see something wrong about it? i wanna use variable bias.

and last thing, i'd like the option of NFB (since 5g9 doesn't have it), but i don't think it's going to be a problem.


my ultimate goal is a nice 10-15w amp, with an eq, nice break-up, super nice tremolo, moderate output volume (less than 5e3, more than 5f2)
what do you think you guys of my idea? is there something wrong?

thanks guys

[tubeswell]

The stock 5G9 circuit is great.

[pietro_moog]

yeah, i guess so. but i don't need 2 channels, i need one eq, and the rectifier thing is just for using stuff i already have..
i guess i'll come out as a sort of fender/mini plexi. could be cool. i'm even thinking about configuring the first stage as gain stage+ cathode follower driving eq, master volume and tail pair PI. low gain but it can be nice. i have to think about that.

i'll make a video sample when i'll finish

[tubeswell]

If you only want one channel, you could wire the V1 stage as a switchable parallel/single triode (using two tip-switching input jacks) and then have a tweed princeton vol and tone control setup going into the LTP. Just sayin'.

[pietro_moog]

are you saying that the amp has a ton of gain of his own?

[tubeswell]

No its only about a 12-15W amp (depending a bit on the size of the output tranny you use). But that's what you get for 2 preamp stages (including the LTP) and a pair of fixed bias 6V6s. The stock circuit starts to break up around 8 but never gets very gritty. But they take pedals verrry well, and when you stick a boost/gain/OD pedal in front, it turns into a screamer. With the V1 tube stages in parallel it has more drive, it you cascaded them there would be even more (but you might want to experiment a bit more with coupling of the stages a freq roll-off points etc if you did that, because of the way in which the extra stage would affect the sound). I've attached an untried design for switchable single/parallel V1 derived from Merlin Blencowe's suggestion in his 1st book, which is another possible way of tackling that - but I have not implemented this myself yet, so no guarantees.

[pietro_moog]

that's an intelligent design, thanks for the advice.
what do you mean with LTP as gain stage? i thought it was unity gain, just better balanced than a cathodyne

[Bruce / Mission Amps]

Hmmm... less volume then a 5E3 but more then a 4 watt Class A SE Princeton?
Yikes!! A really good running 5E3 only makes about 10-12 watts.
A good running tweed 5E11 Vibrolux is about the same 10 watts or so but uses a 10" speaker.
How about a cathode biased 5E11?
Although not the same, take a look at a tweed Harvard too.

[pietro_moog]

Hi Bruce. i'll take a look at those designs, but my mind is almost set for now.
i'm thinking a classic BF preamp with no cap on the cathode after the eq, and a tube screamer for plexi-crunchy stuff.
the only thing i miss to figure out now is how i wanna build this NFB option.

cathode biased? i don't know, what's the sonic difference between fixed and cathode one?

[tubeswell]

what do you mean with LTP as gain stage? i thought it was unity gain, just better balanced than a cathodyne

Quote from Ch 8 of Merlin Blencowe's 1st book 'the gain to either plate of a LTP is about half that which it would be obtained from the same single triode if used as an ordinary gain stage with the same plate resistor'. In other words its not unity gain - there is an actual increase in gain.