OD with cathode follower

[10thTx]

So no tone stack on the clean channel?

I found I hardly ever adjust the bass pot, so I did 3 types of psuedo PAB boost with spdt center off & the mid boost. It actually gives quite a few different tones. And the 250k treble pot does add or subtract some treble.

guess that for the clean mode you will still need a buffer/cathode follower. V1b will be the effects driver in clean mode and will be loaded wrongly if you would use an effect with low input impedance. In OD mode v2a will be the driver for the effects and as it is a cathode follower it will indeed have the proper output impedance.

See schematics for two options in doing that.

I have built 2 amps with just a 5879 pentode as the OD and it sounded very good to me, so I am thinking the CF behind the single pentode would sound good and give an even smoother overdrive?

With respect, Tubenit

[Structo]

Ah, thanks.
I had completely missed that 250K treble pot.

[titser_marco]

Hi! Would you happen to have any sound clips of this? I am considering to do another rebuild based on an ODS but with a cathode follower preceding the phase inverter just because the junk amp I got has an extra 12ax7. Am curious as to how it sounds like if I run a full ODS drive section (essentially 2 12ax7s) into a cathode follower then into the phase inverter. Thanks!

[10thTx]

Here are soundclips of the amp that has the schematic attached to this post. I don't know if that will be helpful to you or not?

http://www.soundclick.com/html5/v3/play ... i&newref=1

http://www.soundclick.com/html5/v3/play ... i&newref=1

With respect, 10thtx

[stelligan]

Does seem a bit more Marshall-y with an ODS like sustain. Cool tones and playing. Allman Bro-ish tones.

[MakerDP]

I built the amp in that last schematic. It is one of the nicest sounding/feeling amps I've ever played.

[titser_marco]

Thanks for the responses guys. Given my current limitations, it seems that I would only be able to build one using 12AX7s. Would this design work (all tubes 12ax7 units):


V1a -> Vol + Tone - > V1b -> [switch] -> trim pot -> v2a -> gain -> v2b -> volume -> v3a recovery -> v3b CF

[MakerDP]

Consider this...

V1a -> vol -> V1b -> MOSFET CF -> Tone -> switch -> v2a -> 5879(v3) -> MOSFET CF -> eff send -> v2b (return) -> PA

V1 - any 12A_7 variety
V2 - any 12A_7 variety
V3 - 5879 pentode
MOSFET - IRF820

I think that would more closely match the feel of what 10thTx is describing and actually is the exact same topology, just uses one less 9-pin socket by replacing one with the two MOSFETs acting as cathode-followers.

edit: I skipped the vol and tone in the OD stage but you get the drift I think...

[10thTx]

Same schematic with mosfet CF substituted. I don't hear any significant change in tone using mosfets in the CF position.

with respect, 10thtx