Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => PC Express and JSchem - Schematics and Layout diagrams => Topic started by: Geezer on January 30, 2011, 01:07:50 pm

Title: HoSo56 amp (revised) "psuedo channel switching"
Post by: Geezer on January 30, 2011, 01:07:50 pm

OK, made a few small (but important) changes in the HoSo56 II & it's the best yet.
I have played it w/ the band & it was the most natural sounding, fun to play & easily cuttin' thru the mix amp I've built.

The changes?
After reading Merlin's info about using grid stoppers to sculpt overdrive sections ( http://www.freewebs.com/valvewizard/gridstopper.html ), and using some of the experience I've gained from the Dumble-style builds, I added some strategic stoppers to the OD "channel" only.

Schematic attached

It really smoothed out the OD, giving it a pleasing tone & removing any hint of blocking distortion. It also gets the "vowel"-like tone when you dig into the strings....very touch sensitive to that.
I was also able to increase the V2a Rk cap from 0.68u to 4.7u & remove the 68p bright cap (although, as always, these should be tailored to your own taste if you build this amp).

Wow!
This amp is more "Dumble" sounding than any of the "real" D-style amps I've built, plus it's a very simple circuit.

Geezer

Title: Re: HoSo56 amp (revised) "psuedo channel switching"
Post by: tubenit on February 03, 2011, 06:47:57 pm

Here is a DRAFT Bill of Materials for Geezer's revised HoSo56.

PLEASE check this against the schematic and layout.

I suggest ordering extra resistors and caps from Hoffman for "tweaking" purposes.

With respect, Tubenit

EDIT:  I have added a version to try using 6V6's and a PPIMV.  The tone stack values, the coupling cap value changes and the 100uf power tube cathode cap allow for a tighter bass response.  The tone stack values give the amp less chime and crunch and more smoothness instead.  4-13-2015