Convert Dogzilla for Hi-Fi output

[tryonziess]

I had previously posted with my plan to build an amp with the supply of 807 tubes I have on hand. Fred Nachbaur has done a superb job of detailing the build of the Dogzilla amp on his website. What I would like to know is what exactly makes this design an instrument/guitar amp? There are numerous schematics posted on the web for Hi-Fi amp designs and I do not see the tremendous difference in the overall layouts.
Since the Dogzilla build is so very well layout out at Fred's site what changes would have to be implemented to make it Hi-Fi quality.

Tad

[tryonziess]

Here is the link to the Dogzilla amp.
DOGZILLA - Power Amplifier

Tad

[DF96]

General comments (not about any amp in particular).

Hi-fi has wider OPT bandwidth, lower distortion (hi-fi often deliberately avoids distortion, guitar amps often deliberately include it). Guitar amps have large grid stoppers, which actually work down to the upper audio range - instead of preventing VHF parasitic oscillation they set the treble limit for the amp - but this means that poor layouts will not oscillate. Guitar amps often have excess gain, but then lose it in tone stacks, voltage dividers or clipping.

They really are quite different animals!

[Miniwatt]

After building a few hifi amps I ventured into building a guitar amp, and realized I had to start over learning. Quite striking how all that's important in a hifi amp is to be avoided in an instrument amp..

OTOH, the power amp schematic you posted seems fine to me for hifi. The preamp is where the most harm is done

[tubelab.com]

Assuming that you are not including the guitar amp specific front end, I have two comments about the amp circuitry itself. Fred stated that C26 imposes a 15 KHz upper frequency limit. This is actually C25, eliminate it. Fred also states that he is using a 100 watt OPT at the 200 watt level and deliberately mismatching it. This is acceptable in a guitar amp since the lowest note on a guitar is 80 Hz. If you want 200+ HiFi watts you need a 200+ watt OPT rated for 2500 ohms. The big Hammonds are 1900 ohms which is probably OK with 6 tubes, but better handled by 8. The 1650T is good for 120 watts and the 1650W is good for 280W. I am using a BIG Plitron toroidal OPT that is rated for 400 watts and 1250 ohms. It works great at 2500 ohms up to 300 watts or so. The rest of the output (Part 5) and driver (part4) circuitry does not contain anything that would restrict it to guitar specific applications.

[tryonziess]

These answers are exactly what I was looking for. Being very new to tubes and DIY audio as whole I thought that this layout with all of the data included would be a nice place to jump in.
I was thinking on using a much larger output transformer than the single 100 watt Hammond. If there are anymore small changes or improvements that would help this build in Hi-Fi please feel free to add them.

And Tube we are all aware of your and a few other members fabulous deal on the 400 watt Plitrons. It is a wonder the cops did not come for a visit at the price you all paid. Real good heads up. I have been visiting there site a couple of times a week looking for something as good.

Get this nice project up and running and the GU-50's then on to the MC3500 build. I have been researching the unity coupled aspect of the Mac amps and it seems quite a complex winding job. Also, the elements related to loading each output separately in the OP tranny. They say it cuts the impedance to one quarter of total with the tubes run on the edge of max.

May be years before I get that project done. Just one at the time. And thanks Tad