Brian May Ac30 vs Ac30hw vs Dr Z Mazariti GT

[cap217]

I read somewhere that the Mazariti GT by DR Z was based on a Komet. But I also read that it ended up the same as the Brian May ac30 model with 1 knob. That got me thinking that this might be the same as the vox ac30hw HOT TB circut where it takes the tonestack out (I think).

Anyone know these circuts and care to comment?

[rooster]

I think you are looking at things in an odd way? The BM model is the Normal channel typically found in the AC30/6. This is a single triode stage going into the PI, no tone stack. Are you familiar with the EF86 tube and how it was used by Vox prior to the AC30/6. It's a triode/pentode going into the PI without a tone stack. As you can imagine, there is more gain to be had in the second example. Not clear on the other amps you mention but these are the options. Just look for the EF86 in the tube compliment, that will probably answer your question.

BM gets added gain from his germanium treble booster, BTW.

[M Fowler]

And the BM amp has a fixed 220k resistor and .0047 cap for the high cut circuit rather then 250k pot/cap.

The Mazarati GT by DR Z is not based on a Komet, completely different circuit. The Mazarati went through many changes before it became the GT version.

[cap217]

And the BM amp has a fixed 220k resistor and .0047 cap for the high cut circuit rather then 250k pot/cap.

The Mazarati GT by DR Z is not based on a Komet, completely different circuit. The Mazarati went through many changes before it became the GT version.

Going to send you a pm

[randalp3000]

It was me, I said the BM and GT were a bit similar.

https://tubeamparchive.com/viewtopic.php?t=20221 here's the info on the BM and my quote. If I understand this correctly both these amps are 2 gain stages in series with a single volume control. The GT having a tone/cut control with a .01 cap instead of the vox .0047. There is a schematic easily available for the GT on the net but it is a bit different from one of my GT's I have traced.

More info, the Mazerati V1 is a 4 el84 version of the Carman Ghia with a smaller OP trans. The V2 is the same with larger OP trans, the GT is a totally different beast.

[JoeCon]

Here's the BM schematic I've seen. Looks like the Normal channel uses only 1 gain stage ( thru his Rangemaster first I'm sure) but there is another input marked Booster which looks like both sections of the tube get used.

Wow single control of volume and no tone stack this is a minimalists dream amp!! Even I like at least a Tone control to go with the Volume...

[cap217]

I wonder if the ac30HW hot/cool option was based on the BM no tone stack idea? In cool, it works as a normal TB ac30. In hot, it drops the tone stack and sounds ultra aggressive.

This is why I asked. As for the GT, I just thought this was the same idea but I am probably wrong.

[Masco]

The BM has the robust choke filtered plate supply.
Here's all the BM info I have:

Edit: Just realized I attached the power amp twice and forgot the preamp. Here's all 3 Fryer schems.

[rooster]

Masco, these are nice looking documents. So this is unique for an AC30 based amp, running the B+ through a choke before it sees another stage. Hm, any chance of learning the resistance of this choke? Thanks.

So the screens in this amp are seeing more voltage (relative to the plates) than they would in a trad AC30.

[Colossal]

Masco, these are nice looking documents. So this is unique for an AC30 based amp, running the B+ through a choke before it sees another stage. Hm, any chance of learning the resistance of this choke? Thanks.

So the screens in this amp are seeing more voltage (relative to the plates) than they would in a trad AC30.

Choke is 7H. I ran a sim on it and get somewhere in the 140-155ohm DCR range. The drawings Masco provided are the Greg Fryer version. The documents for the Brian May one knob AC conversion are by Dave Peterson of Shere Sound.

[M Fowler]

Colossal we never did build this amp, oh well we don't need anymore stinking amps.

[Masco]

So the screens in this amp are seeing more voltage (relative to the plates) than they would in a trad AC30.

FWIW, individual screen R's have been increased.