EL84hrm

[10thTx]

Very grateful!! Thanks for sharing it. Very kind of you.

With respect, 10thtx

[dcribbs1412]

Thanks for sharing
going on the list

[M Fowler]

Colossal;

Dave is this one different then the one I have already?

Mark

[danotron]

thanks for sharing....nice drawing too...BTW

[Colossal]

Dave is this one different then the one I have already?

Hi Mark,

Yes it is different. The one posted reflects the specifics of Mat's amp. The one I sent you is just stock 101HRM mated with the stock AX84 power amp. Mat made quite a few changes, tailoring the HRM to his tastes (very tasty!) and is also using a different PT and a modified power supply.

[M Fowler]

Thanks Dave, now the secret is out about your great schematics

Nice work as usual.

[danotron]

What did you use for the drawing?

[10thTx]

Is the bright switch on the volume a DPDT with center off?

How much of the time do you use the mid boost?

What is the purpose of the 22M resistors on the PAB switch?

The grid resistance value going straight into the EL84 is 280k & there is
no dropping resistor to ground like you'd see on a Hi-Octane. Correct?
(with cathode not fixed bias)

with respect, 10thtx

[Colossal]

What did you use for the drawing?

I use EazyDraw for Mac. <i>Very</i> powerful and easy to use.
http://eazydraw.com/

[Colossal]

Is the bright switch on the volume a DPDT with center off?

10thTx, yes, that is a center-off switch. I will update the drawing to reflect it.

The grid resistance value going straight into the EL84 is 280k & there isno dropping resistor to ground like you'd see on a Hi-Octane. Correct? (with cathode not fixed bias)

I saw that myself but copied Mat's schematic verbatim. That was how it was shown but there's got to be a grid reference. The AX84 HO power amp uses 1MA to ground in that position with a 5k6 grid resistor. Both the AX84 and Mat's amp are cathode bias. Mat used 120R/220uF where the AX84 is 130R/100uF.

Perhaps Mat will chime in here to clear up the grid issue.

[10thTx]

Reviewing the schematic, perhaps the Mstr Vol is acting as a grid reference? However, it would make sense to me to have a fixed resistor to ground in there also?

Thanks for the replies! This is an intriguing amp and I sure like the sound clips that were posted. Very cool tone to it, IMO.

With respect, 10thtx

[Colossal]

Reviewing the schematic, perhaps the Mstr Vol is acting as a grid reference?

On the AX84 schematic, that is definitely the case. The 1MA is acting as the grid reference, just in front of the 5k6 grid resistor.

I heard back from Mat. The Mini HRM schematic is correct as shown with 180k and 100k in series as the grid resistor for the EL84. He found that this (280k) sounds best. The 1MA Clean Master and 1MA OD Master act as the grid-to-ground reference, depending on which channel is selected of course.

I corrected several typos and housekeeping issues on the schematic and posted the updated version (page 2 of this thread). I removed the optional fixed bias circuit as the output would need to be changed from what Mat had and I do not want to add confusion to what is basically straightforward and already sounds great as is.

[paisley_tele]

can anyone make that into a layout

[mat]

http://soundclick.com/share?songid=8956976

Strat clip with Kinmans on it. Drive full, PAB on, Midboost on + I upped the internal prevolume trimmer to 1:00 o'clock. Drive master at 12:00. Guitar volume not full on the beginning of the clip. First take. Horrible

[Structo]

Man that must be an awesome studio recording amp.
Sounds great!