Peavey Donar amp layout, updated... again

[Bob-I]

I picked up a Peavey Classic VTX chassis on ebay for $40. The owner claimed it was operational until a fuse holder broke. I have no desire to fix this hybrid SS preamp/Tube power amp.

I've gutted it and I'm planning to use the iron for a Dumble clone. The OT us UL so I figured I'd go ahead and use the UL taps just to see the results, easy enough to change if it doesn't work out.

I drew up this layout based on Norm's hybrid layout. I won't be using reverb so I took that part out, and replaced it with an HRM tone stack. I haven't completed the tone stack switching yet but I will include bright, mid boost, jazz/rock and boost. Some will be push pull pots and others will be mini toggles.

This chassis is huge, 25" wide so there's plenty of room. Check out this layout for obvious mistakes.

Thx.

EDIT: Since the max resolution is 600x400 I cut this into the 2 main sections to add detail.

EDIT: I completed the layout and uploaded a hi-res hpg to an ftp site. You need to download this to get the full resolution.

http://www.patmedia.net/bob-ingram/DClo ... 0Board.jpg

[Bob-I]

:added

[Bob-I]

54 views and no comments?

[Chad]

I wish I could coment Bob-I but your knowledge far exceeds mine But I would like to use your version of Norm's layout with the HRM stack on my recent build,But I can't get a clear Res. when I bring up the files. I hope that I can get a good look soon though ! Thank's, Chad

[Normster]

54 views and no comments?

Actually, it was just six of us each looking nine times.

Looks good, Bob. I may use this in my 100W build.

[Bob-I]

54 views and no comments?

Actually, it was just six of us each looking nine times.

Looks good, Bob. I may use this in my 100W build.

Then you should each be able to find 9 mistakes

I'm hoping for a verification of the tone stack wiring, especally the switches.

Sure, steal my work ... wait... I started with your layout.... never mind

[dogears]

Hi Bob!

Here is my obligatory point out the mistakes bit.....

The HRM treble cap is 500pf. The 330pf on the schematic is confirmed inaccurate.

The HRM amps must use the lowgain network to feed V2a. 470k w/47pf bypass cap into 200k into 25k trimmer w/4.7k tail. Adjust with PAB engaged only.

No snubbers.

I'd try a 180k on the V2B grid. Compare the 150k to 180k, it is noticeable. 180k was the usual value.

The 500pf grid bypass on CL2 really fattens things up. That is the preferred Dumble value. In fact, aside from one possible amp, I have only ever seen 500pf in this position. Use a full 500pf, not 470pf

The regular tonestack should have a 330pf treble cap. If you use the 270pf, the HRM OD tone will suffer as the amp is designed to be run in PAB mode.

5uf on V1b and 1uf on V2b. This is crucial!

V2a cathode is 2.7k

OD master should have no bright cap. Important! The Dumbles did not use it, except in a couple of cases. Even then, 30pf is way huge.

Non Skyline stack deviations are OK (except treble cap) as the amp is designed to run PAB mode in OD

Super critical.... The Drive pot must be a 250k! Or, use a .0033 cap instead of the .0022 to feed a 130k that then feeds your 100kb pot. This maintains the correct knee for HRM tone.

You are missing the 100k resistor between the HRM treble trim and the OD master.

Sorry to be obnoxious with my changes, but I did spend over 6 months tweaking my HRM with every combination of values. Some thing are gray but then there are things that are plain wrong and sound really bad.....

Call me if you want to chat!

[Bob-I]

Hi Bob!

Here is my obligatory point out the mistakes bit.....

The HRM treble cap is 500pf. The 330pf on the schematic is confirmed inaccurate.

Excellent. I was questioning that one.

The HRM amps must use the lowgain network to feed V2a. 470k w/47pf bypass cap into 200k into 25k trimmer w/4.7k tail. Adjust with PAB engaged only.

Again another question. I saw that one the schematic but it didn't make since to me. That's an easy one to fix.

No snubbers.

You know, I knew that....

I'd try a 180k on the V2B grid. Compare the 150k to 180k, it is noticeable. 180k was the usual value.


The 500pf grid bypass on CL2 really fattens things up. That is the preferred Dumble value. In fact, aside from one possible amp, I have only ever seen 500pf in this position. Use a full 500pf, not 470pf

Gotcha

The regular tonestack should have a 330pf treble cap. If you use the 270pf, the HRM OD tone will suffer as the amp is designed to be run in PAB mode.

Really? PAB mode whenever OD is engaged. Sounds a bit limiting but I trust you.

5uf on V1b and 1uf on V2b. This is crucial!

I knew dat.... really I did.

V2a cathode is 2.7k

OD master should have no bright cap. Important! The Dumbles did not use it, except in a couple of cases. Even then, 30pf is way huge.

Non Skyline stack deviations are OK (except treble cap) as the amp is designed to run PAB mode in OD

Super critical.... The Drive pot must be a 250k! Or, use a .0033 cap instead of the .0022 to feed a 130k that then feeds your 100kb pot. This maintains the correct knee for HRM tone.

You are missing the 100k resistor between the HRM treble trim and the OD master.

Gotcha

Sorry to be obnoxious with my changes, but I did spend over 6 months tweaking my HRM with every combination of values. Some thing are gray but then there are things that are plain wrong and sound really bad.....

Call me if you want to chat!

Don't be sorry, you've always been right in my book. That's why I posted before building.

I'll give you a call when I get closer, I'm in planning mode now, another week or so before the power up.

Thx Scott, you're always a big help.

[Pete]

I'm following this and would like some clarification (thank you)

5uf on V1b and 1uf on V2b. This is crucial!

I thought the dogears recommendation was 5uf, 1uf (or 1.5) then 5uf and 5uf. Or is that for the non HRM only?
With 5, 5, 5, 1 for HRM?
Just wondering
Pete

[tonelab2]

25"chassis
What about adding the dumbleator(relay/switchable) to make
things more interesting since you have the room.
The layouts are to blurry for my poor eye sight.

[Bob-I]

25"chassis
What about adding the dumbleator(relay/switchable) to make
things more interesting since you have the room.

I was thinking of that, but for a later addition. Thx for the suggestion.

The layouts are to blurry for my poor eye sight.

Download the one on my ftp site, link above. It's much clearer.

[Bob-I]

I updated to dogears suggestions. I also reworked much of the layout.

I'm also hoping to hear what folks think of the UL output section. It may be a bad idea but the taps are there so why not try it.

http://www.patmedia.net/bob-ingram/DClo ... Board2.jpg

[tonelab2]

Thx for the Link, my eyes are getting that bad I missed it in your first post.
I have a couple of DR OTs with UL taps one of which I had planned for a
6v6 ODS but have no idea how well it will work. I'll be a keen watcher of your project.

[Darkbluemurder]

I'm following this and would like some clarification (thank you)

5uf on V1b and 1uf on V2b. This is crucial!

I thought the dogears recommendation was 5uf, 1uf (or 1.5) then 5uf and 5uf. Or is that for the non HRM only?
With 5, 5, 5, 1 for HRM?
Just wondering
Pete

5,1,5,5 works great for non-HRM. That's what I use in 2 modded amps.
Another has 5,5,5,5 but I will reduce it to 5,1,5,5.
I understood from Dogears that for HRM you need plenty of bass before the OD, i.e. 5,5,5,1.

[dogears]

Right......

HRM gets loads of bass up front. Then trimmed on the ass end. It leaves lots of overtones. My amp has switching for fat CL2 or OD2. Both ways sound great but the traditional way is the recognizeable tone with the artifacts. The thin/fat way is softer attack and more bloom. But, lacking the harmonics.