Friedman Dirty Shirley thoughts.

Marshall Amp Discussion

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Mark
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Re: Friedman Dirty Shirley thoughts.

Post by Mark »

Did you see the TMB 18 watter built by Richie Hall?

http://www.ceriatone.com/ceriatone/wp-c ... iatone.jpg

There were a few issues with these amps, it was to do with overdriving the output stage as far as I can remember. I think this would be an issue putting the 2204 circuit onto the EL-84's, I think the issue is the 84's have more gain than 34's as well as the grid bias voltage which is around 13 volts as opposed to 30 to 40 volts in 34's. Of course I'm sure this is common knowledge and you know this.
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Mark Abbott
burger
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Re: Friedman Dirty Shirley thoughts.

Post by burger »

sonicmojo wrote: Wed Sep 27, 2017 7:35 am I can be too curious sometimes. Here are some voltages readings from a DS Mini. Sizable PT on this.

Wall Voltage 119.1-119.6 (was creeping up during measurements)
Heaters - about 6.25 VAC
Gain switch on highest setting

V1
1 - 154.6
3 - 1.44
6 - 202.4
8 - 1.736

V2
1 - 168.1
3 - .879
6 - 274.2
7 - 168.2
8 - 169.2

V3
1 - 204.2
2 - 36.1
3 - 52.84
6 - 192.4
7 - 34.43
8 - 52.90

V4
3 - 11.39
7 - 353.1
9 - 346.9

V5
3 - 11.40
7 - 353.5
9 - 347.3
Anyone got equivalent readings for a DS 40?

Or can anyone confirm the output on the PT, is it 345V CT?
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burger
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Re: Friedman Dirty Shirley thoughts.

Post by burger »

Recently finished my own build of the DS40 based on the Pety the Pitbull's preamp schematic along with info gathered across the Net re the exact JTM45 power amp setup. Cracking amp, really happy with it.
http://headfirstamplification.com
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Darkbluemurder
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Re: Friedman Dirty Shirley thoughts.

Post by Darkbluemurder »

I also have converted one of my amps to that circuit. I have 5k6 as default cathode resistor on the second stage and add another 5k6 plus a .47uf cap for a gain boost. I also upped the cathode bypass cap on the first gain stage to get fuller clean tones at low gain settings. And my mid control is a 100k audio instead of a 25k linear. Power amp is 2 cathode biased 5881s.
Great amp, does everything from cleanish to raging crunch.

Cheers Stephan
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M Fowler
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Re: Friedman Dirty Shirley thoughts.

Post by M Fowler »

Well I have built an 18w JCM800 with EL84's and the only thing I had to do was increase the voltage to get it to sound great.

I started with a Matchless Lightning home build I didn't like and converted it to JCM800 so it did have choke and tube rectifier.

I used Weber chassis with Mojotone faceplate

The tube rectifier was converted to diodes with plug in converter rather then take out the rectifier tube socket.

Mark
JCM800 18w gut 2.jpg
JCM800 18w front.jpg
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Guy77
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Re: Friedman Dirty Shirley thoughts.

Post by Guy77 »

Looks really nice Mark! Ever since I built my rocket amp , el84s are my favourite tube! I will have to compare this JC800 preamp to the rocket preamp to see how similar they are. Sound clips if you get a chance!

Cheers

Guy
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M Fowler
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Re: Friedman Dirty Shirley thoughts.

Post by M Fowler »

Thanks,

Mounted the chassis into an 18w Marshall small box 1-12" combo cab and sold it last summer. So not available to me.
LedZepp007
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Re: Friedman Dirty Shirley thoughts.

Post by LedZepp007 »

lovetone wrote: Wed Sep 20, 2017 7:17 am This might help not sure how accurate it is found it an the web a few months back.

It may answer a few questions, may be someone can redraw it.

Cheers
Hey, does anyone know the pot values for this amp? I converted a 50-watt plexi into, essentially, a SS-rectified DS40. The Gain and Master controls are next to useless after you get past noon (becomes far too distorted). Both pots are 1MA, but I’m guessing they should be 500KA or less.

Thanks!
Roe
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Re: Friedman Dirty Shirley thoughts.

Post by Roe »

try a 10% audio taper perhaps
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Express, Comet 60, Jtm45, jtm50, jmp50, 6g6b, vibroverb, champster, alessandro rottweiler
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jayfitt
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Re: Friedman Dirty Shirley thoughts.

Post by jayfitt »

So I'm building one of these. Have everything ordered but the transformers. What OT would you guys suggest for the pair of 5881s? Someone on another forum used a signal generator to determine the OT Dave used is a standard Marshall 50w with 3.6k primary impedance.

-j
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Guy77
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Re: Friedman Dirty Shirley thoughts.

Post by Guy77 »

I believe there are a lot of 3.3K models built by various companies like Hammond and others. Then you could switch between 3.3K and 6.6K like the JTM45 had. Or go with 3.6K and you could switch it to 7.2K by moving one step on the dial. JM2C

Cheers

Guy
Mark
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Re: Friedman Dirty Shirley thoughts.

Post by Mark »

I'd talk to Brian Wallace of Marstran, he knows his Marshall style transformers.
Yours Sincerely

Mark Abbott
burger
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Re: Friedman Dirty Shirley thoughts.

Post by burger »

Dave has confirmed that the DS has a 50w plexi style OT - with a 3k6 primary.
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guitarmike2107
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Re: Friedman Dirty Shirley thoughts.

Post by guitarmike2107 »

tweedeluxe wrote: Sat Sep 09, 2017 2:22 am I've repaired two dirty shirley amps in which the internal can caps were miswired. One of the anodes grounded, the other at HVDC, with a voltage divider built off it for a positive DC heater reference (but mistakenly wired to the cathode).

Once wired correctly, both amps sounded VERY good, in my opinion. Before that, only so-so. You can see the miswired cap in the attached photo.
Wow, that is not what I would expect for a amp that sells for that much, chassis is not even welded. I assume this is one of the earlier ones??

Thanks for sharing the photo though
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ampmike
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Re: Friedman Dirty Shirley thoughts.

Post by ampmike »

I got the bug on for one of the mini dirty Shirley 'Going to look for a used one.I think there's a few on reverb,my wife will kill me I'll be taking a chance. :D
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