Friedman Dirty Shirley thoughts.

Marshall Amp Discussion

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Mark
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Friedman Dirty Shirley thoughts.

Post by Mark »

The Dirty Shirley amp is very Marshall like it's sort of like a cross between JMP-50 and I and JCM 800. I tried one yesterday and I really didn't know what to think of it. It seemed to me that speakers were very important to this amp. The Vintage 30 didn't seem to work for me.

Has anyone else tried this Friedman amp?
Yours Sincerely

Mark Abbott
mojotom
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Re: Friedman Dirty Shirley thoughts.

Post by mojotom »

I did build an amp with a similar preamp/PI and like it a lot but I noticed I needed a good Creamback/G12M/G12H30 cab to balance the amp (I would have thought so with a higher gain Marshall preamp).
I tried various speakers and got the same feeling as you, especially my favorite 10' (supposed to work on everything). Even plug an Alnico as a test (White one) and it was awful.

So for me very speaker dependent. But I thought it was the case with all higher gain Marshall type preamp (CAE 3+ ch 2 topology is very close to the DS and always enjoyed a greenback cab) and with those kind of amp never like the V30 bite.
Mark
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Re: Friedman Dirty Shirley thoughts.

Post by Mark »

Thanks for your reply, the more I think of if the more the Dirty Shirley isn't my sort of amp. I much prefer the AFD amp to the Dirty Shirley.
Yours Sincerely

Mark Abbott
mojotom
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Re: Friedman Dirty Shirley thoughts.

Post by mojotom »

I have to take a look at that AFD schem I got. It seems very close.

I like that DS myself, kind of a stoner amp but like I said I didn't try a Friedman, I just build a 6V6 based amp along the line of the DS.
Maybe you don't like the bass resonance due to the 220k/4n7 network before the feedback R. I used a pot instead of the 220k and a switch to choose between 4 and 8r feedback. It did sound more vintage without the network, more modern with it. Same for 4R feedback R vs 8.

What do you like on the AFD vs the DS ? I'm interested !
tweedeluxe
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Re: Friedman Dirty Shirley thoughts.

Post by tweedeluxe »

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.
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mojotom
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Re: Friedman Dirty Shirley thoughts.

Post by mojotom »

Thanks for the picture !
Mark
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Re: Friedman Dirty Shirley thoughts.

Post by Mark »

Likewise thanks for the picture. What is wrong with the cap wiring I can't quite make it out.
Yours Sincerely

Mark Abbott
Mark
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Re: Friedman Dirty Shirley thoughts.

Post by Mark »

Likewise thanks for the picture. What is wrong with the cap wiring I can't quite make it out.
Yours Sincerely

Mark Abbott
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mhartman
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Re: Friedman Dirty Shirley thoughts.

Post by mhartman »

What's the deal with the Phase inverter? Where you normally see 1M-470R-1M, the DS has 470k-470R-1M. I haven't played with this type of setup, does anyone know the effect of putting it "off balance" like that?
tweedeluxe
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Re: Friedman Dirty Shirley thoughts.

Post by tweedeluxe »

It's hard to make out but you can see one positive lead of the internal f&t cap is wired to ground. The 470k won't affect the "balance" at all, it just drops the PI input impedance down to a bit less than 1M (from 2M), so it will move that corner freq up an octave and load down the preceding circuit slightly more.
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mhartman
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Re: Friedman Dirty Shirley thoughts.

Post by mhartman »

tweedeluxe wrote: Tue Sep 19, 2017 3:54 pm It's hard to make out but you can see one positive lead of the internal f&t cap is wired to ground. The 470k won't affect the "balance" at all, it just drops the PI input impedance down to a bit less than 1M (from 2M), so it will move that corner freq up an octave and load down the preceding circuit slightly more.
Thanks!
lovetone
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Re: Friedman Dirty Shirley thoughts.

Post by lovetone »

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
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Mark
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Re: Friedman Dirty Shirley thoughts.

Post by Mark »

Got to love Pety, he has more stuff but it is different to access on the iPhone. Post it if you can get it.
Yours Sincerely

Mark Abbott
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sonicmojo
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Re: Friedman Dirty Shirley thoughts.

Post by sonicmojo »

Does anyone know how the three-way gain switch is implemented? I'm assuming it is probably just ground resistors to the gain pot but it's not reflected in that schematic so maybe it is just on newer versions of the amp.
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Bryan
populartsl
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Re: Friedman Dirty Shirley thoughts.

Post by populartsl »

Its basically different values of resistors and capacitor on the 2nd gain stage cathode.
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