Friedman dirty shirley

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shane
Posts: 129
Joined: Fri Jan 14, 2005 2:18 pm
Location: birmingham UK

Friedman dirty shirley

Post by shane »

Having seen some nice demo's of this amp and being quite impressed! Just wondered if anyone had any idea of its circuit topology and whats going on inside!

Cheers
Shane
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John_P_WI
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Joined: Wed Aug 15, 2007 4:29 pm
Location: Wisconsin

Re: Friedman dirty shirley

Post by John_P_WI »

Rumor and speculation is that it is a JTM45 with an extra gain stage up front, think Dave's "hairy brown eye" mod...
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shane
Posts: 129
Joined: Fri Jan 14, 2005 2:18 pm
Location: birmingham UK

Re: Friedman dirty shirley

Post by shane »

Ahh OK. I've heard of this mod but don't know what it is. Any idea?

Cheers
Shane
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John_P_WI
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Location: Wisconsin

Re: Friedman dirty shirley

Post by John_P_WI »

Your usual California mod, something like a 320k plate load, 2n2 coupling cap, 2k7 cathode r with 0.68uF bypass cap. Big attenuation needed with a v-divider around 1M/68k to the next stage. Look at a chupacabra or any other Cali High gain amp du jour first stage for inspiration. Bypass the plate r if too bright, season to taste...
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M Fowler
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Re: Friedman dirty shirley

Post by M Fowler »

Youtube video description appears to be mix of JTM45 tube recto, 5881 power tubes but has JCM800 type preamp to me. Hi/Lo inputs, gain and MV.
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kdmay
Posts: 52
Joined: Mon Nov 01, 2010 11:26 am
Location: Melbourne, Australia

Re: Friedman dirty shirley

Post by kdmay »

John_P_WI wrote:Your usual California mod, something like a 320k plate load, 2n2 coupling cap, 2k7 cathode r with 0.68uF bypass cap. Big attenuation needed with a v-divider around 1M/68k to the next stage. Look at a chupacabra or any other Cali High gain amp du jour first stage for inspiration. Bypass the plate r if too bright, season to taste...
+1 - that was my guess!

The extra gain stage requires a lot of tuning to get right.

[IMG:800:532]http://i641.photobucket.com/albums/uu137/kurtdmay/Maytone%20JTM/file_zps391e31b9.jpg[/img]

[IMG:800:532]http://i641.photobucket.com/albums/uu137/kurtdmay/Maytone%20JTM/file_zps12326130.jpg[/img]

[IMG:800:532]http://i641.photobucket.com/albums/uu137/kurtdmay/Maytone%20JTM/file_zpse7537efb.jpg[/img]

[IMG:800:532]http://i641.photobucket.com/albums/uu137/kurtdmay/Maytone%20JTM/file_zps7192db80.jpg[/img]

[IMG:800:532]http://i641.photobucket.com/albums/uu137/kurtdmay/Maytone%20JTM/file_zps387b8ad7.jpg[/img]

[IMG:800:532]http://i641.photobucket.com/albums/uu137/kurtdmay/Maytone%20JTM/file_zps78a54e32.jpg[/img]

[IMG:800:532]http://i641.photobucket.com/albums/uu137/kurtdmay/Maytone%20JTM/file_zps60015082.jpg[/img]

[IMG:800:532]http://i641.photobucket.com/albums/uu137/kurtdmay/Maytone%20JTM/file_zps41f451c8.jpg[/img]

[IMG:800:532]http://i641.photobucket.com/albums/uu137/kurtdmay/Maytone%20JTM/file_zps25d2c57d.jpg[/img]

[IMG:800:532]http://i641.photobucket.com/albums/uu137/kurtdmay/Maytone%20JTM/file_zps397def04.jpg[/img]

[IMG:800:532]http://i641.photobucket.com/albums/uu137/kurtdmay/Maytone%20JTM/file_zps15cd78ca.jpg[/img]

[IMG:800:532]http://i641.photobucket.com/albums/uu137/kurtdmay/Maytone%20JTM/file_zpsc29139ec.jpg[/img]

[IMG:800:532]http://i641.photobucket.com/albums/uu137/kurtdmay/Maytone%20JTM/file_zpsde697f60.jpg[/img]

[IMG:800:532]http://i641.photobucket.com/albums/uu137/kurtdmay/Maytone%20JTM/file_zps38d5fac8.jpg[/img]
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Colossal
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Re: Friedman dirty shirley

Post by Colossal »

Freakin gorgeous man. Wow, clean build.
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John_P_WI
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Location: Wisconsin

Re: Friedman dirty shirley

Post by John_P_WI »

Colossal wrote:Freakin gorgeous man. Wow, clean build.
+1000, now that is how it's done Ladies and Gents.

Beautiful, just beautiful.
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Smokebreak
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Re: Friedman dirty shirley

Post by Smokebreak »

Gorgeous! Good idea with that side pot. Is that your heater ground by the input?
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kdmay
Posts: 52
Joined: Mon Nov 01, 2010 11:26 am
Location: Melbourne, Australia

Re: Friedman dirty shirley

Post by kdmay »

Colossal wrote:Freakin gorgeous man. Wow, clean build.
John_P_WI wrote:+1000, now that is how it's done Ladies and Gents.

Beautiful, just beautiful.
Thanks guys! I just love the look of it and the homage to the original, which is of course a homage to the first Marshalls.

It's a big chewy fat tone and certainly nails what I can hear in the original DS clips.
Smokebreak wrote:Gorgeous! Good idea with that side pot. Is that your heater ground by the input?
Yeah the side pot is important in tuning that extra stage and it can go from (all the way off) a great "boost" for the Lo input to (all the way up) a pretty hairy gainy monster! But it really depends on the impedance of the divider and how it loads/compresses that extra stage and the resulting brightness.

And yes, that is the heater ground on the input jack. My attempt at making it a quiet as possible and I think that, with the other anal grounding, certainly helps with the noise floor.
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shane
Posts: 129
Joined: Fri Jan 14, 2005 2:18 pm
Location: birmingham UK

Re: Friedman dirty shirley

Post by shane »

Thats a very nice build! and pretty much answers my original question I'd guess!

Couple of things I'd like to ask you if I may.

What value is the side pot? and is the gain pot wired backwards for any particular reason?
Oh yes and what is that huge cap on the presence control?

Bloody well done mate!

Cheers
Shane
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Reeltarded
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Re: Friedman dirty shirley

Post by Reeltarded »

Seriously angry looking machine ya got there KD.
Signatures have a 255 character limit that I could abuse, but I am not Cecil B. DeMille.
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cbass
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Re: Friedman dirty shirley

Post by cbass »

That's freakin beautiful my builds are such crap I should just quit
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Smokebreak
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Location: Texas

Re: Friedman dirty shirley

Post by Smokebreak »

I'm guessing 1M side pot, so you can get the 68K/1M little gain stage, or run it like 68K/68K Jose or anything in between. Drilling side holes in all my chassis now!
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Roe
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Re: Friedman dirty shirley

Post by Roe »

what kind of OT do you recommend for this type of amp?
www.myspace.com/20bonesband
www.myspace.com/prostitutes
Express, Comet 60, Jtm45, jtm50, jmp50, 6g6b, vibroverb, champster, alessandro rottweiler
4x12" w/H75s
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