Debate on Eddie's Plexi

[jcm800nut]

I think it is pretty much summed up in George's 68 kit. Here is a clip, guitar, Echoplex and 68 Metro 100w; volume on 8:
http://soundclick.com/share?songid=9451688" onclick="window.open(this.href);return false;
I'm not saying this is the exact tone (low E string snarl is not there yet), but allot of the earmarks are there for an amp that is not even broken in yet.

Dude! That is smokin'! Only 2 gain stages, and only on 8? It sure has the crunch, man. That is just the stock '68 kit setup with an echoplex in front?

[rgorke]

Not being a techie, I've been following this thread with great interest from the sidelines. Is there someone who could sum up all the findings in layman's terms?

Was it simply a 12 series Plexi with a bass mod and later, a JMP OT? Any help would be greatly appreciated, b/c all of the cap values are like Greek to me. Thanks.

Bill

I think it is pretty much summed up in George's 68 kit. Here is a clip, guitar, Echoplex and 68 Metro 100w; volume on 8:
http://soundclick.com/share?songid=9451688" onclick="window.open(this.href);return false;
I'm not saying this is the exact tone (low E string snarl is not there yet), but allot of the earmarks are there for an amp that is not even broken in yet.

Are you serious? That sounds fantastic.

Please start a thread with this rather than having it buried in this one.

Almost as good as your pod

[Strat78]

I think it is pretty much summed up in George's 68 kit. Here is a clip, guitar, Echoplex and 68 Metro 100w; volume on 8:
http://soundclick.com/share?songid=9451688" onclick="window.open(this.href);return false;
I'm not saying this is the exact tone (low E string snarl is not there yet), but allot of the earmarks are there for an amp that is not even broken in yet.

Dude! That is smokin'! Only 2 gain stages, and only on 8? It sure has the crunch, man. That is just the stock '68 kit setup with an echoplex in front?

That's all it is, oh and the flanger for the intro bits. Attacking the strings helps too. The 68 kit is George's gift to the world!

[plexified]

VHJunkie , The 12 series is a short run because it has the volume of a louder 50 watt head . This is obvious with 20 watt celestions . With 30 watt celestions not so much . So they had to redesign the output stage for more volume . Think bass . The bass amps were guitar amps essentially . If your bass amp can't hang , your in trouble . So very few 12 series exist . The Larger transformer was the response with increased filtering and voltages . The JMP otx has a lower primary impedence working the tubes to their max . It increased voltages too . It also has alot more magnetic radiation . So the big replacement transformer in the 12 series chassis introduces a world of huge changes that cannot be dienied .

Its the biggest most obvious piece of the puzzle .

Read my past posts , it spells it out , especially the lineage .

Some food for thought . The 6ca7 can be run without screen resistors . It can also be run without grid resistors .

[plexified]

bore em at the forum ,

The 62 blonde bandmaster is the key . Eds ears led the way . All the way to Fender !

Really though , 6ca7 points that way , 6l6 with Peavey points the way .

The 12 series has alot of commonality with the 6G7A Bandmaster . Mostly the OTX was small and driven hard . It leads to compression and to be general the frown curve on an EQ .

Also Ed running the 8 Ohm tap on the Plexi is another cue .

Cranked up its got crystal clear cleans , sustain and big compressed tone .

Thats the amp that NEVER left the house .

[jnewlyn]

VHJunkie , The 12 series is a short run because it has the volume of a louder 50 watt head . This is obvious with 20 watt celestions . With 30 watt celestions not so much . So they had to redesign the output stage for more volume . Think bass . The bass amps were guitar amps essentially . If your bass amp can't hang , your in trouble . So very few 12 series exist . The Larger transformer was the response with increased filtering and voltages . The JMP otx has a lower primary impedence working the tubes to their max . It increased voltages too . It also has alot more magnetic radiation . So the big replacement transformer in the 12 series chassis introduces a world of huge changes that cannot be dienied .

Its the biggest most obvious piece of the puzzle .

Read my past posts , it spells it out , especially the lineage .

Some food for thought . The 6ca7 can be run without screen resistors . It can also be run without grid resistors .

Hmm. I've got some Sylvannia's. What can one expect if one were to remove aforementioned, said resistors?

[vh junkie]

I've been working w/ some of these guys getting there 12xxx series kits together, and there PT voltages are like my 69 kits(~500vdc)

All of the 12xxx series otx configuration I have found (including Georges kits) typically come with the
Dagnall Clone c1998 w. 1.75k input impedance.
You can also find Drake type 1202-132 w. 1.75k input impedance.
Was there an earlier model OT used in the 12xxx series that had more an input impedance more like a 50watter (i.e. 3.4k)?

VHJunkie , The 12 series is a short run because it has the volume of a louder 50 watt head . This is obvious with 20 watt celestions . With 30 watt celestions not so much . So they had to redesign the output stage for more volume . Think bass . The bass amps were guitar amps essentially . If your bass amp can't hang , your in trouble . So very few 12 series exist . The Larger transformer was the response with increased filtering and voltages . The JMP otx has a lower primary impedence working the tubes to their max . It increased voltages too . It also has alot more magnetic radiation . So the big replacement transformer in the 12 series chassis introduces a world of huge changes that cannot be dienied .

Its the biggest most obvious piece of the puzzle .

Read my past posts , it spells it out , especially the lineage .

Some food for thought . The 6ca7 can be run without screen resistors . It can also be run without grid resistors .

[plexified]

I don't have the specs on the transformers to reference , only my experience owning alot of heads and fixin a bunch . But the 12 series had a smaller power transformer and output transformer . By design for grind . It just fell short volume wise for the super rock bands and the bass amp exploited that . Sounded killer for guitar but just not enough power .

The low voltages true to the preamp and the boosted voltages on the power amp in addition to the lower impedence drove the tubes way harder . Max actually . Here you have more odd harmonic in the output section and more grind .

The factory update for 6550 tubes was running the boosted bias circuit and the switch to the 4 ohm tap . Introducing more feedback and more sizzle .

My comments regarding the ruggedness of the 6550 ( GE ) or 6CA7 (Sylvania ) means you don't need the stock circuit as I described earlier . The tubes were bad ass enough without it . Here you would have more high end . I suggest you run the BASS circuit with this suggestion . Free high end to add to the huge bottom end . Here you run the amp at like 8 or 9 to squelch the huge bottom and keep it tight . OR use a tube screamer which is designed to roll a little bass , yet keep the kill switch on .

[wjamflan]

Not being a techie, I've been following this thread with great interest from the sidelines. Is there someone who could sum up all the findings in layman's terms?

Was it simply a 12 series Plexi with a bass mod and later, a JMP OT? Any help would be greatly appreciated, b/c all of the cap values are like Greek to me. Thanks.

Bill

I think it is pretty much summed up in George's 68 kit. Here is a clip, guitar, Echoplex and 68 Metro 100w; volume on 8:
http://soundclick.com/share?songid=9451688" onclick="window.open(this.href);return false;
I'm not saying this is the exact tone (low E string snarl is not there yet), but allot of the earmarks are there for an amp that is not even broken in yet.

Thank you for the response. I, too, think your clip sounds fantastic. Alot of the earmarks of the brown sound are present for sure.

That little bit of snarl you refer to was put there by (I believe) an MXR 6-band eq. That's just my experience - I've tried it, and it works. I have to be honest and say I don't have experience with other output transformers etc. that could possibly change the frequency response of a 12 series Marshall. If plexified and others have verified that this is the difference, I believe they must be on to something I'm going to have to try when I get some more money.

Anyway, I appreciate the response and was just trying to verify that I was following the conversation to some degree.

If someone else can summarize what has been talked about in layman's terms, it would be really helpful to me (and I gotta believe others as well).

Thanks for your (collective) patience.

Regards,

Bill

[jnewlyn]

Great stuff.

[vh junkie]

Is there someone who could sum up all the findings in layman's terms?

I sent you a PM a while back...

[wjamflan]

Is there someone who could sum up all the findings in layman's terms?

I sent you a PM a while back...

Got it. Thank you. I pm'd you back.

[jnewlyn]

I've got a 1.5" opt trannie from Chris Merrem that kills. I would highly recommend it along with George's dual B+ power trannie.

[leadguy]

Not being a techie, I've been following this thread with great interest from the sidelines. Is there someone who could sum up all the findings in layman's terms?

Was it simply a 12 series Plexi with a bass mod and later, a JMP OT? Any help would be greatly appreciated, b/c all of the cap values are like Greek to me. Thanks.

Bill

I think it is pretty much summed up in George's 68 kit. Here is a clip, guitar, Echoplex and 68 Metro 100w; volume on 8:
http://soundclick.com/share?songid=9451688" onclick="window.open(this.href);return false;
I'm not saying this is the exact tone (low E string snarl is not there yet), but allot of the earmarks are there for an amp that is not even broken in yet.

Great stuff. That's just about it really. Better recording and a few minor tweaks and that's it.

rgalpin had similar results with a EP-Pre.

A lot of it has to do with the Echoplex/Plexi combo.

[spaceace76]

Strat78, comparing your clip to the recording, you're very VERY close considering the amp isn't even broken in yet. I would say that a fully broken in amp and the specs spelled out here will get the low end to where it should be to get that signature ATBL snarl. Beyond that, the only differences between your clip and the original would be the recording method. Have you tried this setup with a variac?

Anyway, great stuff man. Glad someone came through with a clip, and just listen to the results!