S.I.R. 100w SuperLead

shredaholic

shredaholic

New member
Here's a cool schematic I think some of you guys might be a little interested in... :wink:

It was posted on the Hoffman forum, here's the post:

...Also, I work at SIR in LA, and there is a marshall superlead 100 that was modified by a guy that used to work there in the 80's. I guess he did alot of steve vai and warren dimartinez' stuff. Anyway, I had to tear it apart and see what was doing, I made a schematic, and reworked my 50 watter(for the 6000 time) and good god, it is probably the best sounding marshall type sound I have heard) any way, if you guys want it I can post it for you...

...here is the preamp, the power section is basically the same as the original. I know it is not that far from the original, but it's not near as harsh as a regular marshall. and it sounds alot fatter also.
Click to expand...

http://www.hoffmanamps.com/Forum/yabbfiles/Attachments/superlead.jpg

http://www.hoffmanamps.com/Forum/yabb2/YaBB.pl?num=1141274264


It won't be the Caswell mod, but I think this is by the guy who copied Stock #39 onto the Stock #36 amp which was used by Slash on AFD. His name was Frank Levi - this appears to be one of the same 'typical Frank Levi 80s mods' as I've seen described elsewhere.

I think it's fair to assume that having seen the Caswell mod he might be influenced by it in his own mods. Remember this part of the Stock #39 story?

Another interesting variation between #36 and #39 was that the modification to #36 was always “on.” Whereas #39 had a metal toggle switch mounted in place of one of the amp’s four input jacks (which was used to turn Tim Caswell’s mod on and off), the modification to #36 did not include a toggle switch or any other mechanism to turn the mod off. In fact, to someone looking at the outside of #36, the only perceptible modification would have been the addition of a master volume knob. Even this master volume control would only have been noticeable to the trained eye, since it was done in such a manner as to preserve the amp’s otherwise stock appearance.
Click to expand...

So even though the mod isn't switchable, it still could be close to the Slash AFD amp people are lusting over. Once I get a second amp, I'll be trying all these mods.
 
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Re: S.I.R. 100w SuperLead

JACKPOT!

Dude, you made my year... my UK brother!

I've been hoping and praying this would be leaked ever since the first post was made on here. This summer, this is definately going to be my amp project. I guess I have to choose between this amp or a guitar project for now, and I think I'll wait till the summer to do this but dude... seriously... PM me and let me know how things go and if it does in fact sound like the AFD tone. DEFINATELY keep me updated!
 
Re: S.I.R. 100w SuperLead

Hehe - see, I told you I'd figure it out eventually. I tried figuring it out from a picture of Mr.Minimite's modded amp, but I still couldn't get a clear shot of the cathode values for the extra stage and how the switch inserts it into the circuit path.

I've also developed a switchable gain stage mod with an extra tube that could be configured to work like this mod (or the Caswell mod if they're different). It's 100% bypassed when the switch is off. If you're interested in seeing the diagram for that for a 1959 style amp, PM me your email address and I'll get that sent.
 
Re: S.I.R. 100w SuperLead

It's not a heck of lot diffrent from a standard JCM800 2203/2204. The same amount of gain stages actually. It has few diffrences among the cathode caps, and I see caps going past the plate resistors....
 
Re: S.I.R. 100w SuperLead

I hope you all don't mind my overly technical observations, but I'm interested in analysing just how it may differ from a regular JCM800 2203 in practical operation.

One obvious diffrence is the location of the master volume. On a standard JCM800 master amp, it's in between the tone stack and the PI. Here, it's before V2, and it doesn't pad the signal, pre or post PI, letting the power amp distort more.

On this mod schematic we have 100pf and 180pf caps across the 100k plate resistors of V1. This should allow the each triode to run a bit hotter, than on a JCM800. V1B on a Jubilee has a similar arangement, but on the Jubilee it's actually a slightly larger bypass.

The cathodes on a JCM800 2203, are a fairly standard 27K/.068 for V1A, and a 10K for V1B. On the mod schemtic, it's 3.3K/100uf - 2.7K/.08uf for V1A and V1B. The current flow through the V1 triodes is much, much greater on the mod, compared to a stock 1959 or the JCM800.

As a interesting side note the Soldano SLO and the Jubilee do a similar trick at the tube triode overdrive points. On the Jubilee, V1B has considerably more current flow than a JCM800 2203.

The Soldano has one more gain stage, than this mod, or a JCM800, but the second triode of the extra Soldano gain tube, has a cathode resistor that should severly limit head room (if I'm thinking about it right), and should clipp the signal at that point. The first triode of the extra tube on the Soldano, allows slightly higher current flow than the 1959 mod, the Jubilee, or the 2203.
 
Re: S.I.R. 100w SuperLead

Yeah, I couldn't believe my luck when I found the post. It's not the kindof thing I'd expect from the Hoffman board, which discusses predominantly Fender amps. But the key to it is that it confirms the 'typical Frank Levi' mod spec I found once from a guy on a forum, and links in that particular mod in with S.I.R.

I've almost got the Stock #39 mod drawn up, it just needs tweaking a bit. I suspect that the 'Stage One' mod is a DPDT switch that changes whatever cathodes you have for V1b/V2a to 3k3/100uF. That would make a lot of sense if it were the case, and I can get any amp to follow that schematic above by using that switch and another 3PDT switch to engage the extra stage. It seems like the pieces of the puzzle have all rapidly fallen together tonight; soon hopefully I'll be able to show you guys how to do the Stock #39 mod yourselves.
 
Re: S.I.R. 100w SuperLead

Lake Placid Blues said:
I hope you all don't mind my overly technical observations, but I'm interested in analysing just how it may differ from a regular JCM800 2203 in practical operation.

One obvious diffrence is the location of the master volume. On a standard JCM800 master amp, it's in between the tone stack and the PI. Here, it's before V2, and it doesn't pad the signal, pre or post PI, letting the power amp distort more.
Click to expand...

I think it's to curb the amount of gain so the player can dial in how much gain is from each stage, which should open up some interesting tonal options.
 
Re: S.I.R. 100w SuperLead

OK tonight I changed one of the gain stages in my Plexi to the values of the first gain stage in this SIR mod. Already my amp seems to sound a lot closer to the AFD tone. Can't wait to get the rest of the parts needed for this mod!!!
 
Re: S.I.R. 100w SuperLead

shredaholic said:
OK tonight I changed one of the gain stages in my Plexi to the values of the first gain stage in this SIR mod. Already my amp seems to sound a lot closer to the AFD tone. Can't wait to get the rest of the parts needed for this mod!!!
Click to expand...
Dude you;re absolutely KILLING ME! I CANT WAIT TO DO THIS THIS SUMMER!!!!
 
Re: S.I.R. 100w SuperLead

Here's some sound clips of a guy called Mark playing with his plexi rewired with this mod installed for just 3 tubes like the schematic, non switchable.

the 100p and 180p are not on the 100k plate resistors and doesnt have the .001 on volume pot
the tone stack is 33k/500p and no .001 on volume pot.

http://media.putfile.com/2203-cas-levy-whatever-mod

http://media.putfile.com/cas-levy-mod-2203-rhythm

He's not trying to nail the AFD tone in these clips so hasn't messed with the settings and changed his playing style to capture the sound of the mod. And it's not exactly like the schematic:

the 100p and 180p are not on the 100k plate resistors and doesnt have the .001 on volume pot
the tone stack is 33k/500p and no .001 on volume pot.

But it sounds great. This is just with a normal preamp master volume. I'm gonna have a diagram soon so one can switch between this sound and a 100% stock plexi with the 'Stage One mod' and 'Stock #39 mod' switches. Looks like the mod is versatile then for getting more sounds out of it than AFD tones.
 
Re: S.I.R. 100w SuperLead

dude youre 17 yearls old and making all this mods , i can barely change tubes:dance:
 
Re: S.I.R. 100w SuperLead

That does sound great...the clips you just linked to...

tho I believe I prefer your mods (based on your own clips). Your amp sounds a little tighter and crunchy without being "too" tight like a Splawn/VHT, etc.

I never understood the love for AFD tone anyway...it had a nice crunch and sparkle to it, but it was extremely thin sounding for a LP/SL combination ..no "balls" (possibly from production and not the amp itself tho)
 
Re: S.I.R. 100w SuperLead

Thanks Jeff, I think the reason my switchable extra tube gain stage mods didn't end up so thin was because partly they used phase inverter distortion, but also as I didn't put any 'bright' caps over the gain stage's 470k resistors (i guess they'd be the mixer resistors, or equivalent at least). The cathode in the extra gain stage just copied the first stage's cathode, ie 2.7k/.68uF.

I might start offering to do these mods for a few people in the UK soon, as I really need money for a Neve 1272 preamp module.
 
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Re: S.I.R. 100w SuperLead

shredaholic said:
Thanks Jeff
Click to expand...

You're Welcome :)

I think the reason my switchable extra tube gain stage mods didn't end up so thin was because partly they used phase inverter distortion, but also as I didn't put any 'bright' caps over the gain stage's 470k resistors (i guess they'd be the mixer resistors, or equivalent at least). The cathode in the extra gain stage just copied the first stage's cathode, ie 2.7k/.68uF.
Click to expand...

:eek13:

Is this a "yes" or "no" question?





:laugh2:
 
Re: S.I.R. 100w SuperLead

I can't get any of the picture links to work in this thread or also in the MetroAmp forum either. I'm a member over there also...
 
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