Marshall Super Lead build, sort of

[Chuck H]

I have a '93 Marshall 1959slp that is heavily modded and not worth a lot as is, BUT...

I have to pay back some repairs for my work truck so I'm going to sell it. I've decided to rebuild it as a turret board '68 super lead for the current market. I bit the bullet and spent the requisite $250 to populate it with period correct mustard caps. The Welwin screen grid resistors are still readily available and I sprung for NOS Piher carbon films for the power supply resistors just for the aesthetic (also at some expense). I'm already $40 over budget on my estimate but it should look pretty damn cool. Eye candy for sale really. What I absolutely CAN'T find is the right bright channel and treble caps. They are strictly unobtanium anymore for years now. Most made by Lemco and some rebranded by Radio Spares as RS. The desirable caps would be anything marked Lemco or RS in the 470pF to 560pF range in the flat, rectangular silver mica. Also the "bright" cap at .005 or 4700pF in ceramic. Also popular is the "dogbone" caps (hollow ceramic) in the 500pF (+/-) range. I don't know the maker on these, I think it's still Lemco?. They are red in color.

These are literally unobtainable pieces anymore. I'm posting this because I know there are several people here with old stock and pull inventory and I'd like to find them, AND/OR to let members here know that if they do have parts like these they are worth their weight in gold on the current market and so there might be a chance to profit and offer something desirable to people that really want these items. So there's no shame in charging for exclusivity. Everybody wins in the exchange because these parts are simply no longer available otherwise.

[mozz]

Pictures? Too lazy to search. I have lots of caps but mostly US made, some mustards but 160v, micas, etc.

[Chuck H]

Well the 160V .68uF/680n Mullard/Phillips mustards currently go for about US $80. If you can find them. I ended up sourcing these caps as Bianchi/Phillips mustards. All the rest are Mullards. Because of rarity even the Bianchi mustards in 680n are quickly becoming expensive too. If you have any 680n/160V mustards you should set them aside because they're rare and collectible now.

I'm not bent on sourcing the above mentioned bright channel and treble circuit caps. I have enough pizazz going for this build already without them. Mostly I just wanted members here that may have hoarded any of this rare stuff to know that they may be sitting on some real treasures. I'll find some pics and post them.

[Chuck H]

Here's some images of the Lemco and RS mica caps and one of the Lemco ceramics. I couldn't find the dogbone (dog bone) caps of the most desirable values in isolated shots. They're that rare now. The lower left board pic has the red dog bone caps. The lower right board pic shows the mica caps in place as well as the scale of the 680n mustards.

Also desirable would be the mica caps in 250p for JTM45 builds. And 100n (.1uF) mullard mustards in 400V are just starting to get rare too.

Most desirable (in order) would be the dog bones in 250p or 500p. Lemco or RS ceramics of the same values. Lemco or RS rectangular micas in 250p, 470p, 500p and 560p. Lemco or RS ceramics in 5000p or 4700p. Mustards in 680n/.68uf/680k at 160V. mustards in .1uF/100n at 400V.

[Helmholtz]

Those "Mustard" caps are Philips type 311 metallized polyester caps, also made in license and sold by Mullard, Valvo, Bianchi, Mazda and probably other members of the then large Philips (Netherlands) family.
They typically don't carry a brand name. Just found that Bianchi caps do.

'67 to '69 Marshalls also used Wima and Dubilier film caps.
Also yellow box-shaped Philips type 341 (polycarbonate) caps can be found.

I keep a few of each type (including dog bone ceramic and RS/Lemco mica caps ) for reference and restoration purposes.

The blue/yellow Dubilier caps tend to develop leakage (I suspect they are PIO types, but haven't verified) showing by low Q value.
No so with the other types.

[Chuck H]

Those "Mustard" caps are Philips type 311 metallized polyester caps,

Shhhh!!! The tone hounds drink the KoolAid and believe they are strictly film and foil caps. "metalized" is considered heresy for vintage tone caps.

I actually DID discover that they were metalized caps (with very little research actually) but dominant lore on line is still that they are strictly film and foil. Even the modern replica caps that are supposed to be made just like those original mustard caps perpetuate the film and foil aspect in their promotion and the word metalized NEVER comes up.

[Chuck H]

While we're on the subject... When researching the "Super Lead" one can't help but run across references to "THE" amp. Eddie's Marshall. Notoriously colluded regarding it's actual specs and whether it was modified or not, etc., blah blah blah. Here's what I found...

It was NOT modified, BUT a few well respected amp guys that now make their own product have been inside the amp and have come forward with what was actually on the circuit board. Like Fender, Marshall also fudged circuit values sometimes to fill orders. Eddie's amp was unusual in a couple of regards that absolutely could be factory done but make a huge difference.

Eddie played through the bright channel with all knobs raked up to ten. Reported by Friedman, Suhr and others that were in the amp at some point is that this particular amp had an 820R/680n cathode circuit for the first triode of the bright channel. The schematic reads that it should be 2.7k/680n. So there's a pretty good bump in gain right there. Eddie's amp also had a 560pF treble cap (not sure about the mix resistor bridge cap but likely also 560pF since that's what they seemed to have on hand?). The amp also had a factory installed 50k pot for the mid circuit. Remember that Eddie raked the knobs. So this would be another big gain boost. This amp was a 12XXXX issue and so had the 680n bypass cap across the 820R V2A cathode. As far as I can tell this was more prevalent than the schematics suggest, but it was only standard in '68. There is a schematic from '70 that also has this arrangement though other schematics from that year do not. This would also be a gain boost, BUT... This implementation also included moving the 47k NFB resistor from the 4R tap to the 8R tap on the OT secondary. Spice analysis of this confirm that it's a wash as far as gain is concerned, but another BUT... Eddie's amp did have the V2A bypass and the 47k NFB resistor was on the 4R tap. So less NFB.

Players marveled at how much gain Eddie seemed to be getting from this "stock" Marshall. But with the (factory implemented) differences mentioned above the amp had about twice the gain of a schematic correct Super Lead. NOW...

Add to that the notorious Variac operation. Said to be 90V from a standard 120V wall outlet corrected for Eddie's amp having been reported as a non domestic (to the US) model. As it happens when you combine the differences in Eddie's amp with reduced preamp voltages the clipped wave form becomes much more symmetrical with an 80mV to 100mV input signal. At un reduced Marshall voltages with a schematic correct circuit there is considerable asymmetry with this nominal input voltage range. So...

Was Eddie's amp different? YES!!! Was it stock? YES!!! Just one of those things that happen sometimes.

So if you want your Marshall Super Lead to sound like VH1:

1) Change the bright channel cathode resistor to 820R
2) Make the treble cap 560pF rather than 470pF
3) 50k mid pot
4) Move the 47k NFB resistor to the 4 ohm tap on the OT secondary
5) Make sure to have the 680n bypass cap on the V2A triode feeding the CF
6) Increase the B+ rail dropping resistance to the PI and preamp from 20k to something higher to reduce PI and preamp voltages (about 112V on V1 IIRC from the simulations).
7) Add the associated delay and phase/flange effects

This isn't going to be the quintessential "Marshall" sound. But it should sound like VH1 if that's what you want.

No mojo, no magic. Just analysis.

EDIT: Also... It's reported that Eddie had an EQ pedal in on his pedal board at the time of VH1. Later he changed from using an instrument cable to a wireless and the EQ pedal disappeared from his pedal board. I remember that at that time wireless systems had the ability to be adjusted for greater output level. I suspect he was using the EQ pedal as an input boost and later used the wireless adjustment for the same purpose. "I" use to use a BOSS GE-7 for the same purpose into the above mentioned amp back when I gigged with it. So this may be another aspect of "that" sound.

[pdf64]

Great summary, thanks
Just to note for the sake of completeness, there’s also the 6CA7 thing too. I suspect the pair of 6CA7 pulls Ive got may be somewhat tired, so dunno how much actual electrical / tonal difference they made.

[Chuck H]

Great summary, thanks
Just to note for the sake of completeness, there’s also the 6CA7 thing too. I suspect the pair of 6CA7 pulls Ive got may be somewhat tired, so dunno how much actual electrical / tonal difference they made.

Yep. With the higher gain and lower NFB the amp can get a little mushy in the low end. Dave Friedman and Peter Thorn did a *outube video where they implement some of the above differences with switches. It's pretty convincing. Then they remove the standard EL34 power tubes and replace them with 6CA7's and it's the icing on the cake. Tightens up the bottom end a bit.

[dai h.]

While we're on the subject... When researching the "Super Lead" one can't help but run across references to "THE" amp. Eddie's Marshall. Notoriously colluded regarding it's actual specs and whether it was modified or not, etc., blah blah blah. Here's what I found...

It was NOT modified, BUT a few well respected amp guys that now make their own product have been inside the amp and have come forward with what was actually on the circuit board. Like Fender, Marshall also fudged circuit values sometimes to fill orders. Eddie's amp was unusual in a couple of regards that absolutely could be factory done but make a huge difference.

Eddie played through the bright channel with all knobs raked up to ten. Reported by Friedman, Suhr and others that were in the amp at some point is that this particular amp had an 820R/680n cathode circuit for the first triode of the bright channel. The schematic reads that it should be 2.7k/680n. So there's a pretty good bump in gain right there. Eddie's amp also had a 560pF treble cap (not sure about the mix resistor bridge cap but likely also 560pF since that's what they seemed to have on hand?). The amp also had a factory installed 50k pot for the mid circuit. Remember that Eddie raked the knobs. So this would be another big gain boost. This amp was a 12XXXX issue and so had the 680n bypass cap across the 820R V2A cathode. As far as I can tell this was more prevalent than the schematics suggest, but it was only standard in '68. There is a schematic from '70 that also has this arrangement though other schematics from that year do not. This would also be a gain boost, BUT... This implementation also included moving the 47k NFB resistor from the 4R tap to the 8R tap on the OT secondary. Spice analysis of this confirm that it's a wash as far as gain is concerned, but another BUT... Eddie's amp did have the V2A bypass and the 47k NFB resistor was on the 4R tap. So less NFB.

Players marveled at how much gain Eddie seemed to be getting from this "stock" Marshall. But with the (factory implemented) differences mentioned above the amp had about twice the gain of a schematic correct Super Lead. NOW...

Add to that the notorious Variac operation. Said to be 90V from a standard 120V wall outlet corrected for Eddie's amp having been reported as a non domestic (to the US) model. As it happens when you combine the differences in Eddie's amp with reduced preamp voltages the clipped wave form becomes much more symmetrical with an 80mV to 100mV input signal. At un reduced Marshall voltages with a schematic correct circuit there is considerable asymmetry with this nominal input voltage range. So...

Was Eddie's amp different? YES!!! Was it stock? YES!!! Just one of those things that happen sometimes.

So if you want your Marshall Super Lead to sound like VH1:

1) Change the bright channel cathode resistor to 820R
2) Make the treble cap 560pF rather than 470pF
3) 50k mid pot
4) Move the 47k NFB resistor to the 4 ohm tap on the OT secondary
5) Make sure to have the 680n bypass cap on the V2A triode feeding the CF
6) Increase the B+ rail dropping resistance to the PI and preamp from 20k to something higher to reduce PI and preamp voltages (about 112V on V1 IIRC from the simulations).
7) Add the associated delay and phase/flange effects

This isn't going to be the quintessential "Marshall" sound. But it should sound like VH1 if that's what you want.

No mojo, no magic. Just analysis.

EDIT: Also... It's reported that Eddie had an EQ pedal in on his pedal board at the time of VH1. Later he changed from using an instrument cable to a wireless and the EQ pedal disappeared from his pedal board. I remember that at that time wireless systems had the ability to be adjusted for greater output level. I suspect he was using the EQ pedal as an input boost and later used the wireless adjustment for the same purpose. "I" use to use a BOSS GE-7 for the same purpose into the above mentioned amp back when I gigged with it. So this may be another aspect of "that" sound.

IIRC the feedback was supposedly 100k off the 4 ohm tap. Also, the big cap on V2a cathode 470uF(or thereabouts) does seem to be a mod. Also, probably used a hotter pickup (like a Super Distortion or something like that--if memory serves somebody mentioned a Might Mite clone of the SD). Additionally, in an early interview he mentioned plugging into a different setup for Eruption (maybe a higher gain one?), so possibly a source of confusion (by people who swear he was using a secret pedal or had gain mods to the amp--I don't think the big cap makes a huge difference). Also, possibly one less filter stage (there but not hooked up). Also the phase inverter (sorry...) output coupling caps (maybe?) higher (I've actually seen a stock Lead (split cathode) Trem 100 like this with 100nF instead of the usual 22n). (IIRC) according to Dave Friedman the cap across the mix R was a red ceramic (10% tol.?), the treble cap was a mica, and I think there was a 5nF on the lead ch. vol. pot (probably had a loose tol.). Also, the phase 90 possibly modded (brain is foggy but EVH might've mentioned Jose doing something--I've tried a mod by Gus Smalley to change to slow the sweep (I tended to think this was believable since it only involved changing one cap (I used a reissue modded to the old circuit)). Also there's good stuff on Youtube on the Tone Talk Youtube channel (D.Friedman and M.Huzansky), also the Pete Thorn channel, and another guy whose name escapes me (Jim Gaustad?). Apparently he did turn up the voltage but on an amp where the line voltage was set for a European setting (230 or whatever). Also D.Friedman apparently doesn't like the lower B+ Marshalls (but apparently thinks the EdVH with the Variac-lowered works better (partly?) due to the effect of the heaters being lowered). re: an urban myth I've seen sometimes about him running the amp so hard (and red plating) they could be easily destroyed with a flick of the finger at the end of a show--apparently he used to run unmatched tubes and there were problems with reliability which were amended when Jose A. advised to use matched tubes. Also a bit of de-tuning of the B to get the major interval to sound more consonant (apparently a tuning tweak not entirely unique to Ed VH)--I guess this is a problem made worse by the distortion? Also, he apparently liked Telefunken EL34s but it wasn't clear to me if this was the W.German one or the RFT(E.Germany). Dave Friedman was apparently asked by Ed and had no idea where to get them, so maybe it was the W.German EL34 (I don't go shopping for tubes any more but when I did they seemed to be super rare--I think I saw one used one; the E.German RFT still seem to be available even today).

re: Marshall caps, the first JTM45 (5F6-A copy) didn't have mustards. After, the first one, yes. Maybe a certain amount of consistency with the parts types early on since (apparently) they bought out of the Radio Spares catalog but later looked for less expensive sources. Besides some of those mentioned, also orange boxed TCC(Telegraph Condenser Corp) E(?)Lectropack, a "squashed" looking green Hunts cap (metallized since smaller-looking?), maybe some oil for the bright cap coupler in some early 70s leads. Maybe some CDE film when the US distributor modded a bass to lead. Sometimes Dubilier (of England) radial for the 680nF. (IIRC someone here mentioned long ago that the Dubilier (two-tone or solid color) were film and foil (he had a damaged one if memory serves). A mix of (cement-coated?) mica (Lemco = London Electrical Manf. Co.), non-temp. compensating ceramic (both dogbone and disc), temp. compensating ceramic (the Murata N750 (purple mark) 250pF disc and N750 500pF "dog bone"(or sometimes seemed to be referred to as "rod" type). Also, even some with .01uF disc ceramics in parallel in place of the 22nF films. I think someone (hardcore Marshall enthusiast) mentioned the treble pot could be audio taper in some amps, and someone else stating the presence could be (a bit) higher in vintage amps (so might be a bit more feedback). Also, some amps look weird with the parts placement (the really big rectangular micas(coupling somewhere?), tone stack cap looking quite close to a B+ dropper (heat = value change?).

re: the red 500pF-ish ceramics, they seemed to be super rare (when I've searched for them). Another one that also seemed rare was the yellow "chicklet" in early 70s amps. I actually ran into some here years ago (apparently sold by a weird brain enchanted with mojo guy selling vintage parts) but got sticker shock (in hindsight obviously should have bought them since I haven't seen the exact period ones--I've seen ones from later which seemed more common).

Also, I thought the Philips "mustards" were polyester film and foil?
(this datasheet says "P.E.T.P"--I have a different one that says "polyester")

https://vintageaudioparts.shop/3229-...-caps-petp.jpg

(FWIW, according to John Suhr, his testing found Mallory 150 (which are metal. poly.--he uses these in his versions of a Plexi) close to the mustards and apparently doesn't use Sozo (but seemed open to the idea if testing could confirm).)

[Helmholtz]

Add to that the notorious Variac operation. Said to be 90V from a standard 120V wall outlet corrected for Eddie's amp having been reported as a non domestic (to the US) model. amp

This point I don't understand.
All the early Marshalls I've seen had a multi-tap primary PT and used a voltage selector switch accommodating line voltages of 110V, 120V, 200V, 220V and 240V.
Also showing on original schematics.

Now assuming the standard US export version had a dedicated 120V PT, what would Eddie's model have used?

You said "corrected" the voltage for his amp. That would indicate a lower than 120V PT, maybe a dedicated 100V version for the Japanese market?
In that case the voltage reduction by the Variac would be only 10%.

In any case, if his PT did not have a 110V/120V primary, results with a 120V PT and Variac set to 90V will be different.

So the essential question remains, what were his resulting B+ and heater voltage values.

[Helmholtz]

Also, I thought the Philips "mustards" were polyester film and foil?
(this datasheet says "P.E.T.P"--I have a different one that says "polyester")

My old Philips/Valvo databook say Mustards were metalized polyester caps. PET and polyester means the same, namely Polyethylene terephthalate.

Yellow chicklet caps are metalized polycarbonate.

[Helmholtz]

Reported by Friedman, Suhr and others that were in the amp at some point is that this particular amp had an 820R/680n cathode circuit for the first triode of the bright channel.

That wasn't uncommon. Both my '67 ST and my '68 SL have this wiring. Biasing V1 rather hot.
Somewhat earlier amps used a shared 820R resistor like JTMs.

[Helmholtz]

Dunno about the EVH amp, but Marshalls up to around mid '68 used less filter capacitance which IMO helps sound and feel.

[The Dude]

Stories are stories, so I can't verify (or even remember sources). I do remember reading that the EVH variac thing was a myth and that he never used a vaariac.