You Vote: BOG EL34 vs. 6550

[Tone seaker]

The JTM 45/100's were bass amps. The leads had a bright cap added to make it brighter and thus a lead the bass did not have the cap. They were the same amps except the cap on the volume pot.

[basile865]

Its not the amp that marshall used and its not the Dickinson amp. This is a different one for sure. The guy somehow had seen the Dickinson amp up close and he said something like there was tape residue over the word super in the back which is what marshall did when they made it a bass circuit - they would tape over that word or something like that - I dont know. They said it was noel redding's amp or something like that. The circuit proved it as well according to them, which is why its incorrect in comparison to jimi's actual circuit. They said the circuit used for the Hendrix signature amp was based off that bass circuit which is more round and not what he actually used.

[basile865]

Ok guys, through a few emails with him I've gotten as much info as I could gather which he was comfortable with releasing.

Honestly, its not much different than you might expect.... Essentially, the original vintage stuff really is essential to nailing it - the original g12h30's are way different then any reissue, rendition, tribute, whatever you like to call it. I've heard that from a few owners of original examples. They say nothing sounds like them and when you hear them, THAT is the sound.

As far as the tone stack is concerned - the values used in the hendrix amp are wrong - apparently they're more bassy rounder sounding values in the tribute, where as in the real deal they were much smaller for a brighter crisper sound. He couldn't reveal the actual numbers because he promised the owner. I think I do recall reading an article where hendrix requested that his first marshalls have more treble. I think in that circuit with the stock values, the low end gets flabby when cranked, so that may have been in effort to tighten it up at those loud volumes he played at.

Outside of that he said the PT, OT, and choke were very important to get right. Everyone swears by certain brands and theyre all slightly different tonally, I just think its important to get the most accurate ones you can get. Following that he said mustard caps helped.

So essentially you want the most accurate jtm45/100 you can build, with attention to detail in the tone stack, transformers/choke, and caps. I mean after that, using original speakers and an original univibe pretty much make that tone happen. For those of us who dont really ever dream of being able to buy original things like speakers and univibes I think there are modern day things that will suffice. He did say that jimi preferred 75hz version g12h30's, and that he really disliked the 55hz - I dont think they allowed for the same control of feedback and harmonic freedom.

NOW, with that said, regarding the BOG thing he said he was still inclined to believe it was an EL34 based superlead for that show. He said the tone of that show had a lot to do with the natural reverb of the hall. He also said his friend has owned tons of original superleads and as well as maybe 15 or 16 jtm45/100's through the years collecting and selling. According to him, the values of the amps varied quite a bit so that it would be impossible to really say what it was based on any circuit.

Thats really all the info I was given, and I dont think thats too new to many people, but hopefully it can help shine a little light to guide people with their tone search.

Outside of everything just said, I still personally believe BOG was a tube other then an EL34. Whether its a superlead running a 6550 (I forget if 6L6's are even possible), or his favorite JTM45/100 with KT66's, I personally think thats what he used. I was recalling when I played a 68 bassman and how close I felt it was tonally to the BOG sound. That is a 6L6 powered, somewhat marshall-esque fender amp. The next thought to me is the jtm45/bassman similarity - then I think jtm45/100. It makes sense to me. I do really want to stress that I have NOT used a superlead with 6550's or played a jtm45/100 before. I'm just trying to offer my opinion.

Anyhow, thats about everything. Hopefully people can take something away from it. The only way to ever know is to build it or buy it, and trial and error afterwards. After all, its about finding your own sound and trying to have a little knowledge to guide us in the right direction.

[Xplorer]

Oh nooooooooooo ! : /

so disapointed. But why ?? A bit selfish not to share the original hendrix amp. That's what i was saying about rich owners .....
Like : "hendrix is mine"....

No pictures, no values, and it's christmas.. Snif
it makes no sens. Thanks basile, Really, but i'm so disapointed by the friend of your friend.Sad in fact.
I feel like i know nothing more than i knew before.not totaly true... But you know...

Can't you argue with him to make it endly happen ?
Building a pure jtm45/100 clone, vintage parts and vintage 75hz speakers, and........ ?

[Xplorer]

yeah, sad, but Merry Christmas by the way ; ) ! to Everyone !
i'll talk to you later if you're ok, cause i don't understand everything you've said about the wrong values etc ... it maybe makes sens for you, but not really for me.

do you mean , as a base : an authentic jtm45/100 clone like this work :

http://forum.metroamp.com/viewtopic.php?f=32&t=31853" onclick="window.open(this.href);return false;

or this work :

http://forum.metroamp.com/viewtopic.php?f=32&t=26395" onclick="window.open(this.href);return false;

??

And then .... mystery ..... ; )
oh no ... what can i do to convince this guy to let me enter ; ) for my deep obsession since 20 years ? i can pay ! lol

[Tone seaker]

As far as the tone stack is concerned - the values used in the hendrix amp are wrong - apparently they're more bassy rounder sounding values in the tribute, where as in the real deal they were much smaller for a brighter crisper sound. He couldn't reveal the actual numbers because he promised the owner. I think I do recall reading an article where hendrix requested that his first marshalls have more treble. I think in that circuit with the stock values, the low end gets flabby when cranked, so that may have been in effort to tighten it up at those loud volumes he played at.

The super JH 100's are clones of the Dickenson amp which has the tone stack modified for a brighter sound not bassier which is what Hendrix ask for.

[basile865]

About the amp, the first 2 560pF and 500pF caps in the tone stack are
what were used in the bass circuit amps. I cant tell you the exact
values of Jimi's as I promised the guy I wouldn't and especially for
it to be spread around on a forum. I can tell you though that the
values are much smaller for more brightness and crispness. Otherwise,
the main part of the tone is in the PT JTM100 style output transformer
/ 1202-84 with the 560v secondary tap and the OT JTM100 style output
transformer / 1202-84 and a 10 Henry choke, not the C1990 one that
sounds like Van Halen.

This is what he told me. I hope that clears it up some. Merry Christmas everybody

[Xplorer]

I feel a bit better now ; )
thanks for this !!!
Maybe in the futur, do you think that you can convince him that the eventual spread of the infos on the forum is the opposite of a bad thing ? isn't it true ? I worked at the unesco once, in the world heritage patrimony, and jimi should be registered there, just like french food culture was some months ago.

Who are they ? Thanks to them too
They should really transmit this jimi hendrix treasure before it gets lost...
It's important !
Can you transmit all these discussions to them please ?

Or it'll be a legend or something, when the real amp exists, and some day, who knows what can happend... And the world loose a big part of one of the most important sound ever produced by a human in the human culture.
Yeah, no, i don't smoke crack ; ) just a bit a dreamer, i also mean it when i talk about this impirtance..... When you start to think about it, well, it's not really wrong i think...

Anyway, this amp doesn't make you being hendrix, but it's so interesting.

Will you try these mods ?
Have a nice christmas evening

[Roe]

About the amp, the first 2 560pF and 500pF caps in the tone stack are
what were used in the bass circuit amps. I cant tell you the exact
values of Jimi's as I promised the guy I wouldn't and especially for
it to be spread around on a forum. I can tell you though that the
values are much smaller for more brightness and crispness. Otherwise,
the main part of the tone is in the PT JTM100 style output transformer
/ 1202-84 with the 560v secondary tap and the OT JTM100 style output
transformer / 1202-84 and a 10 Henry choke, not the C1990 one that
sounds like Van Halen.

c1990 should be c1999 - this is the dagnall choke introduced in 68. before this the radiospares 20h choke was used and the drake 3h -114 (similar to the c1999). occassionally, other chokes may have been used on the early amps. I've heard of a jtm45 with a 10h, so its possible that a 10h was also used on a super 100 amplifier (somewhat incorrectly referred to as jtm45/100.) the bass circuits do not use those caps mentioned. they only use a 250 or 270pf cap in the eq and a 500/560pf over the mixer resistor. the lead amps also used bright caps, 100pf and 500pf. Smaller value caps in these three positions will hardly give more brightness. rather, they will give less mids. the mysterious amp mentioned seems to be a stock super 100 amplifier with a 10h choke, nothing extraordinary at all.

[Xplorer]

if it's this jtm 45 that was used for woodstock, and for the bog shows , here we have more answers about the tubes possibilitys.
we were maybe wrong, on the superlead way ( althought he might have use them , linked with the jtm wich was mic'ed ) , with 6550, el34 etc .

[basile865]

I dont know much about the technicalities myself, I was just trying to pass along info to those interested. I think a lot of the mojo to his amp was the transformer (not sure if it was the OT or PT - I think PT) was overwound quite a bit. Apparently it could get crazy fuzz and feedback/sustain when dimed because of it.

[Xplorer]

yes, it seems to be very close to an original jtm45/100, except for the power transformer, a big part of the way the amp behaves.

[VintageCharlie]

The most important part is the Output trannie. The PT is good as long as it forks out the correct voltage - 560v in this case if you can run nos tubes ,which should endure this kind of voltage. As i'll be running moder ntubes for now, it will be 490v in my case and i think Basiles friend also doesn't run neither nos tubes nor 560v - and it still sounds spot on.

Not sure about that owerwound OT story. I think Roe told once that a similar behavior can occur when going for 8ohm instead of 16ohm negative feedback tap, IIRC. The amp will sound similar to some point, but when really dimed it can get some fuzz-like thickness.

It sounds to me like there's a lot of confusion. The mysterious amp described seems to be pretty much close to stock, or simply stock. And if it has "much smaller values" than 500 or 560pF in tone stack, then it's probably 250pF or 270pF (which indicates stock values) or something and it definitely won't sound brighter or anything - maybe even a bit darker at same settings.

What i find strange is that according to this the Dickinson amp might have been Noels main amp and the other amp (that sounds like it ought to be pretty much a stock amp) would be the Hendrix amp. While a 500pF tone stack should actually be better suited for guitar and a stock amp should be better choice for bass. According to this story it's the other way around. I thought there was good photographic evidence that #7026 appeared very often as nr.1 in the chain, etc. - or was this wishful thinking by the seller?

But, no matter if it's possible to find out THAT value(s) on the other mysterious amp, i don't think it makes a big difference - getting the right chain and the amp itself as close to proper spec will have a far bigger effect than 500pF vs 250pF in the tone stack. + the right speakers and one should be there. Either way, i'll try various values when mine is ready, just to check. But even before this topic was raised here, i decided to go with stock values in the tone stack (except the tone stack resistor maybe). This made me curious again at least to the point where i think i'll experiment with the values.

I have the Marstran 3h choke and i think i will stick with that one, but it would be interesting to try a proper 10h choke. Besides Mercury Magnetics, who puts out a 10h choke?

[Tone seaker]

What i find strange is that according to this the Dickinson amp might have been Noels main amp

If you look at the Monterrey footage you can see shots of Hendrix's amp with the exact broken Plexiglas by the input jacks that is on the Dickinson amp thus making it Hendrix's not Noels. There are other pictures to prove it also floating around.

[VintageCharlie]

Thanks Tone Seaker!

Somehow it would make more sense than imagining an amp with later lead spec mod being preferred by a bass player. It sounds to me like a lot of the statements about that mysterious amp are based on the confusion that smaller value tone stack caps give a brighter sound and higher ones (500, 560) are too bassy, which simply isn't the case afaik.
On the other hand, IIRC Jim Marshall told Jimi bought 4 rigs from him in 66 (4 full stacks). So, either way, it is possible it is one of the other amps used by Jimi and maybe this one wasn't modded, or at least not to that extent as the Dickinson amp.