The 6550 Experience

[daveweyer]

It's all a little hard to reconcile. There are too many variables, at least four or five major ones, so you may just have to keep trying things and hope you land right on it by accident. The guitars I always noticed, made the biggest difference in how the overall rig sounded, and just the variables in that are mind boggling.
In fact maybe the whole exercise is a fools game; perhaps it would be better to just try to get the tones YOU love, obtaining them in any way you can irrespective of your rig being identical electronically to what Jimi used at the time.
There is a real possibility that duplicating exactly what Jimi used at the various performances has now become impossible. Remember the story I told about Bob Hovland trying to duplicate the original paraffin wax for use in an identical reproduction output transformer? Some things are now out of reach because the materials we had and the methods we had to make things no longer exist, and unfortunately, a lot of the information about those processes has also vanished with the men who designed them. And the original materials have now also aged and changed their composition.
So let the experiments rage, by any means, and don't feel confined to only getting those sounds through the exact pathways Jimi had available to him at the time.

[shakti]

Dave,

this is very much true. I must admit that I obsess over things like these way more than what is healthy. I actually just want to close up my amp and start concentrating on the playing. Nevertheless, from previous experience I've found that often when you find the missing piece of the puzzle, everything becomes clear and the minor little details become just that - minor little details in the big picture. Case in point - Duane Allman's tone, particularly on the Fillmore East album (coincidence, BTW?), is another tone which a lot of people have searched for. When I got the right speaker (a Cerwin-Vega ER123), everything fell into place, and the stuff almost plays itself!

I feel with this new approach - 6550s biased in class B, and the discovery (for me) that some kind of large-ish volume bright cap absolutely must be in place - I am closer than ever, and should soon wrap this up and go on.
Theories about magic fuzzes with two switchable stages of gain and whatnot - it gives me a headache to even contemplate it at thos stage! But by all means, if anyone else feels like continuing down that road, I would be interested in the results. For me, I am going to stick with what is most likely, the stuff that is best documented, and that is:
- Early '69 Super Lead
- possibly some minor mods inside (stuff like V1 cathode, V2 cathode bypass cap, maybe the size of some coupling caps...but this is minor stuff in the big picture IMHO)
- 6550s biased in class B, possibly 12AT7 in V3.

One *major* thing in the big picture that no one has even touched yet, is the possibility of different speakers in different cabs. This is a much bigger thing than any fuzz, any tube type or any minor circuit mod IMO. But I'll admit it's such a big can of worms that I'm not sure I want to go there. I have a pair of 64-65ish alnico G12s which are quite similar to the alnicos you talked about, Dave. Subbing them in didn't really bring out anything I detected as typically BOG, so for now I am sticking with T1281s. But if anyone wants to experiment, I think this is one area where you could disocver some large differences.

I also thought about a couple small things, that nevertheless could contribute to what we are hearing on BOG vs other Hendrix performances of the same era:

- the room (Fillmore East) itself. Is it a coincidence that another hallowed live album of the same era is from the same room? I have tons of Allman Brothers Band recordings, and none of them sound quite the same, and none of them sound quite like the Fillmore East recordings. Even within the same week there are recordings which sound different enough that we are still speculating whether it was JBLs for this gig, Cerwin-Vegas for that gig.

- the recording itself. I know Xplorer will say that the audience recordings still show "trademark" BOG sounds, but then you have the room factor playing in. Another example of a great live album is The Who's Live at Leeds. I've researched that tone ad nauseam as well. Between all the Who live recordings from that era (summer 69 - summer 70), none sound quite like Live at Leeds, and that's even if they are using the *exact* same gear. Take Isle of Wight, for example---same exact gear as Live at Leeds, but it sounds very, very different. That's the room factor playing in, as well as the recording factor, and one more thing....anyone else notice how shitty Hendrix' sound is at IOW? Same thing with the Who - sounds like poop compared to Live at Leeds... Maybe there was a power problem? Which brings me on to...

- variances in voltage. BOG was recorded during winter. Is it possible that what we are hearing is partly due to a slight brown-out? Even if Dave says they were going for higher voltage, if we take a stock Dagnall T2562 as a starting point, it has a plate voltage of around 490V under "ideal" conditions. What if the incoming voltage dropped just 5 V? You'd end up with a plate voltage at least 20V less. I have another Marshall clone which is more like a '68, but with increased screens filtering, so it's ultimately the same as my '69 clone in every respect, *except* it has much lower plate voltage (around 460) and is biased hot with EL34s, and the preamp filtering is 32+32. In some respects, I get a nicer and more BOG-ish response with this amp. If I had another set of 6550s I could make some A/B clips, but you may have to suffice with EL34s vs 6550s in the higher voltage amp.

Any thoughts on my comments?

[daveweyer]

That's what I meant about variables, it's just too hard to know what might be contributing to a particular sound on a particular recording. You have the amp thing fairly dialed in, and at least there is some consistency to that--even some agreement from the other players here--but the speakers for instance are rather huge in their creation of the overall tone. So was Jimi using T1088s, Jensen C12Ns, or any of the ceramic variations of Celestion speakers which were known to be in his cabinets at any one performance? And how would you go about finding out? Even about 6550s for that matter, since I was not the only tech working on Jimi's equipment.
I really really should have documented everything for history's sake, and now that I look back on it and see what a phenomenon the Experience really was, I observe a huge failure on my part to recognize the social significance of it--I really totally missed it, probably too stoned and enjoying the moment to bother with some simple photographs, specifications, even invoices, which would have told a wonderful story.
It actually bothers the shit out of me that I cannot unequivocally prove Jimi had his frets notched to create his Foxy Lady thing, or that he had some major mods in some of his amps, or that he had T1088 speakers in some of his bottoms, or that he had special FF circuits made by West Coast Organ and Amp, or any number of other things which the forum members would love to know for sure. I'm hoping relics will turn up somewhere, but that's kind of a long shot, a hope which would be unnecessary with the foresight to have taken just a few simple pictures.
I can definitely do the Wah, because I have one of Jimi's pedals here, and I can do the Guild Quantum amp because I know the guy who has it--not that it matters here, because everyone is a Marshall freak--and at least that provides circumstantial evidence of mods, re-amping, and a good copy of the West Coast Organ and Amp sticker.
So for now, we have a super multiple variable equation which is too complex for any of our minds to solve, except for perhaps accidentally landing on one tone and letting your ears verify that you have it. If so, be sure to document it!

Now here is a little tidbit; there was this guy building speakers in his garage, Bob Hovland took me over there to meet him and look at his products. He had a new theory about how to make decent loudspeakers, and was producing a few of them at a time to test in the marketplace in Los Angeles. He was using outside casting outfits and magnet makers, even cones from suppliers made to his specs, since he was just a garage operation. Anyway, his speakers started showing up in equipment around Hollywood, even stuff that came into West Coast Organ and Amp. They were loud, and had good reliability, at least up to the point of the state of the art in high temp glues and so on.
Anyway, his name was Gene Cerwinski. Sound familiar? It's the Cerwin, in Cerwin-Vega. His speakers became quite popular and had a real effect on the rock and roll sound of the day, some good, some bad.

[Xplorer]

Alright, i'll may be alone on this way and i'll maybe have to continue all by myself but i'll keep you posted if you like.
Thorleif, it's understandable for sure that there were many variables, but let's not be too pessimistic, well ... i'm maybe too much optimistic but maybe because i don't look so much at these variables, knowing that behind all these ( the winter voltage was a very good one to read ! ha ha, and very possibly true ! ) , there's something that can be recognized : the amp's DNA .
it's like hearing a fender or a marshall, an el 34 or a 6550. here, it's something different from everything else but earwise it's possible to find the graal.

if you start to look at the break up caracteristics from a stage values point of view, or room , or recording, etc ...
you'll never end, because you'll never be able to put these variables all together.
these variables count, but when you hear in any environment something still recognizable, the amp's DNA, you know you've got something.

the west coast amp mod sounds like it has this DNA , through all your various clips, and that's something clearly showing my point : that through all your various environments, recordings, even through iPhone, various speakers, various tweakings, various setups , even pickup heights.
the 45/100 ( sorry to repeat myself, sincerely ) has this DNA, maybe even more , something that can be heard with variable results but you'll still hear something coming down to the DNA.

now if you look at the dynamics and break up, saturation etc , it's after all not so difficult to get there with a simple fuzz.
so when you've got a setup that works nicely , just picture that in a better environment and there it is, you're grabing the few % of effects on the tone, and i think that they don't make a huge difference in this case, since if you compare a 6550 amp or 45/100 Under home made attempts, to the record of bog , the gap isn't really huge.
this is luck ! because in some cases, of course, the variables can change the tone way more than that.
luck, because this particular DNA is very pronounced.

So for now, we have a super multiple variable equation which is too complex for any of our minds to solve, except for perhaps accidentally landing on one tone and letting your ears verify that you have it. If so, be sure to document it!

a few months back , if you remember, we didn't know about the west coast mods, and we were having the same conversation, giving all the credit sometimes to the environment, recording, etc ... when the main thing still was the amp's DNA, changed thanks to the west coast mod, and which can be heard in an unusual way to play a 45/100 ( no silicon fuzz or univibe or such speakers or pickups back in 66 - 67 with the Experience )
see what i mean ? let's not be too pessimistic. we've narrowed down things a lot, earwise, and i really think that we didn't reach a point where we're stuck.

i have high hopes about the magic fuzz, which is way more simple than all the variables you're looking at in your amp, i'm surprised that it gives you a headache.
this is a very good thing to focus your attention on , because once you've got the right amp DNA, it complete things for almost all caracteristics you were looking for. the switchable levels, input and output caps, that's really something regarding the cleans / break up / chaos and endless notes tone.
for example, see how your olympic fuzz makes your amp sound, even in a different environment from Jimi's BBC recording ???
Veeery close !
we won't get there 100% , but we can get there 99,5 % , because we're more Lucky than you think.

[Xplorer]

That's what I meant about variables, it's just too hard to know what might be contributing to a particular sound on a particular recording. You have the amp thing fairly dialed in, and at least there is some consistency to that--even some agreement from the other players here--but the speakers for instance are rather huge in their creation of the overall tone. So was Jimi using T1088s, Jensen C12Ns, or any of the ceramic variations of Celestion speakers which were known to be in his cabinets at any one performance? And how would you go about finding out? Even about 6550s for that matter, since I was not the only tech working on Jimi's equipment.
I really really should have documented everything for history's sake, and now that I look back on it and see what a phenomenon the Experience really was, I observe a huge failure on my part to recognize the social significance of it--I really totally missed it, probably too stoned and enjoying the moment to bother with some simple photographs, specifications, even invoices, which would have told a wonderful story.
It actually bothers the shit out of me that I cannot unequivocally prove Jimi had his frets notched to create his Foxy Lady thing, or that he had some major mods in some of his amps, or that he had T1088 speakers in some of his bottoms, or that he had special FF circuits made by West Coast Organ and Amp, or any number of other things which the forum members would love to know for sure. I'm hoping relics will turn up somewhere, but that's kind of a long shot, a hope which would be unnecessary with the foresight to have taken just a few simple pictures.
I can definitely do the Wah, because I have one of Jimi's pedals here, and I can do the Guild Quantum amp because I know the guy who has it--not that it matters here, because everyone is a Marshall freak--and at least that provides circumstantial evidence of mods, re-amping, and a good copy of the West Coast Organ and Amp sticker.
So for now, we have a super multiple variable equation which is too complex for any of our minds to solve, except for perhaps accidentally landing on one tone and letting your ears verify that you have it. If so, be sure to document it!

Now here is a little tidbit; there was this guy building speakers in his garage, Bob Hovland took me over there to meet him and look at his products. He had a new theory about how to make decent loudspeakers, and was producing a few of them at a time to test in the marketplace in Los Angeles. He was using outside casting outfits and magnet makers, even cones from suppliers made to his specs, since he was just a garage operation. Anyway, his speakers started showing up in equipment around Hollywood, even stuff that came into West Coast Organ and Amp. They were loud, and had good reliability, at least up to the point of the state of the art in high temp glues and so on.
Anyway, his name was Gene Cerwinski. Sound familiar? It's the Cerwin, in Cerwin-Vega. His speakers became quite popular and had a real effect on the rock and roll sound of the day, some good, some bad.

even if you didn't take pictures back then, what you remember and tell us is a lot, that's fantastic.
As you said, some other factors and other builders affected the tones but we have quite a big picture of Jimi's gears and tone anyway. And some things might still pop up, who knows ?

i think i remember that you had a clip from you guys at the shop, back then, on Jimi's amps ? maybe i'm wrong.

looking at Jimi's wah, wow ! this would be fantastic, that would be the first time ever ! yes please

about Jimi's strats and Neil Moser working on it sometimes, i remember that you mentioned a change of pot, by some Allen & Bradley. Was it still a 250k ? i opened an old RS pot once, a 500k i think, but i measured about 750 k ...

did he also change the cap ? and was there a special setup for the pickups sélections / pots used for tone .. ?

There was this man who built pickups, who passed about a year or two. I think i remember that he also worked on some of Jimi's strats. I'm not sure to remember his name, there was maybe "Lawrence" in his name. please correct or complete me if i'm wrong. and the saying was that he wired the middle pickup in a way that it could blend with the neck pickup, with a pot.
something like that, that was interesting.

Edit : yes, it was Bill Lawrence.

about Jimi's strats , i have a friend who has one of these, ( and i think i started playing guitar on this one back when i was twelve, after school ) but i think it's from pre experience, it may not feature the notch but i'll ask him someday if i can. he doesn't respond much to my mails even if we learned guitar together. too bad.

it may be out of topic but , here, some things about bill Lawrence from internet :

"Why Low Capacitance?

1. The higher the capacitance of a cable, the less highs reach the amplifier.

2. High-capacitance cables shift the resonance towards the lower frequencies which dramatically alters tone. For example, Jimi Hendrix used a coiled cord with 3,000 picofarads (.003 microfarads), shifting the resonance below 2,000 Hertz on his Strats. This was the secret of Jimi's tone. Shifting the resonance frequency at 2,000 Hertz has a similar effect to a midrange boost. However, when he recorded and needed a typical Strat sound for some tracks, Jimi switched to a short, low-capacitance cable.

3. There are some very expensive high-capacitance cables on the market with a sound you might like for some tunes, but then you are stuck with that one sound. Using a low-capacitance cable, you can easily change the circuit capacitance by using a push-pull tone control to switch capacitors -- one capacitor for clean sounds and another for distortion. This allows you to choose the right capacitor values to match the pickups, aiming for a 600-700 Hertz resonance for clean sound and a 1500-2200 Hertz resonance for distortion."


there's this middle pickup schematic, blending in some of the neck pickup for darker tones. can't find it, but i read things about it here and there. Seomthing he did for Jimi. Neil might remember it perhaps ?

edit : this may be the Hendrix strat mod made by Bill : http://www.harmonycentral.com/forum/for ... 1/1161228-

[daveweyer]

Lots of stuff there Xplorer, wow..............

We should consider a couple things though; the capacitance in a cord depends on how long it is, since the cord has so many pf per foot, AND, the resonance (if it is to have a large effect) formed between the capacitance in the cord and the inductance of the source depends on there actually being an inductance in the circuit, something that only occurs when the pickup goes directly into the cable AND the cable is terminated at an extremely high impedance that won't affect the "q" of the circuit--when the signal goes into a FF, the equation changes completely since that input is practically an AC short. And the same goes for a Wah. So talk about more variables!
There always has to be a certain impedance that the resonant circuit sees in order to predict its resonance effect on the signal because that impedance is like shunting a resistor across the capacitance, which is supposed to form the PI filter to ground or the parallel resonant circuit or both. And what happens when there is also a resistor and a capacitor across the pickup winding, as happens in the volume/tone circuit, or when other pickups are added?
And if that coiled cable actually has .003 uf capacitance total, then the pickup must have 2 henries of inductance to resonate at 2KHZ!
Ever measured your pickup inductance?

I think we over-simplify to claim we have a 2KHZ mid range boost because we use a coiled cord. Maybe in one absolute controlled circumstance.

But hey, some more variables are always nice. Let's get back to the amp DNA.............

[daveweyer]

You've probably heard of 75 ohm cable, most cable has an impedance around that number, 110 ohm for digital transfer cable, 600 ohm for transmitting twin lead, and usually lower for common shielded cable. The number means that all the little capacitances and inductances in the cable cancel each other out at that impedance, turning into zero reactive components, just pure resistance; which means you can run a thousand feet of it without degrading the signal in any way except for lowering its level.

So when a guitar is plugged into a FF unit which is on, and has a very low input impedance, the cable, whether coiled cord or anything else, has absolutely no effect on the signal, other than being a resistance. No roll-off, no mid range boost, nothing.
As the impedance of the input falls, the effect of any reactive components from the cable become less and less till finally they cease to exist.

Something to keep in mind when expecting cables to add some effect to the signal.

[shakti]

Lots of interesting info Dave.

I made V1 cathode quickly switchable from split to shared. For BOG tones I think shared cathode sounds better. There is a certain "relaxed" sort of fullness to it, whereas split sounds thinner and more spikey. You get more of that super sweet low midrange grunt and woodiness that Billy Batz talked about with shared.

I added up silver mica caps to come up with 5000pF, and it's a great value for the bright cap in this amp. I gotta install this value in both of my Super Leads now!

Finally, the V2 bypass cap I am a bit torn about...for some tones I prefer it withoutl and there's less hiss. But it definitely does something cool as well, a slight upper mids and treble boost that makes it cut a little better. I'd have to try it at full volume and in a room, but this is one parameter that I actually think it would be useful to have on a switch, so I may consider making it switchable.

This really is the closest I've come yet, by a pretty good margin! Xplorer, I urge you to try these simple mods on your Super Lead, you might be suprised...
- 6550s biased cold, maybe 12AT7 in phase inverter
- 47k @ 8 ohm negative feedback
- shared V1 cathode
- 5000 pF bright cap
- try V2 with and without the .68uF bypass cap

[Xplorer]

This really is the closest I've come yet, by a pretty good margin! Xplorer, I urge you to try these simple mods on your Super Lead, you might be suprised...
- 6550s biased cold, maybe 12AT7 in phase inverter
- 47k @ 8 ohm negative feedback
- shared V1 cathode
- 5000 pF bright cap
- try V2 with and without the .68uF bypass cap

ok thanks Thorleif, i will try.

did you change the power transformer ? and the OT ?
did you change the power caps to 100 uf ?

i planned to do these mods on my second 45/100, almost finished, because it has this marstran 560v PT ( my metro superlead doesn't ) , and this amp was made to experiment some mods. for now i'm testing it stock but soon it'll be :
A- Dynaco A431S OT ,
- a 12AT7 from Dave,
- some 100uf power caps. ( btw i'm stupid, i told Dave it required 5 of them on the 45/100 , Dave sent me 6 , and i only now realise it requires 7 ha ha. just when i'm finishing the power cap board with 32uf stock for now )
- i don't have any 6550 for now.

so i'm not sure how to manage these superlead mods on a 45/100 preamp. does it matter so much ?

for now it doesn't feature the 5000 pf on the volume, and also it's on 27k connected to the 16 Ohms tap.

did you try a nice silicon fuzz only with its volume, with your 45/100 ? i urge you back to try it

when you say "surprised" , what do you mean ? is it very different from all the clips you guys made ?

[Xplorer]

Edit , double post

[shakti]

By surprised I mean that you may find you like it a lot and that the DNA is all there... After all, with a shared cathode, and possibly without the V2 bypass cap, the circuit does come closer to a bass preamp. And the 6550s take it slightly towards your beloved KT66s, at least with a Strat.

I didn't change any transformers or experiment with higher voltage. Again, we have no visual evidence of transformer swapping in Jimi's amps. I don't doubt what Dave says, but we don't know when it happened, and for me that is going too far, especially as I like it just fine as it is. Also, don't forget that none of my clips really come close to capturing what I hear in the room.
IMHO, a voltage change from around 500 to 560 is going to sound different, but not *that* different. And you can probably easily make your SL jump to that voltage. Measure your wall voltage - say it's 240V...set your transformer tap to 230V or maybe even 220V, and the plate voltage will increase a good deal.

Yes, I want to try it with a silicon fuzzface like the blue/turquoise Dunlop. Will pick one up next time a cheap one comes along (happens every now and then). For now I've been using a germanium fuzzface with the volume up full, and fuzz about halfway up. It comes close to the sounds that I hear, but is a bit too sparkly with guitar volume rolled back, and not quite enough gain with guitar volume on full. The BOG fuzz may well be a West Coast mod one, and as far as I understand it is set up so that the guitar volume controls the amount of fuzz, possibly without the fuzz changing character as much as it does with a regular fuzzface. That does rhyme well with what I hear on BOG - a very seamless transition from "clean fuzz" to full on fuzz - the saturation and thickness doesn't change as much as the sustain does.

[Xplorer]

i understand. cool thing is that i'll can compare both DNA

i also like the way the 6550 react when the preamp is hotter, like on the early clips from bill, it's very interesting, and he got endless notes.
i could use that for sure.

with the guitar volume rolled back, and on a 45/100 , you get the sparkles of "new rising sun" on the west coast Seattle boy version. ( hear my clip ) . but your germanium may react differently. there's still some thickness but in a good way, with the blue one.
for the cleans and break ups, i don't need to look further, about fuzz , for bog. it really does it. it lands on it almost by accident, and makes sense too.
Now i just need to implement something switchable which may push it harder and give endless notes, but still quite transparent regarding the fuzz gain effect . and a switch between both positions, it's all i need perhaps.
and this stage wouldn't be about more fuzz, but even more volume ( again, not that it wouldn't sound a bit fuzzy ) . i
t already features an input bias pot, which helps for the cleans and break ups, letting the strat volume quite higher that you do.
it's not the most difficult thing to reach i suppose. and it'd solve the bog puzzle for me.
i'll try to show it anyway.
adjusting the preamp and gain directly in the amp, well ... i'll come to it but i don't think it's as important as what pushs the amp now.

I didn't change any transformers or experiment with higher voltage. Again, we have no visual evidence of transformer swapping in Jimi's amps. I don't doubt what Dave says, but we don't know when it happened, and for me that is going too far, especially as I like it just fine as it is. Also, don't forget that none of my clips really come close to capturing what I hear in the room.

i understand, but i just want to completely follow what Dave says, and see.

After all, with a shared cathode, and possibly without the V2 bypass cap, the circuit does come closer to a bass preamp. And the 6550s take it slightly towards your beloved KT66s, at least with a Strat.

do you mean that i wouldn't really need to change the 45/100 preamp to make it like a superlead ?
well, this could be done i guess, since it's just a few components to change.

i'm almost finishing the power cap board. the rest is done, soon, a new 45/100 at home !
will put the kt66 , 12ax7 and start biasing it.

[daveweyer]

Well there might be some verification of a bigger Jimi mod on the horizon; a guy got ahold of me who claims to have one of the big mods, but it remains to be seen if he is willing to share what's there, or even if he's willing to let me have a close look at it to see if I can identify any West Coast Organ and Amp changes.
But at least it's something and I'll keep working on it.
I'd love to show one of these amps to everybody on the forum if I can get permission, and this one definitely has the transformers to show, if they were indeed from West Coast Organ and Amp.

In the mean time, the changes seem to be having the right effect, and I'm very glad to hear about them.

Maybe we can ship the old 6550s all around Europe so everyone can get a chance to see how they sound in their own tweaked amp.

[Xplorer]

Fantastic news !!!!

[Xplorer]

Just finished my amp !! a few tweaks , bias, voltage charts and it'll be nice i suppose.
i just played it a bit, with the bias pot down to zero. it' looks ok , cleans , saturation and 45/100 tone are there and i'm relieved that the preamp used worked this time.
i previously used this preamp in my first 45/100 build and there was a bug impossible to find. i rechecked every components after unsoldering some legs, changed a few résistors and caps. there was nothing very out of spec so i'm surprised but this time it seems to be alright. cool

i'm going to use this one for the west coast Dave Weyer mod.

http://imgur.com/a/MaMkT