Jimi Hendrix' Gear and Mods at West Coast Organ and Amp

[Xplorer]

it must have been fun at first, to mic some amps, re amplify them, and experiment among all the fedbacks

By the way, the 45/100 modded really well, they usually had the transformers I wanted to use. I never kept the KT66 tubes, the transformers on those amps were too powerful. If someone wanted to use KT66 tubes, I'd get a plexi transformer and get the plates down, maybe to 450v if possible, even lower.

thank you. so you removed Jimi's kt66 from his 45/100 and put some 6550 too ? And did you do some other mods Inside these , compared to the later SL69 ?

[frenchie]

Frenchie,
You bring up a very interesting point. The re-amping idea has evolved, changing from just re-amping to form a wall of cabinets doing basically what several stacks would do ( but being a whole lot more reliable), to using truly huge PA systems to take over from the amps by miking them.
That is a fundamental shift which has occurred over quite a few years. There were a lot of steps in between, with various combinations of each, gradually giving way to the current practice of miking everything and obtaining the power factor through the 100,000 watts of power available in a large venue system.
It would take a thousand Marshalls to get to that point. (sounds kind of fun, I'd like to try it)

I know Jimi was trying both methods. In 1969, the PA systems had a long way to go, most of them being just collections of stuff put together by techno geeks trying to make a living as contractors. All manner of systems were tried, my favorite being the line array, which finally came into its own rather recently. Even the most powerful solid state amps had 300 watts, and sounded rather strange besides. Eventually the wall of guitar amps had to give way, if for no other reason than practicality.

But there is just something about a wall of guitar cabinets which is unobtainable by just miking a guitar amp. The problem is, as you succinctly point out, it is out of the control of the front of house mixer, and the overall sound cannot be controlled to suit the venue, either loudness or tone.

That's a big problem. But in the right circumstances, there is absolutely nothing like it. Of course all the musicians go deaf, since they have to stand in front of it.

My secondary point is this; if you plug a Fender Deluxe, say, into three transformer coupled solid state amps of 240 watts each, into six Marshall style cabinets loaded with high Q speakers, there is an acoustic feedback path between the big speakers and the Deluxe speaker, there is a feedback path between the guitar and the Deluxe speaker, and there is also a feedback path between the guitar and the big speaker cabinets. These paths are mechanical, but they end up having electrical effects, as everything works on everything.
I did this at West Coast for a number of guitar players, one of them being your favorite, completely blowing their minds with the fluidness, the ramping distortion, and the control it gave them; the strings want to play themselves, and you just sort of let them go into whatever they will do.
I never forgot the sounds and reactions from all who tried it. It's where Jimi was heading at the time. Nowadays it is quite fashionable to use a guitar speaker as a mic.
Not advertising a product here, just offering this to maybe make the sounds you are hearing come into focus a little better.

By the way, the 45/100 modded really well, they usually had the transformers I wanted to use. I never kept the KT66 tubes, the transformers on those amps were too powerful. If someone wanted to use KT66 tubes, I'd get a plexi transformer and get the plates down, maybe to 450v if possible, even lower.

Here's another tidbit; Triad made a transformer I liked to use as the PT, had a lot of current, and provided 560 volts for the plates. It was a vertical model, but if you took the end bells off, you could use the Drake covers and it would fit into the chassis, keeping the original Drake number. Sometimes you couldn't tell the mods were there, well, George could probably tell.

makes a lot of sense daveweyer ....Besides when it comes to photo evidence , there are two mics on the last stack of the daisy chained plexis , one on the bottom cab and on on the upper cab , slipping two seconds into the shoes of a sound ingeneer of the sixties , in the heydays of 8 band mixer tables , i'd have a hard time wrapping my head around around a theory basically saying the mics were there just to record the guitar sound , as if the guys could have thought " hey let's record a bottom cab with G12H celestion speakers , and a cab with G12M celestion , we'll blend them on the record to make it prettier " .... It's not as if in situ they had the luxury to multiply endlessly all the lines of recording at the time ....
If i was to conjecture a reason for two mics it'd be more leaning towards a primitive "pan left/right system" with two P.As

[frenchie]

Now all this talk lead me to another possibility ....
Could it be that the traynor/yorkville Ysm1 voice monitor on the bar seat next to jimi , in fact wasn't there to monitor him his voice or anything else , but to have a speaker allowing him to have a mechanical feedback line next to him ( i guess when it comes to controlling feedback , one speaker is more managable than a whole stack ) , so that he didn't have to travel 5m just to let it scream , but having a device allowing him to control feedback at hand like almost another instrument or a pedal box ...I mean during the performance you see him often turning his guitar to this monitor , at first when we didn't even know this box was a speaker , explorer even thought it was some sort of huge effect box .....

[Tazin]

You won't see huge visual differences in some of these modded 1959s.
But you should see a 20K on the cathode of V3, you should see 4 green sandy surfaced 7 watt tubular (with a slight bulge in the middle) power resistors with a great big W printed right on the side, the value being 2.2K, and you should see TWO of the plates of the output tubes stopped with 47 ohm 5 watt resistors (some 2 watt carbons).
Marshalls had an oscillation problem up in the above 50KHZ range when under square wave clipping conditions. Using one plate stopping resistor per side eliminated something they call "lumped constants", where all the little capacitances and inductances add up at the same place and cause enough phase shift to make an oscillator out of the amp.

If my notes here in an old spiral bound notebook are accurate, the Governor should have 545 volts on the plate, 100uf filter caps, and a 12AT7 in V3 position. I thought that the power transformer was a Drake 1204-43, but it might have been the 1203-80.

Once again unfortunately, I don't see the things you outlined above....Just the standard (stock) Marshall stuff for this time frame.

Any other pics of the West Coast shipment? There should be some stand up transformers.

One of the amps does have a standup PT.

[shakti]

Tazin,

I bow to your knowledge about the fine details to decipher when these different amps were made. The amps you're referring to - which timeframe do you put them at? And do you know where they were obtained from by their current owners? I.e. were they Hendrix' European touring gear or US? Presumably he had sets of amps on either side of the pond, although I could be mistaken about this.

Don't take this the wrong way anyone - but it is a bit of a surprise to hear of such extensive modding when (so far) there is no pictorial evidence of any such modding. *Maybe*, if you want to see it, the rear of Hendrix' Woodstock amps show 6550s. But that's about it.

As for a JTM45/100, he may well have kept and used some even late in his career, but again there's not one single pictorial evidence to back it. All onstage shots show JMP-style amps, which is fairly easy to see due to the jack location closer to the front cutout (no "JTM45" text to the right of them).

[daveweyer]

Tazin,
I think there were three of the Marshalls in the 69 shipment which went through with just a hot transformer, 4 6550s, bias set to 25 ma per tube, and maybe a little tweak in the circuit. I was hurrying through a huge stack of equipment, including several existing Marshalls. I know every one got 6650s.
I didn't keep track of the numbers, but if you find one of the "big" West Coast mods, there will be more visual clues.
We did try to make them look stock if we could, we had the red varnish and all that, and the transformers looked identical. If I didn't have one I wanted I fitted a Triad into the end bells, and at least one Stancor.
Making them look "original" was also part of the process; we were the warrantee center for Marshall, and felt we had at least a prima facie obligation to protect the company and promote these products as Marshall, even though everyone knew there were things to be fixed for these units to do super road duty.
Yup, there is even a political aspect to the mods, always more complicated than it seems.
I would really like to see a shot of one of the super power Marshalls we did, but so far nobody has found one that I have seen. I think there might be a picture of some of them when they were first done, because we had a camera at West Coast, and thought the projects looked pretty industrial. I'm not sure where to start on that one.

So, if the historians of this equipment never find any of the modded amps, and there are no pictures of the time which can provide any visual evidence of the mods, then the whole story of the famous 69 Marshall shipment will have to be filed under theories with testimony, but no evidence. What I did, and know about the time and situation, is just something I know from memory and my notes in an old spiral notebook, and will have to be taken with a grain of salt. If it were the Wah Wah, I could show the evidence because I have one of Jimi's pedals.
I don't have any of his Marshalls to prove what we did. Visual clues, like the Tele neck on the Strat are easy to spot, and Jimi posed with our little creation to cement the historical record.
But at least I have offered some clues as to what to look for, and what to measure, if you find one of the amps with mods.

Thanks so much for sharing your views of these old units. I wish I could have them to measure them and look for telltale West Coast signs. On some units I wrote something in the corner of the chassis, maybe my initials or the word "Jimi's".
It was in pencil, so probably faded. I did see my writing in the corner of Jimi's 66 Guild Quantum amp, because the owner sent it to me for repair. The tag was still faintly there.
Anyway, I sure appreciate your looking at the pics of these amps.

[swankmotee]

Shakti,
It was well known that Jimis amps were tweaked by Dave,Andy Marshall,and others and some mods were done to keep the back line running so I'm sure as time wore on with some of these left over Hendrix amps other changes were made due to failure or age and that is why we're not seeing a lot of the original changes. Also some of these units might be outright fakes or head boxes with another chassis that was substituted. Who knows ha know just saying!

[frenchie]

And as dave said , by enlarging and augmenting the contrast the woodstock pic in which a guy is sitting on the 100w superLead ... The sticker is effectively 5 lines of centered justified format , with what i guess is blue lettering ... for which outlines goes perfectly with :

FOR SERVICE
CALL
WEST COAST
ORGAN and AMP SERVICE
462-8683

[stalkertwo]

Hi, i now i saw settings amp, on concert berkeley intro is move to hendrix amp and cox amp. But is normal quality, so i see bad number. Is it Jimi Hendrix Plays Berkeley.

[Tone seaker]

So did his European Marshall's get modded too? It sounds like they wernt even really Marshall's he was using from all the modds. More like Marshall Head boxes only. No way to make a old plexi sound like Hendrix. To do that you would have to buy a 1959 HW or Metro Kit and mod it.

[shakti]

To Dave Weyer:

I certainly don't want to come across as doubting your info. I very much appreciate your efforts to come here and set the record straight. In fact, I am almost ecstatic that finally we get some hard info on what went on with Jimi's amps from 69 and onwards! Perhaps one day we can see photos...let's keep our fingers crossed.

I just want to make sure I get this right. If we stick to the three amps that only saw minor modification you're saying that..

- they got a "hot" transformer, meaning one with a high plate voltage? Was it the stock transformer that just happened to err on the high side, or a replacement?
- 6550s fitted with bias at 25 mA. Did you swap the 220k bias grid resistors, and for what value?
- output transformer remained stock?
- screen grid resistors replaced with 2k 10W ones?
- anything else? Like shared cathode on V1, replaced/changed value coupling caps? What about the 5000pF "bright" cap on volume 1, did you keep that?

Also, you're saying the G12H 30W Celestions were replaced with alnico Celestion T1088 speakers? However, earlier you said that Hendrix preferred bassy sounding speakers if I recall correctly? AFAIK, T1088s have a higher resonance frequency than the 55Hz T1281s that came stock in "100" cabs.

[Tazin]

Tazin,

I bow to your knowledge about the fine details to decipher when these different amps were made. The amps you're referring to - which timeframe do you put them at? And do you know where they were obtained from by their current owners? I.e. were they Hendrix' European touring gear or US? Presumably he had sets of amps on either side of the pond, although I could be mistaken about this.

There all USA export amps (with a Polarity switch) and have a March '69 date written on the Tag sheet. I'm sorry but I cannot disclose owner history; past or present.

Tazin,
I think there were three of the Marshalls in the 69 shipment which went through with just a hot transformer, 4 6550s, bias set to 25 ma per tube, and maybe a little tweak in the circuit. I was hurrying through a huge stack of equipment, including several existing Marshalls. I know every one got 6650s.
I didn't keep track of the numbers, but if you find one of the "big" West Coast mods, there will be more visual clues.
We did try to make them look stock if we could, we had the red varnish and all that, and the transformers looked identical. If I didn't have one I wanted I fitted a Triad into the end bells, and at least one Stancor.
Making them look "original" was also part of the process; we were the warrantee center for Marshall, and felt we had at least a prima facie obligation to protect the company and promote these products as Marshall, even though everyone knew there were things to be fixed for these units to do super road duty.
Yup, there is even a political aspect to the mods, always more complicated than it seems.
I would really like to see a shot of one of the super power Marshalls we did, but so far nobody has found one that I have seen. I think there might be a picture of some of them when they were first done, because we had a camera at West Coast, and thought the projects looked pretty industrial. I'm not sure where to start on that one.

So, if the historians of this equipment never find any of the modded amps, and there are no pictures of the time which can provide any visual evidence of the mods, then the whole story of the famous 69 Marshall shipment will have to be filed under theories with testimony, but no evidence. What I did, and know about the time and situation, is just something I know from memory and my notes in an old spiral notebook, and will have to be taken with a grain of salt. If it were the Wah Wah, I could show the evidence because I have one of Jimi's pedals.
I don't have any of his Marshalls to prove what we did. Visual clues, like the Tele neck on the Strat are easy to spot, and Jimi posed with our little creation to cement the historical record.
But at least I have offered some clues as to what to look for, and what to measure, if you find one of the amps with mods.

Thanks so much for sharing your views of these old units. I wish I could have them to measure them and look for telltale West Coast signs. On some units I wrote something in the corner of the chassis, maybe my initials or the word "Jimi's".
It was in pencil, so probably faded. I did see my writing in the corner of Jimi's 66 Guild Quantum amp, because the owner sent it to me for repair. The tag was still faintly there.
Anyway, I sure appreciate your looking at the pics of these amps.

Dave, believe me when I say I'm not disputing anything that you have graciously shared with us about Jimi's gear. All I'm saying is that these particular pieces don't seem to exhibit the mods that you outlined. That's not to say that the other reputed Hendrix amps out there don't have the mods you mentioned....I have NOT seen all the amps that Jimi supposedly owned.

Shakti,
It was well known that Jimis amps were tweaked by Dave,Andy Marshall,and others and some mods were done to keep the back line running so I'm sure as time wore on with some of these left over Hendrix amps other changes were made due to failure or age and that is why we're not seeing a lot of the original changes. Also some of these units might be outright fakes or head boxes with another chassis that was substituted. Who knows ha know just saying!

Fakes...Anything is possible. I can say this about the info/pictures that I have; they are old (pre-internet boom). Also, I've seen a fair share of plexi amps (perhaps hundreds) built between 1963 thru mid 1969, so I have a decent knowledge of Marshall amps which helps in spotting fakes or lash ups. Anyhow, these ones look pretty legit to me.

[Xplorer]

Now all this talk lead me to another possibility ....
Could it be that the traynor/yorkville Ysm1 voice monitor on the bar seat next to jimi , in fact wasn't there to monitor him his voice or anything else , but to have a speaker allowing him to have a mechanical feedback line next to him ( i guess when it comes to controlling feedback , one speaker is more managable than a whole stack ) , so that he didn't have to travel 5m just to let it scream , but having a device allowing him to control feedback at hand like almost another instrument or a pedal box ...I mean during the performance you see him often turning his guitar to this monitor , at first when we didn't even know this box was a speaker , explorer even thought it was some sort of huge effect box .....

Ha ha no, i've never said or imagined that the traynor speaker was a huge effect box

[daveweyer]

Tazin and Shakti,
The normal situation would have been to leave the 220K resistors; you couldn't go much lower without affecting the gain of the phase splitter stage. I changed the values when I used the full Mullard cathode coupled circuit.
Any changes in the bias supply would have been in the bias circuit itself, most likely the 27K.
It all depends on the transformer, sometimes I could get sufficient bias without changes.
I think that the stuff coming in during 1969 used the Dagnall transformers for the most part, although I remember seeing Drakes occasionally.
I had three stacks of transformers which I sorted for plate voltage and regulation. The Dagnalls were quite varied.
As I said, if the lamination stack was thicker, I most likely changed the core and used the existing bells. If I had a Drake handy I might have used it instead. Perhaps you could check on the numbers to see which variety it was.

But yes, hot transformers had more plate voltage. I liked to get over 500 volts if I could, preferably 550, but as I remember that was quite a stretch for the Dagnall. Some of the Drakes could do it easily, and the Triad cores I used could also do it. If I got a high plate voltage PT, I would look for an OT with more primary impedance, just to save the output tubes from overwork. That's something to check for if you ever have an opportunity.
If I remember this correctly, the Dagnalls had a pretty low primary impedance, less than 2K. I'm just not sure you can tell without actually measuring it because the numbers may or may not factually identify the part.
I do remember hooking the cathodes together on the input stage, but I was never convinced it meant anything; after all, if the electrolytic was good quality, there was only DC on the cathodes either way, hardly a big sound changer, especially if they were bypassed with a film cap, which I often did.

The 500pf cap bypassing the pot was left or changed depending upon a sound check, some amps came out sounding real trebly, so we tweaked for that. Sometimes the second stage cathode was bypassed too.

If the amp had good 1K screen resistors, I often left those if we were in a big hurry. But I really liked to change them out when I had the chance, and I do remember doing that on some of his equipment.

From what I was able to find out at Thomas Organ Co about the "higher power" alnico speakers it appears that it was the increased voice coil inductance which rolled off the high frequencies, the speaker resonance in this case had nothing to do with HF response. I still have no independent verification that there was a suffix on the speaker model to indicate a higher power rating, and the "experts" on Celestion speakers insist there was no such model, that the power handling was only 15 watts. But Bob Hovland and I tested them with 60 watts each, and they would handle 120 RMS watts all night long in groups of 4, at least those units we took off the shelf at the Vox factory.

We probably modded over a thousand amps during West Coast's brief life, and would often have help, a student who could solder well and make the mods look clean.
To be honest, I never tried to think of myself as a Marshall expert, or a Fender expert, or an Ampeg expert for that matter, and I had absolutely NO idea that Jimi would become the guitar messiah, or anyone would ever give a rat's ass about his equipment. I always thought I was just moving toward ever better, more refined, and more rational amplifier design, not bound by tradition or the canon of Fender amp law, least of all Marshall amps, which I thought had some serious design deficiencies in total power/dissipation considerations. It all came as a big surprise to me in the ensuing years after Jimi's death that time had stopped. Had I known, I would have hung on to more of his stuff. In retrospect, I was in a position to have made a lot more changes than I did. It seems the whole affair has turned into a forensic exercise, different than the actual experience, but exciting nonetheless.

Thanks again for your super diligence on this historical record. It means a lot to me. I'd love to find out more too.

[shakti]

Thank you very much, Dave!

So the three or so amps that only received minor mods - did they all keep the stock electrolytics? And did you use a 12AT7 in V3 on those?

I am lucky enough to have clones of 4 different 100w Marshalls, including a 68-style Super Lead which has increased screens filtering to 50uF (16uF stock), has a lower plate voltage around 460-70 and is running EL34s. Super crunchy and easy to play. I also have one based on a '69 very much like the amps you received in March '69, down to the same WIMA TFF caps. I had intended all along to set it up with 6550s per the rumours about Hendrix' mods around that time. So getting the little details -right means a lot to me!

I have already tried it with KT88s, and bias grid resistors lowered to 150k, but while it did have increased clarity over the EL34s it ultimately sounded a touch thin to my ears. Maybe thin is the wrong word with KT88s, but it didn't knock me out. I have some new things to try now:
- try 6550s instead
- keep the 220k bias grid resistors
- mismatch impedance with cab so I can increase primary impedance from 1k7 (stock with a Dagnall C1998 when matched) to 3k4
- a side effect of that is that negative feedback is lowered. NFB is attached to the speaker jack, so now I have effectively 47k@16 ohm. If I mismatch and set the selector at 8 ohm, I will get feedback closer to what Hendrix would have used. His amps also had NFB at the speaker jack (most likely) and ran two cabs in parallell, so most likely would have had the selector switch (and thus NFB) at 8 ohm
- play around with plate voltages and bias. Stock I get around 500-510V when biased cold.
- maybe try a 12AT7 in V3 and try it with a shared cathode, play around with bright cap value