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

[Tone seaker]

I Glad you hung in there Tone.

Thanks

Did you notice how much fun the little girl in the dark red shirt was having, right in front of Jimi. What ecstasy!

.

I always love how he plays for those two girls on the front of the stage. They look like the had a when he played his strat between his legs and with his teeth for them

The tone on that recording is amazing.

[Xplorer]

tone, that may be this box.

and wow, this girl Under him while he plays ha ha ha, so funny

[daveweyer]

It looks just like an Altec crossover too. And the 604 was pretty popular then for both PA and studio monitor use.
And in one shot there appears to be a mic on the Marshall bottom, so for what ever reason, the crew decided they needed a signal from the guitar, even if it was just for recording the show.
So what was Jimi listening to through his monitor?

[frenchie]

So what was Jimi listening to through his monitor?

dunno but the volume knob on the monitor doesn't seem to be all the way up .... one poor altec , low volume .... pretty weak in front of two daisy chained super leads 100w huh ?

[daveweyer]

If I remember the 604 right, the knob controlled the high frequencies only. So that might explain something. It was easy to blow the HF part of the speaker too, meaning the knob would be held back some. Still, a 604 is no match for two super leads. Maybe that's why he seems to be leaning so close.

[frenchie]

If I remember the 604 right, the knob controlled the high frequencies only. So that might explain something. It was easy to blow the HF part of the speaker too, meaning the knob would be held back some. Still, a 604 is no match for two super leads. Maybe that's why he seems to be leaning so close.

anhan ....so what's the point of monitoring a bass with a tiny speaker on the corner of the stage of with you have to stand just two centimeters in front to hear anything ? For a guy known to occupy and gimmick all around the stage area it's quite weird no ?

[daveweyer]

Frenchie I'm with you on that one. The 604 wouldn't make much of a bass monitor, at least in a 110 db environment.
Four Guild cabinets with two 15's in each would be a little different story.

[frenchie]

ya know dave i dunno anything after all ... besides i'm just a moron like some highly regarded people say ... it's just that some unsignificant things puzzle me , is all ...

[daveweyer]

Adrien,
The PIG amps, the #1966 and #1967 both had the extra tube and the big Drake PT, but the 1967 had the tone stack change that you mentioned, because Marshall found out it sounded better for a PA system amp. Remember the tone stack was in the NFB loop on those amps, a whole different system.
Some people liked it better for guitar too, and it became a mod for super leads and 45/100s.
Now for the screen resistors; either value will work, the 2K2 10 W resistors are safer for the output tubes, and they mellow the percussive part of the tone some. But I did a lot of mods where I left the other ones in there, especially if the amp had lower plate voltage and couldn’t spare the power loss from the 2K2 resistors. If you do a 45/100 mod with 600 volts on the plates, it's best to use the 2K2 resistors.

Now, comparing the #1959 super lead and the 45/100: it just so happens that the 45/100 was ballsier than the 1959. It had more plate voltage, by a long ways in some cases, and was a much better candidate for modding because you could get so much more power. Other than the transformers, the amps were almost the same—the output tubes had 5K grid 1 resistors on the super lead, and the tone stack was just a bit different, the 45/100 had a 220pf and a 56K. The PT circuit on the 45/100 was the old standard full wave CT, instead of the full wave bridge as on the #1959. The bridge gives somewhat better regulation because of a lot less turns on the secondary, but the old Drakes were powerful and fat.
It looks like you have a Heyboer replica PT of the Drake, using standard full wave SS rectifiers with the center tap to ground.

So what happened in 1967 when Jimi did Castle Made Of Sand? Well, I wasn’t modding the amps yet, so it’s not likely they had 6550 output tubes. Those amps could have had the tone stack mods, and my guess is that they also had the big Drakes with the 3” stack. I saw some of those on Jimi's old equipment when it first showed up at West Coast Organ and Amp, and those amps had 630v or more on the plates, hot!
There is one other possible factor; in 1966 and 1967 Mullard made a batch of super EL34 tubes, my friend Bob Hovland the engineer at Vox bought a bunch of them for some stereo amps he was building and told me they were a lot like the 6550s we used in a bunch of amps we had built together. Of course those Marshall amps still blew up a lot, and that’s one reason why Marshall decided to go with a much lower plate voltage on the #1959 super lead. Plus it was cheaper to build the super lead because the transformers had a lot less copper and steel in them.

One real tonal difference in the super lead comes from the stiffness of the full wave bridge supply. The lower plate voltage meant that the OT primary impedance could come way down too, and that’s a major difference as well. A lot of folks prefer the 45/100 sound, but there is a nice sweet spot in the 4K range P-P impedance which works real well for mods. Say a Dynaco A431, they sound really good in those mods on the 45/100 and really bark when you need it.

If you want to use a 12AT7 as the PI, change the plate load resistors to 56K and 68K instead of 82K and 100K. Change the (cathode) grid bias resistor to 1200 ohms from 470 ohms, and change the lower constant current source resistor from 10K to 22K. Use a plate supply voltage of 440 to 450 volts with around 300 on the plates of the tube. It will draw 2.5 ma, so ..0025 x 56K will give you 140 volts drop across the resistor for 300 volts on the one plate, a little more drop on the other plate.

Bigger main filter caps help the 45/100 sound more like a super lead in some respects.

Anyway, hope this helps, and I am posting this for others too as requested.

The tonal difference with the extra tube is a lot more power amp gain, and a nastier full out tone.

[Xplorer]

thanks for posting this here, i found that it was very interesting.
and indeed, the castle made of sand tone .....
did anyone notice the tiny delay / echo, on the first notes of castle made of sand ? it's just during the first seconds of the intro, just after the power slide riff.

here is a picture from Dave, about some nice transformers :

http://i.imgur.com/hJtf6kZ.jpg

[daveweyer]

The transformers Xplorer posted were my two favorite mod units, and I did a lot of Marshall mods with them other than Jimi's amps. That PT is the Triad unit I've mentioned several times 400-0-400@500ma, and the black one is the Dynaco A-431, a 4300 Ohm P-P primary impedance 60/120 watt unit. 400 volts by the way, gives you 560 on the B+ terminal in a capacitor input system such as the Marshall, Fender, etc in a standard full wave CT system.
You can get both these units today under different brand names. A West Coast mod with these units gives you about 160 watts to play with.
Just thought you'd like to see them.

[C J H]

Oops, doublepost

[C J H]

Next test, the Fuzz, completed.

Ive had the Fuzz-circuit from a JEN doublesound fuzz/wha laying around for ages (.. preferred tha wha on its own with some mods).
Been planning to put the fuzz to use for some time so why not now?

I used the original circuit with the following changes;
- Replaced the R controlling fuzz-level with a 2K pot
- Replaced Q1 and Q2 with bc109s, dont know what the ones in there were but couldnt get them to sound good
- Added a 50k input bias pot.
- Hardwired output to board (no volume pot)

Heres a quick schem I made


Not exactly a Fuzzface to start with, but not far off. It sounds good, not as sharp and trebly as the RM axis fuzz I have. With the fuzz level turned up that smooth saturated ala Live at Isle of Wight (all along the watchtower for instance) is right there. I understand this is a tone of Jimis that most aficionados dont seem to care for that much, I however have loved that gig since I first saw it as a kid. Havent had enough time to experiment with the lower Fuzz-levels yet but the firts impressions is that it sounds very cool as well, fattens up the strat nicely. I find the bias pot mostly affects the amount of control you have via the guitarknobs, especially how it cleans up without thinning out. If dialed back fully the pedal moves in to octavfuzz-territory. I will hopefully get some clips together during the holidays. Oh, it works perfectly with a wah (fulltone clyde have yet to try it with that vintage JEN).

Thanks to Dave again for all the input and to Xplorer for sharing the schematic on his fuzz!

Heres a pic of the fugly little thing

[daveweyer]

Try moving the end of C3 off the voltage divider and down to the collector of Q2, and then tell us what happens.

[daveweyer]

I'll also try to get two of the original West Coast Organ and Amp fuzz units running, and then have Xplorer post the schematics on the forum so you can try them.
One is a mod of the two transistor FF unit, and the other is a three transistor version.
The fuzz posted above is quite similar to a West Coast mod.