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

[daveweyer]

Tek, transistors are on way to QC. Some have gain as high as 180. Xplorer and Shakti will finally have their Jimi fuzz units. Fuzz down to about 1 or 2, and gain up will really capture the BOG thing.
All the transistors were taken out of Allen Organ equipment that I found lying around, the ones with grey tops were painted by Allen to denote low noise, and were used in the preamp stage of the T 50 amplifier.
Shipped by US mail. No charge, happy to contribute.

[Tek465b]

Wow thanks you very much!
Gain as high as 180 damn, this is a treasure right there.
Can't wait to try it, i studied the circuit(of course) and it look promising.
Yes dont worry, i will pass the transistor for free to Xplorer and Shakti.(i will match them too of course)

Where should we install the grey top/ low noise ones?in Q1 seem the best place to me.

[niknik]

While I'm waiting for some missing parts for the Major project, I'm going to start to assemble the 3 trannies fuzz.
I have got some 2N591s with hfe 83, 136, 251(?!), 99
One 2N525 with hfe 43
Two 2N527 with hfe 109, 94
and two 2N526 with hfe 55, 56.
Reading the schematic, I am a little off specs with these transistors.
Is the hfe the most important thing ( so I could try some others PNP germanium transistors with right hfe), or do I need to go with 2N591s and 2N525s, for the best result?

[daveweyer]

2N591s with gain of 83 for the first and 136 for the second should work great. The 527 at 94 should work in the third spot, but the 525 in the 40s would too. A gain of 251 would indicate leakage instead of actual gain, unless by some magic they made a PNP in the late 60s with that much current gain.
You just have to get the bias right for the first stage, the control takes it to cutoff at one end and you need to stay just away from that. The sound of the unit changes quite a bit between the limits of conduction which are set with the zener and associated resistors: at one end there are prominent second order harmonics. You'll hear the limits when you get it built.
Or, I made a recording of the sound of the unit with a Strat feeding back on a single tone, and ran the control from end to end to hear how the harmonics unfolded-- if anyone wants to hear that to compare it to their own tones, I can ask Xplorer to post it on his sound cloud.

[niknik]

Thanx Dave.
Yes, hfe 251 was strange also for me.
I'll try to procede like you said, and I'll post my result
And I really would like to listen your clip of the pedal in action, if it's possible

[Tek465b]

Nice, i got Dave's transistor in the mail today.
They all have the HFe marked on them .
Thanks you very much!

I tested for the leakage and they are all under 250µA. Very good.
Here are the HFe:
194
164
134
132
118
114
93
92
68
60
60
58
51.

Am thinking for your friends explorer and shakti.
134/114/68(i re-tested the 68 and its more around 64)
and
132/118/61
Seem like a good match?

I got the 2x 2Meg pot, they are huge, will see if they can be fitted on the pcb or needs to be mounted externally on a bigger enclosure.

[daveweyer]

Generally speaking, the fuzz gurus think that the higher beta device should go in the second slot; the conferred wisdom seems to be that around 80 for Q1 and 100-120 for Q2 is the magic relationship. I think that's about the numbers I used in the Jimi prototype. So you should have a pretty good trio for each of our boys out of what you found. And they do seem to vary somewhat from meter to meter, I used a handheld Tektronics gain and leakage meter, also noticing that some devices changed gain a bit after they sat in the machine for a few minutes.
I'm sure you'll have them up and running in their best colors before long. Yeah, the 2 meg pots are huge, if you look at the date codes you can see they are from the '50s. 2 megs in the AC feedback path gives insane gain and fuzz.
Cheers

[daveweyer]

Well I have some good (I think) news for you all; my son Will just made a little video on his iPad of the Marshall Major amp upgrade, and posted it on youtube, so you can see and hear the amp for yourself. Deniz Tek, of Radio Birdman fame, was over from Australia the day we made the video, and played a few licks through the amp. Please enjoy, and let me know if there is anything else you would like to see about the amp.

https://youtu.be/0GSke3u-HPA

[niknik]

Dave, wow!
I think this your Major is one of the most awesome sounding amp I have ever listened! Overdrive seems really powerfull, organic, with perfect balance between dynamic and compression! I've never heard a master vol amp that really behaves like a great cranked nmv amp! Awesome!
I really would like one day my Major could go near to your amp, I'm working for this dream
Other than all the improvements, like voltage regulator, more efficient driver, more efficient eq stack, and all the other great things, I think the heart of this amp is this compressor module, with six different amounts of drive available.
I presume it is an original project by you, and I would like to buy one of these, if it's possible. Also I have somewhere a filament tranformer I can use for extra tubes (already purchased)
Awesome job Dave, like usual

[JimiJames]

daveweyer:
https://youtu.be/0GSke3u-HPA
"...helps keep them from blowing up. Any of us Marshall fanatics have experienced that..."

heh
____

"...O.K., For those of you with a technical mind..."

haha!
_____

...didn't have enough room to see the transformer, but most anybody that's seen Marshall circuits knows what that's all about. Anyway, that's the general rundown of this...so, those of you that are a bit geek minded can see whats goin' on..."

Great stuff & sounds !
I like the sheen and hum balance control features.
(Constant 408v, hmm.)
Thank you, Sir.

[Tek465b]

I spent the whole day sanding, cleaning, anodizing, toner transer, etching, drilling the enclose.(actually its my 3rd try so, i spend the last 3 day on this loll)
It need a good cleaning/buff but its how it looks like now.
It's not perfect but it's original
I could not fit the big 2Meg pot inside sadly :/
But am thinking of adding a wild mode switch that add a serie 1Meg resistor with the 1Meg gain potentiometer to have that extra wide range of gain.


Also, here is the drilling template/toner transfer for 1590B enclosure(will update/add it to my webpage later)
It is a Gimp file so you will probably need to download and install gimp:
http://www.mediafire.com/file/m4tfkp924fiofxz/fuzz.xcf

[daveweyer]

Great job Tek!!!!
You got it all inside. Well, the 2 meg pot came from a different era, when things were BIG. Easier for old guys to see.
Cheers

[Tek465b]

Thanks,
What do you think about the wild mode switch that add a 1Meg resistor with the gain pot for a total of 2meg when maxed out?(its gonna do the same thing to me). I was also thinking of a 3 position switch that disconnect the FeedBack loop for a very wild mode
Yeah, its a bit of a tight fit in there, for people trying this in a 1590B enclosure make sure all the hole are well centered, there is no room for error.
In fact i don't know how i managed to insert a switch in there(the empty space on left side is for the transistor and i did NOT want to route the Feedback wires too far from the board).
Gonna finish this one tomorrow:

[shakti]

Many, many thanks to Dave and Tek for the conception, transistors and execution! Can't wait to try this fuzz out with my West Coast amp, which is sounding better by the day. If you see the 6550 thread, I have made a cascade mod on V1 which actually sounds terrific for Band of Gypsys tones - keeping the gain down the cascade mod just adds thickness, touch sensitivity and harmonics, but keeps the base tone of a 69SL with the West Coast mods. I am probably going to add an FX loop to the amp as well.

When all is up and running I'll try to make a good recording to demonstrate how it sounds now. I'll give the Dave Weyer Major clip a spin now.

[Tek465b]

Yes, i really think that Dave is doing an amazing work and he has impressive knowledges.

When i first looked at the major schematic i was impressed. But when i watched the video and seen the inside i was thinking.
Oh my god he must be some kind of electronic god to fit all that inside and still make it look soo good
And this amp sound super amazing, i wish we could hear more of the wild/cranked tone at the end.


Cascade mod look interesting, something i want to try since a while now.
I think the West Coast fuzz will have massive volume output when maxed, maby thats why the cascade mod help