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

[daveweyer]

If you send the signal into a 1M pot it will still only dissipate .0009 watts if your amp is cranking out 100 watts into the speakers. A 500K pot would dissipate .0018 watts, and so on. A 100K pot is completely safe. An 8 ohm pot would dissipate 100 watts, so that would need to be a pretty large wire wound unit. The point is that the greater the resistance across a constant voltage driving source, the less power it will draw.

A DMM will work fine to measure the output from your divider, especially if it is a true RMS meter, otherwise you will only get an average output, not true RMS. Still the error won't be great enough to hurt your experiment. In the end you will have to fine tune by ear to get the right amount of overdrive and feedback.

[Xplorer]

If you send the signal into a 1M pot it will still only dissipate .0009 watts if your amp is cranking out 100 watts into the speakers. A 500K pot would dissipate .0018 watts, and so on. A 100K pot is completely safe. An 8 ohm pot would dissipate 100 watts, so that would need to be a pretty large wire wound unit. The point is that the greater the resistance across a constant voltage driving source, the less power it will draw.

i understand, and that's why a 16 ohms L-pad is very big, because it needs to handle a lot of watts, while a 1M 2w pot can handle it. got it, thank you.

i have a fluke, it should be fine. i might go by ear, using a 100k pot 2w after the L-pad. starting from maximum resistance, and low amp volume. it should be safe then i guess.

but to measure the limit acceptable in this setup i might try to measure the conditions that make the setup to get the signal over 0,5 volt.

am i correct ?

[Tek465b]

With 100k pot you can safelly use 1/8 - 0.125 watt pot. or smaller. any 100k pot will work, you can use any wattage 100k pot you have on hand.
Power dissipation is going to be no more that 1/40th of a watt.
let's say 50vRMS to be save.(that's 156watt into a 16ohm load)
50²/100k=0.025 watt(25 milli watt)

Measuring the signal will be a waste of time, start from zero like you said, and raise the level to taste.

[daveweyer]

Anyone reading this thread is encouraged to plug their amps in series; it's cake to do, and really offers some tone expansion. If you have an old pot lying around you can do this easily.

Now to take it a step further, get into the follow amp, find the grid of the phase inverter, and inject the signal right there, avoiding the preamp/tone control section. (I used to run a wire from that point out to the second input jack on the front panel so that you could easily plug the Marshall output from the speaker jack on the first amp into the front panel of the second amp and get the re-amp effect, while still being able to use the second amp in the regular way.)
As an alternative, if you have a 1959 copy, where the tone circuit is the last thing before the phase inverter grid, inject the signal right into the top of the tone stack. This way you'll have some tone control, but no preamp gain. Then drive the output stage as hard as you like--you can drive it pretty hard.

That's the way Jimi had me set up his Guild Quantum amp for re-amping. It's too cool to pass up. I'm surprised by all the interest in Jimi's tone that never considers the possibility of re-amping in the equation.
I'm pretty sure you'll never get some of those tones without doing it. I know you can't see anything on stage that gives it away, but I also know he did it because he asked me to set it up for him.

Here we go again.

[Xplorer]

just tried !! it works !!

i can't test it at higher volumes yet but i did it without a 100k pot, just the 45/100 at zero level ( the normal channel also has to be on zero because when it's increased it has a real loud effect, even if no strat is plugged in ) , and i put that into the attenuator : one of the speakers output ( one on four )from a "virtual 4x12 layout" ) is going into the top left channel of the superlead : the superlead goes into the 1x 12 ...... oh damned !!! a 100 watt amp into a 1 x12 ! no , this is not good, i'll change that right now lol ... that's why it was loud ! very bright and clean.

anyway, it works, and i didn't imagine i could do that, i thought daisy chain was to plug your strat into the top left channel of an amp, then run a cable from the bottom left plug to the input top left channel of a second amp. not the same thing ..

[Tek465b]

anyway, it works, and i didn't imagine i could do that, i thought daisy chain was to plug your strat into the top left channel of an amp, then run a cable from the bottom left plug to the input top left channel of a second amp. not the same thing ..

That is daisy chained.
What you just did is re-amping. 2 different thing.

[Xplorer]

you're right, now i won't forget lol

[Tek465b]

lol don,t worry. re-amping is alot more

[amp23Collect]

Since I granted permission for a series of pictures to be shared on this forum of an amplifier I own, I thought I would share the portion of it's history that I know, I am a drummer, 64,and have for many years maintained a jam room where ever i have lived. I purchased this amp at a pawn shop in the mid 80's, I am somewhat of a hoarder and could probably locate the receipt If I looked hard enough. I was looking for a practice bass amp for the jam room with a little more punch than the Ampeg Porta-flex that was being abused, something tube as i detest most S.S. amps, and something I could afford. The CATMOTHER side was up and did not ring a bell, a large aluminum bracket was on top as a handle [originally the mounting bracket for a Quantum Cab]. I did not even notice the J.H. EXP. WITH CARE until I got it home and went to wipe off the grime. I showed it to a few of my "jam room" friends, but didn't really think that much of it, we called it "the Hendrix amp and jammed on. I did not have or want a computer, when I moved from Bottomline Studio, in the late 80's I sold off much of my gear but kept enough to keep jamming. I moved way out in the country...still no computer, we used the amp in my jam room here and in a couple of bands, even when I had to tape front panel [short] , short finally got worse and amp was getting noisy so I put it aside.....fast forward a few years into the new century. I finally relented and got a computer and Internet became available out here.I got the amp out and decided to take a closer look. I found the sticker from West Coast Organ & Amplifier Service, so I did some Internet research, saw same stencil on Hendrix gear, saw a pedal with same label strip, and finally contacted David Weyer telling him that I had an amp I thought he might have Modified for Jimi Hendrix ...he has examined the amp and verified this. I have enjoyed the use and sometimes "bragging rights" of this amp for 30 years, for many of those years I really had no Idea of the treasure I had found, I am getting older,don't play so much anymore. I am seriously considering putting it up for sale...I am not sure how to best go about this...maybe on Reverb...or ? my wife and I would like to see Hawaii and I would like to locate the drummer from Catmother and donate some of proceeds to him as I saw online he is living in his car.

[Tone seaker]

I reamp all the time with my Ultimate Attenuator, It uses a load to absorb the entire output then a second amp to power a speaker. you can use the line out to go into another amp. It sounds great.

[Xplorer]

it looks like it offers some very interesting possibilitys, but i couldn't test this setup in some ideal conditions. i need a 4x12 and setup a 12k pot into a little enclosure with jacks, for fine tuning

[amp23Collect]

To the administrator: wondering if my post about the much debated Guild amp reached you...edited because original post is now here

[Roe]

The Fryette Power Station is great for reamping

[daveweyer]

It's best if you can leave the first amp wide open, the speaker connected to the output tranny with no attenuation. This loads the first amp with more of a reactive element. From that you reduce the voltage level for the second amp.
Resistive speaker loads never give the same kind of overloading. That's one of the reasons that smaller amps are favored for the first amp, they're not that loud to begin with. Another reason for amps like the Fender Deluxe is that, at least on the earlier versions, it has no overall feedback loop. This also makes the AC-30 a good candidate for reamping.
With no overall feedback in the first amp, the output tubes have very little control over the speaker, and this means the air movement from the second amp has a much greater effect on the speaker in the first amp--some very good sustain can come from this. In the end it's a lot like a positive feedback loop for the second amp--it picks up its own signal from the speaker in the first amp, essentially making the first speaker into a partially controlled microphone.

[Xplorer]

What do you fo if the first amp is a 1x12 ?
You plug the second amp in parallel xith the first one, accross both poles of the unique speaker ? Or in serie ?