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

[neikeel]

ha ha. yeah, why not.

i don't realise what daisy chain really is, and how it affects the tone. i tried once to plug a jack between the bottom high channel of an amp to the top high channel of another but ... nothing really.

i may daisy chain two 45/100, two superleads , and later a vox ac30 clone, a super reverb clone, a cp103 clone ...
i'll need a lot of speakers

i bet that Neil or thorleif and roe tried that !

But of course

[daveweyer]

Reamping works best when you start with a smaller amp, like a Fender Deluxe or an Ampeg Jet. You take the signal off the speaker, then plug it into your Marshall from there. You may need to reduce the signal with a resistor divider, like a 10K and a 1K across the speaker, taking the signal from the dividing point and ground.
You will likely get the best results with a speaker in between the amps because it contours the sound and allows for some air impedance to affect the signal.
Two Marshalls can work as well. Guitar players in Hollywood asked me to build switch pedals which would allow them to do this on stage, and then switch back to the two amps being in parallel, with the guitar signal going into both amp inputs similar to Hendrix.
It's a wonderful effect and can be done live.

[Xplorer]

please, can you repeat ? , is it really what i'm understanding ? i'd be too scared to take the 100 watts output of a marshall, with some speaker cable, and plug it into the usual jack inputs of another marshall. is it really this ? no harm to the amp, sure ?

maybe, starting with a low volume on the first amp, kinda closer to a small amp ?

You will likely get the best results with a speaker in between the amps because it contours the sound and allows for some air impedance to affect the signal.

like having the small amp and its speaker ... then putting that in parallel with the input of the second amp ?
> one pole of the speaker connected to the ground of a jack, and the other pole connected to the signal of the same jack > jack going into the second amp's input ?

i've never tried, or heard such setup and effect ; ) but it looks very cool

[Roe]

please, can you repeat ? , is it really what i'm understanding ? i'd be too scared to take the 100 watts output of a marshall, with some speaker cable, and plug it into the usual jack inputs of another marshall. is it really this ? no harm to the amp, sure ?

maybe, starting with a low volume on the first amp, kinda closer to a small amp ?
...
i've never tried, or heard such setup and effect ; ) but it looks very cool

try a line out, eg. suhr iso line out or the line out on the scumback db limiter/alex att

[Xplorer]

why a suhr or alex attenator line out ? to decrease the watts ?
i have a home made attenuator, four lines out, like four 30 ( 50 watts ) speakers. two of them are controlable with an L-pad. maybe that would do the trick ?

and by the way, what output impedance is ok, between 8 or 16 ohms, to put that into another amp's input ?
thanks.

[Tek465b]

You need to have speaker or a load on the first amp. and match the amp impedance to that speaker/load as usual.
Then you use a resistor voltage diviter to bring the signal down to an acceptable level for the 2nd amp input.

If you plug the output of an amp directly to the 2nd amp without any speaker.
First, the output impedance of the sending amp will not be matched, you will probably burn the tube or OT for that amp.
So you need a speaker or a load.
Now the 2nd receiving amp.. it has a very high input impedance so its not going to be 100Watt.
If you have 35 volt RMS into a 8 ohm load that about 150 watt. but that same output signal into the high impedance amp input (let's say 1M but its alot higher) it mean 0.001 watt. Very little power in fact.
But you'll have way too much signal drive.. so you need the voltage divider to bring the signal down to guitar/acceptable level.

Dave said it correctly:
You may need to reduce the signal with a resistor divider, like a 10K and a 1K across the speaker, taking the signal from the dividing point and ground.

you can simply use an attenuator set to load(or with some speaker) and use the line out to send to another amp.. Most line out has a potentiometer to control the signal level. That's a good thing. And in fact a potentiometer is an adjustable voltage divider in this application...
About attenuator.. i like to use them in parallel with the speaker as a load..

[daveweyer]

An L-pad would do the trick. Just make sure there is a speaker load across the output of the amp. You can dial down the output from the L-pad to a half a volt or so, plenty enough for driving a Marshall input.
The line out thing works okay too, but it never gets the contoured reaction of the speaker--you want that output tube distortion and the interaction of the speaker with the air, cabinets, and your guitar, all that to be reamplified. It exaggerates everything you like about the amp/speaker/guitar interaction.

[Roe]

why a suhr or alex attenator line out ? to decrease the watts ?

it was only examples of line outs.

[Xplorer]

thanks guys. my English, or simply my understanding, aren't helping me. i'm a bit scared to try so i tend to think i'm making confusions when you talk about the dividing point, the voltage divider etc.

let's put it that way : imagine an amp plugged in a 16 ohms cab 4x 30 watts speakers, classic stuff.
now, imagine that for three of the speakers : one is a real speaker, adjustable with an lpad. the two others are just big resistors.
Now the fourth speaker : instead of being a speaker, it's a 16 ohms 30 watts load controlable with an lpad, connected to the second amp's input . is it safe and right like you said, the three other speakers / resistors being the parallel load you're talking about ?

how can i know the limit of signal / voltage / watts i can send to the second amp without burning anything ? you said 1 volt, plenty enough. well, i'm not sure of how much a speaker receives of voltage, but i suppose it's way more than just 1 volt.

"But you'll have way too much signal drive.. so you need the voltage divider to bring the signal down to guitar/acceptable level."

yes but if i compare my guitar output signal to a speaker output signal, even with an lpad, the guitar signal is like zero .. active VS passive signal .. no ?
even if i set the lpad to almost maximum resistance ( that's what i usualy do to play at very low level in my bedroom ) , i don't know if it's the range of what you're describing.

"If you have 35 volt RMS into a 8 ohm load that about 150 watt. but that same output signal into the high impedance amp input (let's say 1M but its alot higher) it mean 0.001 watt. Very little power in fact."

what's the formula again ..
yes, it's meeting more than 1M at the input of the second amp, but can these little fragile looking 0,5 watt resistor handle such power ?

[daveweyer]

If your amp can output 30 volts across the speaker load, it's a typical 100 watt amp. If you run that signal across a 1 Meg resistor, nothing will happen to that half watt resistor because the power it will draw will only be .0009 watts. That would be the voltage squared divided by the resistance, power for an AC signal.

But the Marshall input doesn't need anywhere near that much voltage, a half a volt is usually sufficient. So use a divider which can take 30 volts and give you a half volt output, 60:1. Your L-pad turned to minimum will work for a start, and if it overdrives the Marshall input too much, just use a couple of resistors to divide that voltage some more.

[Xplorer]

i suppose that i should first measure the voltage of the attenuator's output, before putting that into another amp's input.

playing through the first amp, and the amp > 16 ohms output > attenuator able to handle about 200 watts , divided as a classic 4x12 layout, between two 50 watts résistors, one 30 watts speaker, and the last output we're interested in, that i'll measure, for use into the second amp . not sure it'll be 0,5 volts though. maybe the amp's volume at low level will help ..

i thought you said at some point that it was possible to send the output of the first amp directly into the input of another amp, daisy chained. i guess my memory isn't good about it.

[Tek465b]

60:1 or -36dB will do.
The l-pad is a good idea because you can set how "hard" you are driving the preamp of the next amp.

[Xplorer]

i'm affraid i have no way to measure the number of DB that the attenuator puts out, nor the 60:1, not sure what it is.

but i could measure the voltage on a jack plugged into the attenuator, and unplugged on the other side, while the three others "speakers" Inside the attenuator take some of the load.

[Tek465b]

i'm affraid i have no way to measure the number of DB that the attenuator puts out, nor the 60:1, not sure what it is.

but i could measure the voltage on a jack plugged into the attenuator, and unplugged on the other side, while the three others "speakers" Inside the attenuator take some of the load.

For measuring signal you'r better with an oscilloscope.
If you want to do it with a DMM. try and inject a sinewave(and avoid overdrive/clipping) because the guitar's signal will mess up the RMS function, it will be easier to measure with a sinewave. Otherwise, your meter will probably return bad reading.
Or simply wire a potentiometer to the line out(as a voltage divider).. so you can externally control it from Zero to full line level.. If you end up with the pot at max then you can remove it, and just use the line out/l-pad.

[Xplorer]

good idea, i should use a pot there, for fine tune.
but me and mathematics .... lol ...
30 watts meeting more than 1M input impedance making it 0,000 something watts, this is already rocket science for me, or magic. ha ha

so excuse my insistance but if i send the load ( which usualy is sent to a speaker, making it super loud in my room > a lot of power i guess .. ) into a little potentiometer , like those we use into our amp builds, before the second amp's input, will something burn ?
should i use a 1M pot perhaps ?