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Topic: 2 amp heads and 1 speaker cabinet -- How? |
Richard Sinkler
From:
aka: Rusty Strings -- Missoula, Montana
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Posted 24 Apr 2015 8:08 am |
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Just watched a Joe Bonamassa video. He was playing through 2 Marshall heads, but only one Marshall speaker cabinet. I have seen this a lot, even back in my early Grateful Dead era. How are they hooking these up?
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Carter D10 8p/8k, Dekley S10 3p/4k C6 setup,Regal RD40 Dobro, Recording King Professional Dobro, NV400, NV112,Ibanez Gio guitar, Epiphone SG Special (open D slide guitar) . Playing for 55 years and still counting. |
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James Holland
From:
Alabama, USA
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Posted 24 Apr 2015 9:52 am
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| Marshall makes stereo cabinets, separate circuits to accomodate two amps, or two channels. |
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Richard Sinkler
From:
aka: Rusty Strings -- Missoula, Montana
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Posted 24 Apr 2015 10:37 am
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I was wondering about the cabinet wiring. Do other brands do the same?
_________________
Carter D10 8p/8k, Dekley S10 3p/4k C6 setup,Regal RD40 Dobro, Recording King Professional Dobro, NV400, NV112,Ibanez Gio guitar, Epiphone SG Special (open D slide guitar) . Playing for 55 years and still counting. |
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Tom Gorr
From:
Three Hills, Alberta
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Posted 24 Apr 2015 10:46 am
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| There's also a number of products called Head Switcher's.... never used one myself. |
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Richard Sinkler
From:
aka: Rusty Strings -- Missoula, Montana
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Posted 24 Apr 2015 11:33 am
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Ah yes. Head switchers. Forgot about those. But how far back in time do they go? I remember seeing the Grateful Dead with more Showman heads than speaker cabs. That would very early 70's.
_________________
Carter D10 8p/8k, Dekley S10 3p/4k C6 setup,Regal RD40 Dobro, Recording King Professional Dobro, NV400, NV112,Ibanez Gio guitar, Epiphone SG Special (open D slide guitar) . Playing for 55 years and still counting. |
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Tom Gorr
From:
Three Hills, Alberta
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Posted 24 Apr 2015 11:53 am
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| Theoretically...a head switcher could go back to the invention of a double pull double through plunger style switch and a metal box....or something like that...the need and solution in close proximity...not a lotof creativity required. |
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Lee Warren
From:
Nashville, Tennessee, USA
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Posted 24 Apr 2015 1:48 pm
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Hi Richard,
Is it possible that the 'extra' heads are spares that can used, in case of an amp failing during the show?
A lot of players push their gear to the brink.
This way a stage hand can easily move the speaker cable to a fresh, 'not blown up' amp, that is ready to go ...
Lee |
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Richard Sinkler
From:
aka: Rusty Strings -- Missoula, Montana
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Posted 24 Apr 2015 3:29 pm
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One time at the Fillmore, I saw a stage hand take a Twin that Weir was using, on top of an Acoustic cabinet, that failed and just dropped it behind the line of amps, and stuck another there, hook it up, and the song never stopped. I don't think that is why they were there on stage, and turned on, although Fenders do have the standby switch.
_________________
Carter D10 8p/8k, Dekley S10 3p/4k C6 setup,Regal RD40 Dobro, Recording King Professional Dobro, NV400, NV112,Ibanez Gio guitar, Epiphone SG Special (open D slide guitar) . Playing for 55 years and still counting. |
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Dave Campbell
From:
Nova Scotia, Canada
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Posted 25 Apr 2015 3:03 am
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you can run two heads into a single cab as long as the cab has multiple speakers, and it is wired so that each head goes into half the speakers (in effect, you'd be running two heads and two seperate speaker systems, just housed in one cabinet).
to switch heads is a little more involved, as the head not being used still needs to see the speaker impedance to balance the circuit. this is especially critical for tube amps.
radial makes a headbone, but it's about $300. you can make a diy version, but it's far more complicated than a simple a/b box.
i've often thought that the perfect guitar/steel combo would be a deluxe reverb with upgraded speaker, and a showman head running into the same speaker. |
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Tom Gorr
From:
Three Hills, Alberta
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Posted 25 Apr 2015 6:53 am
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The switch I had in mind...
for the first pole would direct the input signal to the head in use and ground the other. The second pole would switch the amp output being directed to the speaker and ground the unused amp through a load resistor.
...not perfect... it is not fail safe.. but might be proven to be safe enough. The intermittency of the switch may cause probkems unless the guitar was muted before switching.
The best fail safe solution would be to have an unswitched load resistor or modern day attenuator in parallel with each amp output and switch the speaker into and out of that parallel circuit...The impedance would be doubled for the off amp...thats generally an acceptable mismatch for tube amps.
Last edited by Tom Gorr on 25 Apr 2015 7:16 am; edited 1 time in total |
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Stephen Cowell
From:
Round Rock, Texas, USA
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Posted 25 Apr 2015 7:15 am
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| Tom Gorr wrote: |
The best fail safe solution would be to have an unswitched load resistor or modern day attenuator in parallel with each amp output and switch the speaker into and out of that parallel circuit...The i impedance would be doubled for the off amp...thats generally an acceptable mismatch for tube amps. |
If you don't want to lose power to the resistor (and if you don't want to have a full-power-rated resistor), you can do what Radial does... basically, during the switching process the dummy load is connected during the switchover, then left on the quiet amp. This way you only need one dummy load, and it doesn't have to be a 100watt capable load... the switching has to be make-before-break, and accomplished with relays and sequencing... there has to be a little overlap.
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Too much junk to list... always getting more. |
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Tom Gorr
From:
Three Hills, Alberta
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Posted 25 Apr 2015 7:49 am
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Haha...I was developing that option while you were submitting. ..
Seems there are mechanical switches that make before break that should be able to do it without relays etc. Now we are into detailed design phase. ...I will leave now..lol...
The input signal could be handled more securely as it could be completely grounded prior to any intermittent sharing of a load resistor between heads. Still a bit not fail safe as switches are known to fail.
Radial produces a lot of very simple circuits that they sell for big dollars. ... basic functionality stuff like heavy duty A B Y boxes....guitar boxes have got to be high margin... even Mesa has got into the dirt box business. |
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Richard Sinkler
From:
aka: Rusty Strings -- Missoula, Montana
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Posted 25 Apr 2015 9:35 am
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| Dave Campbell wrote: |
you can run two heads into a single cab as long as the cab has multiple speakers, and it is wired so that each head goes into half the speakers (in effect, you'd be running two heads and two seperate speaker systems, just housed in one cabinet).
to switch heads is a little more involved, as the head not being used still needs to see the speaker impedance to balance the circuit. this is especially critical for tube amps.
radial makes a headbone, but it's about $300. you can make a diy version, but it's far more complicated than a simple a/b box.
i've often thought that the perfect guitar/steel combo would be a deluxe reverb with upgraded speaker, and a showman head running into the same speaker. |
A band I was in did this. We wanted coverage with every instrument at both sides of the stage. The guitar player (on the other side of the stage) had a Randall "stack". On his side of the stage, we placed one cabinet. He played through 2 of the 12's, as well as my amp in the other 2 12's. I played through the other 2. His other cabinet went on my side of the stage. The guitar player played through 2 of the 12's, and the bass player through the other 2. Balanced the sound out, and everyone could hear everyone else without having to play at ear blistering volumes. Everyone in the club could hear every instrument, no matter where they were seated.
_________________
Carter D10 8p/8k, Dekley S10 3p/4k C6 setup,Regal RD40 Dobro, Recording King Professional Dobro, NV400, NV112,Ibanez Gio guitar, Epiphone SG Special (open D slide guitar) . Playing for 55 years and still counting. |
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