1 Footswitch to control 2 amps?

Let's say I have 2 Electra Dyne amps and I want to use 1 Footswitch to control them both..can it be done? This would need 1 TRS split to 2 TRS. I only see Y adapters in TRS out to 2 mono cables, but that won't do.

I'd like to run an Electra Dyne with a Royal Atlantic at the same time and use 1 footswitch.

You will likely have to build a "parallel-TRS box". I just built a "series-speaker connection box". Go to your local hardware store, and purchase a platic AC junction box and the lid that goes with it. Then go to an audio store and buy 3 TRS female jacks. You then should wire it in a 1-in, 2-out fashion. You will probably need one of those 3-to-2 prong 120V AC ground lift adapters to use on one of the amps to keep the "hum" monster away. 8)

Thanks. I think I found adapters.

http://www.redco.com/HOSA-YPP-118.html

http://www.redco.com/Redco-PM-TRS-TRS.html

Do not use your amp with a ground-lift adapter on the 120 V electrical plug! :!: The ground is there for safety, and if you lift the ground and touch another amp or other equipment it can shock the piss out of you. I have played with jack-asses that have the ground plug broken off of their amps and I have been shocked, I wanted to punch them for being so foolish and putting me in danger like that. I doubt if you are going to have any noise/hum introduced if you use the channel switching pedal to control both amps. If you are using an ABY type box to control the input signal to both amps, then get an ABY switch that has the ground lift option on the switch itself. to use if necessary. But, don't ever defeat the ground on the electrical plug, it is dangerous.

shimmilou said:

Do not use your amp with a ground-lift adapter on the 120 V electrical plug! :!: The ground is there for safety, and if you lift the ground and touch another amp or other equipment it can shock the piss out of you. I have played with jack-asses that have the ground plug broken off of their amps and I have been shocked, I wanted to punch them for being so foolish and putting me in danger like that. I doubt if you are going to have any noise/hum introduced if you use the channel switching pedal to control both amps. If you are using an ABY type box to control the input signal to both amps, then get an ABY switch that has the ground lift option on the switch itself. to use if necessary. But, don't ever defeat the ground on the electrical plug, it is dangerous.

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FWIW, I only suggested that the ground be lifted on ONE of the TWO amps. The common footswitch will connect the grounds of the two amps together, and protect the player from shock. I have a Lehle Dual ABY switch that effectively does the same thing. There was no mention of switching amps in the original post, only running the pair in a stereo setup. I, too have been shocked by an amp that had its ground disconnected. An old Ampeg SVT that had a repair plug on the cable end. :shock: OUCH!

Not fun is it? :shock:

Really, you shouldn't lift the ground on the 120 V plug on either amp, ever. I would not depend on the foot switch ground, it can easily become disconnected, or switched out of the circuit. The difference in lifting the ground when using an ABY foot switch is when using the isolation transformer for one of the amps, lifting the ground on the signal side, not lifting the 120 V ground which is a solid connection for safety.

Since the OP was talking about a TRS cable foot switch, this is the cable for switching channels, and other amp functions, so I don't think any ground lift will be necessary as using this foot switch on both amps shouldn't introduce any noise as it's not in the signal path. If you get any noise when connecting two amps signal paths together with an ABY switch, the safe way to get rid of the noise is to use a switch with an isolation transformer and lift the ground on the switch if necessary.

I HAVE been lifting the ground on 1 amp when I have 2 connected because of the TON of noise you get when you use 2 amps. I use a Strymon Mobius out to the input 2 amps, and have a delay, and a boost/buffer pedal connected to both effect loops. No problems with anyone getting shocked.

I stand by what I've said. Just because something hasn't happened, is not proof that it can't happen. There is no noise caused from simply using two amps, the noise occurs when connecting the two amps signal paths together, and the signal path is where the noise should be dealt with. :wink:

Look at step 1 in the instructions of this wiring diagram. http://www.grailtone.com/forum/viewtopic.php?f=3&t=19316

JOEY B. said:

Look at step 1 in the instructions of this wiring diagram. http://www.grailtone.com/forum/viewtopic.php?f=3&t=19316

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And there you go. Mesa's instructions versus some anonymous dude with 9 posts on a gear forum? I'd listen to Mesa.

Whatever peels your banana. :lol:

It doesn't matter to me where the bad instruction originates, it's still bad instruction.

I have an old engineering book around here somewhere, written by a guy with a PhD, that states; "Use the back of your hand to check for electricity". :shock:

I understand the idea, using the back of your hand means that if the circuit is live, your hand will contract away from the electricity, but it's still wrong to use your hand to check electrical circuits. The book also mentions the difference in taste between AC and DC, so go for it if you like. 8)

Well hooked up the Royal Atlantic and Electra Dyne but no hum or loud noise at all, no footswitch connected but I have a Strymon Mobius into both amps inputs, and a delay pedal in both effects loops. No ground lifts needed so far.

The earth ground on the line voltage input in a high-voltage tube amplifier is there to help protect the user. Period.

Personally, I would never lift the ground of any tube amp (and never had to), even if Mesa is telling me so, YMMV.

I understand that the second amp will be grounded, I'm just not willing to put my life on the fact that the lifted amp is only grounded through an instument cable shield.

I think shimmilou's advice is good advise, and factual. No need to bash him.

I will usually lift the ground on one end of a patch cable (or two) to break a persistant ground loop.

I know a few players that use ground lift adapters with no issues, I will not.

It's your amp do as you wish.

Dom

Thanks domct203, I didn't take it personally. After-all, I am an anonymous dude, and Mesa has engineers and everything. :wink:

I suspect that the Mobius uses isolation transformers, or some other means of isolation as many switchers do, to eliminate ground loop noise. I know that the Mesa switcher mentioned also uses isolation transformers, so it seems odd, as well as dangerous, that Mesa would advise to lift the ground on the amps. Maybe we misunderstand what ground they meant? Why not design the switcher without the ground, since it is connected to ground through the instrument cable? Stereos and many other appliances, as well as double-insulated power tools don't use/need a ground. Amp switchers only need to deal with the very low voltages of the signal anyway. In discussions about noise caused by using multiple amps on other forums, the solution was always a better switcher with isolation transformers in the switcher itself. Some noticed a change in tone when using isolation transformers, but I would think that the altered tone could be easily remedied. In my years of experience I have found that grounding is a subject that is misunderstood by a surprising number of people, even by those that should know better. I always like to quiz "electricians" by asking them about their understanding of the difference between neutral (common) and ground. :idea:

domct203 said:

I understand that the second amp will be grounded, I'm just not willing to put my life on the fact that the lifted amp is only grounded through an instument cable shield.

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Yourself and your guitar are connected to earth ground through the shielding in the cable plugged into your guitar, in a mono amp setup. Not bashing anyone, just sayin' . :wink:

Understandable JOEY B., but therein lies the problem, as you can now become a path for the electricity to go to ground should a fault occur in the ungrounded amp. Electricity always takes the path of least resistance, and ideally that path would be through a solid ground as close to the amp as possible, and not through your body. Each person's body has a different resistance, but the body's resistance is typically much higher than the couple of ohms of an earth ground on an amp. You might have heard of the infamous "death cap" on some of the older ungrounded amps that had a "ground switch" or "polarity switch" ? This cap, if shorted, could put high voltage onto the amp chassis, and since the older two-prong electrical plugs had no grounding conductor (ground plug), the path for the electricity could then become the player's body. :idea:

JOEY B. said:

domct203 said:

I understand that the second amp will be grounded, I'm just not willing to put my life on the fact that the lifted amp is only grounded through an instument cable shield.

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Yourself and your guitar are connected to earth ground through the shielding in the cable plugged into your guitar, in a mono amp setup. Not bashing anyone, just sayin' . :wink:

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And that is where the problem lies. It's not about grounding the player, it's about grounding the amp. You don't want to be the path to ground if there is a short in the ground lifted amp.

BTW- using a wireless will insulate you from a direct connection to the amp, and any shock hazard, and that is one if the reasons I use one when I gig regardless of stage/club size.

Dom

domct203 said:

It's not about grounding the player, it's about grounding the amp. You don't want to be the path to ground if there is a short in the ground lifted amp.

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It's definately all about grounding the player, especially if it is me. FWIW, I would never lift the ground on a mono setup. I have been the easiest path to ground, and it hurts. :shock:

Now you have me looking at a wireless setup, after I sold my last one due to "Noise". :evil:

JOEY B. said:

Now you have me looking at a wireless setup, after I sold my last one due to "Noise". :evil:

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I'll recommend any of the Line 6 Relay units, or the old X2 units, very quiet & clear. I use the X2 XDS-95 in my main rig & a Relay G90 in my backup rig.

I just bought a backup X2 XDS-95 off eBay for $110, in mint condition with the original box.

Dom