Question about running stereo amps

Lullabies

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2,054
Want to start running stereo (from stereo outs on Boss Tera Echo at end of pedal chain)

My main setup would be 76' Ampeg VT-22 and an Ampeg GVT15H into a ported 1x15 Peavey cab. But at rehearsals I am going to use two Marshall JCM2000 DSL half stacks at either side of the room.

My question is with this type of stereo setup (not using an ABY) will the sound be affected ? I have heard it can thin the sound out if there is no phase switch as with some ABY splitters. I don't get to try it till later tonight at my rehearsal. I am curious!
 

Lullabies

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2,054
Good to know!

So I guess using my 2 different ampegs will cause issues then ? I will eventually get ABY splitter when I have spare cash. Would be nice if I could just the use the boss for now though or even indefinitely if it works well without phase issues. My board is pretty full now
 

DaveKS

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16,704
Good to know!

So I guess using my 2 different ampegs will cause issues then ? I will eventually get ABY splitter when I have spare cash. Would be nice if I could just the use the boss for now though or even indefinitely if it works well without phase issues. My board is pretty full now
Not necessarily, phase pops up when you different numbers of gain stages in the amps, will depend on amp, # tubes and how their wired and what function they do. The two amp may work perfect in clean chan but switch one them to another channel and phase issue will be there.
 

Lullabies

Member
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2,054
Not necessarily, phase pops up when you different numbers of gain stages in the amps, will depend on amp, # tubes and how their wired and what function they do. The two amp may work perfect in clean chan but switch one them to another channel and phase issue will be there.
Ah ok thanks for the insight. I use both amps clean and pedals for everything else. But both Ampegs are pretty different tubewise. The VT-22 has like 11 tubes and the GVT15h has 4 :roll

I guess the only way to find out is to try. I'll see how it goes and if I do need a ABY I will know where to ask!
 

riffmeister

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16,617
You really only hear the thin, out-of-phase sound if the amps are close together. If the amps are on either side of the room you probably won't have to worry about phase issues.
 

Silent Sound

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5,427
Don't worry about phase issues. Sometimes two out of phase signals can sound better. For instance, if you have two amps on opposite sides of the room pointing at each other, then they will often have more bass and sound tighter if they're 180º out of phase from each other.

Also keep in mind that anytime you have the same sound coming from more than one source, you will have phase issues. Phase issues have as much to do with the distance between two speakers as they do with the polarity of the signal feeding them. And when you factor in the room which also plays a role in all of this, you've got an extremely complex math equation to use to figure out what would be the best "phase" to use on each amp. Even on a 4x12 cabinet you're going to have phase issues between each of the 4 speakers because they're not occupying the same physical space (which would be impossible).

Or you could do what professional engineers do in the studio... Try it one way, see if it sounds good, then try it the other way (flipping the positive and negative terminals on the speakers on one amp is an easy way to do that without buying any new equipment) and see which way it sounds better. It doesn't matter which way is "in phase" because they will all be somewhat out of phase. You can't have sound emanate from two separate points and stay in phase for all frequencies at all other points in the room. It's impossible. But you can figure out which way sounds better, forget the math, and just go with what your ears tell you.
 

Bossanova

Gold Supporting Member
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Did you do it? I started doing this 2 weeks ago and I'm hooked. Of course, working on plans to "go quad" next!:Devil
 

Lullabies

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Oh man did I ever do it!

I did stereo for the first time tonight. Marshall JCM2000 halfstacks at each side of the room with volume up quarter way on both. Delay with my malekko sloika(low drive) sounded amazing! the second I plugged in and played a chord it was a freakin revelation! There is no way in hell I can ever go back to one amp now lol. It sounded too damn good...Both clean-ish with delay and all out Russian Muff fuzz mode it sounded intense as hell. Finally got the surround sound room filling effect I have always envisioned in my head. Blew my mind haha
 

michael.e

Silver Supporting Member
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20,530
I have been running one amp dry and one amp with delay in order to keep the phase in line. I find that when I use the polarity switch to even things out, the pick response and tone of that one amp suffers.
 






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