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#297741 - 03/21/10 10:00 PM Best way to run two channels off one pre-out?
michael_d Offline
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Registered: 07/23/04
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I want to experiment with my center channel. To bore those who know and to inform those who don’t, I am running two M22’s right now for my center channel. I am going to order a VP150 and play a bit. I want to mount the VP over my screen and keep the M22’s where they are, under the screen about 24” apart. I am using a 3808 for a pre-amp and I have ten, 200W / 8 ohm channels to use. I want to power the M22’s off one channel and the VP150 off another channel. The problem is, the 3808 only has one center channel pre-out. I’ve read (don’t recall where or who) that it is not a good idea to use a Y off the pre out. I don’t know how else I can do this without using a Y.

I know that many of you will think this is a dumb idea, and it most likely is. I just want to experiment as I don’t think anyone has ever done this before… I will more than likely just end up buying a second VP150 and mount it under the screen to have one over and one under, but for now, I just want to settle my curiosity.

So….. is using a Y a bad way to do this? Is there another way to do this?
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#297745 - 03/21/10 10:08 PM Re: Best way to run two channels off one pre-out? [Re: michael_d]
pmbuko Offline
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I don't think it's dumb, per se. You'll just be splitting your pre-out voltage in half. As long as you're connecting each side of the split to a different amp, I don't see what problems can come from it. As you know, you can compensate for the voltage drop during calibration.
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#297756 - 03/21/10 10:30 PM Re: Best way to run two channels off one pre-out? [Re: michael_d]
JohnK Offline
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Mike, you might have read something I commented on in the past, but you don't recall the point clearly enough. The problem with Y-connectors isn't going one into two(or more), it's going two into one. When you try to combine two voltage outputs into one input simply by using a Y, the dumb voltage doesn't know that it's supposed to go only into the connected input. Instead it also runs up the other branch of the Y into the other output, causing at least distortion, and possibly damage.

So yes, Mike; no one has ever done that before. Your success with the experiment will assure your undying fame in the annals of Axiom.
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#297778 - 03/21/10 11:19 PM Re: Best way to run two channels off one pre-out? [Re: JohnK]
Ken.C Offline
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John's answer is very confusing to me, but as I understand it, running 2 channels off a pre-out has to be how Axiom expects people to use the A1400-8 to run 2 center channels, right?

In other words, I would think that Peter's got the right answer here.
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#297780 - 03/21/10 11:26 PM Re: Best way to run two channels off one pre-out? [Re: Ken.C]
Wid Offline
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Registered: 06/22/03
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Yes, Peter has it right.
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#297782 - 03/21/10 11:29 PM Re: Best way to run two channels off one pre-out? [Re: Wid]
CV Offline
Founder, Axiom Upgrade Club
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Once his tall wife puts her stamp of approval on it, then it will be official.

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#297787 - 03/22/10 12:23 AM Re: Best way to run two channels off one pre-out? [Re: CV]
pmbuko Offline
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My wife is of average height.
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#297801 - 03/22/10 03:04 AM Re: Best way to run two channels off one pre-out? [Re: michael_d]
JohnK Offline
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#297808 - 03/22/10 07:56 AM Re: Best way to run two channels off one pre-out? [Re: JohnK]
ClubNeon Offline
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Registered: 02/06/09
Posts: 3466
Loc: Western Maryland, USA
So in summary: dividing is OK, summing is bad.

Dividing: One output driving two amps. (One sub-out to two subs.)
Summing: Two outputs being combined into one amp. (L&R outs into a mono amp.)
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#297812 - 03/22/10 10:01 AM Re: Best way to run two channels off one pre-out? [Re: JohnK]
michael_d Offline
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Registered: 07/23/04
Posts: 4195
Loc: Up yonder
 Originally Posted By: JohnK
Mike, you might have read something I commented on in the past, but you don't recall the point clearly enough. The problem with Y-connectors isn't going one into two(or more), it's going two into one. When you try to combine two voltage outputs into one input simply by using a Y, the dumb voltage doesn't know that it's supposed to go only into the connected input. Instead it also runs up the other branch of the Y into the other output, causing at least distortion, and possibly damage.

So yes, Mike; no one has ever done that before. Your success with the experiment will assure your undying fame in the annals of Axiom.


You assume too much John. The Axiom forums are not my only source of reading material. My question was specific to using a Y off an output, not to combine two outputs. I have read that that is not a good idea. Two outputs into a Y would make no sense, in any application. So what’s with the condescending tone anyway?

Peter - Thanks. That's what I thought, but wanted to verify.
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