An odd idea

Got a question for all of you . . . .

I've been battling with the problem of optimizing 2-channel performance without compromising the coherence of my HT setup. I only have one room which is usuable for A/V gear, and it's loaded to the gills with speakers for HT.

I'd like to upgrade my amplification for 2-channel, but don't want to have to buy SEVEN channels of "good stuff," since that's a healthy chunk of cash and I'm happy with the HT performance of my Rotel gear.

So here's the question -- anybody ever tried hooking up one set of speakers to two different amplifiers? I'm thinking of a modified shotgun biwire cable, run backwards -- single end to the speaker, split ends to two different amps. Obviously you'd have to make sure you NEVER had both of the amps turned on at the same time . . . .

It seems to me that this would be preferable to using a switcher box, because that would put an additional "thing" in the signal path, where the split speaker cables would not.

Of course, my understanding of electronics would fit into a Vibrapod, so there might very well be a screamingly obvious reason why this would be a disaster in the making . . . .

Would this work? If it did, it would allow the use of completely different amps for 2-channel and HT without having to worry about the interaction of one with another, same for preamps.

I'd really appreciate any feedback anyone had here . . . .


Why can't you use the 2 channel amp that you want to use for audio/music, to also run those two channels for HT?? This is actually not an uncommon setup.
I agree with Sugarbrie. Use a 5 channel amp for the surround (center, rear, rear, side, side) and a 2 channel for the stereo. I may be too clumsy or risk averse, but I'll bet that, sooner or later, an accident will happen and both amps will be on at the same time in your configuration. You are right to try to avoid a switch within the stereo path (unless that's your only safe option).
The only problem with using the 2-channel in the HT setup is that I've gone to significant lengths to ensure that my HT setup is as cohesive as possible -- speakers with identical drivers all the way around, and identical amplification (at least in terms of sonic signature), and if I throw something different into the mix, the main L and R speakers are going to SOUND different than the center, rears, and sides, which is what I'm trying to avoid.

I'm assuming that a $2000+ 2-channel amp (Bryston, Aragon, McCormack, etc.) is going to have a very different signature from my $1200 Rotel 5-channel . . . . for the price difference, it had better! ;-0)

Then again, maybe the difference wouldn't be that horrific. Unfortunately, I live in the sticks, and there are NO, repeat NO high-end dealers around here, so I don't have the opportunity to borrow something to audition and see how the mix sounds . . . .
You could also just use speaker cables with banana plugs, and then just manually switch the cables at the speaker to change between amps.
Sugarbrie --

That was my second choice idea . . . . you don't think I'd eventually cause wear damage to the speaker terminals through the repeated plugging and unplugging?
Putting a better amp on your main speakers will not hurt your movie sound at all,it will make it better. I have done it. Your speakers are a good match for each other so it will sound fine.
If you run the output of one amp into the output of another amp your going to smoke the amp even if it is off. Had a friend that had the same idea as you using a Rotel 6 channel amp and an aragon 8008bb. As soon as he turn on the aragon amp (the rotel was off) the rotel went up in smoke. Cost over $300.00 to repair the rotel. Best thing to do is to have two sets of speaker cables and just reach behind the speakers and swap cables.
I had the same problem that you did. I run Infinity IRS V on the front, IRS betas for surrounds and an IRS Gamma on the center. I use different amps for the front and back. The difference is sound field is VERY negligible. I could make the sound totally seamless either by upgrading all my speakers to IRS V and better amps, which isn't something I can afford, or I can downgrade my mains to equal the quality of my surrounds, which is also something I am not willing to do.

Any system that plays a large percentage of music would do well to upgrade the mains at the expense of the other channels.
One nice thing, I guess, is that with using two sets of speaker cables as an option, I can always go ahead and try the amp in the HT system, and then use the cable swapping maneuver if I'm not happy with the cohesion.

Thanks for the suggestions!

Prpixel --

Ouch! Remember that Vibrapod worth of electronics knowledge I mentioned earlier? THANKS for the warning . . . I will relegate that idea to the same dustbin as Communism -- "It SOUNDS like a good idea, but . . . ."

Mrpoindexter --

Thanks for the input -- like you, buying 8 channels worth of Aragon or McCormack isn't really an option, so it's good to hear from someone else who has successfully integrated "good" with "really good" and not had any issues.

Thanks again to all!
One of the regulars on this forum who is also an electrical engineer can correct me if I'm wrong, but I think that having your speakers connected simultaneously to two amps -- even if one of them is turned off -- may produce an undesirable electrical interaction. The electrical signal coming in from one set of speaker wires can still feed down the speaker cable going to the unplugged amp (assuming both sets of speaker wires are connected to the same binding post), which can lead to anomalies in the resistance/impedance, and may even produce undesirable EMF (electromotive backforce) similar to the current produced by the rearward movement of a speaker cone.

In short, even if one amp is always turned off and you NEVER make a mistake of leaving both amps on, this is probably a very BAD idea from both an electrical and audio viewpoint. I'd recommend doing what I do, and what others above have suggested: use a 2-channel amp for your main speakers, and a separate 5-channel amp for your center and surround speakers
One thing to remember about Home Theater is that there really is no 'reference' standard. Unless you have precisely the same speakers for Left, Center, and Right, channels your center channel will sound different than the others. In home theater, much of the sound comes out of the center channel, so you might want to upgrade your front three channel amplification (just a thought).

The other thing about home theater is that DVD recordings/sonics are not that good when compared to two channel audiophile recordings. Having speakers that are matched gets you 98% of the way there for good home theater balanced sound. Amplification is almost a secondary concern per se. What a better 2 channel amp will give you that you probably will notice is better bass response in the front two channels. I run 7.0 channel sound with my two channel system driving the L and R channel. My L, R, and C channels are all matched (Vienna Acoustic); however, my rears and sides are from a different speaker manufacturer altogether (Acarian Alon). The sound still is truly amazing. My L and R speakers play so low (22hz) that I have no need for a sub.

If you want a large leap in performance from your Rotel without breaking extreme budget, I would suggest going with something like an Aragon 3 channel amp used. Another option that could be very good would to be going with Monarchy SE100 monoblocks. I once drove a complete HT system with Monarchy monoblocks. These little amps sound awesome and are very good deals used.

There are a lot of ways one can go with amplification.

What I would not worry about is the different amplifiers driving your speakers. YOu have matches speakers, and that is 98% of the battle.

NEVER feed one amp's output into another's! The output impedence of the "disconnected" amp is MUCH lower (0.1 ohms or less with ss) than any speaker, and you'll quickly blow up the unused amp, right?
Unless you feel your system is lacking in dynamics or sounds like it's straining at your listening levels, you might not want to replace the amp just yet. There are a bunch of tweeks you can to to the typical H/T setup to improve performance. The first would be to adjust speaker location and make sure there is plenty of room between the TV and L/R speakers. You may even have to move them forward so that they are not on the same plane as the TV. TV's are bad for sound and the bigger they are, the more problems they cause. Even better would be to get a plasma and get rid of the box altogether.
You could also try is getting new CD's. One reason people are happy with home theater performance is because movie soundtracks are recorded at a higher sampling rate and sound much better then your typical CD. But there is alot of variablity even amoung redbook cd's. Look for newly remastered copies, HDCD's or enchanced versions of your favorite songs, DTS cd's, or even DVD video. I wish there was more out there in terms of multi-channel audio because the sound really is fantastic.
As a last resort you might want to consider a tube CD player. Some people like the tweekability aspect they provide, but i personally never found them to improve the sound as much as finding a better recording.
Again, thanks to all for the suggestions!

Tok2000, you make a good point . . . . I guess the speakers are the key, moreso than the amplification.

Subaruguru, thanks for the warning!

Perkadin, interesting suggestions! My speakers are already set up as you suggest -- about 2 feet out from the TV (any farther and they are too close to the side walls) and about a foot in front of the TV. I hadn't considered the CD quality issue, though . . . . and my system is definitely not lacking in power or dynamics. I've thought some about the tube CD player idea, too.

I think what I'm going to do is finish all the tweaks I can with the existing hardware -- install the 2-channel passive preamp, upgrade the 2-channel path cables from Audio Ones to Audio Twos, upgrade the power cables on both the 9000ES and the Rotel 985, and apply some isolation/damping treatments to both -- and try to isolate what I feel are the system's shortcomings in a little more detail.

I also want to play around a little with some room treatments -- I don't know much about that, but I figure that there's no shortage of places on the web to learn.

THEN, if I decide the new amp is a necessity, I'll pick one based on what I want for 2-channel, without worrying too much about HT integration, since I know that a) it should work OK, and b) I can always go with seperate speaker cables if it doesn't.

Again, thanks much to all!

I had a similar experience. I have a home theater system consisting of PSB speakers and a Yamaha 5.1 amp. I wanted to use a Cambridge A300 integrated to just run the mains. I could not, and still can not figure out a way to use both of the amps at the same time without turning up volume on both of them as the movies played. I ended up going to Radio Shack and buying a switch box for just the mains. As some of you pointed out, a mistake will eventually be made. I'm just lucky that the protection circuits in BOTH amps were up to the task and kicked out when I had both amps connected together at the same time. I like the idea of using bannana plugs and NEVER having the amps connected together.
Here's one that'll make you smile :) (And yes, this is a serious suggestion...) replace your TV with a front projector - and then use a retractable screen. This will eliminate a large sonically reflective surface right between the main speakers, becaues the screen will be retracted when you're listening to 2-channel. It has a surprisingly audible impact on 2-channel imaging. I learned this by accident, because I upgraded to such a setup purely due to space concerns when I wanted a big screen, but until I find enough money to build a dedicated theatre room (as opposed to a combined theatre and concert room), I'm not going back!

Also, I've gone down the same path as you have - my speakers aren't identical but they're pretty close. However, I discovered that even adding some very different surround speakers made less difference than I would have expected. In my case, I upgraded my surrounds from Triad Silvers (dipole in-wall cone speakers) to MartinLogan Scenarios (bipole floorstanding electrostatics), and I found that both worked equally well with the main MartinLogan panels up front. Their signatures are different, but this is only perceptible when playing 5-channel audio. I don't perceive the difference AT ALL when watching movies, except that the Scenarios obviously have more bass punch. There is a difference in 5-ch music, of which I have little so far.

I can also report that my amplification is quite different front to back, and this too is not an issue. I have vertically biamped my ML Odysseys with a Classe CA200 for the cones and a Counterpoint SA220 for the panels. (This took a little tweaking!) That's the equivlaent of 800wpc@4 ohms with mixed tubes and transistors for the fronts. The surrounds make do with just a single 3-channel B&K ST3140, at 175 wpc@ 4 ohms, all transistor. This is a pretty big difference, and the only one that can be readily identified is that there is some timbre change from the mains to the center and back. I don't notice the difference to the surrounds very much. I will have to upgrade the center amplifier sometime, although I'm having a hard time imagining precisely what I would put there...
Ah, a projector. I'd like to have a projector . . . . I'd like a pony, too. Unfortunately, they both have about the same likelihood of working out in my living room. Too much light for the projector, I fear (and too much rented carpeting for the pony). ;-0)

Thanks for the suggestion, though -- I'd wondered idly about the feasibility of retractable screens, so it's nice to know that they work.

And thanks for the info on using umatched speakers and amps -- now I'm not so paranoid about trying a partial upgrade.

Thanks again to all!

You might be surprised how much light you can tolerate with the newer high-output DLP and LCD projectors. Although you cannot manage with either the sun or even a ceiling lamp shining on the screen, the colors are less washed out than you might expect. I have two unshaded windows in my room, and I can watch TV during the day (football, auto racing) quite happily, except the 20 minutes or so that the sun shines directly through one window onto the screen.

Try it - you might like it!
Blw --

I live in a rented house, so cutting holes in things isn't an option . . . . can I get a projector and screen that I could mount without doing major surgery to the ceiling? Screws and bolts in the ceiling are no problem.
Projectors are pretty flexible today. At the moment, I am in a temporary room because we're in the process of building an addition. My projector is sitting on a shelf behind and over my head. Believe it or not, the screen is actually mounted on a 2x4 frame that is free standing. If you're sufficiently determined, you can definitely arrange for this. Drop me an email and I'll send you a photo.

In my last house, both the projector and screen were bolted to the ceiling. In my case I ran the cables through the ceiling and walls, but of course that's not 100% necessary.