Y adapter to 2 receivers-Dangerous?

[KEW]

I am wanting to compare two pairs of speakers and would like to have the same sub in operation with them. My setup is two identical receivers so I can mute one of the receivers and after that, every time I hit the mute button the sound instantly switches between the receivers.
However, I run the risk of having both receivers on at the same time.
I think combining two two-line level signals into the same sub will increase the volume, but not double the wattage or do anything severe. But can someone confirm this is safe?

Thanks!

 

[ImcLoud]

Ive done worse, I wouldnt think it would hurt anything... In my old system I had my home theater feeding the sub and my ipod with a 2.1 system feeding the same sub with different towers, and I used to forget the theater on all the time while playing music, and I would have it loud, ONe time I noticed the bass was all crazy rumbly while listening to Johnny cash, I turned the tv on and spiderman was playing, so I was listening to johnny cash spiderman 3 remix...

 

[ahblaza]

I am wanting to compare two pairs of speakers and would like to have the same sub in operation with them. My setup is two identical receivers so I can mute one of the receivers and after that, every time I hit the mute button the sound instantly switches between the receivers.
However, I run the risk of having both receivers on at the same time.
I think combining two two-line level signals into the same sub will increase the volume, but not double the wattage or do anything severe. But can someone confirm this is safe?

Thanks!

Hey Kurt, I can't comment on the safety of this procedure, just the fact that you are asking is an indication that it may not be safe. Wouldn't a simple speaker selector work for your application?

 

[Grador]

I'd be more worried about applying voltage to the output of the receivers than increasing voltage to the subwoofer. It'd probably be fine, but it is a risk.

 

[KEW]

Hey Kurt, I can't comment on the safety of this procedure, just the fact that you are asking is an indication that it may not be safe. Wouldn't a simple speaker selector work for your application?

I can't match the SPL with a normal speaker selector. With two receivers I have independent volume controls. I really want instantaneous, level-matched A/B switching.

 

[KEW]

I should mention that these are Marantz SR 6001 receivers.

 

[KEW]

I'd be more worried about applying voltage to the output of the receivers than increasing voltage to the subwoofer. It'd probably be fine, but it is a risk.

That is an interesting point! Imcloud seemed to get away with it on his setup.
I know when I used a Y to feed my cd player to both receivers, I could not just turn on one system and listen to it. Apparently the signal was going into the "dead" receiver and running rampant among the circuits, then feeding back into the cable to the active receiver. It didn't seem to hurt anything, but sounded like crap. Once I turned on the second receiver everything sounded fine.

I don't think line level signals have enough voltage to do damage to any circuits. And I wouldn't be applying a higher level of signal to the output than what that output would normally see from within its own receiver. But I know just enough about electronics to be seriously dangerous!

 

[Alex2507]

I'm hoping to see TLS come along before you launch something into orbit.

 

[ahblaza]

That is an interesting point! Imcloud seemed to get away with it on his setup.
I know when I used a Y to feed my cd player to both receivers, I could not just turn on one system and listen to it. Apparently the signal was going into the "dead" receiver and running rampant among the circuits, then feeding back into the cable to the active receiver. It didn't seem to hurt anything, but sounded like crap. Once I turned on the second receiver everything sounded fine.

I don't think line level signals have enough voltage to do damage to any circuits. And I wouldn't be applying a higher level of signal to the output than what that output would normally see from within its own receiver. But I know just enough about electronics to be seriously dangerous!

My concern isn't so much an instant damage but more of a long term application, excess voltage can and will cause damage, from my limited knowledge as well, I have increased current (amperage) but did not exceed stated voltage with no apparent side effects. I am far from being an electronics engineer but as you say the voltage from line level sources should not be excessive enough to cause any damage, I wouldn't take my word for it though.

 

[ahblaza]

I'm hoping to see TLS come along before you launch something into orbit.

I'll second that............

 

[Grador]

That is an interesting point! Imcloud seemed to get away with it on his setup.
I know when I used a Y to feed my cd player to both receivers, I could not just turn on one system and listen to it. Apparently the signal was going into the "dead" receiver and running rampant among the circuits, then feeding back into the cable to the active receiver. It didn't seem to hurt anything, but sounded like crap. Once I turned on the second receiver everything sounded fine.

This reminds me of another possible issue, the muted receiver could present an excessive load to the one that is currently sourcing. Excessive current draw on the pre-outs could also be dangerous.

 

[markw]

You want to combine the sub outs from two different receivers into one sub input?

Dunno for sure, but that would feed the output of one of the receiver's sub out right back into the sub out of the other receiver as well as to the sub itself. Or, two outputs into one input.

That's exactly the opposite of the way I've always seen them used: For splitting one output into two inputs.

Electrically, I'm not too sure that's kosher, but I'm not an engineer.

IIWY, I'd hold off until I got a definitive answer, say from Marantz?

 

[ahblaza]

You want to combine the sub outs from two different receivers into one sub input?

Dunno for sure, but that would feed the output of one of the receiver's sub out right back into the sub out of the other receiver as well as to the sub itself. Or, two outputs into one input.

That's exactly the opposite of the way I've always seen them used: For splitting one output into two inputs.

Electrically, I'm not too sure that's kosher, but I'm not an engineer.

IIWY, I'd hold off until I got a definitive answer, say from Marantz?

Or at least until Mark (TLS) guy chimes in.

 

[KEW]

You want to combine the sub outs from two different receivers into one sub input?

That is the wiring configuration I am considering.
It is not my intent to have both outputs live at the same time, but it is very likely to happen inadvertently for short periods of time.

Unfortunately, I haven't had much success from Marantz answering questions like this in the past. I think it is beyond their CS rep's pay grade and they don't have a good system of passing difficult questions up the technical ladder.

If anyone knows a good contact point with Marantz, I'd love to know it!

 

[markw]

I don't know why I didn't think of this yesterday.

A simple analog selector box like this will work just fine for what you want to do. Safely select between multiple line level inputs to one output with the push of a button.

Ther are others out there. Just go to Amazon, Electronics, and search for "audio input selector box".

I've used that ugly silver Philips one, a few rows down, with component video selection in the past and it worked fine, at least before HDMI came along. I also have a bare-bones Rat Shack one from the stone age that works for just audio but I don't think they make 'em that simple any more.

 

[TLS Guy]

I am wanting to compare two pairs of speakers and would like to have the same sub in operation with them. My setup is two identical receivers so I can mute one of the receivers and after that, every time I hit the mute button the sound instantly switches between the receivers.
However, I run the risk of having both receivers on at the same time.
I think combining two two-line level signals into the same sub will increase the volume, but not double the wattage or do anything severe. But can someone confirm this is safe?

Thanks!

Here is your problem. An output source is almost always low impedance on an output. It is just good practice to keep source impedance low. The input impedance is high at the load. (the sub).

So if you use a Y-connector to connect one output to two sources, everything works fine.

Now if you go from two sources to one load as in your case, then each output is going to load the other with a low impedance load, and you will actually get less volume. Worse, as has already been pointed out you will load the circuits of each receiver with the other. Since none of the voltages will be higher than what each receiver sees at its respective outputs, you are not going to damage anything. However you have degraded your LFE signal significantly with this hookup.

The correct solution is a buffer amp with two high impedance inputs, that sum to one output from a low source impedance.

Does your sub have left and right inputs? If it does connect one receiver to left and the other to the right. These sub inputs, when there are right and left, are always buffered in the manor I described above. If you have left and right line level inputs on your sub, then that is how you should hook it up.

 

[KEW]

Thanks Mark!

If I follow you correctly, I think I am fine.

Essentially one of the receivers will always be muted when I am listening!
The only time both receivers would be active at the same time is a fluke when the mute button did not work on both receivers at the same time. When that happens, it is obvious, because both pairs of speakers will be playing at the same time as well, so I catch and correct it.

Just to make sure I follow properly - If one receiver is active and the other muted, do you see any issue to the SQ?

 

[TLS Guy]

Thanks Mark!

If I follow you correctly, I think I am fine.

Essentially one of the receivers will always be muted when I am listening!
The only time both receivers would be active at the same time is a fluke when the mute button did not work on both receivers at the same time. When that happens, it is obvious, because both pairs of speakers will be playing at the same time as well, so I catch and correct it.

Just to make sure I follow properly - If one receiver is active and the other muted, do you see any issue to the SQ?

Yes there is still a problem, the receivers outputs will load each other with the same low impedance load, whether they are on or off. Not good.

Your cheapest solution is the switch box, the most seamless solution is a buffer amp. ATI have one that can be configured as I outlined.

 

[Alex2507]

Or at least until Mark (TLS) guy chimes in.

Despite what Rick says, the other Mark is okay too.

 

[KEW]

Thanks Mark, Mark, and Ahblaza for suggesting the switch box.
I guess I'll have to suck it up and press two buttons. Life can be such a 8itch!