A question of connections....

Agrippa · « **on:** 27 May 2005, 03:58 am »

Perhaps someone versed in matters electical can answer this for me....

I am currently running a bi-amping setup, with two ss amps. However, I am shortly buying a tube power amp, which will take over the mids and highs from one of the former. The thing is, I would like to keep the second ss amp in the system for when I just want to watch movies or TV. Un-doing and re-doing connections all the time may become something of an annoyance though, so I wonder if there are any problems attached to having two amps connected to one set of posts permanently? In other words, I would have the tube amp turned on and the ss amp turned off when playing music and vice versa when watching moves or TV, with both of them permanently connected to the same speaker terminals.

Am I likely to blow something up here, or perhaps compromise the performance of speakers and/or amps?

Regards,

Agrippa

Ethan Winer · « **Reply #1 on:** 27 May 2005, 01:57 pm »

Agrippa,

> I wonder if there are any problems attached to having two amps connected to one set of posts permanently? <

Don't do that. You could leave the line input connections in place to both amps and buy a switch for the speaker wires. But never connect two outputs together, even if one device is turned off.

This begs the question: If you're not satisfied with your solid state amp, why not just buy a better one? There are a number of pro-quality amps out there for reasonable prices.

--Ethan

jcoat007 · « **Reply #2 on:** 27 May 2005, 03:23 pm »

Quote from: Agrippa

Am I likely to blow something up here, or perhaps compromise the performance of speakers and/or amps?

Personally, I would never do this. Why? Because I know me and I know that at some point I would be a few sheets to the wind and need to crank some tunes. I would forget about the other amp and "kapleweeeee"

, both amps would die an untimely death.

But that's just me.

If you don't drink, this may not be a problem for you.

Agrippa · « **Reply #3 on:** 27 May 2005, 03:26 pm »

I'm quite happy with the amp, or amps, I simply felt the need to check out what all the hoohaa about tubes is all about.

Thanks for answering and for the warning. I'd love to have a "why" as well though....

Regards,

Agrippa

Ethan Winer · « **Reply #4 on:** 28 May 2005, 03:35 pm »

Agrippa,

> I'm quite happy with the amp, or amps, I simply felt the need to check out what all the hoohaa about tubes is all about.

<

Ah, all the hoopla about tubes. In a nutshell, mostly higher distortion, but sometimes poorer frequency response too.

> I'd love to have a "why" as well <

Amplifiers have a low output impedance that expects a much higher load impedance. So an amp that drives 8 Ohm speakers may itself have an output impedance of 0.01 Ohms or even lower. So when you connect one amp's output to another's output, the second amp loads down the driving amp and creates distortion.

--Ethan

Agrippa · « **Reply #5 on:** 28 May 2005, 11:56 pm »

"Ah, all the hoopla about tubes. In a nutshell, mostly higher distortion, but sometimes poorer frequency response too."

From what I read here and there I get the distinct impression that this might not be the full and complete picture.....

In any case, I care little or nothing for the supposed "correctness" of my gear and rather more for what reaches my cochlea in the end. I'm the one and only judge of what is "right" and "wrong" in my house.

"Amplifiers have a low output impedance that expects a much higher load impedance. So an amp that drives 8 Ohm speakers may itself have an output impedance of 0.01 Ohms or even lower. So when you connect one amp's output to another's output, the second amp loads down the driving amp and creates distortion."

Lovely, that's what I wanted! Thanks a lot, question answered.

Regards,

Agrippa

Ethan Winer · « **Reply #6 on:** 29 May 2005, 02:45 pm »

Agrippa,

> I care ... rather more for what reaches my cochlea in the end. <

And that's as it should be!

Also, on connecting two outputs: You can think of it as connecting two batteries together in parallel, not in series as is common to get more voltage. In parallel, unless both batteries are exactly the same voltage (down to sub-millivolts) each battery ends up as a short circuit for the other. So they both draw/supply so much current that they heat up quickly and die.

--Ethan

Agrippa · « **Reply #7 on:** 29 May 2005, 03:27 pm »

Gotcha!

However, as stated originally, one or the other would be off at all times. I'm NOT talking about driving the speakers with 2 amps simultaneously. I ain't THAT daft. Not quite...

Regards,

Agrippa

Ethan Winer · « **Reply #8 on:** 30 May 2005, 04:20 pm »

Agrippa,

> one or the other would be off at all times. <

Yes, I understood that. But a power amp that's turned off still should not be connected to anything else. In that case the output transistors will still be "in the circuit."

--Ethan

fabaudio · « **Reply #9 on:** 30 May 2005, 04:46 pm »

Agrippa

I hear you! I'm constantly switching back and forth between 2ch ( with tubes ) and 5.1 HT ( digital amp ). My fingers have corns from so much doing and undoing interconnects and speaker cables!

It' a pain in the butt!

Agrippa · « **Reply #10 on:** 30 May 2005, 10:24 pm »

Yup, that's what I'm dreading.

I suppose a switchbox would be the solution, but I've yet so see one of good quality. If I could get one I didn't think would degrade the sound, it'd be great, but I'm not so sure such a beast exists.

Regards,

Agrippa