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Torn between two amps

I would like to use two different amps, but not at the same time. My Cary Rocket 88 sounds better with CD's and my custom OTL amp sounds better with vinyl. I am not sure the best way to hook these up in my system. I do not want to be switching I/C's and speaker cables every time I want to change source.

This is what I thought of but not sure it's the best way;

1.) I did a quick check on the web and saw a Bryston speaker switch box. Thinking I could run the speaker cables to the box and then back out to each amp. (this scares me a bit as who knows what damage can be done if both amps get turned on accidently and/ or speaker A & B buttons get pushed in at the same time ).

2.) Get an interconnect Y adaptor connecting the pre out to each amp.

Will either of the above degrade the sound?

Anyone know a better way to do this?
markpao

Showing 2 responses by almarg

almarg's avatar
almarg
9,670 posts
 
I agree with Stan. I'll add that the effects of a y-connector arrangement will be highly dependent on the output impedance of the preamp. The lower it is the better.

The preamp will see a load impedance that is equal to the product (multiplication) of the input impedances of the two power amps, divided by the sum of those two input impedances. If the two power amps have equal input impedances, that corresponds to a combined impedance of 1/2 of the input impedance of each amp.

That combined impedance should be at least ten times (and very preferably 20 times) greater than the output impedance of the preamp at the frequency at which that output impedance is greatest (which is likely to be 20Hz, unless the preamp has a dc coupled output, meaning no capacitor in series with its output).

Also, the capacitances of the cables running to each amp will sum together and possibly introduce some amount of upper treble rolloff, if the capacitance per unit length of the cables is high and the cables are long and the preamp output impedance at high frequencies is high.

Regards,
-- Al
almarg's avatar
almarg
9,670 posts
 
Neither amp should be energized if no direct connectivity is made to an existing speaker load.
Excellent point, Jim. A tube amp, or at least a tube amp that has an output transformer, should never be operated without a speaker load.

I believe, though, that that may not apply to an OTL. But as a matter of good practice, and not taking any undue chances, I would avoid doing so anyway.

Best regards,
-- Al
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