Can I use Balanced and Single Ended Inputs on the Same Multichannel Amp? - AVS Forum
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post #1 of 8 Old 05-19-2001, 11:02 AM - Thread Starter
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See, what do I know?? Just goes to show don't hazard a guess, find out for sure first.

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post #2 of 8 Old 05-19-2001, 11:15 AM
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Don't do it!

I posted on another forum about my incidence with the 7B's when I was too lazy to turn the power of while switching preamps (balanced vs unbalanced) and as soon as I flip the switch...

Fortunately the B&W's were built tough enough to take the static burst and no harm done but I learnt my lesson and am in the process of getting another set of amps for the extra preamp.

PF

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[This message has been edited by pmf (edited 05-19-2001).]
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post #3 of 8 Old 05-19-2001, 12:02 PM
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You may want to contact the manufacturer to check if these are really 2
separate inputs or if they are internally connected. The switch may
just be grounding pin 3 of the XLR input and pin 2 may be wired to the
RCA input (with the grounds tied together internally). If this is true
the amp may not like both inputs hooked up at the same time. If they
really are separate then you are in business!
The above is the route I am taking with some mcCormack Amps modified by Steve McCormack presently so I can connect different line level outputs from HT processor and multichannel dvd-a/sacd multichannel preamp combos to the same amps with switches and extra inputs for the center channel monoblock and rear channel stereo amp. My front left and right channels are connected into a 2 channel analogue preamp which feeds 2 monblocks.I'll use different stereo inputs into that preamp for main right and left channel source material from the different processors.

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post #4 of 8 Old 05-19-2001, 01:07 PM
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I spoke to Krell about this situation and they do not recommend using both inputs. I am building a switch box to get around this problem.
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post #5 of 8 Old 05-19-2001, 10:26 PM
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Situation:

1. Two Krell amps (KAV-250a two channel amp, KAV-250a3 three channel amp).

2. Each amp has a balanced and a single ended input. I currently am using the balanced inputs of each from the balanced outputs of a HTS preamp/processor.

3. I am considering adding an analog preamp/processor to the mix.

4. What I am hoping to do is this: use the single ended outputs from the analog preamp/processor, to go into the single ended inputs of the Krell. This would mean that two different preamps would be inputted into the Krell amps at the same time, though both would never be on at the same time.

Any problems with this approach? Nothing in the Krell manual speaks to the issue.

Any help is greatly appreciated. Thanks in advance.

Nick http://www.avsforum.com/ubb/cool.gif
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post #6 of 8 Old 05-19-2001, 10:44 PM - Thread Starter
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My Bryston 7B amps also have balanced and single ended inputs, plus a little tiny switch on the back to choose which inputs you want to use. If the switch is on balanced but single ended is connected - no sound.

Do your Krell amps also have such a switch?

Check with your Krell dealer to make sure, but I betcha it has a switch that you can do this, provided you're willing to get up off your fanny and hit the switches!!!

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"Doug Winsor" used to troll at some AV Forums as "Steve Bruzonsky"! My home theater at:
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post #7 of 8 Old 05-19-2001, 10:54 PM
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No, it's not possible. It's should also be stated in the manual. The center pin of the single ended is wired in parallel with the balanced pin 2. You could damage your gear if you do it.

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post #8 of 8 Old 05-21-2001, 11:22 AM
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Hi,

That's an interesting question. My Pass Aleph monoamps have also XLR- and RCA-outputs - but no switch. I mailed Pass, if it is possible to connect two preamps at the same time.

That's their answer:

Dear Walter,

It is possible, in theory. The challenge you will face is to not have inputs coming from two different preamps simultaneously. Most preamps are designed to be left on all the time, and they will produce a low level signal even if not in use, depending on their circuitry. This will cause "confusion" in the power amp (receiving signals from two different inputs). Also, if you were to drive two signals by accident into the amp you could cause problems.

So, if you experiment, be very careful to only drive one signal at a time into the amplifiers!

Best regards,

Peter Perkins, North American sales, Pass Labs and Volksamp

I am not sure, if I should trie it.

greetings, Walter

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