Using RCA & XLR connections at same time on Amp

Thank you everyone for your input. I think I will have to stick with the processor or get a seperate pre with a HT bypass. Below I have included the response from Pass Labs on the issue which I think pretty much ends the discussion as I don't really want to degrade the HT performance.

Thank You

Chris

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Chris,

Your dealer is partly correct. I will indeed work, but it will not be optimal on the RCA inputs. You will note in the instruction manual that we place a jumper between pins 1 and 3 of the XLR when using the RCA connections. Failure to install the jumper will loose you 6 dB of gain and
quite a bit of headroom on the RCA. However other than acute loss of power there is really no other great sonic penalty. Stressing the X3 is certainly not at issue. Keep in mind that the center channel of the X3 will swing
quite a bit more current than right and left channels.

Good luck
Pass Labs

Mcaintosh has the switch---and the folks at McIntosh are very emphatic:

"Don't do it!!!!"

Audioengr -- That's the reason I bought PCA-2 pre-amp, so I've excellent 2ch with HCA-2 and use HT bypass when I use the processor for home theater combining with a 3ch amp.

Rkmca - what you are doing may sound okay in some cases, but it is a really bad idea.

I've done something similar, it works but sound quality varies, which I think was due to impedance mis-matching.
I've used PS HCA-2 which is balanced and have both RCA and XLR inputs. I've hooked up my Wadia 301 using XLR to XLR of HCA-2 and front L/R pre-outs from my Parasound processor using RCA to RCA of HCA-2. Just turned off the Parasound when I was using the Wadia, worked perfect.

The difference I've noticed was that if I don't turn off the Parasound and switch the source to a input which is not hooked up and play the cd player, sound level, resolution, bass evrything was higher. But if I turn it off and just use the cd player, sound level just drop and I've increase the volume level on Wadia.

I ended up getting a pre-amp with HT bypass and everything is perfect now. I run the Wadia with full volume through the pre-amp, get bigger soundstage, better resolution. I may lose some detail as Wadia is better in detail if you run direct to an amp.

I think you should try a pre-amp with HT bypass like PS PCA-2, ML 38/380. There may be others, I sure someone can provide you with some advice. Try to audition using a pre-amp before you buy a new cd player.

If the amp does not have selector switch on the back for RCA/XLR, then it is very likely that the inputs are common (+ for RCA = + for XLR). Therefore, you do not want to connect two sources to the amp at the same time. This will essentially short the two sources together. If they are low-impedance, this could do damage. At a minimum, the sound will suck because of the loading caused by the other source.

I'm doing the same w/ Bryson 7b-st's, I think you should be O.K. w/ your Pass. Yet just to be on the save side I would take good ol'e UncleJeff's advice. Call or email Nelson Pass & see? Good luck!

Warning: Some amps, especially those that are not truly balanced share some parts at the balanced/unbalanced ports. So, while you are using balanced, you might be sending a signal back up the line to the unbalanced components. The switch, in this case, is not designed as a 'cut-off', but more like a router.

If you happen to have both systems on at the same time, you might be in for some serious, big time trouble.

I understand McIntosh would be one case where you must avoid this.

BE CAREFUL!!!!!

Don't have any specs on the ML-#39, but one thing that will work for you is a two input/one output transformer volume control (passive pre). I have one that has both XLR and RCA inputs..it has balanced output to my Krell amp. I can switch between the two on the front panel of the passive unit (no need to switch amp cables).

I may (not sure yet) sell my unit in a week or so if the amp I have for sale on Audiogon does not sell.

There may also be some kind of high quality switch box you could buy, not sure about that one.

Dave

I did almost exactly what you describe with a Bryston power amp and a Resolution Audio CD-55 player (which does have XLR outputs and an analog volume control). Works like a champ, as long as you can easily reach around to the back of the amp to switch the input.

So your just reaching behind the amp, & switching from a Xlr connected system, to a Rca connected system. Sure this works, 2 systems all on one amp with just a flick of a switch. Bypass a preamp w/ the 39 & connect right into the amp via variable out, & enjoy!