Pass Labs Aleph Question - balanced vs unbalanced?

Right - but remember I have no hum in my system on RCA cables at full pre-amp output and CD player having just played music and then hitting pause and turning pre-amp all the way up...

So in that case then there is no reason to convert back and forth, right? If I have no RCA hum, then is there any sonic reason to use balanced?

Interesting... It says in the manual for the Aleph 5:

"For the lowest possible operating noise in any environment, the amplifier is equipped with balanced inputs featuring a common mode noise rejection of greater than 60 dB. Balanced operation is accomplished through a passive network tied directly into the input stage of the amplifier, not with additional active input circuitry as in other products. This assures that the noise benefits of balanced operation are not accompanied by the degradation of more semiconductors in the gain path.

The input of the amplifier is flexible and can also be operated with unbalanced sources. The input system will exhibit full common mode noise rejection with passive balanced sources, where the negative input is connected to ground at the source through the appropriate source impedance. This allows adaptation of unbalanced sources to balanced operation with passive cable connections in a manner that achieves the noise rejection of active balanced sources. Pin 1 of the XLR input connector is ground, pin 2 is the positive input, and pin 3 is the negative input."

And in the beginning: "The Aleph 5 integrates power Mosfet devices and pure single ended Class A operation in a simple two-gain-stage topology"

Okay - so that means the basic topology is single ended and there is a passive network to direct balanced signal to the single ended amplification pathway? Well, there is no reason to convert to balanced if the amp is just going to turn the signal back into single ended and amplify it there - I have no hum when running under RCA. I was under the impression it was a balanced through-and-through amp. Do I understand this right?

Wloeb - I thought something like that may be the case - because Nelson Pass says in his materials that air is single ended in how it relates to sound and that made me think the words meant something else...

Okay - so the Pass Alephs are internally balanced? So if I go RCA, the RCA input has to be converted to balanced? That makes sense... I had thought they were fully balanced years ago.

If an amp is balanced internally then its got to be at least a hair better with balanced inputs - even if that hair is not discernable. (Because of additional conversion step).

Oh - but then there are those who might say that conversion could improve the sound and we get into our basic audiophile philosophy about equipment...

Bottom line - amp is internally balanced, so balanced should be better - recognizing that one needs to listen for final conclusion as odd things happen in complicated systems. Cool.

A quick comment about the shorting pin - I don't know why but my current Comcast HDTV feed is very low in volume. Commercials are normal, which is infuriating as I have the volume super high for the show, and then the commercials are defeaning - but anyway - The Aleph 5 is not powerful enough without the shorting pins in place when used via RCA in for me.

All that to say, 1) I hate Comcast, and 2) with the shorting pins in, you will get more power.

I'll quote the aleph 5 manual:

"The Aleph 5 is shipped with a shorting plug between pins 1 and 3 of the input XLR connectors. This shorting plug sets the gain of the amplifier to 26 db when you are using the RCA unbalanced input. Removal of this plug will set the gain to 20 db. Needless to say, you will remove this plug when using the balanced input. There is no penalty for not using this plug withunbalanced operation, and if you ahve particualrly efficient loudspeakers, you may find that you prefer it this way."

Note that I haven't had the chance to get shorting pins (originals lost long ago) and I am currently using 2 twisted and bent paperclips in each pin, with no noticeable decrease in sound quality. He he.....

Agreed - I know he is big on 'fewer gain stages are better' in general, maybe it skips some amplification circuitry - shorter circuit path? Must be something like that. With pin in place it must somehow participate in circuitry involved with the balanced operation??? Agree that without asking its all conjecture...... (But perhaps the one thing we can be definite about is it skips some amplification stage and should have shorter circuit path).