Balanced cables

Fsonicsmith, as a point of information ARC line stages and preamps do not meet the criteria Atmasphere cited in his post that I referenced that would minimize or eliminate sensitivity to differences between balanced cables.  Certainly, at least, with respect to his criterion no. 4:

Atmasphere 3-22-2013
...  4) the output of the preamp should be capable of driving a low impedance load (2000 ohms or less) without loss of voltage, without increase in distortion and without loss of bass (this is the other big area where high end audio preamps have a problem, and also results in cable sensitivity).

ARC's recommended load for nearly all of their line stages and preamps is a minimum of 20K, and in some cases a minimum of 60K is indicated as being optimal.

So when "ARC stresses in their manual that the quality of the XLR going into the Ref 150se is critical," as you indicated, they are indeed "telling the truth."

Regards,
-- Al
 

Al, I always read your posts with interest. You clearly know far more than I do about technical aspects of electronics. I can not read a schematic and never understood concepts of loading as it pertains to amps or phono cartridges :-). With that spirit in mind, I think I know this; say what you wish about ARC, but their 40 year history of building top-tier preamps is incontrovertible. I am going to venture a guess that while Ralph is most likely correct, there are also drawbacks to designing a preamp that is capable of driving low impedance loads. Even if it were true that with certain preamp designs, the quality or "pickiness" of the XLR choice were minimal, is that attribute a "freebie" without trade-offs? I can't help but think of the relatively high negative feedback employed by ARC in the Ref 150se. It's a buzzword in the industry that "no negative feedback" or "minimal negative feedback" is and of itself a mark of distinction and superior sound. Again, I only know that I am getting hair raising chills on the back of my neck and total immersion in the music with the tonal density I had hoped for and without any perceptible bloat, with a wide and deep soundstage that was not critical on my wish-list, but a happily accepted bonus. As with many hobbies, there are certain buzzwords that tend to predominate as accepted truths, but the reality is that "it all depends". 

I have an all Ayre system (with Vandersteen speakers). I’m hearing a kind of metallic sound from the system which I’d like to pin down. As I stated above, its totally balanced from cartridge/CD player through the amp. I even removed the tweeter and mid from the boxes, sent them to Vandersteen who deemed them in excellent health. A while back I tried different XLR cables which had a minimal effect on the total sound....but that was awhile ago (Wireworld top of the line). I’m sure my hearing has changed (I’m a violinist and sit next to the piccolo) and just thinking about change. My amp is about 14/15 feet from the preamp, and no one has that length to try without a firm purchase.......still thinking. Re: Cardas......no luck with that brand. Colleen Cardas told me that it probably needed more time to break in (months?)....although I haven’t heard their newest offerings.

BTW-There is no such thing as a "balanced cable". That term implies that an XLR/Cannon connector was only designed to be used with fully balanced left/right channel audio components which is very misleading and completely false. There are solid state components that are fully balanced with both RCA and XLR connector's. The inventor of the XLR never used the term "balanced" for his connector. When the very first stereo receiver was invented by Sydney Harman in the 1950's, the Festival 1000, it was a fully balanced design in twin cabinets with the left channel in one cabinet and the right in the other. with a control panel on the front of each unit. A classic dual mono design. The unit had RCA connector's only. The term "balanced" was a label put on XLR cables by Audiophiles in the 80's. You can label an RCA cable as well as a "balanced cable" if its used between fully balanced components. 

Fsonicsmith, thanks. I essentially agree with everything in your post above. There are always myriad tradeoffs in a design, and the net result of those tradeoffs often will not conform to commonly stated paradigms.

For example a major reason, and perhaps the most major reason, for ARCs 20K minimum load recommendation is their use of a coupling capacitor at the outputs of their line stages and preamps, which of course is very commonly done in tube-based line-level components, and which among other things causes a substantial rise in output impedance at deep bass frequencies. And while that effect could be minimized by simply increasing the value of the capacitor (i.e., the number of microfarads), doing so would most likely increase the sonic colorations introduced by the capacitor itself, and/or result in the capacitor being a larger and potentially impractical physical size.

And an alternative approach that is used in some tube designs, using a transformer instead of a capacitor, certainly can have tradeoffs of its own.

Regarding feedback, yes, ARC power amp designs tend to use more of it than many and probably most high quality tube amps from other manufacturers. Consequently they have lower effective output impedances and higher damping factors than those other amps, which in turn can be either an advantage or a disadvantage or neither depending on the particular speaker that is being used. And the downsides feedback can potentially have with respect to the intrinsic sonic character of the amp will depend on numerous other aspects of its design.

As you aptly summarized, "it all depends."

Stringreen, I have no particular knowledge regarding the sensitivity of your Ayre components to cable differences. An experiment that could possibly be informative, though, would be to **temporarily** put a cheater plug on the amp’s power cord, to defeat its safety ground connection. If that results in a perceptible sonic difference it would suggest that ground loop effects may be present, which in turn can result in sensitivity to cable differences especially when the length involved is long. Note Ralph’s criterion no. 2 for minimizing the sensitivity of balanced interfaces to cable differences, in his post that I referenced earlier:

Atmasphere 3-22-2013
... 2) Ground is ignored- the signal occurs only between pin 2 and 3 (this is where most high end audio preamps have a problem- as soon as there are signal currents in the shield of the cable, the construction of the cable becomes critical).

Regards,
-- Al