While trying to decide what cable to buy to connect my BHK preamp to my M700’s now that they are much farther apart (I need 5 or six meters of balanced interconnect), I ran across a thread on Audiogon where Ralph Karsten of Atma-Sphere alleged that many components that purport to be balanced aren’t really. Specifically, they violate the terms of the ‘balanced line standard’. Quoting Ralph:
'"Here is the standard:
- pins are: pin 1 ground, pin 2 and 3 are signal.
- 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).
- the cable will be a twisted pair for the signal with a shield (tied to pin one only)
- 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). "
I’m quite sure the output impedance of the BHK is not an issue, but I wonder about the wiring of the balanced and single-ended outputs. According to Ralph, a preamp that includes both single ended and balanced outputs, and can run them at the same time, is likely to be wired in such a way that there is some signal going to pin 1 of the XLR and from there to the cable shield.
Responding to a poster who had poor results with a particular Mogami cable, Ralph said, "likely what is happening (as this is very common) is that the preamp puts signal current on the ground connection of the cable (If the preamp has XLR outputs and also RCAs that both work at the same time without operating a switch, then this is the case). "
Well, of course, the BHK has both XLR and RCA outputs that work at the same time without a switch. So my question is, how is this managed? Are there separate output stages for the single-ended and balanced outputs? Or do the RCA outputs come off the same output stage as the XLR’s and thereby undermine the fully balanced character of the XLR outputs?
Since I understand very little of what I have just written and quoted, it is entirely possible that my question is poorly posed. My apologies, if so.
Later on in the thread the point is put this way by another seemingly expert poster: " even if the equipment has very low output impedance and very good drive capability, it does not meet the standard if it connects XLR pin 1 to circuit ground, as opposed to chassis.
As Ralph indicated, and as is indicated in Figure 1b and some of the text in this paper, it is very common for pro equipment (as well as consumer equipment) to connect pin 1 to circuit ground, in violation of the standard."
Here is a link to the Audiogon thread where all this is hashed out:
Any information that one of the PS Audio experts can provide will be greatly appreciated.
OH… Why does this matter? Well, according to Ralph, if all the connected equipment is truly balanced one can get by with rather inexpensive balanced interconnects. It is the violation of the standard that creates conditions where more expensive balanced cables have some value.