How balanced is the BHK preamp?

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:

  1. pins are: pin 1 ground, pin 2 and 3 are signal.
  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).
  3. the cable will be a twisted pair for the signal with a shield (tied to pin one only)
  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). "

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:

https://forum.audiogon.com/discussions/what-tube-pre-amp-match-up-with-a-solid-state-amp

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.

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Just addressing your question about XLR interconnect length I just had that conversation with @rower30 about any length issues that might exist. My new system needs 25’ long XLR’s going to active speakers. He suggested that for consumer level stereo gear that 50 feet of cable would not be a problem. I am using Iconoclast Belden BAV XLR’s which have high flexibility and crush resistance while also meeting a very high performance and quality standard at a very reasonable price.

I’d love to hear Galen’s comments on this, re. the XLR vs RCA

@RonP - we know XLR vs. RCA response… I’m more interested in violation of the XLR standard and the implications from a cabling standpoint. The BHKPRE is <100ohms output impedance so driving is not an issue as mentioned above… more interested in the what pin 1 is tied to and the impact of that choice…

I don’t have the BHK schematics, but I think I disagree with Ralph a little: there are multiple ways of wiring “parallel” balanced and unbalanced connectors, not all of which mess up the balanced connection when the unbalanced connection isn’t being used. In the case of the DS the XLR is across the whole output transformer winding and the RCA is from ground to one side: if the RCA isn’t being used it doesn’t unbalance the XLR or affect how the XLR connector has to be wired. Similarly on the DS Jr the output comes from a balanced input and balanced output differential opamp and once again has the RCA from the ground to one side and the XLR across the whole output. I have no reason to believe that the BHKs (being a balanced design thruout) would be at any comparative disadvantage.

IMO you can indeed get by with more cost effective balanced cables compared to single ended cables in a given situation, but it’s still the case that many will hear a difference with better designed cables in either configuration.

@tedsmith - thanks, great explanation. I’m interested in understanding specifically how XLR pin 1 is connected.

Someone else will have to answer that for the BHKs. The DS does connect pin 1 to the chassis and signal ground which isn’t ideal in all situations. All of these connections in the TSS are configurable with relays.

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@tedsmith - thanks for the DSD & TSS explanation. Also, the BHKPRE HP output is single ended. I have very short; high quality IC cables so the question is more general than it is for me specifically. I love both the DSD & BHKPRE components. Using the unbalanced BHKPRE HP output seems excellent SQ on my Utopia HP. Some would argue about balanced HP output…

Thanks, for that info. If I’m following, though, you are implying that the balanced output of the DS would be unbalanced if the user ran RCA cables from the single-ended output to, say, a subwoofer. Which is what I did before I got the BHK.

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Yes using both the RCA and XLR at the same time will add more capacitance to one side of the transformer. This is also true for the Jr, but it matters a little less no. With both output in use some of the noise (if any) from the RCA cable and/or device connected via RCA might affect the balanced output or cause the balanced connection to not reject as much noise. This could be a problem in some systems, but probably not most systems. If you have any problems with hum in your system you probably don’t want to unbalance balanced connections.

ICONOCLAST uses;
PIN 1as chassis shield ground at both ends, and this should not be connected to signal reference ground.
PIN 2 is hot, or signal positive to the signal reference point, or center tape.
PIN 3 is low, or signal negative to the signal reference point, or center tape.

PIN 1 has to be assigned internal to the jack on equipment, not the plug, As Ted points out.

Just because a cable is called balanced does not mean there is no CUB, or reactive capacitance unbalances, in the system. The hardware is unbalanced a bit as well as the cable in reality. I touch on this in the white papers. MIL standard is 3% max CUB, but I design for half that.

XLR is design tilted for S/N ratio over ultimate sound. It is a far more complex system than single ended RCA. If there is zero noise, RCA has a signal advantage since there is no CUB. Add noise and the situation switches.

ANY analog signal going down a cable will be changed by current coherence and reactance. Balanced output is not a free lunch on cable quality, it actually NEEDS to be better to counter CUB. But, the cable can’t fix the balanced circuits ability to provide an equal and opposite signal magnitude.

The BAV XLR is designed for lowest cap for several reasons: cost, AES/EBU impedance compliance, and total reactive loading in long lengths. This means a single wire quad arrangement is best for the pro market.

You can’t cheat the system and more wires, 16 in the 4x4 XLR, mean higher cap, but this isn’t an issue for home use, and the improved current coherence much improves the sound.

Of course, the RCA can add signal wire as a 1x4 design, too, and it is cheaper.

It is all based on noise quality verses signal quality.

Galen

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Attaching PIN 1 to signal ground is not a good idea, and injects noise into the reference point.

The virtual ground reference has to be a stable, and not lifted or dropped by noise injection from PIN 1.

Assume a 4V differential voltage. The hot and minus signal is relative to each other. 2 from -2, 1 from -3, 3 from -1 are all 4V.

Noise is ignored with a virtual ground, too:
If we add 1 volt of noise to to the reference point, we have +3 verses +2 on PIN one. PIN 3 now has -1 verses -2 volts. The difference between the two remains 4 volts.

As long as the ground is virtual, we can’t get ground loops. If we add an EARTH verses a SIGNAL ground, we now have a ground loop as wire that separates each PIN 1 point at each end of the cable has resistance. The current times the shield resistance is our interference voltage. Why would you want to add this to the balanced system? PIN 1 is designed to REMOVE added EMI noise that is created by CUB unbalance by routing it to earth ground, not the virtual signal ground. CUB causes a remainder offset voltage, 2.1 V should be 2 V, and the opposite leg is still -2 V, we have a 0.1 volt noise current in our system.

Each leg has to be equal and opposite magnitude relative to the virtual ground point. CUB and ground loops mess that up.

Galen

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Thanks so much for the detailed explanation, Galen. If I am comprehending, what you say here largely reinforces Ralph Karsten’s point: that it is sub optimal and somewhat contrary to the whole point of having balanced line connections to wire one’s equipment in such a way that the XLR ground pin is connected to anything but the chassis ground. I’m also guessing that this disadvantage may be largely theoretical in many cases.

I also hear you saying that there are other elements of cable construction and design that influence sound quality, even in a properly balanced cable connecting properly wired gear. For those of us who can’t afford cables costing $1000 and up, that is disappointing.

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Don’t worry, we have you covered with the BAV line, which is far cheaper and meets the pro market requirements spot on…and that means price, too! Price your XLR assembly out at iconoclastcable.com and make sure you select the BAV XLR design.

The ICONOCLAST is different, it is audio performance in first place, everything else is behind that. We are still well uner the market prices for high performance leads, however.

And yes, there is more than just using balanced cable to get it sounding the best. CUB, current coherence and where the dielectric is lowest with respect to the wire surface all make differences.

Best, Galen

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@tcatch Just as an example you can get a 3 foot stereo pair of BAV XLR interconnects for $260.00. That is really hard to beat for the quality and performance. And you get to discuss all of it at length with the designer of the cables in person. :grin: You can also return them if you are not satisfied. That is a win-win. I have no affiliation whatsoever.

Unfortunately, I was persuaded a couple of years ago that it was a good idea to get my rather tall equipment rack out from between my speakers. So it is over against a side wall, well back from the first reflection point and more or less parallel to my listening position. That leaves me needing either very long speaker cables or very long interconnects. Currently I’m using long speaker cables, but I wanted to try long interconnects and putting the M700’s right behind the speakers. That requires interconnects in the neighborhood of 20 feet or 6 meters. Plain Jane balanced interconnects from Blue Jeans Cable are barely over $100 for a pair at that length. GAC-4/1 UltraPro from Gotham Cable, which some folks like better, is a bit more than $200. BAV is $600 for the length I need. Higher grade Iconoclast is more, of course, as are the other so-called ‘mid-price’ options that get recommended.

In the end, I’ll probably have to buy several and see if the differences are worth the price. Or move the equipment rack back to the front wall and keep all the cables short.

Still curious to find out how the BHK preamp XLR connections are wired.

It also crossed my mind to wonder if it would be possible to disconnect the RCA jacks or make some other simple mod to eliminate any connection of pin 1 to something that would ‘unbalance’ the XLR.

On my other system I originally had Mogami gold interconnects and tested the BAV and Iconoclast. The BAV were much better than the Mogami and so close to Iconoclast that I probably could have just kept them and forgot about it but I ended up buying Iconoclast. They were only in the 5 feet long if I remember correctly.
Just from that experience I decided to go with the BAV this time and as I said before they need to be 25 feet long. They are $700 plus tax and shipping but I feel they are still a bargain all things considered.
I don’t have both XLR and RCA connected at the same time so I don’t think the output wiring on the DSD or BHK preamp will be an issue.

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Thanks, Baldy – you may be right! Your use-case is practically the same as mine, so your experience is highly relevant. And I may end up there myself. Still hoping to save the extra 5 or 6 hundred dollars. (And still curious about this XLR wiring/grounding issue.)

I have a DS senior DAC feeding BHK 300 power amps directly.
I just assumed I would get Iconoclast XLR cables when I upgrade from my current XLR cables.
If I understand correctly the RCA cables may or may not sound better.
If so, how do I know which one to choose?