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In Reply to: RE: It is all implementation dependent posted by jsr on September 30, 2015 at 11:02:05
Without having the schematic, I can presume that you indeed have balanced interface to power amp. It is not hard to generate good balanced signal out of single-ended one, so if your incoming signal is good, there will be less chance of degrading it from that point on.Now, that can be done many different ways, with various degrees of imperfection. If one's goal is to achieve perfect symmetry, then he will likely resort to some solid state inverter/splitter - either discrete, or an IC. It can also be done with a more "purist" approach, for instance, a simple long tailed pair, either tube, or solid state. Looks like your preamp is solid state.
Going whole hog after the ultimate signal symmetry will most likely result in sonic degradation, due to the use of IC's - all, of course, IMHO.
A tube phase splitter, while being less perfect, might provide better sound. That is why we usually try to strike the right balance between the perfection and sound. Audio interface is not designed the same way the electronic instrumentation is done.
All this is academic, because you are not changing anything internally, so this is purely for the sake of general idea.
Many people believe, that even less than perfect balanced signal will beat the single-ended one. I certainly do.
For this reason I suggested earlier, that it might be perfectly fine to use both outputs at the same time, provided your load is not a heavy one. I would try to find out the input resistance of your power amp, and your sub. If both happen to be in the 20-47K range, then I would sit back and let your ears guide you. If below, say, 10K, then I would still sit back, but do a more careful comparison.
One test you could do would be as follows:
Move the sub out of your room, but have enough cable to connect it to your preamp. Listen to your main amp, with the sub plugged in, and unplugged. Hopefully there will be no noticeable difference.
If moving the sub out is too cumbersome for whatever reason, do it with its volume set at zero.
Edits: 09/30/15Follow Ups:
Victor, nice to see you posting here.
First of all, I owned BAT equipment (VK200, VK30, VK60 monoblocks) for many years because I was intensely interested in having properly implemented balanced circuitry throughout my system from source to amp. I admire your capabilities and execution, enough to spend lots of my money in obtaining your products.
Your response to my post about degradation of the signal due to deriving balanced signal from SE source is in conflict with what you posted here. Please clarify.
I maintain that, unless there are extraordinary system requirements, a SE connection throughout will usually sound better than deriving a balanced signal from a SE source. I've heard it myself on some equipment. Perhaps BAT gear is an exception of excellence, but, typically, the only thing to be gained is 6db gain and possibly some modest CMR with long IC's. I agree that a true balanced source will make a balanced system sound better than SE.
I agree that your test is an obvious method to determine whether there is, in this specific case, any sonic degradation. I wouldn't even bother with moving the sub and using crazy long cables which may introduce their own negative effects. Simply turn down the sub volume (not quite at zero) and play the mains with the sub plugged and unplugged. What could be easier and more definitive?
As you wrote, I would expect negative effects only if load impedance gets too small. Probably not an issue with properly designed SS amps.
Peace,
Tom E
Thank you for your kind words!
Regarding the subject, I think we should start with your statement:
"and possibly a slight detriment due to the extra circuitry,"
I have been long maintaining that there is no extra circuitry or complexity in balanced INTERNAL implementation (there's some in its connectors and cables, but that is another story).
Sure enough, one can build a very simple one-triode single-ended gain stage, and such things exist. But the question is - would this be the ideal way of implementing a gain stage? To me the answer is a NO... as such a stage would be suffering from many ills.
Very long ago... longer, than I care to remember, one of my first mentors taught me the beauty of balanced gain stages. We were designing "serious" electronics back then, and pretty much all our linear tracts were done using balanced gain stages. The reason was their unquestionable superiority in terms of signal integrity, stability, linearity, predictability, etc.
So many years later, when I decided to build some audio circuit, I didn't have to think twice, I simply started with what I thought... or knew... was best.
This situation is not unique to me - you should ask yourself: why did some great designers of the past use balanced gain stages long before the word even appeared on the audio horizon. The answer is - because that made things better... OK... in their minds.
Not just the gain stage itself is much more accurate, but also the way it interacts with the power supply is much less demanding. We all know that the power supply is in the signal path... well, in the balanced circuit it is substantially removed from it, so in essence its quality is multiplied manifold.
When moving onto the interface issue, we need to realize that in "serious" electronics the signal return is never combined with the chassis ground, for many good reasons.
The reason these two totally alien to each other functions were combined into single ground had nothing to do with quality, and everything with cost, so it seems only logical to leave that bad heritage behind and do things the way they should be done... hence - a symmetrical signal drive.
So the next question then is: given the single-ended signal, how should you handle it? In my view, the sooner you convert it into balanced, the better you are, because you will avoid many degradation mechanisms down the road.
Of course I am somewhat sympathetic to the idea of using as few components as possible - it has some merit, but Einstein was smart when he said: "Make things as simple as possible, but not simpler".
Every design is balancing act - there is that word again... :) I am presenting a bit of our philosophy, but the proof is, as usual in the pudding. :) What I am describing does not guarantee the superiority of every balanced component over every single ended one - in both worlds there is plenty of room for mistakes.
So I don't know if this answers all your questions, but this is how I tend to approach it.
Thanks. You mean that the sooner the signal is balanced (differential), the better. The amplification, or gain, is accomplished more accurately in differential mode than SE.
A true, not derived, balanced source such as DAC or CD or phono stage would be the best way to maximize those advantages without additional circuitry. Yes, simple as needed, but not simpler.
I am perplexed that more CD players do not have balanced outputs, as a balanced signal is easily obtained from the DAC. Making it SE is simpler than needed.
I also agree that transmission of ground on top of one leg of the signal can be a significant compromise. One should evaluate whether a SE to balanced stage is worth avoiding that compromise. You maintain a design and corporate philosophy, but not every company is so adept at implementation. If you ever adopted the SE industry standard for any equipment you manufactured, you would need to change your name to BAT/SEAT. That might not fly!
Peace,
Tom E
Well, thank you again Victor for your time and expertise.
I tried a version of the test you suggest, but I will try your version, as its obviously better.
If I hit the Lotto tonight, I'll be buying a full kit of your stuff. Soooo, it looks like I'll have to make do with what I have for now.
Again, my deepest thanks.
You are welcome, and I suspect you will be happy with the dual connection.
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