Is better sound with RCA cable or XLR cable?
- Thread starter gian60
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Ron,
Well I am not impressed, I know Ralph since long.
I have seen Ralph having this debate several times with great expertise and patience, even in other audio forums. For those wanting to understand the whys it is not simple, particularly because, as Bill Whitlock wrote the true nature of balanced interfaces is widely misunderstood. Just consider that some known manufacturers of excellent sounding gear implement their balanced the way ACK refers.
IMHO if we want to debate the pros and contras of balanced mode we must fully understand it. Otherwise it will be one more discussion of gear preference. IMHO this discussion has been very civilized, compare it for example with that on tonearm size... All IMHO, YMMV.
Simply because a lot of other manufacturers do not share the same opinions. It's really very simple.
It is why a civilized exchange of posts, preferably containing trusted accessible references other than Wilipedia, is needed in these cases.
This happens to me constantly. I was in high school when I joined DIYaudio... I can't find every post I've ever read. But I get lots of requests.
Might I suggest that to help Al, one should explain how the voltage is developed in the cart, so it will make sense about how the phono preamp(s) is able to accept signal that looks like it is from 1 wire, into effectively 2 preamps (all things balanced are doubled) for a single channel. I think that is where a lot of the confusion is found, here. (yes, I'm letting everyone else do the heavy lifting, as to not incur silly semantics about myself being wrong when I'm not, as I try to laymen up everything nicely)
I have no idea where you are going with this?!??! We all know how voltage is generated, but go ahead and explain.
I agree with Ralph on the use of Pro balanced interconnects, with amps and preamps, that "adhere to the design standard" are the way to go. The question remains which manufactures meet the standard, and which, "fudge" the balanced connection. I believe Pass Labs meets the balanced design standard, and cheap pro XLR interconnects, beat or match, expensive "audiophile" XLR interconnects. That is my experience, as I have tried both, and use inexpensive Canare Star Quad Pro XLR's with great results. When I use RCA from Arm to Phono stage, I chose what sounds best to me as the RCA cable has a sonic characteristic.
On the other hand, I feel cartridges are not balanced. I think Ralph is wrong on the need for grounding.
Is the ground on the arm, as part of the XLR shield, referenced exactly to what? Earth, the arm assembly, cartridge body, phono stage chassis, a common phono preamp ground, or power cord ground pin. What if the phono stage is "floating" with no ground? Does the cartridge body or any cartridge pins have a real ground?
An XLR interconnect from phono preamp, to preamp, or to power amp has a real ground for a true balanced connection, but not a cartridge,
Cartridges are not "true differential" balanced, IMO, and that of Pass Labs designer Wayne Colburn.
Like Ralph I am an EE and long time audiophile.
On the other hand, I feel cartridges are not balanced. I think Ralph is wrong on the need for grounding.
Is the ground on the arm, as part of the XLR shield, referenced exactly to what? Earth, the arm assembly, cartridge body, phono stage chassis, a common phono preamp ground, or power cord ground pin. What if the phono stage is "floating" with no ground? Does the cartridge body or any cartridge pins have a real ground?
An XLR interconnect from phono preamp, to preamp, or to power amp has a real ground for a true balanced connection, but not a cartridge,
Cartridges are not "true differential" balanced, IMO, and that of Pass Labs designer Wayne Colburn.
Like Ralph I am an EE and long time audiophile.
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A cartridge is a true differential balanced source, as balanced as it gets. Wayne is simply wrong, and if he still has this opinion, have him give me a call. Its just like a tape head in that regard. I admit I am struggling with how to explain this despite how simple it really is. To answer your questions though, the arm ground is then the shield of the cable, and then tied to pin 1 of the XLR of each channel at the preamp input, which is traditionally the same circuit as the ground post on any phono section. The phono stage won't have a floating input, simply because tubes and transistors need some sort of connection to ground but it could be built that way.
I think this might be easier to understand if opamps are used, since their operation is well-known. From them its easy to construct a balanced input and output:
Now an opamp needs an input resistor in series with the signal and its gain is controlled by the feedback resistance vs the input resistor. So far, no resistors to ground. What we would do to construct a balanced input would be to merely have the cartridge + and - outputs tied to the + and - inputs of the opamp. So far no ground connection. The output is single-ended so do deal with that, we add a second opamp, whose inputs are also connected to the cartridge, in the same manner but out of phase with the first. Now we can add feedback from each output to the minus input pin of the opamp, and so have balanced feedback around the pair of opamps, and a balanced output as well. So far no grounds. None is needed, but we do need an input load (47K) for the cartridge. That can be accomplished by two resistors of 23.5K to ground but could also be done with a single 47K between the opamp inputs, in parallel with the cartridge.
So the cartridge in this hypothetical case is a balanced source with no need of a center tap in its coil. Since the cartridge coil is balanced between the opamp inputs, either side has the exact same impedance with respect to ground. Now some opamps might have offset issues as they are not perfect opamps, so using a pair of 23.5K resistors to ground solves that, however the resistors will now dominate the formula as far as the CMRR is concerned- quite literally the CMRR value will be dependent on the match of the load resistors.
This is how balanced inputs are often set up in modern solid state studio gear, although input transformers are often used, especially if the circuit is single-ended.
In our preamps, since we don't like transformers, we just match the resistors that set the cartridge load. Any additional loading of the cartridge BTW is between the two inputs rather than ground, so we just use one resistor for that, should anyone feel the need for a lower cartridge load, and we provide a set of screw terminals for that purpose. The beauty of this is that only one resistor per channel is needed to set the cartridge load, since its operating true balanced differential.
I am far from an expert, but I have now endeavored on a college class regarding this by way of my invested time I chased every opinion from one end of the tech spectrum to the other basically what I came up with after compiling all the suggestions yes, that balance signal is better than unbalanced. If you go with RCA, you’re taking an unbalanced signal and putting it into something that’s balanced. Or vice a versa the new trick connectors balancer but you don’t have signal strength so you need a stereo, balance line leveler conversion, which is pricey, but they have it. I bought one the circuitry boost the signal and convert it from RCA on balance to balance, and increases the signal so it’s clean as it goes into whatever you’re sending it to. Here’s the connector. I am talking about. I’m not sure if we’re going to or from but the same company has different types of set ups for two channels single channel heavy using RCA analog right left and it has that that’s what I’m using. Good luck hope it helps you.
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