John_tracy, just for the record, to do things balanced does not double the parts (its about 50% more) and the noise is actually **lower** for a given stage of gain, not higher! The noise is theoretically 6 db less per given stage of gain; this can really add up over several stages so when you are done, you often can get by with less gain stages overall. |
John (12-19-09),'a potential fly'. In the context of (ASR)
Basis Exclusive I mentioned the recommendation from Schaefer (ASR owner) to use RCA out when using balanced inputs. Alas I was not able to explain the issue. But your
statements regarding the OP amps may explain the 'actual fly' in connection with Basis Exclusive?
Regards, |
Manufacturers do it because SE is cheaper (half the number of parts ;-) ). In phono preamps, designers have traditionally used SE architecture because adding the other half for balanced will increase the inherent circuit noise. That would be a good example. The MC pick-up is naturally balanced. Connecting it that way to the primary of an MC input transformer, then connecting the secondary SE is quite common. |
Cool. But I was not totally wrong; you need to feed a balanced signal to the primary. I don't know why one would want to convert a perfectly good balanced signal to SE, except if you are a transformer-phile. (I'm just kidding; you probably have sound justification for this approach.) |
Lewm, if you feed a balanced signal to a transformer and the primary winding is either "floating" or wired balanced (CT grounded), you will have CMR even if the secondary is wired SE. If the signal is the same on each leg of the primary (common mode) the potential difference is zero! No magnetic flux, no signal transfer, therefore high CMR. The primary does not care how the secondary is connected as far as CMR is concerned. |
As far as I know, in SE mode, one side of the input transformer IS grounded. That was my only point. You need to input a balanced signal to a transformer and take its output as a balanced signal in order to realize CMR. I am sure you know this; I was trying to clarify the point for others. |
Wow, Thanks again Ralph for a more complete explanation and understanding. I
must have had my recollection of my conversation with Jim White confused
somehow and that explains what Lewm was trying to tell me which I misread .
Sorry folks for the added distortion, I still have a few things to learn.
Happy Holidays Ralph and AudioGon Friends and as always...
Happy Listening! |
Lewm, of course I was refering to the use of transformers as an input device. That was the context of the discussion. Even when used as the input for a SE (balanced to SE conversion) you still have high common mode rejection. If you apply the same signal to each leg of the transformer primary, as in common mode noise, you cannot generate any magnetic flux in the primary and thus no signal. This would be different if you were to ground one leg. A tranfomer "naturally responds to a differential signal. |
R_f_sayles, almost all phono cartridges are balanced sources. Many arms are too. The signal is converted from balanced to single-ended usually in the way the RCA cables are connected to the arm. That is why there is that weird grounding wire that other single-ended sources seem to lack.
For this reason you can operate a phono completely balanced, and if you have a balanced preamp and amp, the signal can be balanced from needle to speaker. In our systems, that means a total of 4 stages of gain, so the signal path is actually simpler than many single-ended setups. The cables sound better (its a common myth that you don't need balanced unless you have long cables but the real reason for balanced lines is to eliminated interconnect cable artifacts) and there are blacker backgrounds... IOW there are immediate benefits. |
Am I missing something here, still? What pray tell, is the use of putting a balanced (xtr) connector on the end of a cable from a cartridge/tonearm when in fact the signal coming from it is single ended (rca) in every case? Is not this a wasted effort?
Happy Holidays & Listening! |
Dear John, Can you cite me a reference for your statement that "transformers have some of the highest CMRR ratings"? This might be true if a transformer is properly implemented at the front end of a balanced circuit. But when transformers are used at the in- or output of an SE circuit, as is often the case, I don't see how you would get any CMR. |
The type of plug does not determine whether a connection is balanced or not. I am using a "balanced" connection from my cart. to my fully differential phono pre. However, by choice, I am using RCA plugs. Why? XLR plugs fitted on my OL arm would not fit through the arm pod on my Nott. table. Balanced or single-ended is a function of the circuit topology, not the type of plug used. |
VPI arms can have either a junction box that accepts XLR cables, or one that accepts RCA's. If your equipment is REALLY balanced from input to output as Ayre stuff is, with no electronic trickery in the circuit to make the single ended circuit balanced, there will be a definite advantage in using balanced from cartridge to speakers. The difference is not subtle, if and only if you have the proper gear to accomplish this. |
Buddy,
using adaptors (XLR RCA, or what ever) with *any* phono-cable is one big NO NO!
So my advice: DON'T!
BTW, the GCPH wants to see a single ended (RCA) input, and only then it is converted (via OP-amp) into a differential signal and further handled like such. So the GCPH is not fully differential from input to output (kind of demi-differential :-)
It is this OP-amp chip XLR conversion at the input that makes some purist cringe, and some not bother to use the XLR output (unless desperately in need of the extra 6dB I mentioned earlier on)
Greetings,
Axel |
Romaxim, I was planing on connecting RCA to XLR adaptors on the output of the VPI JWM tone arm when I realized the
GCPH has only RCA for inputs. However, outputs from this amp are true XLR so I guess that part is solved by default |
Just to point out a potential fly in the ointment, not all true balanced inputs (outputs too) are created equal. One needs to measure the CMRR (Common Mode Rejection Ratio) at the input. Many manufacturers use OP amps to implement balanced inputs. Most of these have poor CMRR. Also, for good common mode rejection the source impedance of the two halves of the balanced output on the other end should be equal. BTW, though much disparaged by many in the audio community, transformers have some of the highest CMRR ratings and equal source impedance is a given. By my count there are 18 Lundahl amorphous core transformers in the signal path of my system and it sounds great, no noise, hum or RFI interference. |
Spaninc, the output of your VPI is in fact RCA balanced, not SE. It would make much more sense to go balanced from the cartridge to the phono preamp, see for example www.mr-labs.net, than from the phono preamp further. |
Lewm, thanks for the clarification. Having a conversation once with Jim White of
Aesthetix, I recall going over this point due to the fact that he offers XLR and
RCA interconnects on virtually every possible location of his gear except the
phono input of his phono amp the Rhea. This made me wonder why anyone
would then offer it, for the same reason that we have the conversation time and
time again about the effectiveness of offering XLR inputs/outputs on equipment
that do not truly have a balanced architecture... and I'm sorry to say, no Rogers
teaching English Composition in our family. Architects, industrial designer,
carpenters, a watchmaker, gunsmith... crafty folks but, few scholars.
Spaninc, I would say yes on the XLR from phono to pre!
Happy Listening! |
I don't know how the RCA inputs on the GCPH are configured. They COULD be set up for balanced mode, IF the ground connection on the RCA actually carries the negative phase of the audio signal. To test this, you could see whether there is electrical continuity between the ground of the RCA jack (the outer barrel shaped part that touches the flange of the male RCA connector) and the chassis. If there is continuity, then the GCPH is seeing the phono signal as SE. As for your phono cables, do you have a separate wire for grounding to the preamp chassis? If so, then it is possible that you can get a balanced signal out of the cables, if the shield of the cable is not otherwise grounded, either via that discrete wire or at the input jack. It's a confusing mess, I know. Best advice is to enjoy what you've got. |
The outputs on the JWM tone arm I have are RCA SE as are the inputs on the GCPH, so after the signal is processed by the phono preamp (GCPH) it comes out through the balanced outputs to the amp...balanced I suppose! No other way out unless VPI figures a way to connect the cartridge to tone are and enables XLR outputs. I will let you know how it goes. Thanks for the great input
Rique |
Dear Rfsayles, Yes, most cartridges, with very few exceptions, are inherently balanced devices. Neither side of the output wires are grounded. In an MC cartridge, the two outputs come from either end of the coil, etc.
By the way, I had a wonderful English composition teacher when I was in college, by the name of Roger Sayles. Could you be him or his son? (He would have to be in his 70s at this juncture.) One of the most important figures in my academic life. |
To my understanding, all stereo cartridges are basically(or at least could be) made with "balanced" circuits.
I also agreed "balanced to balanced from there on out is the best bet" especially with longer cable length.
Dan |
Am I missing something here? Is any phono cartridge balanced? It would appear that until your signal is at a balanced architecture of the preamp or phono stage there is nothing but being single ended. To my mind balanced to balanced connection from there on out is a best bet.
Happy Listening! |
I went to the Cambridge Audio website. It is really impossible to tell from the verbiage on the website whether the actual circuit is a balanced one or not. However, the comment in the letter, that the XLR input "gives cancellation to common mode noise", does suggest that the circuit is balanced. Why not try the balanced input and see if you like it when driven by the balanced output of the GCPH? |
Hi, all I got a response from Cambridge Regarding the XLRs electronic inputs plesae see below.
"Dear Enrique,
Thank you for your email.
The XLRs do connect to a balanced input circuit, which gives cancellation to common mode noise picked up on the balanced signals."
Kind regards,
Ben Beaumont |
Dear Pete, Spaninc, et al: Here we go again. Based on all that I have been able to read at the websites of the respective manufacturers, the GCPH does have balanced phono circuitry, whereas the Xono does not. This may account for Pete's observation that his Xono sounds "better" via the RCA outputs. Often when the circuit is single-ended, the "balanced" XLR output is derived at the end of the chain by inserting either an additional active device or a transformer. Both tricks could add coloration to the sound and cause one to prefer the single-ended or RCA outputs. This is no proof at all that SE circuits are superior to balanced ones. I am not saying that the Xono is inferior to the GCPH in any way. In fact, it is likely to be superior, just because it costs more and is more elaborately conceived, and because I have great respect for Pass as a designer. (I have never heard either one.) I am just trying to cut through the bullshit surrounding SE and balanced circuits. For phono, there is no question in my own mind that, all else being equal, there is an advantage to running the cartridge in balanced mode all the way from the stylus to the linestage (and beyond if possible, but the advantages diminish the further you are away from the transducer.) Spaninc, you should still check to find out whether the internal circuit of the Cambridge is balanced before spending moola on balanced ICs. That's my $.02 |
Me again, this is what Cambridge sais: The Azur 840E makes room for eight inputs, including two fully balanced XLR inputs! guess that responds some questions. Enrique |
Thanks everybody, I guess I will have to experiment. By the way I will let you know if the Cambridge 840E is truly all balanced.
Enrique |
Agreed with others that it would be no definite answer. Experiments make our audio system perfect. With your decent audio gears, you should hear some sonic differences by switching RCA and XLR connections. The reasons behind are due to a bit more output and differences(lower, I guess) in impedance of XLR connections.
IMHO, if you want to unleash the full potentials of your vinyls, put your phono amp closer to TT and use a pair of decent phono cable(shorter & with lower capacitance the better)in order to prevent excessive signal loss or "twists" at the very beginning. You may hear a lot more sonic improvements if you could run a short "TRUE" DIN-XLR balanced phono cable from TT to phono amp.
|
A fellow Audiogoner suggested the single-ended outputs on my Pass Xono sound better than the balanced outputs. I tried both and also contacted Pass Labs. They said they listen to the Single-ended outputs and this is what I prefer also. So I switched even though the rest of my Pass system is balanced. The advantage of extra gain and noise cancellation at this point in the chain was less important than using the simpler circuit and it simply sounds better. More low level detail, cleaner and slightly better staging. Your equipment will certainly sound different, so I would just experiment. |
This question, and ones in a similar vein, comes up all the time. In this specific case, if your linestage (the Cambridge 840E, I guess) is balanced, then there is an advantage to using the XLR outputs on the GCPH. If your linestage is single-ended, you may as well use the RCA outputs from the GCPH. When I use the terms "balanced" vs "single-ended" with respect to your linestage, I refer to the internal circuitry, NOT to the fact that it may or may not offer XLR input jacks. The problem is that many manufacturers use "fuzzy" language in describing their circuit topology, now that balanced circuits are somewhat in vogue. It is safe to say however that if your Cambridge preamp offers only RCA inputs, you may as well use the RCA outputs from the GCPH. |
I'd get a pair of XLR cables from monoprice.com and try it out. |
Hi,
I had the GCPH and apart from getting 6dB more output with the XLR, you will also find to get some more depth of detail.
Having said this, detail is NOT everything and you may find that the RCA could sound a bit smoother, or musical by comparison. If your system is more on the bright side (some glare? - and who has not some these days) the RCA may be the preferred way to go, if you do not hanker after the last bit of *detail* in favour of some slightly more harmonic balance.
Ergo, you will not be able to do this one on *paper* first / alone, as you would have it... :-)
Greetings,
Axel |
