Using XLR for Phono out

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?

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.

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

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.

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.

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.

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.

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.)