See this paper regarding interfacing a single-ended preamp output to the balanced input of your power amp. It's a bit technical, but well worth reading. As you'll see on page 2 of this paper, and as JAllen suggested, an adapter cable can be used. But alternatively, for better noise rejection, a QUALITY transformer (such as the ones made by Jensen Transformers) can also be used. http://www.jensen-transformers.com/an/an003.pdf You can find lots of adapter cables and adapters here: http://www.bhphotovideo.com/c/browse/Cables-In-Line-Accessories/ci/1667/N/4294549275 Here is one example: http://www.bhphotovideo.com/c/product/133649-REG/Comprehensive_XLRP_PP_6ST_EXF_3_Pin_XLR_Male.html#features More generally, concerning balanced vs. unbalanced, I'll add a few additional thoughts to the excellent comments which have been made. Besides the noise immunity advantage of balanced interfaces, single-ended (rca) interfaces are far more prone to hum and ground-loop problems than balanced (xlr) interfaces. That is because a single-ended interface uses the shield of the interconnect cable to both carry the signal return current, and to connect the chassis of each of the two components together (which are in turn connected to both signal ground and ac safety ground). So any voltage offset or noise differential between the ac safety grounds of the two pieces of equipment will result in an extraneous current flowing through the shield, which the receiving component cannot distinguish from signal current. Besides sometimes causing problems which are difficult to troubleshoot (as evidenced by many threads here at Audiogon), that can limit your flexibility in providing separate filtering of the ac delivered to different components, and using multiple dedicated ac lines to prevent cross-coupling of, for instance, digital noise into analog components. Also, it is important to distinguish between components which are "fully balanced," and those which are not. A fully balanced amplifier or preamplifier provides a completely separate signal path internally for each of the two polarities of the input and output of each channel. A component which is not fully balanced just has a differential input and/or output stage, but has a single-ended signal path internally. Your MC402 appears to be fully balanced, as indicated by this statement in the manual: Exclusive Double Balanced Circuity: Each channel of the MC402 consists of two balanced power amplifiers operating in push-pull with their outputs combined in a McIntosh Autoformer. This double balanced configuration from input to output cancels virtually all distortion. An amplifier which is not fully balanced would typically cost less, would not provide the (at least partial) cancellation of internally generated distortion which this paragraph refers to, and might actually sound worse with the balanced interface than with an unbalanced one, because of the extra stage which is introduced into the signal path at the input and/or output, to do the single-ended to balanced conversion. It would, however, provide some degree of rejection of noise pickup, which may or may not be important in the particular setup. Finally, re long cables, it should be kept in mind that regardless of whether the interface is single-ended or balanced, if both the output impedance of the preamp (or other driving component) and the capacitance of the cable (which is proportional to length) are too high, upper treble rolloff will result. That's not a concern under most circumstances, particularly with solid state gear, but if the driving component's output impedance were say upwards of 500 ohms, and the run were say 30 feet or more, I would make a point of avoiding high capacitance cables (e.g., choose cables that are around 20 or 30 picofarads per foot, and definitely avoid those that are around 100 pf/foot or more). Regards, -- Al |
Not meaning to give Kal (Kr4) a hard time with this post, as his responses on this forum are hugely valuable and much appreciated, but I *am* surprised, Kal at your response here. I remember quite well your excellent review of the Bel Canto PL-1A in which you noted that it sounds better through its balanced outputs. For about four years the PL-1A was my main source (your review being something that put me onto that unit in the first place), and I agreed with your review completely, including your pointing out that it sounds better through the balanced outputs. |
The balanced line system was designed to solve (and very effectively) three different problems: noise in cables, length limitations in cables, and finally (IMO the most important thing to audiophiles) preventing sonic artifacts from cables. IOW **if your balanced line system is set up properly** you will finally hear no difference between a cheap cable and a very expensive cable. The length will have little bearing on the sound either, plus of course you will have blacker backgrounds as there will be less noise. Now **it does not matter how long the cable is**! If the cable is only three feet long there is still an advantage, due to the fact that the cable has no sonic artifact. If you **do** hear artifacts (IOW if one cable seems to sound better than another) then your 'balanced line' system is not set up right. Decades ago (over 50 years...) this stuff was figured out. All LPs were recorded using balanced lines, in many cases with 150 feet between the microphones and the input of the recorder. If the cables were a problem, we would all know it by now, but as our stereos improve, the merits of many vintage LPs continue to improve- the cables used to make those LPs were/are completely transparent. To take advantage of balanced lines, the amp has to have real balanced inputs! Some amps have the connectors, but the input is really single-ended. If the circuit of the amplifier is single-ended, sometimes the balanced input is accomplished with an input transformer. This transformer has an artifact; IMO/IME you are always better off with a real balanced input. |
