DIY balanced interconnects

Another good value is Belden 8412 - this is the professional standard microphone cable. It doesn't reject hum quite as well as star-quad configurations, but has a lower capacitance, which is a good tradeoff for most line-level interconnect applications as well. It works perfectly with the strain-releifs on both the Neutrik and Switchcraft connectors, both of which I like as well.

Some cable manufacturers do indeed tie pin #1 to the shell, but I don't like this practice - it can create ground loops within the equipment (though if it's properly designed this shouldn't happen). Also, if done at the male (destination) end, it will usually defeat the operation of an input ground-lift switch, if the equipment has one.

I remember seeing a local recording engineer set up the mics a good 150 feet from the recorder, and the recording was fabulous. Years later I had that event in mind in setting the goal to support the same operation.

It's interesting that you say this . . . typical mic preamp inputs have usually strived to provide an input Z many times the source impedance. Old (transformer-coupled) tube consoles are usually in the area of 1200 to 1500 ohms, and were driven by microphones with very low sources impedances (an RCA 44BX is like 30 ohms). Nowadays, most microphones are standardized to have 150 ohm output impedances, and console input impedances have risen as well - 2.5K to 5K is common, and some have higher (like 10K). The main reason is that microphones generally have a flatter (or at least more predictable) response into higher loads, because their source impedance (especially in dynamics and ribbons) can vary significantly with frequency. 600 ohms is about the very lowest input impedance that even a microphone is likely to see (maybe when splitter transformers are used) . . . and consumer audio balanced outputs very frequently have higher output impedances than a microphone's 150 ohms.

I think we've been down this road about 600 ohm terminating resistors before, but I would still like to remind everybody that 600 ohms is a MEASUREMENT standard borrowed from telephone equipment - which are power-transfer systems (equal source and termination impedance). The standard in audio interconnection, whether balanced or unbalanced, has always been a voltage-transfer system. Audio measurement equipment has frequently had 600-ohm source and termination impedances so that they could accurately measure signal level in dBm (dB refererred to 1mW into 600 ohms).

I absolutely agree with you that high-end consumer audio equipment, that has XLR outputs, should be able to drive a 600 ohm load with full performance. I also understand that there exists much equipment with transformer-coupled inputs, where the designer has chosen to increase the transformer step-up ratio to improve noise performance, resulting in an input impedance that may be as low as 600 ohms.

But adding a 600 ohm terminating resistor doesn't make cable reactance disappear, and it's certainly NOT a "standard". Even if you wanted to treat the interconnect as a transmission-line (say you had 1000-foot runs between your preamp and amp), then both the source and termination impedances should be the same as the cable's intrinsic impedance, which is more like 150 ohms. (That's why AES/EBU is balanced and operates at 110 ohms . . . it was designed to use standard studio microphone or interconnect cables).

In the end, when a manufacturer chooses to put in a 600 ohm terminating resistor, it's a good bet that the equipment driving it (especially if its from a different manufacturer) will not be performing at its best. Their main effect is to swamp the effects of any impedance unbalances in the input circuitry, thus improving the equipment's common-mode rejection performance. A crude trade-off, IMO, and again, definately non-standard.

I use Mogami Gold between CD and amp. Clean, and available at the nearest Guitar Center.

Oldears, I don't think I've seen any cable wherein the barrel of the XLR was tied to anything. I would ignore that connection. The only ground you need to be concerned about is pin 1, which is always the shield at **both** ends of the cable.

Tvad, its not really a VHS/Beta thing- the point is that if you want to get off the cable merry go round, using the low impedance standard is the ticket. Otherwise feel free to pay whatever you have to to get an unterminated cable to do the same thing :) the way I see it, you either pay for the technology to make it happen, or you pay for the cable to make it happen. Seems to me using the technology to advantage is cheaper.