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Re: [ARSCLIST] Aren't recordings original sources?

At 06:20 PM 2008-10-20, Larry S Miller wrote:
        The current discussion of power cables brought me back to my
days as an audio equipment salesman.

Hello, Larry,

I fully agree with you that making changes in the system can make improvements. In the case of the audio cables making a difference, and I agree with you that the synergistic effects are the general cause.

Another phrase for this is "using rubber gloves for leaky fountain pens". I will credit one of my mentors, the late Hans Schmid, for this.

In my past days as director of engineering for McCurdy Radio in Toronto, a maker of high-end broadcast audio consoles, we were asked to make an eight-bus mixer for a client. The systems engineer placed the card-mounted buffer amplifiers for the bus submaster faders in the equipment pedestal, about 15 feet away. He also used relatively high-impedance faders (I think balanced 5K or 10K ohms). The test department discovered that the frequency response of the console through the submaster chain varied depending on where the faders were set. Well, this is no surprise, a 10K potentiometer will provide about a 2.5K ohm source impedance when the voltage level is at half. The cable capacitance was loading this down. We replaced the miniature shielded twisted pair audio cable that we usually used inside the console with heavy (like about 0.4" diameter) data twinaxial cable with far lower capacitance per foot and the response variations were then well within specification, and much smaller. The ideal solution would have been a buffer amplifier directly at the fader, but we did not make enough of this configuration to warrant this additional module in our line.

This comes around to the Nakamichi Dragon cassette decks that have a similar configuration, but unbalanced. I use short, reasonably quality jumper cables between these and the IHF balancing units (Aphex 124A) and then run the balanced cables to the patchbay. Only those units within about six cable feet of the patchbay use the balancing units in the patchbay. In addition, with this high-impedance signal being unbalanced, longer runs are more prone to hum pickup even from segregated AC Mains cables.

As to the hospital grade receptacle, this could be one of several things including lower impedance on the current carrying conductors and/or a lower impedance ground connection.

I continue to see comments disparaging my use of the phrase "properly designed". I do think that we need to get after manufacturers to properly design equipment so that these synergistic cable effects are minimized. One major mistake that I think has been made over the years -- and I see some correction in this regard -- is insisting on unbalanced interconnections between audio components. Balanced, low-impedance, voltage-matched (i.e. not power matched) interconnections make a lot more sense than unbalanced ones.

Remember my statement at the beginning of this post about "rubber gloves for leaky fountain pens". Sometimes you may wish to continue to use the fountain pen for sentimental reasons or it has a nib that works just right for you, but in a production environment, purchasing decisions should avoid purchasing the leaky fountain pen in the first place.



Richard L. Hess email: richard@xxxxxxxxxxxxxxx
Aurora, Ontario, Canada (905) 713 6733 1-877-TAPE-FIX
Detailed contact information: http://www.richardhess.com/tape/contact.htm
Quality tape transfers -- even from hard-to-play tapes.

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