Power cord? Why?

sean and others...

1. About the A/D. Of course I meant 100K samples/second.

2. The amp load will be Magnepan MG1.6 speakers, 4ohms ,and with impedance characteristics like a dummy load. (Of course I will listen, but that is not part of my test plan).

3. The input signal will be real music, of various spectral characteristics. I find that real music works best for most things like setting speaker levels, and subwoofer gain and phase.

4. I thought that my initial setup measurements using two super cords provided the reference for comparison. Of course I could do it with the original cords as well.

5. Some of you guys didn't understand the objective of my test. I am not (at this time) evaluating audio quality. I am testing to see if the electrical signal applied to the speaker changes in any way when the power cord is replaced. If it does, then listening tests would be in order. (And I will apoligize to all those I have offended). Viridian..I agree with you about listening being the best test of sonic quality, but I just don't want to fool myself, which is easy to do. If there is no change, listening tests might be fun but can prove nothing).
My speakers only "know" about what comes in to them as an electrical signal from the power amp. Maybe your speakers have psychic powers and can discern the type of power cord in use. That's too far out for me.

6. By the way, when I said that the original power cords were "crummy" I really meant it. They don't even have a 3prong (grounded) plug...but maybe that was by design. I will need to try the super cord with and without ground.

7. The Kenwood LO7Ms may be old, but they were top rated by T.A.S and Stereophile. They are comparable to the best available today. (Besides they are what I have on hand. If you have Krells, or the like, feel free to use my procedure).

8. One procedural detail...I will make the electrical hookup such that I can switch cords without shutting down power, or interrupting the signal measurement process.

9. Hey this could be a money-maker! If I find a power cord effect I can sell the data to power cord manufacturers. If not, they can pay me to keep it under wraps.

10. Finally...(for now)...how about some suggestions about the design of the super power cord(s).

TWL wrote: "I'm currently using a large capacity lead acid automotive battery with 650 cold cranking amps, located about 24 inches from my amplifier. I have the terminals directly connected to the power input barrier strip on the amp, with 12ga OFC copper stranded wire."

24 inches of ANY wire represents a large inductive impedance. You need what is referred to as "decoupling caps", which essentially decouple the power source from the load by providing local energy storage. This means low ESR (equivalent series resistance) capacitors located as close as possible to the load. And a combination of HF caps (.01 UFd to .1 UFd) and some swamping caps (1 UFd to 100 Ufd) are needed to supply current at a broad frequency of transient currents. It would not hurt to have even a 1000Ufd close-by as well.

You may not be able to measure what you hear. Depends on the noise floor of your sampling oscilloscope. You MUST use differential probing technique for this to avoid ground-loop noise as well. This is not a trivial measurement.

You would be better off to measure the voltage drop (scope capture) across the power cord when transient music passages are being played. IF two cords have different voltages, this means that more current is getting to the amp with one than the other. If the cords didn't matter, then the currents should be identical.

Following Audioengr's comments, especially since i know what he's getting at, i would suggest a cable of very low inductance against a "typical" zip style power cord of adequate gauge. Using the "crummy" stock cord as a reference should work fine since the manufacturer thought that it would more than suffice at the time of design / sale. The engineers there obviously took into account such things as current draw and thought that it should be "plenty good enough". At least, according to theory.

If the "fancy" cord was of a high capacitance nature, all the better ( in my book ). The directions on how to make a very basic cord that offers good performance and is suitable for this specific installation is what follows. It should by no means considered my idea of "the ultimate" power cord or a power cord with universal application. It is however, a good starting point for someone that wants a good cord for pennies on the dollar : )

If using this for an amp, look for a cable that uses four 16 gauge ( at least ) or preferably four 14 gauge individually insulated conductors. These should be arranged with two conductors stacked on top of the other two. Since your amp does not use a "ground" per se, this should be easy for you to work with since you don't need to add an extra wire for an external ground.

The internal wiring should use staggered polarities as we go around in a circle i.e. hot, neutral, hot, neutral. Not only should the polarities be staggered to reduce inductance, lower EM radiation, reduce the susceptability of RFI, etc.., all four conductors should have a spiral twist to them. This rotates the wires within the main jacket so as to never have them running in a straight line. Hence, we end up with what is called a "spiral wrapped star quad" arrangement.

While looking for a cord of this nature, i would see if i could find one that used as little dielectric insulation material between conductors as possible. Obvously, you have to take into consideration safety factors in terms of rated voltage and current and remembering that the cord itself will be bending / flexing, but finding a suitable candidate should not be tough. Once you've found such a design, terminate it with good quality connectors and have at it.

As to my comments about the Kenwood L-O7M's, the "review" that i have on their bigger brother ( L-09M ) was not very complimentary at all. Then again, these amps probably "measure" quite well as far as "standard test procedures" go. Given the similarities between the two models of similar design and vintage and the more reliable than TAS or Stereophile ( at least as far as i'm concerned ) comments that i read, that is what i based my comments on. None the less, am amp is an amp and the results will speak for themselves.

One other thing though. You will need to be able to feed the amps a mono signal. Then again, i'm sure that you knew that : ) Sean
>

PS... we all know that it is the sound that counts. By properly conducting tests and applying the knowledge derived from those tests, we can work towards making more consistent and reliable products that DO sound better. In the past, coming up with the right tests has been the problem, but we are slowly learning more and more as we do more testing. As such, scientific testing CAN be a means to an end if applied in that manner OR it can help to explain how we arrived at the end when broken down and reverse engineered.