John Curl's Blowtorch preamplifier part II

[Soundminded]

Originally Posted by john curl

I have heard differences in power cords too. I guess that is a subjective 'fact'.

I love it. A subjective fact!!! You heard it. A vast power distribution grid of thousands of miles of wire, hundreds of generators, transformers, miles to your substation, hundreds of feet from the nearest transformer to your circuit breaker panel, dozens more to your receptacle, and the last three feet of power cord makes all that difference. My, my. Only one conclusion to draw from that. Your power supply stinks.

[scott wurcer]

Originally Posted by simon7000

So when my measurements show -120db in a circuit that is not a bridge that may come out as -80. Don't yet have exact numbers, but the math shouldn't be too hard.

Since thermal distortion goes as V^2 you've got an 80db discrepancy there which one should be able to track down.

[john curl]

NOT my power supply, the STAX Lambda Signature Tube drive power supply for the headphones.

[Joshua_G]

Originally Posted by simon7000

If the power cord affects the sound of an audio thingy, I would start looking at the induced AC onto the chassis, as that is really easy. Next I would look at the power supply.

I find it hard to believe that my phono stage, CD player, pre-amp and power monoblocks (all are commercial ones), all have PSU malfunctions.

[Joshua_G]

Listening to music, both live and reproduced, is subjective.
You know, on my stereo set I listen to music with my ears, not with measuring equipment. So, everything influencing the experience of listening to reproduced music have, necessarily, a subjective aspect to it.

Your mileage may differ.

[john curl]

No, Joshua, but some power supplies are more resistant to outside influences than others. There is no engineering standard for that.

[simon7000]

Originally Posted by scott wurcer

Since thermal distortion goes as V^2 you've got an 80db discrepancy there which one should be able to track down.

Yes we agree on this It is both level and that my reference should only be 6db lower than the source is resulting in low resultant readings.

[simon7000]

Originally Posted by Joshua_G

I find it hard to believe that my phono stage, CD player, pre-amp and power monoblocks (all are commercial ones), all have PSU malfunctions.

Have you ever tried inverting the AC supply lines? Try disconnecting all of the interconnect cables and measuring the voltages between all the chassis. Also check to ground. Yes there always is some capacitive coupling. Now swap AC power lines for the lowest reading. You will be pleased with the results.

Why? Because the manufacturers have no standard for that and do what works best for them, so unless all your gear comes from one place expect some differences.

[Joshua_G]

Originally Posted by simon7000

Have you ever tried inverting the AC supply lines? Try disconnecting all of the interconnect cables and measuring the voltages between all the chassis. Also check to ground. Yes there always is some capacitive coupling. Now swap AC power lines for the lowest reading. You will be pleased with the results.

I haven't done it, however, none of it explains audible differences between different power cords and power distribution boxes.

[Soundminded]

Originally Posted by john curl

No, Joshua, but some power supplies are more resistant to outside influences than others. There is no engineering standard for that.

Oh really? Are there no IEEE standards for shielding, line and load regulation, and AC ripple? No regulations for impedence. No standard for rating power supplies capabilities according to established specifications and accepted test procedures? What about FTC or can you just make any claim for any power supply?