Home Propeller Head Plaza

Technical and scientific discussion of amps, cables and other topics.

Re: Much simpler answer

Your original question is meaningless, because there is no such definition as 'neutral audio'. How do you measure that?
Personally, I can measure to 1 million to one, with THD and IM distortion. This appears to be about 10 times better than 'Stereophile' typically measures. This is about -120db. I also can separate individual harmonics and noise from the measurement, and accurately measure harmonics to 100KHz. There is even newer and better test equipment out there, but I cannot personally afford it. However I doubt that an even lower measurement would gain much. After all, sooner or later, an extremely low value in distortion, by itself, must be meaningless, even to the 'objectives' of this world.
I will give an example however of how I once changed the sound of a power amplifier that even surprised me.
It was 1973, and I was hanging out at Mark Levinson's house. We were making a new phono pre-preamp together, to be called the JC-1, and Mark also made some discrete line level modules for the Grateful Dead, for use in their new sound system.
Mark had retired his Marantz 9 tube power amps and bought a Phase Linear 700 power amp that went well with his new DW electrostatic loudspeakers.
Both Mark and I thought this combination pretty good, and well balanced. However, Mark's mother (did I mention that Mark lived with his family?) complained that the new setup hurt her ears, so Mark and I discussed the problem.
I told Mark: "We could change the bias and cut out the protection circuitry."
I knew that the Phase Linear 700 ran next to empty in bias, because I could just put my hand on a heatsink after some time in idle and it would be just barely perceptably warm over the ambient.
Well, we did what I suggested on his workbench. The bias was slightly increased to reduce the xover distortion to where I could just feel a slight difference in the heatsink temperature. (you must remember that by 1973, xover distortion had been proven to be inaudible in DB tests) and the protection circuits were snipped out.
Well what happened? After we got the unit running again, Mark asked me: "Where did the highs go! Did you change something that would affect the frequency response? " I said: "No, Mark, I just removed some of the xover distortion in the amp.
Well, the next time I came to visit, Mark had an electrostatic tweeter mounted on top of his big electrostatic speakers. Subsequently, the electrostatic speaker came out with a MK2 version with a piezo tweeter (ick) on top. Apparently, the electrostatic speaker manufacturer had exaggerated the actual high frequency performance of his speaker in his literature, but this was originally taken care of by the addition of higher order harmonics from the bigger amps that were necessary to drive the speaker properly.
So much for the inaudibility of xover distortion.
Now I want to ask you engineers out there: Why do Motorola piezoelectric tweeters sound the way that they do? What can I MEASURE to show how they sound, and why doesn't everyone use them?


This post is made possible by the generous support of people like you and our sponsors:
  Parts Connexion  


Follow Ups Full Thread
Follow Ups


You can not post to an archived thread.