Bruce Brisson, those MIT white papers are full of zingers. Random reactive noise RRN, a reactance has no real part to its impedance and can not generate noise. Even you can't argue with that.
Anyone who actually studied one of his cables would find it different in construction geometrically from typical cable, but his materials are just typical for average audiophile cables. VDH's cables are made of much better materials and insulation, but have very nominal geometries, more like normal cable. Go figure!
It is difficult to understand what really happens at very low voltage levels in a cable. We do know that impurities and micro-cracks change the optimum resistance of a particular metal slightly at room temperature and a lot at very low temperatures, as this is the residual 'resistance' that reduction in temperature will not reduce correspondingly. But is it actually 'resistance' or is it micro-gaps and diode like components? Who knows? I don't for sure, and no textbook that I have ever found tells me specifically.
If VDH is right, then it is important.
If VDH is right, then it is important.
I think Jean Fadel in France looked into that. He makes cable under the name Fadel Art.
I know the effect from coils and usually use high quality ferrite instead of iron to avoid it.
I know the effect from coils and usually use high quality ferrite instead of iron to avoid it.
I suspect it does, just the name is lost. Iron bearing chassis are thought to sound bad, capacitors with copper plated steel leads are also on the "parts to avoid list."
One recent grad working for me had a theory, that he didn't need to know the old stuff. He was only interested in what was new! His college changed the curriculum so they never graduate someone so ill prepared again! (TRUE STORY)
Jan, the question is whether VDH EVER did the test that he claims, as VDH gave specific results in print. No, he did not write a peer-reviewed paper, like I asked him to do for the IEEE, but the detail that he gave me, more than 25 years ago, was enough to convince me that he did the test.
It would be similar to asking me if I ever did a sine-square TIM test, myself, on all my amp designs, since 1978, I haven't. It is just too hard to do on a general basis and is hard to calculate a 'number' to correspond with a quality factor. Still, I can easily predict the results of future designs, based on measuring previous designs, and noting the trends that promote TIM, such as slew rate.
It would be similar to asking me if I ever did a sine-square TIM test, myself, on all my amp designs, since 1978, I haven't. It is just too hard to do on a general basis and is hard to calculate a 'number' to correspond with a quality factor. Still, I can easily predict the results of future designs, based on measuring previous designs, and noting the trends that promote TIM, such as slew rate.
Hi John
What about Group Delay?
I think that is an interesting topic, especially in global feedback designs. 🙂
Cheers
What about Group Delay?
I think that is an interesting topic, especially in global feedback designs. 🙂
Cheers
I agree with PMA, group delay is important in filters, very important, but not in amplifiers to any significant degree that I know. It is interesting that the late Richard Heyser had the examples of delay: group delay, phase delay, and REAL delay (?). Talk about confusing.
Amplifiers are usually minimum phase so when they have a wide bandwidth, say more then 200kHz -3dB, group delay is flat in the audible range but that is trivial, isn´t it ?
The same is true for bass extention.
Following Blauert that identified 1msec of delay as the audible threshold at some frequencies, constructing an amp with more delay then that whould need spectacular incompetence or a purposely designed additional allpass. Still a lot of German designers go for wide frequency response and claim gains in soundstage depth and resolution in micro detail.
The same is true for bass extention.
Following Blauert that identified 1msec of delay as the audible threshold at some frequencies, constructing an amp with more delay then that whould need spectacular incompetence or a purposely designed additional allpass. Still a lot of German designers go for wide frequency response and claim gains in soundstage depth and resolution in micro detail.
Absolutely! You heard my amp with a bandwidth of circa 250kHz, open loop - lots of soundstage depth and accuracy.
That's the first thing to vanish if the bandwidth gets closed down - well well before any perceivable loss of treble information.
Regards, Allen
Still i wish you could try some feedback, at least a little. I am not in the position to critisise your decissions on the other hand. Your amp sounded wonderfull in my system.
The most natural so far that i heard.
The most natural so far that i heard.
I agree there are big differences between amps in soundstage, details, space, even for those with BW above 200kHz. But I am absolutely sure that group delay is not any issue in this case. Follow another tracks, like dynamic spectra and dynamic noise modulation.
Absolutely NOT interested. But I've tried adding NFB to every previous amp, and they all lose space, microdynamics, and most importantly, the soul of the music. I'll listen for two hours or even up to two days, then the NFB comes out and I let out a big sigh of relief, and get back to the music, rather than the (more sterile) sound of the amp.
Regards, Allen
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