john_ellis said:
Hi John,
My mention of the transmission line effects of speaker cable was only meant to be in the context of their potential to destabilize an amplifier. I did not intend to suggest these effects are audible (unless, of course, they cause the amplifier to become unstale).
Cheers,
Bob
Loaded frequency response of other amplifiers
Hi John,
I have looked at eight other amplifiers reviewed in Stereophile in respect to their HF rolloff into 2 ohms vs 8 ohms. As a single-number measure, I looked at the output level difference at 50 kHz and 1 kHz, and subtracted the latter from the former. The resulting dB number is a relative indication of the HF attenuation due to the heavier 2 ohm load, and is suggestive of the amount of effective output inductance that can be inferred.
The bottom line is that I do not think that the measurement data in this respect is adequately consistent from amplifier to amplifier to justify any inferences. The data that suggests that the JC-1 has a 2 uH effective output inductance is simply not reliable. There may be something in the test setup that may be dominating the rolloff.
So, I was wrong. There is no reliable evidence in the review data to suggest that the JC-1 has that much effective output inductance.
The data was as follows:
Ayre: -0.55 dB
Halcro DM88: -1.1 dB
Chord: -1.25 dB
Mark Levinson: -0.5 dB
Halcro DM38: -0.9 dB
Krell: -1.4 dB
MBL: -1.8 dB
Simaudio: -0.9 dB
I think these numbers are pretty much random and meaningless.
In my view, you are off the hook for output inductance 🙂.
Cheers,
Bob
Hi John,
I have looked at eight other amplifiers reviewed in Stereophile in respect to their HF rolloff into 2 ohms vs 8 ohms. As a single-number measure, I looked at the output level difference at 50 kHz and 1 kHz, and subtracted the latter from the former. The resulting dB number is a relative indication of the HF attenuation due to the heavier 2 ohm load, and is suggestive of the amount of effective output inductance that can be inferred.
The bottom line is that I do not think that the measurement data in this respect is adequately consistent from amplifier to amplifier to justify any inferences. The data that suggests that the JC-1 has a 2 uH effective output inductance is simply not reliable. There may be something in the test setup that may be dominating the rolloff.
So, I was wrong. There is no reliable evidence in the review data to suggest that the JC-1 has that much effective output inductance.
The data was as follows:
Ayre: -0.55 dB
Halcro DM88: -1.1 dB
Chord: -1.25 dB
Mark Levinson: -0.5 dB
Halcro DM38: -0.9 dB
Krell: -1.4 dB
MBL: -1.8 dB
Simaudio: -0.9 dB
I think these numbers are pretty much random and meaningless.
In my view, you are off the hook for output inductance 🙂.
Cheers,
Bob
Johan, you are NOT a 'whippersnapper' you are an 'old coot!' Nobody over 35 deserves to be called such a thing. I'm a 'geezer' myself, and I'm proud to call myself that. 
57 years as an audio amp designer, wow! Did you know DTN Williamson?
57 years as an audio amp designer, wow! Did you know DTN Williamson?
Mikelm, you actually have a point, but it is WAY out of place in the discussion. Still, it is most probably NOT the dielectric absorption that is the problem with a single isolated piece of wire, BUT the insulation will discharge chemicals that will tarnish the copper wire that it contains. That is the real problem. Think it through, before rejecting this expanation.
john curl said:Johan, you are NOT a 'whippersnapper' you are an 'old coot!' Nobody over 35 deserves to be called such a thing. I'm a 'geezer' myself, and I'm proud to call myself that.
Mr. Curl, you might be a little bit more careful, when using words like: whippersnapper, and -found in other threads- children, high school, teach, junior college, newbie engineers and so on. It's really counterproductive and insulting!
BTW, I built my first transmitter and SS-amp 55 years ago, but I haven't the least want to beat my breast over my early achievements and experience over a long time.
Johan Potgieter said:
Hi Johan,
How about this one:
Some people are convinced that 1uH is audible, and even claim that they can prove it.
Cheers,
john curl said:
Ah John!!
What can I say! TRUTH!
, hope not 
Nobody over 35 deserves to be called such a thing. I'm a 'geezer' myself, and I'm proud to call myself that.
No, I never took it that you meant that of the likes of me. Yes, I knew of DTN Williamson; in fact, that venerable publication was what set me off in this field. Some would now wish it never happened (should have gone off studying medicine or politics.) Down here nobody much in the audio field visited RSA. But I did meet the honourable HJ Leak, on visit to this country to promote ... stereo! With his amps, of course.
Seriously, taking the spitit of your reply as respectful, I thank you for that. If tongue-in-the-cheek - well .....
I regret that we would probably never meet. Do have patience with ALL on your way. I try. If that can be passed on down the line long after we have passed on (now in that line I am probably ahead of you!), it would be a greater legacy than all the knowledge one can leave behind.
Kind regards.
mikelm said:
Mikelm,
Not sure whether I was regarded as close to this (you might say, if the shoe fits ....). If so, it might surprise you that I for one totally agree.
An 18th century (now that was a little before my time) physicist said: "Miracles (put in there the unknown) are not contrary to nature, it is only contrary to our understanding of nature." That is an extremely valuable principle for a scientist.
But there are also certain matters (however few) that we have learnt to understand, otherwise I would not have been able to post here, and you to read it on your screen.
For me, to be forced into a tin of 3 + 5 = 11 (yes, OK, SY!) simply on the grounds that the above is always there, is unacceptable. But I do hope to be judged to always have accepted the above.
Regards
Johan Potgieter said:
Upon unexpected results, we use to react either:
"No, I must have messed up, makes no sense"
or:
"This is funny"
Of course most of the time the first turns out true, but breakthroughs can only leak through the other course.
Rodolfo
Johan,
Sorry if my words were unkind and off the mark
I get frustrated sometimes if formally electronically educated bods give the impression that there is nothing more to learn.
I have a reasonably good understanding of analogue electronics - enough to design with a reasonable degree competence but in some areas I guess tend look to you guys with formal training for a bit of back up - particularly in the maths department.
My natural tendency is to think that a comprehensive formal training proffers some kind of overall advantage but when I witness new ideas disregarded apparently without a second thought as if the whole of electronics is a finished science it comes to mind that all that formal training may actually be a drawback.
Professionally, I work with an electronic air filtration technology. The filters are essentially open frame capacitors. Simple - electrodes & plastic & air, but wow, working out what is going on inside those things is quite a big deal - almost endless complexity when you get down to the real nitty gritty details.
It may be that AC passing though an insulated wire or an inductor is theoretically fairly simple but, I think, if all of the possible interactions - electronic, chemical, physical - are carefully considered an apparently simple model ends up being considerably more complex.
cheers
mike
Sorry if my words were unkind and off the mark
I get frustrated sometimes if formally electronically educated bods give the impression that there is nothing more to learn.
I have a reasonably good understanding of analogue electronics - enough to design with a reasonable degree competence but in some areas I guess tend look to you guys with formal training for a bit of back up - particularly in the maths department.
My natural tendency is to think that a comprehensive formal training proffers some kind of overall advantage but when I witness new ideas disregarded apparently without a second thought as if the whole of electronics is a finished science it comes to mind that all that formal training may actually be a drawback.
Professionally, I work with an electronic air filtration technology. The filters are essentially open frame capacitors. Simple - electrodes & plastic & air, but wow, working out what is going on inside those things is quite a big deal - almost endless complexity when you get down to the real nitty gritty details.
It may be that AC passing though an insulated wire or an inductor is theoretically fairly simple but, I think, if all of the possible interactions - electronic, chemical, physical - are carefully considered an apparently simple model ends up being considerably more complex.
cheers
mike
Re: Loaded frequency response of other amplifiers
Wish this attitude were more widespread, it is really not that painful.
Places people in different ballparks altoghether.
Rodolfo
Bob Cordell said:
Wish this attitude were more widespread, it is really not that painful.
Places people in different ballparks altoghether.
Rodolfo
Mikelm, in 1959, when wiring my first Heathkit VTVM with doorbell wire ( the kind of wire that you were referring to in a recent post) I took my first Philosophy course.
I remember the professor telling this story.
He was at a party of 'intellectuals' and he went up to the bar to order a martini.
He asked for it to be a 'DRY' martini, which I think means strong on the gin and light on the Vermouth (I could be wrong on this). Anyway, someone came up and asked him what did he mean by DRY? As in how could a drink be dry, since it is a liquid? Or does it have to do with the weather?
The professor stated to us that this was 'way out of line' because the question was artificial and out of place.
Your earlier question was out of place.
And if you cannot accept this, then 'here is a 'dime' to call your mother ...'.
I remember the professor telling this story.
He was at a party of 'intellectuals' and he went up to the bar to order a martini.
He asked for it to be a 'DRY' martini, which I think means strong on the gin and light on the Vermouth (I could be wrong on this). Anyway, someone came up and asked him what did he mean by DRY? As in how could a drink be dry, since it is a liquid? Or does it have to do with the weather?
The professor stated to us that this was 'way out of line' because the question was artificial and out of place.
Your earlier question was out of place.
And if you cannot accept this, then 'here is a 'dime' to call your mother ...'.
Estuart, I did know how many 'Old Coots' we have here. 55 years ago I was flying model airplanes with little gas engines and wanted to be an astronomer. Except for the 1938 Gibson guitar amplifier that I had aquired in 1958, I did not know much about electronics until high school physics in 1959, when I was hooked.
PS Did you know that I first developed the input complementary differential input stage in 1968, while working at Ampex? That's the sort of thing that I am well known for.
PS Did you know that I first developed the input complementary differential input stage in 1968, while working at Ampex? That's the sort of thing that I am well known for.
john curl said:
Hi Mr. Curl,
when I was young I did it that too (flying) and crashed many times. 🙂
Regarding electronics, I was really young, when I received a box full of transistors (OC44/45 and OC71/72) from my uncle, then head of the tube department of the Philips company. It was really a great gift, worth a fortune in those day!
Cheers,
I love these war storries. I have a couple of them too, but have enough feedback not to bore you here 😀
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