John Curl's Blowtorch preamplifier part II - Page 2705 - diyAudio
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Old 27th August 2012, 02:09 PM   #27041
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Quote:
Originally Posted by simon7000 View Post
My current project in Seattle had a crew of climbers mount the loudspeaker clusters. First time this happened. They managed to get approval to use climbing gear on an OSHA site.
Yah, been there done that, but on a 90 foot Grove. Were they using the sliding lock on a cable, or clipping their lanyard to a hardpoint above their D ring?

From what I remember, in the event somebody ends up dangling from a body harness for a half hour or so, the EMT's MUST have training on how to deal with the person after they get them down. Has something to do with return of blood flow to the legs and how the heart deals with it. Apparently there is a small possibility of cardiac arrest.

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Old 28th August 2012, 02:15 AM   #27042
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Ok everybody, let's get back to audio! '-)
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Old 28th August 2012, 11:59 AM   #27043
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What useful information is lost through all the 'romp and stomp' that plagues this thread, is why I, at least, strive to keep it going, even though I have to repeat myself.
I am not interested here in ready-made circuits, that amateurs can build from their spare parts. I am interested in sharing what it takes to make a really successful audio product, above and beyond just a good measuring one.
This is where the importance of passive parts quality, power supply design and selection, circuit layout, and exterior shielding all play a part.
However, I have proved, at least to myself, that 'acceptable' designs can now be made with IC's, IF you correctly choose the right IC's for the job. In making the JC-3 phono preamp a success in the audio marketplace, I overcame a personal 'hurdle'. Now, this does NOT mean PERFECT or as good as absolutely possible, but satisfactory for many people who cannot afford super hi end, and cannot build something themselves.
I hope to continually impart what seems to 'work' in making a successful audio product, and it is certainly more than just an interesting circuit topology.

Last edited by john curl; 28th August 2012 at 12:10 PM.
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Old 28th August 2012, 02:21 PM   #27044
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Originally Posted by morinix View Post
A woman at 40yo 22khz more likely. I would have to see tests.
Ha ha. Got a time machine?

THE test: "hey turn that thing off, don't you hear that?"
"...what? hear what? I don't hear anything..."

Believe me, life is simpler without hearing ultrasonics... it's troubling sometimes... can't get anywhere near that now.

Hi-fi becomes easier to get "good". Ha ha.

_-_-bear
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Old 28th August 2012, 03:05 PM   #27045
morinix is offline morinix  United States
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Quote:
Originally Posted by bear View Post
Ha ha. Got a time machine?

THE test: "hey turn that thing off, don't you hear that?"
"...what? hear what? I don't hear anything..."

Believe me, life is simpler without hearing ultrasonics... it's troubling sometimes... can't get anywhere near that now.

Hi-fi becomes easier to get "good". Ha ha.

_-_-bear
How do you know the frequency spectrum of the "thing"? Did you, at least, play around with a calibrated oscillator?
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Old 28th August 2012, 03:25 PM   #27046
SY is offline SY  United States
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What's often the case is that the ultrasonics cause lower frequency components from less-than-perfect transducers. That's easy to verify. But still, I have known males near 30 with verified acuity in that range. Male, 40 is not something I've seen demonstrated yet.

Me, no way, even at 30, I was lucky to hit 19k.

And calibration is not an issue these days with digital sources.
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Old 28th August 2012, 04:18 PM   #27047
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At 32, I thought that I had a 'notch' at 19K. John Meyer and I, however, found that my tweeter had a 'notch' at 19K. You never know.
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Old 28th August 2012, 06:23 PM   #27048
morinix is offline morinix  United States
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I was playing in rock bands so I knocked out those pesky HF's by my early 20's. I did hear a story about Sydney Harman in his mid 80's walking in on some of his engineers doing a listening audition of a new amp design. He exclaimed "that amp is distorting!" Every one else was dumbfounded. Tested the amp more and old Sid was right. Go figure.
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Old 28th August 2012, 06:52 PM   #27049
wrinkle is offline wrinkle  United Kingdom
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At work a good few years ago I was repairing a 600 Watt amplifier for a colleague in another department. No speakers in the lab, so we used a bunch of high powered 50 ohm loads. The amp whistled quite loudly and all of us used some calibrated sources, hand covering dial each time and adjust till whistle could just be heard. I was 36 years old and my personal cut-off was about 21.5Khz to 21.6, some of the others were stopping at sub 20K, but one luck 30 year old was hearing up to about 22K.

the proof was that without seeing the dial each of us would consistently stop at our own limit of hearing. If any of us had been trying to cheat it would have been more variable. It was a bit of fun to see where our ears were compared to each other.

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Old 28th August 2012, 07:06 PM   #27050
bcarso is offline bcarso  United States
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The late Gerald Strang, a pioneering composer of computer music, taught a course at UCLA one year. Class was held in the Electronic Music Studio, a little room in the bowels of the Mathematical Sciences building.

Gerald was fairly far on in years and had significant HF hearing loss. He was fond of demonstrating the equipment (Moog, Buchla) during his lectures. He would sometimes have a loud tone going out of one of the oscillators, and would say Well, we can turn the level down over here (indicating a control) OR simply raise the frequency to beyond audibility! At which point, with a grand gesture and big grin, he would turn the frequency control to where he couldn't hear anything, but unfortunately for the numbers of younger ears in the room, leave a most distressing and quite audible high-frequency signal screaming away out of the AR monitors, often right in someone's ear. Eventually someone would get up and turn the level down.
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