John Curl's Blowtorch preamplifier part II

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Some of you are bringing stories about your wives and sound. OK, here is mine:

Recently I have been asked to measure and test several "audiophile" link cables. I have connected one of them into the system, and later started to listen to the music. My wife has immediately told me: "You have made some change in the system, haven't you? It sounds different!"
She did not like the new sound as well as I did not like it.

So this is my recent story about link cables. I am not telling the manufacturer - well known one.
 
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Well one of the things we make around here for a select few are buffered guitar cables. Two versions, one has an fet follower in the Ax end plug to send the signal with a bit more ooph and the other has a driven inner shield.

Both make a difference. The preamp of course reduces the pick up coil inductance interactions and the active shield reduces capacitance.

(Difference is defined as measured and heard FYI)
 
Well one of the things we make around here for a select few are buffered guitar cables. Two versions, one has an fet follower in the Ax end plug to send the signal with a bit more ooph and the other has a driven inner shield.

Both make a difference. The preamp of course reduces the pick up coil inductance interactions and the active shield reduces capacitance.

(Difference is defined as measured and heard FYI)

well imagine that - audible differences where engineering theory predicts differences way above DBT/ABX frequency response thresholds

UIUC Physics 498POM Guitar Pickup Measurements


no one wanting intelligent debate has ever said no cable, transducer ever has an audible effect - when there are engineering reasons, clear frequency response variations
 
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well imagine that - audible differences where engineering theory predicts differences way above DBT/ABX frequency response thresholds

UIUC Physics 498POM Guitar Pickup Measurements

Lets see a pick up coil with an inductance of 4+ Henries of inductance driving a cable of say 750 pf of capacitance into a 2 megohm load. Where do you think the 3 db rolloff point would be?
 
you are so sure I'm contradicting you?

try reading more closely

double negative problem? - try: some cable, transducer combinations do have audible effects - from measureable frequency response variations Above published DBT/ABX thresholds

high inductance guitar pickups, practical cable, preamp input Z are exactly such a situation
 
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Or am I giving values for the lazy?

no - its a reading comprehension problem on your end

given an LCR filter example with a fc near 3 KHz an engineer would say "yeh thats audible"

which is what my posts, ref said


but it doesn't help with the argument of whether speaker cable of the same C from an amp with less than 4 uH output Z shows any audible frequency rolloff from cable C

or indeed if the dielectric properties were varied from air to those of PVC at a kHz rate as a thought experiment - would there be a audible signal change at the (typical ~90 dB SPL re 1W) loudspeaker? - above the human audibility threshold in a anechoic chamber after minutes of accommodation

which is the type of argument I would use for many cable claims – overbound the variation in a cable property claimed to be important, see if it could result in a change in a simplified circuit model of its application, is the difference even expected to be audible in the absence of signal at all above the electronic or our hearing noise floors
 
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We could discuss your grammatical constructions with close repetition and general style.

Or we could progress to Bear's observation that different metals with the same L & C sound different. They also measure different amounts of resistance and extremely small differences in IM distortion. Is there any other measurable difference?

I read into Bear's discourse that he used the same connectors, so is that truly out of the issue?


Scott,

If you had bought $1000 video cables you wouldn't have those issues! (I find that I can get BNC cables for about the same price as RCAs!)

Just down the road is a stadium where the pseudo IT guys installed a video to ethernet system using BNC to F then F to RCA for all of the connections, just waiting to see how long till it all goes dead.
 
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Unfortunately, he admits that he doesn't have any data to support this (he's an honest guy, which I appreciate). No-one else does, either.

In my OPINION there are very small measurable differences. Although at those levels I find it difficult to believe the resistance or distortion differences can be heard. So although the possibility exists that may be what is being perceived there is always the remote chance there is something we are failing to measure.

In my OPINION there can be significant differences in cable insulation having an effect on some systems. As this can add not just capacitance but as Scott has demonstrated dielectric absorption shows up as an increase in noise. I am also of the OPINION that out of band noise can still degrade the reproduction system. So it is not as wild a claim that improved insulation makes a real perceived difference even without going to the extremes of deliberately high capacitance cables.

I don't think there is much debate that connectors can cause problems, only to the extent at which those issues reach levels that can be heard.

Now if you allow the premise that some humans (I know a presumption on my part) can perceive distortions of -140 db to -160 db re the peak sound pressure level, then many of these issues would actually have a basis!

But if I were to bet on it, I would wager that the multiple FFT averages allow looking at conventional issues yet missing something that averages out that our hearing mechanism picks up.

At the recent AES I spoke to a few of the instrument manufacturers about doing some different tests and other than they thought the idea interesting they had no suggestions as to how to go about it!
 
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Problem is, you only get as high as -140dB in the presence of signal at 0 dB. Oooops. The DA noise is a red herring for this application.

So far, no-one has been able to demonstrate audibility of different metals. And that's in accord with the predictions of dull, stodgy, reliable, conventional engineering. Ah well, that frees up people to work on stuff that actually matters.
 
Problem is, you only get as high as -140dB in the presence of signal at 0 dB. Oooops. The DA noise is a red herring for this application.

So far, no-one has been able to demonstrate audibility of different metals. And that's in accord with the predictions of dull, stodgy, reliable, conventional engineering. Ah well, that frees up people to work on stuff that actually matters.

SY

Some of us aren't using recordings! But even with a 24 bit recording (As far as I know there aren't any really there yet) that would allow you more than 140 db of resolution. Noise isn't quite the same issue. If you understand the ears ability to narrow the observed bandwidth (You know that critical band stuff) that allows analysis at another 30 db or more below the broadband noise level. So although it is unlikely there can be a basis for -170 db perceptions! Now has anyone ever demonstrated this ability in a well controlled test? Duh not that I know of. But if I can measure components and reduce the distortion to -160 or -170 db levels without significant cost increases then it would be silly not to.

That is why I talked to manufacturers at the AES show about no cost methods (or even ones that lower costs) to improve their products.

I would find it hard to believe you would argue that an improvement in part quality with no increase or even a decrease in price is a bad thing!

But it was interesting at the AES to find the tweak designers I know, all use resistors that measure very well. The depth of knowledge about part performance that was reported to have been tested by ear and agreed with measured results was most interesting.
 
When you can find anyone who can hear the Sousa band in Bill Waslo's clever demonstration (I think that's only at -65dB?), get back to me about that -170dB stuff.

Do you really want to argue 65 db dynamic range is all you need? :)

Well when I posted ninth harmonic distortion at -60 db only a few couldn't hear that. We could try 9th at -80 db, that shows up on our in house listening test for some folks. So the issue most likely is what are you listening for?

That just illustrates we really don't know exactly what is going on.

I just came back from an arena. There is a light buzz coming out of three of the loudspeakers. They are on a 70 volt speaker line. One wire going to them has shorted to the conduit. I measured 10.5 millivolts across the loudspeakers as a result. That is 76 db down. I still have to fix it cause it can be heard quite clearly even in an arena!
 
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