John Curl's Blowtorch preamplifier part II

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as far as I can tell virtually all SACD capable players today use PCM Audio DACs which take DSD input and internally digitally filter, increasing bit depth before feeding it to the rest of their internal Delta Sigma circuitry common to the PCM path

care to show us actual DSD 5V, ns edges ~ MHz noise modulated carrier "single bit stream" on a pcb - at the input the the required >5th order analog filter?

how is this less HF artifacts?
 
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Again, the real problem, from my point of view, is that audible levels of high frequency distortion are part of virtually every hifi system. It's only when you finally eliminate that as a significant component of playback do you appreciate what's actually happening, and you able to tag any sound you hear immediately as being free of it or not.
Frank

Yes! This is the exact truth. HF distortion is the great evil of digital and transistors.
 
Fas42, i totally disagree. I am sure that, when there is nothing your ears can hear, or your tweeter can reproduce, there is nothing !
If Hf and high order distortion products outside of the bandwidth have some effects we can notice, it is because the IM they produce *inside* our listening window.
Well, there is probably something else which can have an influence, it is the slew rate of the signals. Even when the high harmonics of this signal, necessary to make this fast rise, are upper than the limit. Something in relation with instantaneous acoustical power ?
 
John, i am no more young neither, and my ears don't go so high than in the good old time. But, as you said for yourself, i do not feel like if i have lost too much of my earing abilities: May-be that what we have lost in our natural mikes quality has been a little compensated by better brain separation power ?
My mother was a pianist, and i had verified the same thing with other old musicians or sound engineers as well: 'Culture'.

This said, those last years i was looking (and asking) to my young customers during my mixing session, to be sure i was not doing something bad in the trebles.

You know, those guys that create perfumes ? We call them "noses". They are able to tell-you all the components of a perfume in blind test and much more. One of them explained to me that it is not because he has a better capacity to 'smell', it it because they know the elements and, so, can recognize them. Like you can recognize your best friend in a crowd.

T
 
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Regarding roll-off frequencies ---> group-delay is still important to keep under a certain threshold. Dean Jensen (Jensen Transformer founder and designer) made his fame by winding his transformers for low group-delay distortion (esp. at low end).... little known at the time. But, bares repeating from time to time. especially when talking about filters. CD and the filters used are not always minimum group-delay and can/do exceed audible thresholds. It is also one to test for as a complete end-to-end system. Thx-RNMarsh
 
Fas42, i totally disagree. I am sure that, when there is nothing your ears can hear, or your tweeter can reproduce, there is nothing !
If Hf and high order distortion products outside of the bandwidth have some effects we can notice, it is because the IM they produce *inside* our listening window.
Well, there is probably something else which can have an influence, it is the slew rate of the signals. Even when the high harmonics of this signal, necessary to make this fast rise, are upper than the limit. Something in relation with instantaneous acoustical power ?
The distortion is certainly inside our "listening window", to my ears it's all happening around, say, the 5 to 10kHz area. There's nothing magical about why it happens, it's the end result of all the negative factors degrading the ability of a sound system to reproduce cleanly. I've mentioned in another thread about finding a YouTube clip which records a "live" performance and then a very expensive system reproducing a recorded version of the group. Well, when you look at the waveforms of equivalent sections it's laughable: Venus and Mars come to mind, there's very little correlation between the two. This is "distortion" at a gross level, 100% easily at times ...

I'll aim to put up some screen captures soon to demonstrate what I'm talking about ...

Frank
 
What DOES NOT often get spoken about is what happens WHEN you reduce audio bandwidth with any rolloff, whether deliberate or inherent.
As one of a number of people who have conducted Double Blind Listening Tests on Bandwidth Limitation, I'll remind everyone here that in ALL the reliable tests, those who could tell the difference Double Blind, (ie true golden pinnae who are more sensitive) PREFERRED the Bandwidth Limitation.

In 1971, in a book called 'Audio Quality' by G. Slot, bandwidth was mentioned, but the MOST IMPORTANT factor, once you got to perhaps 16KHz, was the RATE OF CHANGE of the falloff, not so much the frequency. So, 6dB/octave, was very subtle, while anything beyond 9dB/octave was problematic.
I remember Slot's book but not this bit. Was it one of the Philips series?

... with much back-patting and 'proofs' by distinguished professors, more extended formats are being brought forth, as it is now more practical and possible to do so.
Alas, as always, the almighty $$$ and Golden Pinnae myth runs riot over properly conduction Blind Listening Tests.

BTW, I'm still interested in SACD/SACX and other AVAILABLE supa dupa 'high def' music that might be used to repeat some of my Jurassic work on Bandwidth Limitation. Anyone know any true golden pinnae that might want to take part?

I got loadsa test signals that even my Jurassic golden pinnae team can distinguish Band Limiting though it gives them a serious headache for the next 24 hrs.
 
As one of a number of people who have conducted Double Blind Listening Tests on Bandwidth Limitation, I'll remind everyone here that in ALL the reliable tests, those who could tell the difference Double Blind, (ie true golden pinnae who are more sensitive) PREFERRED the Bandwidth Limitation.
My miserable memory tells me that eons ago the same thing happened when attempting to decide on the bandwidth for recording, playback, or something or other. One astute chappy connected the dots, and redid the test with live music, with different acoustic materials in front of the musicians filtering out frequencies. Of course, the "straight" presentation was preferred, and all was saved -- none of the experts who set up the equipment could bring themselves to admit that the system used was stinking with distortion, so of course the audience preferred that which rescued them from the worst excesses ...

To my mind the same is still the case, except the problem is a lot more subtle these days ...

Frank
 
As one of a number of people who have conducted Double Blind Listening Tests on Bandwidth Limitation, I'll remind everyone here that in ALL the reliable tests, those who could tell the difference Double Blind, (ie true golden pinnae who are more sensitive) PREFERRED the Bandwidth Limitation.
My miserable memory tells me that eons ago the same thing happened when attempting to decide on the bandgwidth for recording, playback, or something or other. One astute chappy connected the dots, and redid the test with live music, ...
When bandwidth sound reproduction is preferred, something is wrong with the audio system used. This may easily happen and double blind test will reveal it, not fix it.
It were Dr. Harry F. Olson - Experiment That Saved Hi-Fi

My experiments were circa 1980 with vinyl & mastertapes from the record companies. I thought I'd gone into all this earlier in this thread. :confused:

I'm interested in whether the State of the Art is still at the stage where eg 20kHz brick wall sounds better.

Of course there are those who are uninterested in what sounds better and prefer to have their Golden Pinnae myths unblemished by truth. :D
 
It were Dr. Harry F. Olson - Experiment That Saved Hi-Fi
Of course there are those who are uninterested in what sounds better and prefer to have their Golden Pinnae myths unblemished by truth.
"But the fact that the listeners preferred full-range sound, if undistorted, had now been proved. "

OMHO, i prefer my speakers without tweeters (horn up to 16KHz, time aligned) but i prefer my electronic as fast as possible, and, as i said, a bandwidth up to 200Khz for my amp, and no brickwall for my CD. Hard to explain.
 
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Fas42, i totally disagree. I am sure that, when there is nothing your ears can hear, or your tweeter can reproduce, there is nothing !
If Hf and high order distortion products outside of the bandwidth have some effects we can notice, it is because the IM they produce *inside* our listening window.

It's still an effect of HF distortion.
So, in practice you are not disagreeing :)

Well, there is probably something else which can have an influence, it is the slew rate of the signals. Even when the high harmonics of this signal, necessary to make this fast rise, are upper than the limit. Something in relation with instantaneous acoustical power ?

When HF signals are slew limited something ugly happens :)
You can either filter the hell of it (which introduces phase shifts as low as 1khz), or deal with it (building "fast" amps, like JC does for instance)
 
As one of a number of people who have conducted Double Blind Listening Tests on Bandwidth Limitation, I'll remind everyone here that in ALL the reliable tests, those who could tell the difference Double Blind, (ie true golden pinnae who are more sensitive) PREFERRED the Bandwidth Limitation.

Like most sane people would prefer not to hear HF distortion, even at the price of loosing some upper harmonics.
The hard thing is to reproduce HF well.

It were Dr. Harry F. Olson - Experiment That Saved Hi-Fi

My experiments were circa 1980 with vinyl & mastertapes from the record companies. I thought I'd gone into all this earlier in this thread. :confused:

Yes you did, but you talked about the first experiment only a few posts earlier, which is misleading, if someone doesnt also read Olson paper.

I'm interested in whether the State of the Art is still at the stage where eg 20kHz brick wall sounds better.

IME, it's better than in the 80s and 90s but still far from good fidelity in most cases.
 
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OMHO, i prefer my speakers without tweeters (horn up to 16KHz, time aligned) but i prefer my electronic as fast as possible, and, as i said, a bandwidth up to 200Khz for my amp, and no brickwall for my CD. Hard to explain.
As many others have stated, it's still hard for digital playback to get the upper frequencies right every time. Not because of any intrinsic problem with sourcing from digital, but because there are so many ways for the sound to go astray. There are many techniques for getting around this, yours is one of them. Mine is to steadily, relentlessly eliminate every weakness in the playback mechanism, and this if pursued sufficiently diligently delivers truly superb sound ...

Frank
 
It's still an effect of HF distortion.
So, in practice you are not disagreeing :)
When HF signals are slew limited something ugly happens :)
You can either filter the hell of it (which introduces phase shifts as low as 1khz), or deal with it (building "fast" amps, like JC does for instance)
I don't know. My actual preamp and power amplifier have 1000V/µs of slew rate, and low IM distortion. I can reasonably suppose they do not produce too much of TIM ?
Really, i cannot explain why i do not like any (good) tweeter. May-be more a question of acoustical coherency due to filters.
Anyway, most of us are too old, here, to can experiment in a useful way: we need young girls to talk about HF limits.
I remember when i was discovering the Grateful Dead's records. Their engineer was a women, and the mixs quite different from men's ones in tonal balance. More basses (because women hear them less) and less treble (because women hear them better ?).

I wonder too why women are less interested in HIFI than men ?
 
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I'll remind everyone here that in ALL the reliable tests, those who could tell the difference Double Blind, (ie true golden pinnae who are more sensitive) PREFERRED the Bandwidth Limitation.

My own (humbling) experience exactly. I've written it up here somewhere, but we tried a blind test of an FM multiplex 15kHz filter. Ruler flat to 15kHz, then a steep roll-off of more than 60dB at 19kHz. Lots of phase shift of course.

Of four participants, one stepped out because he admitted not hearing any difference. The remaining three, yours truly among them, all identified correctly the two different situations but inverted: we thought that the situation with the filter switched in sounded the best! We also had similar descriptions of that 'best' situation: brighter, more attack, more transients. As I said, humbling.

I had the Slot book John referred to (no longer, gave it away) but never found that passage.

jan
 
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