John Curl's Blowtorch preamplifier part II

[abraxalito]

Originally Posted by simon7000

As all converters use analog input and output it is important to note that there are more issues than "is the analog as good as the digital?" When you charge a capacitor from a voltage source through a resistance the curve is an inverted exponential curve. Same for your current limited inductor, but of course you rarely see them in modern low level filters. So when you use a low pass filter to clean up your step jumps it is not a true linear average.

Where are you going with this - in what sense is the output of a low pass filter not a 'true linear average' ? Because the settling to the zero order hold DAC output is exponential so the target voltage is never in fact reached, or for some other reason? Are you suggesting there's an inherent non-linearity here?

This also is why timing errors are of greater importance than it would seem at first glance.

Please do flesh out the relationship of DAC setttling time to timing errors if you can, its something that's been a bit of a fuzzy area for me for a while.

[Rod Coleman]

Originally Posted by SY

Again, you've avoided the question of the bias signal on the analog tapes of recordings that you have found satisfying.

The effects of dither on resolution of a CD were clearly shown in the Stereophile review I posted (along with almost all of their other CD player reviews). FAR better performance when it comes to resolution than excellent analog systems. And the Lavry link that Terry so kindly posted. But most of all, the Lipshitz papers, which no-one besides me seems to have bothered to read.

I'm reminded of Max Planck's famous dictum:

"A new scientific truth does not triumph by convincing its opponents and making them see the light, but because the its opponents eventually die, and a new generation grows up that is familiar with it.”

When you have some data showing the audibility of a 16/44 A/D-D/A inserted into an analog signal chain, I'll be most interested to see that.

SY, you're confusing the debate. I called dithering a second-rate solution compared to proper high resolution recording. In no place did I say that dithering wasn't clever, nor that it might fail to improve CD-format recording. But as Terry's evidence shows, the mechanism is programme dependent - Dithering is not the same as high resolution.

For the other question of LP vs 16/44.1, I have compared analogue LPs to 16/44.1 in one repeatable fashion: Digitally recorded & mastered LPs. I have hundreds of these (they're very cheap, and often have interesting pieces on them). Many are EMI pressings manufactured in the same plant as the last of the analogue versions. I do listening tests with a second opinion (first in weighting) - one of the longest serving sopranos at Armonico:

Armonico Consort - Home

She is completely uninterested in records, hifi or the like - she's a acoustic performer. But when I play digital LPs, she has consistently ranked them at the bottom, mostly due to a lack of life or vibrancy; and though the standard of analogue LPs is not at all even, they usually show a realism that convinces her, and me. Yes, we have experimented with SRA & VTA on these LPs, and will often return to within 0.5mm of the arm position she preferred previously.

Whether these faults in these records are down to word size, sampling rate or something else, I don't know. But the effect is not subtle, and I would not believe that tinkering around the edges will be enough to put it right.

CD shows a lot of the same traits to me. I know that the players are flawed, and can be improved greatly, but what I would really be interested in comparing is 16/44.1 against real high resolution - how high do you need to go before you stop hearing improvement?

[SY]

Anecdotes of uncontrolled tests with poor validity aren't exactly data.

And PLEASE read the Lipshitz papers. You keep repeating the same incorrect statement regarding resolution. If you're just interested in mantras, that's fine- just man up and say, "My mind is made up and I don't really want to understand the issue." Nothing wrong with that and it's certainly more honest. But saying something wrong again and again does not make it right.

[Rod Coleman]

Originally Posted by SY

Anecdotes of uncontrolled tests with poor validity aren't exactly data.

And PLEASE read the Lipshitz papers. You keep repeating the same incorrect statement regarding resolution. If you're just interested in mantras, that's fine- just man up and say, "My mind is made up and I don't really want to understand the issue." Nothing wrong with that and it's certainly more honest. But saying something wrong again and again does not make it right.

Reports of real listening may not constitute DATA but are no less real for all of that.

I am not repeating anything!! Perhaps you should clarify what you think Dithered 16/44.1 is actually equivalent to in resolution terms, so that we can debate the same thing, not confused nonsense.

[john curl]

Right on, Rod! Hearing is believing. Dr. Lipshitz disregarded MY measurements and mathematics regarding capacitor DA, because he thinks that very little really matters. So much for mathematical 'proofs'.

[jan.didden]

I am only aware of one test where a 16/44 A/D-D/A unit was inserted (or not) in a playback chain with an effort at test control. That was where Ivor Tiefenbrunn of Linn fame IIRC failed to hear it.

One test participant (who happened to be Lipshitz) WAS able to reliably identify the unit because after some time he realised that there was a slight difference in background noise with or without the digital set.

But those who listened to the music only could not identify what was what.
The test is documented on the Boston Audio Society (BAS) website, look under archive I think.

jd

[jan.didden]

Originally Posted by Rod Coleman

Reports of real listening may not constitute DATA but are no less real for all of that.[snip].

Correct, but that 'data' is only valid for that person, that situation, that equipment, his mood etc. It's worthless for anyone else.

Come to think of it, it is worse than worthless, because it biases people to a certain outcome for their own listening.

jd

[jan.didden]

Originally Posted by john curl

Right on, Rod! Hearing is believing. Dr. Lipshitz disregarded MY measurements and mathematics regarding capacitor DA, because he thinks that very little really matters. So much for mathematical 'proofs'.

John,

I don't think he disregarded your measurements and mathematics as such, he only didn't believe the effects were audible, which was an unfounded assumption anyway.

jd

[jcx]

nobody is actually literally recording 16/44.1 today - oversampling, "24 bit" ADC and signal processing are much cheaper than 20 KHz analog anti-alias filters

broadband S/N >110 dB and differential linearity way down in the noise is the norm for top monlithic audio ADC

target rate brickwall filtering, decimation and bit depth reduction with dither is only used at the final stage of the production process


people should also ckeck out Lukin's dither clips - he provides 8 bit audio clips to exagerate quantization noise artifacts and show various dither's improvement in audible resolution and noise shaping's reduction in dither noise perception

Homepage of Alexey Lukin

[john curl]

[snip]
I have always believed [snip]

Fine!

jd