John Curl's Blowtorch preamplifier part II

[Joshua_G]

I repeat a story. JC sent me an LP from Dave Wilson with identical cuts with "nothing" different in the path but a 50K sampling Soundstream A/D - D/A. I, as carefully as possible, made a 24/96 recordings of each and lined them up to within +-1 sample at the start. They did not line up at all, even 6dB off at some points. My only conclusion is that something very major was missed in the process. They of course sounded identicle.

What does it prove, or indicate? How it may serve us in pinpointing the ways and the degree the original recorded electronic waveforms are being degraded on each step and stage of the reproduction chain?

 

[Joshua_G]

Electronic, recorded, waveforms can be full and exact representation only of the sound waves that were energizing the microphones at their specific locations.

It could be so, should we have perfect microphones, perfect recording amplifiers and perfect recording media.

At this point in human history, none of the above is perfect.

(There is a good chance to achieve satisfactory reproduction, if you replay this recording at that same space through speakers located where the microphones were).

Satisfactory reproduction is one thing.
An electronic waveform which is a full and accurate replica of acoustic sound waveforms is a different thing.

 

[Kindhornman]

Joshua,
To say that there is no correlation between test results and audio sound quality is just a bit of a stretch. That doesn't mean that it is all there is, but if the test results are showing poor results the sound quality often goes along with them. At the same time great test results don't mean that you will always have a great sound quality either. It is the combination of all the factors that create the whole experience and resultant. I agree that there is something that we just haven't been able to quantify or correlate between test results and listening tests, but I sure wouldn't discount testing or listening tests. It is the judicious use of both functions that gets us to the end result.

 

[Joshua_G]

Those who are incapable of changing their own paradigm are stuck repeating the same thing over and over with no possible change in outcome.

Indeed.

Most people with an open mind do in fact change their own predispositions over time, whether that is caused by our own learning experiences through discovery or mistake or listening to others and allowing that information in can shift our own thinking.

I know nothing about 'most people'.

Only those who do the same thing over and over and expect a different result are locked into a specific paradigm that they are not willing to give up.

Indeed.

I learn things on these threads all the time, and that means that I often have to rethink a conclusion that I have previously made.

I didn't say that it's impossible to learn from the words of others.
Have you switched you mental paradigm as the result of reading?

 

[vacuphile]

I repeat a story. JC sent me an LP from Dave Wilson with identical cuts with "nothing" different in the path but a 50K sampling Soundstream A/D - D/A. I, as carefully as possible, made a 24/96 recordings of each and lined them up to within +-1 sample at the start. They did not line up at all, even 6dB off at some points. My only conclusion is that something very major was missed in the process. They of course sounded identicle.

You tested both the accuracy of an AD-DA step and the accuracy of LP playback between two tracks in one single go. So how do you know it was not the vinyl stage that caused the deviations?

The better test would appear to be AD versus AD-DA-AD.

 

[Joshua_G]

To say that there is no correlation between test results and audio sound quality is just a bit of a stretch.

That depends primarily on the way the testees evaluate and describe the differences they perceive.

That doesn't mean that it is all there is, but if the test results are showing poor results the sound quality often goes along with them. At the same time great test results don't mean that you will always have a great sound quality either. It is the combination of all the factors that create the whole experience and resultant.

See my above comment.

I agree that there is something that we just haven't been able to quantify or correlate between test results and listening tests …

That was my sole point.

… but I sure wouldn't discount testing or listening tests.

Neither would I.

It is the judicious use of both functions that gets us to the end result.

In order to have confidence in tests results, I'm yet to find a set of tests (affordable by me) that will have a very good correlation with listening evaluations (both by me and by people who listen to reproduced music in a similar way that I do).

 

[john curl]

Oh, he probably used a Grado cartridge and a cheap D-A, to compare all-analog to all-analog plus one D-A (50KHz), and listened to it with Met 7's.
How much did I get right, Scott? '-)

 

[fas42]

BTW, on hearing acuity: since I discovered that nobody seems to be able to hear a complete sousa band at 60dB below a symphony orchestra, I'm pretty sceptic about our ability to actually hear subtle things.

jan

A very good round of discussion going on, which I haven't finished digesting yet ... but, I couldn't let this one pass without immediately commenting ...

It's already been commented upon several times why this registers as a null, because the "distortion" is totally uncorrelated - the brain, obviously, chooses to focus on the primary musical message and has no trouble isolating this from the background "noise". And, I've suggested an alternative several times: take the primary symphonic track, very heavily distort it with standard DAW techniques, compression, clipping, etc, attenuate the end-product by 60dB and mix back in with the original track. We now have carefully controlled, correlated distortion, which might actually tell us something ... and, of course, not a single comment was made ...

But then again, it obviously isn't relevant, because it's MHW ...

 

[fas42]

I do agree that the two waveforms of a stereo signal can not represent a full 3 dimentional music event in a live space.

Would you say aye or nay to a "subjectively convincing illusion of a full 3 dimentional music event in a live space" ?

 

[fas42]

The issue gets further complication when there are those audiophiles who listen primarily to the 'sound' of the setup, while others are interested primarily in the degree to which the reproduced music is convincing and engaging. Those two major approaches are worlds apart.

I got a shock when I first realised this: at a hifi club meeting, two systems were demonstrated, the first produced typical hifi sound, similar to the "bad" bits in the JA demo video, the second actually created a very nice sense of space, and had excellent potential for taking further, like the "accidental" piece in the church at end of that video. I turned to a key member of the club, who was besides me, and who is a very active contributor on a well known web review site, and said something along the lines of, "Well, it was obvious which came up trumps ...", and he replied, "Yes, the first system was so superior!"

After picking myself off the floor, I mulled over this for some time - it demonstrated to me that many people listen to audio replay in a totally different way than they would for live music ... it was a very interesting "discovery" ...

 

[Joshua_G]

Yes, Frank, at times, first-time revelations are shocking.

 

[jan.didden]

While having little to say other than what's been said already, I would like to mention the typical material I've heard when someone is demonstrating the inaudibility of various brackish and distinctive disturbances played over the main program. Most of the examples are from pop music with rather severely limited dynamic range. It is perhaps not surprising that it masks the disturbing sounds when those are at not-too-low of levels.

When one is fortunate enough to hear music with really high dynamic range, meaning usually live music in real spaces with a very low background noise level, it can be revelatory. Unfortunately this is inaccessible to most people today, particularly those who live in cities. The last time I heard a really good example was many years ago, at a recital of Emma Kirkby, David Thomas, and Anthony Rooley in a medium-sized room at the Huntington Library in Pasadena. The audience was dead still, and the weather had permitted the HVAC system to remain off. This was in the pre-pager/cell era as well. It was simply breathtaking.

I chatted briefly with Emma after the performance and told her such experiences helped remind me how far we had to go with music recording and reproduction. She defended the CD medium, and I hastened to agree that her output was particularly good in this regard. Of course that's just the first part of the chain.

I would have enjoyed seeing what state-of-the-art microphones might have picked up in that room that day and what the real dynamic range was, when the peaks were compared to following the reverberant tails down into the microphone self-noise. My ears were probably a good deal better then as well.

Of course it didn't hurt that the performances and compositions were superb.

Now, if there had been some background disturbance imposed in the quietest passages or during said tails, how low-level might it have been to be unnoticeable? I don't know.

Brad,

This got me thinking. I went back to Bill Wazlo's Diffmaker, and reran the example tests with the sousa band at -60dB. The 'carrier', a Bach lullaby, has some quiet passages although they are relatively short. Mainly the short periods when the choir has to take a breath. I tried all sets several times over a headset, concentrating on the quiet passages, but I cannot hear the buried track through them. Would be interested to know if someone can.

Anyway, I wonder, if you try to identify subtle differences between tracks, whether a high dynamic range piece would be easier than a low dynamic range one. Presumably, when when the track gets very quiet, the subtle differences also get very quiet. In the limit, you can't identify subtle differences in silence.

jan

 

[jan.didden]

It's already been commented upon several times why this registers as a null, because the "distortion" is totally uncorrelated - the brain, obviously, chooses to focus on the primary musical message and has no trouble isolating this from the background "noise". And, I've suggested an alternative several times: take the primary symphonic track, very heavily distort it with standard DAW techniques, compression, clipping, etc, attenuate the end-product by 60dB and mix back in with the original track. We now have carefully controlled, correlated distortion, which might actually tell us something ... and, of course, not a single comment was made ...

That would indeed be an interesting experiment. Hmmm.

jan

 

[jan.didden]

Frank instead of mixing two versions of the same track, one distorted, one not, why not compare the original track against a version with -60dB (or whartever) distortion added?

jan

 

[fas42]

That's exactly what I was suggesting, comparing a clean version of the track with the "slightly distorted" (apologies to Tubular Bells, ) version created by mixing clean with distorted, 60db attenuated version ...

Edit: Sorry, I misunderstood: both methods would probably tell something of note - the key would be having complete control of what sort of distortion is added, and in a DAW perhaps one would have greater flexibility using the mixing technique.

 

[qusp]

That would indeed be an interesting experiment. Hmmm.

jan

I mix in various amounts and kinds of distortion in a DAW regularly, with exactly the same type of method, bounce a copy of the clean file to the effects send then mix the distorted signal back in small amounts to add body to a particularly clean sound, or digital synthesis.

it is always noticeable, I actually use it for effect, if it wasnt noticeable, I wouldnt bother. i'm not alone in this technique; its not novel, or telling, so I didnt comment.

if you (Frank) actually did any of these experiments instead of just throwing them out there into the thread without ever doing it yourself, perhaps they might be taken more seriously.

 

[qusp]

see edit jan, I wasnt accusing you of anything

I use the same technique with compressors, use a sidechain and use the drum track to control the gate on the compressor to add 'pop' and mix that back in. there might be just the 2, or more layers; small amounts of reverb, EQ, compression and distortion might be controlled by the envelope of the actual instrument track, so all correlated.

the reason its used this way is because it sounds more 'natural' and dynamic, its more subtle than just adding an effect over the track, because the effect parameters are driven by the envelope of the sound; but its not invisible.

 

[fas42]

Okay, we've moved a little bit forward. A uncorrelated signal buried -60dbB is almost impossible to discern. A distorted, correlated signal mixed in by "small amounts" is always noticeable. Somewhere between those 2 situations is a border, which most likely will vary per individual, per equipment used, per type of distortion, per precise level of distortion.

Since what a single individual experiences is of little value in improving overall understanding of what contributes to audio quality, it seems reasonable to discuss an approach that everyone can contribute to, to get a best idea of a useful measurement technique.

 

[DF96]

What is being considered as evidence in one paradigm isn't so in another paradigm.

I fear that may be true. When people have different ideas about what constitutes a fact, then there is little chance they can have a meaningful conversation.

Thus, you aren't going to change your paradigm, no matter what I may write.

That is true.

You are free to check your own paradigm, in yourself, by yourself.

I was going to thank you for your kindness in granting me permission, but then I realised that in my paradigm your statement is actually false. I don't check my paradigm against myself, but against external facts. That means my paradigm is capable of being falsified. If I restricted myself to internal checks only then I would always convince myself that I was right so I would remain locked in to my own little set of prejudices. I would become impervious to evidence.

 

[DF96]

After picking myself off the floor, I mulled over this for some time - it demonstrated to me that many people listen to audio replay in a totally different way than they would for live music ... it was a very interesting "discovery" ...

That is an interesting conclusion to draw from the simple fact that two people had different preferences in sound reproduction. I wonder how he would report his conclusions from the same conversation? "I was sitting next to this bloke who seemed not to notice the mid-range distortion and boosted artificial-sounding deep bass on the second system. He must be deaf!".