John Curl's Blowtorch preamplifier part II

[kamis]

Compare them to what? I have in the past been able to compare with live sound, having heard a concert live and then heard the next night's concert at home on the BBC - and heard the same hall (RAH) in each case.


No. Do you?


As I have said more than once: if you think we are measuring the wrong things, then try listening to music on a system with 2.5kHz bandwidth and 25% THD (and maybe -30dB noise). You will soon hear that we are measuring the right things. There may be more things we ought to measure too, but the things we are measuring are relevant to good sound reproduction quality - although perhaps not to everyone's music production taste.


Very tiny amounts are inaudible. Small amounts may be preferred by some people. Problems only occur when they claim that their preferred distortion has better fidelity than smaller distortions.

Subjective test , the same test I use and you find useless. In some capacitor sound quality description you use audiophile jargon and words like transparency, warmth, richness etc. It could be placebo and subjective bias.

 

[gpauk]

Very tiny amounts are inaudible. Small amounts may be preferred by some people. Problems only occur when they claim that their preferred distortion has better fidelity than smaller distortions.

Exactly. It's fine to say "I like this" but not ok to say "because I and/or my group of friends like it, it is objectively better..."
We all like different source material too, different art, there are no objective standards for these things and that's good. Life would be dull otherwise!

 

[scott wurcer]

He just talked about the 'multidimensional' aspects of subjective audio quality.

The sense of this statement is as far from a solid technical point as you can get.

Hypothesis - global negative feedback is always detrimental to the sound. Now follow up with the support for the statement, a citation please.

 

[scott wurcer]

That's possibly one of the reason why amps with lots of GNFB sound subjectively inferior. Not the NFB itself, but the designer does not pay attention to the quality of each stage, hoping that the GNFB will fix everything...

OK so we're back too the GNFB is not the problem, so the hypothesis would not stand up.

 

[scott wurcer]

much easier to exceed the limits of real home listening room noise floor, actual recording mic, studio noise floors

I was lucky enough to hear a demo by Victor Campos years ago that proved to me the source material is of the utmost importance.

 

[Jay]

OK so we're back too the GNFB is not the problem, so the hypothesis would not stand up.

It depends. I'm a "right-brain" person. For me words is not as important as what is between the lines...

Analogy for the hypothesis is: "Medicine is always detrimental to our body".

We need GNFB, but only to cover issues that wouldn't be possible without it. So, in that sense we still need to minimize the use of it. Minimum but sufficient.

I believe that the better we are in open loop, the less GNFB we would need. It is hard to prove whether too much GNFB will be detrimental or not, but I tend to think it will be.

I think you are in a better position to find the possible explanation for that. Yes, it would be microscopic, so we have to put audibility issue aside (before moving on)...

 

[SY]

I think you are in a better position to find the possible explanation for that.

He likely is, despite the fact that the answer does not involve electronics.

 

[scott wurcer]

I see an assumption of monotonicity. For modern amplifiers this is almost never true.

You need to explain this statement. In the strict sense of monotonicity it is almost always true i.e. you increase the input incrementally and the output increases by some increment. Any feedback around a true non-monotonic amplifier would have points of undefined value, hysteresis, or oscillation. Linearity and monotonicity are not the same thing.

BTW, modern amplifiers, what's that supposed to mean?

 

[bcarso]

Is it time to dust off catastrophe theory? Actually kidding here, but expressing nostalgia for when that was a popular buzzword.

And don't ask why I am up checking email at 4:44 PDT.

 

[SY]

I figure you hadn't gone to bed yet.

 

[Coldhead]

No, we have marketing claims or audiophiles hype, against EE knowledge. And challenge, to put both on market to compare validness

 

[bcarso]

That's the weird part, I retired around 10PM. But I awoke to realize it was time to turn off the A/C and put the vent fan in the window. The electric bill is going to be jaw-dropping for this period, but at least mostly deductible from income.

I'm amused when the Gas Co. urges me to keep the thermostat at 78F or above, since the cooling system can't pull all that large a differential anyway by late in the day in my west-facing apartment, particularly after management insisted I take down the Al foil from the windows.

 

[SY]

...particularly after management insisted I take down the Al foil from the windows.

So they're in cahoots with the CIA and their mind-control lasers? Don't do it, Brad!

 

[31697B]

I was lucky enough to hear a demo by Victor Campos years ago that proved to me the source material is of the utmost importance.

most definitely. And the closer you get to the source, the more realistic it sounds. fewer stages, steps, processes.




-RNM

 

[Max Headroom]

Today, using FFT techniques, we can measure much lower amounts of distortion, as well as removing inherent noise from the distortion spectrum, and we get fine results, but they don't seem to mean much, subjectively. We still have to listen to our designs IC or otherwise, to find out if we have been really successful. This is where people cannot understand WHY some circuitry that measures in the -80dB or so, still sounds great, yet other circuitry that might measure -120dB or better doesn't sound so good. It is NOT the distortion residual that creates the subjective difference, but OTHER FACTORS. Finding these 'other factors' is one of the greatest challenges for audio designers, today. We still have a long way to go. Hopefully, someone of Richard Heyser's academic and intuitive stature will come forth and put us back on track.

Mr Heyser was onto it with his pioneering TDS , and had he lived longer I am sure he would have defined the measurable keys as to what sounds good, and what doesn't.

Typical (consumer) gear is full of current/time dependent excess noise...this is one the "OTHER FACTORS" which is not being measured, but imo/ime separates gear of similar specs.
The 'nature' of this signal induced error noise is one factor that allows subjective comfort, or drives the listener out of the room.

Reduce the signal dependent system noise and indeed similar static thd/imd/snr spec'd systems will sound very similar.
Intelligent electronic design is one method, BQP etc is another method, but alas with caveats....neither individually is optimal.

Very high resolution/bandwidth TDS is required to more fully understand equipment detailed behaviour that typical measurements do not reveal.
OTOH, we all have such apparatus on the sides of our skulls.....one just has to learn, understand and use them.

Dan.

 

[wahab]

I believe that the better we are in open loop, the less GNFB we would need. It is hard to prove whether too much GNFB will be detrimental or not, but I tend to think it will be.

That s the other way around, the more NFB the better, as for GNFB the limitations are known and max value at 20KHz for instance is about 35dB.

 

[scott wurcer]

most definitely. And the closer you get to the source, the more realistic it sounds. fewer stages, steps, processes.

-RNM

That demo included being broadcast over FM radio, you just couldn't kill it. That's one reason I don't get some of the comments here. The noise floor was "black", (this was a Luxman T110 measured at 70dB SNR at the factory) the imaging was scary you could hear the seats on either side of you rustle as someone moved even a little, feet scraping incidentally on the stage.

It was a 30 ips master tape played on time logged as engineering so all limiters and other FCC rules were suspended, or so I was told.

 

[jacco vermeulen]

but at least mostly deductible from income.

Isn't private enterprise a peach.

 

[scott wurcer]

for GNFB the limitations are known and max value at 20KHz for instance is about 35dB

Intelligent electronic design is one method, BQP etc is another method, but alas with caveats....neither individually is optimal

Such easily substantiated claims.

 

[jan.didden]

But personally I haven't heard a Hypex product that blew me away, per se, but they certainly are good.

Hypex is middle of the road and OEM these days. Mola Mola and Kii is where Bruno's bleeding edge is nowadays.

Jan