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Correlating measurements to audibility

RayDunzl

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I'm unable to see how a straight wire replaces an amplifying amplifier.
 

sergeauckland

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I'm unable to see how a straight wire replaces an amplifying amplifier.
A SWBT requires two amplifiers. The DUT amplifier drives a suitable load, and the monitoring amplifier drives the loudspeakers being listened to. Bypass the DUT amplifier using a switch and passive attenuator, and listen blind whether the presence or absence of the DUT amplifier can be detected. The load for the DUT amplifier can be as complex as one likes, and the test signals can be normal speech or music.

It does require careful level matching, but so does any blind test.

S
 

KSTR

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I prefer recording the DUT amp + att. vs. bypass in the loopback of decent DAC+ADC device and A/B them (in ABX or whatever) afterwards, do numerical analysis etc. This way, the choice of monitoring amp + speakers etc doesn't affect the signal at recording time and this generates a higher usability of the data, it literally represents DUT vs. plain wire with great accuracy. DAC+ADC in cable loopback vs original sample stream can and should be checked for transparency first, as the baseline.
 

sergeauckland

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I prefer recording the DUT amp + att. vs. bypass in the loopback of decent DAC+ADC device and A/B them (in ABX or whatever) afterwards, do numerical analysis etc. This way, the choice of monitoring amp + speakers etc doesn't affect the signal at recording time and this generates a higher usability of the data, it literally represents DUT vs. plain wire with great accuracy. DAC+ADC in cable loopback vs original sample stream can and should be checked for transparency first, as the baseline.
I agree that these days, the way you propose is accurate and a lot simpler than the physical straight wire bypass I referred to. When I last did a SWBT, digital recording didn't exist, so it had to be done physically. Doing a digital recording removes the practical difficulty of a real load for the amplifier under test whilst at the same time listening on a different loudspeaker.

S.
 

Blumlein 88

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Series amp testing is highly revealing. Amp vs straight wire. I've not tried recording digitally with attenuation at the speaker. I have it mind, but life keeps interfering. If digital is accurate enough (and I believe it is) it should work just fine. One reason I think it works so well is the same reason we can develop distortion thresholds when our transducers have a 1% or so distortion themselves. We hear the transducer and though it may be 1% distortion, we can hear if something upstream in reference to that adds .1% more distortion. Masking would raise the thresholds for some things, but the idea still works.
 

Empirical Audio

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I have made my feelings known before on this topic, but I'll be gentle.

I think the state of measurement equipment is sufficient to characterize any analog component. I think the shortfall may come in the methodology and stimulus. If carefully selected real-world music were used for test stimulus and the before and after waveforms compared directly real-time as well as spectral FFT, I think we might start to see more differences and better correlation to listening tests.

The other thing I mentioned before is that the measurements need to be weighted as to the significance of each based on hearing tests. If for instance jitter is much more audible than THD, then this should be factored into the results. Until this is mastered, I don't believe that measurements alone can be used to predict with any certainty that one well-designed component will sound better or worse than another well-designed component.
 

SIY

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I think the shortfall may come in the methodology and stimulus. If carefully selected real-world music were used for test stimulus and the before and after waveforms compared directly real-time as well as spectral FFT, I think we might start to see more differences and better correlation to listening tests.

Correlation between actual listening tests and measurements is quite good for the things that human hearing is sensitive to, like frequency response and localization. If you want correlation to coached and sighted "tests", there never will be any because it has very little to do with sound and everything to do with commerce and psychology.

Maybe that's why people selling useless gadgets claimed to improve sound never present controlled double-blind listening data demonstrating efficacy. The homeopaths of the audio world- so many excuses, so much hand-waving, so little data.
 

RayDunzl

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A SWBT requires two amplifiers. The DUT amplifier drives a suitable load, and the monitoring amplifier drives the loudspeakers being listened to. Bypass the DUT amplifier using a switch and passive attenuator, and listen blind whether the presence or absence of the DUT amplifier can be detected. The load for the DUT amplifier can be as complex as one likes, and the test signals can be normal speech or music.

Why not just switch the outputs to the speakers?

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MZKM

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if distortion is low, at all frequencies and permitted loads, frequency response flat and noise low, it can't sound bad.
Sure it can (perceivably that is), give it to someone whose setup costs $1M and tell him this awesome measured device costs $100 and is in a plastic DIY case, 9/10 they will say it sounds like garbage. I posted this elsewhere, but in one of Toole’s talks, he mentions a double-blind speaker test, where one speaker’s sighted ratings were heavily reduced as it was a plastic sub-sat system than was <1/5 the tower speakers it was compared with.
 

bobhol

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All would be solved if we all could get our ears Calibrated to the same standard. And I don't just mean what frequencies can we hear, though I admit I'm only half serious about this statement. But the truth is that we all hear things differently. Also being able to rid ourselves of spurious thoughts makes a difference. How long can you sit in silence with out the intrusion of distracting thoughts and images. Maybe people who regularly meditate have a different perspective on sound and music. Sorry for going off topic.
 

Empirical Audio

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I have never, ever, heard a product that measure well but sounded bad. It does require, however, for the measurements to be comprehensive, but if distortion is low, at all frequencies and permitted loads, frequency response flat and noise low, it can't sound bad.

That doesn't of course mean that somebody might prefer the sound of something that measures worse.

S.

I have. I used to search out things at shows that were positively reviewed and measured by JA of Stereophile, like DACs in particular. These were system sounds of course, but the DAC was a big part of that. Mostly dissapointing. Also amps. Searched shows for good sounding amps for many years and finally came up with 2-3 SS amps that I can finally recommend to customers. The only one of these measured by JA was the D'angostino monoblocks. Very spendy.

All of the characterizations you mention are good, but you leave out one of the most important characteristics, dynamics.
 

sergeauckland

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I have. I used to search out things at shows that were positively reviewed and measured by JA of Stereophile, like DACs in particular. These were system sounds of course, but the DAC was a big part of that. Mostly dissapointing. Also amps. Searched shows for good sounding amps for many years and finally came up with 2-3 SS amps that I can finally recommend to customers. The only one of these measured by JA was the D'angostino monoblocks. Very spendy.

All of the characterizations you mention are good, but you leave out one of the most important characteristics, dynamics.
How does one measure dynamics. What units are they in? If you can't quantify it, you can't compare or replicate any results.

S
 

Empirical Audio

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How does one measure dynamics. What units are they in? If you can't quantify it, you can't compare or replicate any results.

S

di/dt and dv/dt is dynamics. Dynamics is how accurately does the device reproduce a reference transient waveform. Does it make the full peak voltage? Does it slow the risetime? Does it have good dynamic response when the transient is not layered on top of other low-frequency information? What about when it is?

Look at the impulse response for DACs or step response for amplifiers. This is really all we have and it's woefully insufficient to properly characterize these devices.
 

sergeauckland

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di/dt and dv/dt is dynamics. Dynamics is how accurately does the device reproduce a reference transient waveform. Does it make the full peak voltage? Does it slow the risetime? Does it have good dynamic response when the transient is not layered on top of other low-frequency information? What about when it is?

Look at the impulse response for DACs or step response for amplifiers. This is really all we have and it's woefully insufficient to properly characterize these devices.
That's covered adequately by slew rate. If an amplifier will provide its full output at 20kHz at low distortion into its rated load, what more do you need?

S
 

Empirical Audio

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That's covered adequately by slew rate. If an amplifier will provide its full output at 20kHz at low distortion into its rated load, what more do you need?

S

Slew rate is not enough. What signal do you feed the amp to measure slew rate? A step? An impulse? How is the other channel being driven when this happens? Not good enough.
 

SIY

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