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Old 7th June 2012, 08:48 PM   #6091
JZatopa is offline JZatopa  United States
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Quote:
Originally Posted by SY View Post
Or three, we can measure things that are actually important (e.g., distortion, phase, frequency response) much more precisely than our ears can distinguish. I'm admittedly one of those crusty reactionaries who believe that good and comprehensive measurements are vital to a designer and fairly meaningless to a consumer.
Define meaningless in relation to the consumer.
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Old 7th June 2012, 09:17 PM   #6092
JZatopa is offline JZatopa  United States
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Yes, I have a test switch for A/B/X x 3 comparisons and everyone can spot position #1 no matter what it is switching. I have not been able to measure what is the exact difference in that position as compared to the others.

Maybe you aren't measuring the right things. If position 1 is always spotted on your switch, then it's time for a new switch and to possibly check your cables.


Quote:
Originally Posted by Wavebourn View Post
DJNUBS;

when making changes to improve it is a totally different story. When I improve something I can't measure directly I construct an experiment that pushes the effect beyond normal conditions, so it is well measurable, then extrapolate.
The different story is, when people try to invent some generalized measurements to test _all_ available topologies for sound quality. It is impossible because number of errors can be enormous compared to number of standard measurements. It is even hard to invent standard tests for most common opamp topology to predict how one amp should better sound than other.
There is a way to create a standard for measuring how things should sound and I have put it somewhere else on this site. Here is the gist of it. To do this accurately we would need to create a new lexicon for audio. We would do this by systematically changing one parameter at a time and measuring and listening to the difference that it makes and documenting it. This would be a long and tedious process and you would have to get at least some consensus on what term=what sound=what change in measurement/system. You could start fresh or you could create some standard and then make changes to it to create the desired effect/term and document it. You could also make a collection of all the subjective terms "flowery" reviews use and then work to assign a specific spec/mechanism that creates that subjective experience. These may have to be sort of "fuzzy logic" terms due to the ability to do so many things the same way in audio but it could still be a standard. You could say that a flat phase response in an amplifier has a PROPENSITY to create a more accurate sound stage and imaging. Even if someone or everyone as a group undertook this momentous job you run into the problem that if you have never experienced that sound + had someone tell you that is what that sound is, you could hear something and never know the proper term. I didn't grow up with tube amps or know what a warm sound was. It was only after reading about it and seeking it out at a young age that I discovered what that sound was and now can assign that label to it when I hear it.

My girlfriend is an artist so painting and photography seem like a good analogy. Think of how colors are both subjective and objective in the art world. They have specific names, colors and measurements attributed to each one. The specs, numbers, etc. matter and in the end they don't because you can use them how ever you want. That doesn't mean you will get an enjoyable finished product in the end though. Photography may be a better analogy. You can measure every part of a camera, the film, and the process but that doesn't make a good photograph. A good photograph requires you know all of that + you know about composition, lighting, narrative, etc. It takes both sides to make something truly great. The reason they have a bigger lexicon then audio is due to how long they have existed in the world compared to audio recording + their formalization in the early years which created a standard to work with or against.

Science is an art; Therefore we can be subjective and objective but by arguing one VS the other we have lost both. The answer is sound quality + measurements. In the end we are arguing two sides of the same coin when we could realize that the coin is just a coin. It is time to take that coin and spend it on some new ideas.

Just mu 2c
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Old 7th June 2012, 09:42 PM   #6093
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You are welcome to tell me what test you think I might be missing.

Last edited by simon7000; 7th June 2012 at 10:02 PM.
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Old 7th June 2012, 09:48 PM   #6094
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Quote:
Originally Posted by simon7000 View Post
You are welcome to tell me what teat you think I might be missing.
And me too.

We explored this issue in this thread several rounds in all details, but I did not change my beliefs even a little bit. To me as designer of high end audio measurements are essential, but I alwayts measure what is essential to the problem I solve. But all proposed generalized measurements are meaningless, if to speak about High-End. I can design you a thingy that is targeted to fool you if I know what and how you measure as if it is perfect, but sounds horrible.
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Old 7th June 2012, 09:59 PM   #6095
PChi is offline PChi  United Kingdom
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The ear appears to be very sensitive to minor differences in frequency response and level down to a fraction of a dB. It's makes it difficult to compare loudspeakers with their uneven frequency responses. They all sound different anyway unlike reasonable power amplifiers.

The A to B switch box that I built had 4 potentiometers to match levels at the inputs of the power amplifiers and 6 change over relays to switch the loudspeaker outputs and connect a level measuring meter.

Any AC coupling of the line level matching circuit (I DC coupled the potentiometers) needs to be generous because with floor standing loudspeakers with decent bass extension any slight roll off is detectable depending on the music used for testing.
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Old 7th June 2012, 10:00 PM   #6096
JZatopa is offline JZatopa  United States
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Quote:
Originally Posted by simon7000 View Post
You are welcome to tell me what teat you think I might be missing.
i didn't go back over the whole thread, could you give me a link to your post and I will read it?
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Old 8th June 2012, 08:15 AM   #6097
dvv is offline dvv  Serbia
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@DJNUBZ

Try these two tests. Take several say TV sets and let the panel decide which has the best picture overall - my guess is they will do it wthin a reasonable time frame.

Repeat the test with the same panel, but using several nominally same or very similar audio devices, and chances are they will never agree.

This is the very funny thing about audio, which goes way over and above say video - it seems our hearing is somehow much more picky and choosy than our eyes.

On the question of components - yes, it's possible to exchange one or several components, get the essentially same measurement results, with differences which are nominally just, er, nominal, yet to be able to hear without fail two different sounds.

I tried this with two almost identical measuring and sounding models from the same manufacturer, specifically Marantz 1152 DC integrated amps. One was left "as is", only the dried up electrolytics were ALL changed for same values and even same manufacturer where possible. The initial result was that nobody on the panel could hear the difference between A and B, after they had been adjusted to the same nominal output voltage, verified by measuing gear. Both linear and phono inputs were tried.

Then, several resistors all related to the input stage and NFB only were exchanged on one of them, the standard 5% carbon resistors giving way to German made Beyschlag 1% metal film resistors of exactly the same value. The difference was quite easy to spot, the sound appeared to be more focused and clearer, with more detail being heard. Not quite a revelation, but easy to hear.

All measurements made related to distortion were practically the same, and any small change was way after the decimal point (e.g. 0.01% and a wobbly 0.01%, meaning it was probably something like 0.015% and the instrument couldn't quite make up its mind with the carbon resistors). Admittedly, my instrument is reliable to 0.01%, it's an older model, but I'm sort of attached to it.

This is, obviously, a very rudimentary test, very, very basic and down to earth, but even so, it shows that it's not all the same.
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Old 8th June 2012, 04:26 PM   #6098
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Resistors .

I agree with DVV .

I remember years a ago Tom Barron of Rotel telling me how Stan Curtice redesigned the RA820 numerous times to allow for the cost of 10 critical resistors . Although a budget amp it didn't sound like one . One must remember Stan's previous amp was Lecson . I always took resistors seriously although still to this day know little worth sharing .

About TV's . I recently bought a bottom of the range Panasonic to replace a Sony . I was very disappointing by how short a life the Sony had . I was equally disappointing by the Panasonic although for 350 what should I have expected ( the Sony cost double ) ? That was until this week . I brought a same make PVR at 130 reduction ( 160 ) . What a transformation and cheaper than a TV of this standard would be ( TV + PVR = 510 ) . Now SD is better then HD was . HD is excellent at times . 80 hours of HD recording and internet steaming ( BBC I player ) . Also a joy to use .

What this says as was always true is that source is important ( front end of the TV , front end of a hi fi ) . I was told the old NTSC master tapes were out of this world good . Somehow it never was true for the consumer . I hope one day I see some .
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Old 9th June 2012, 11:30 PM   #6099
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Default Cascode VAS

My favourite transistor combo is no more . 2SD756 and 2SB716 . I propose to use a cascode of BC550C and BF720 SMD as substitute for the VAS . I suspect I will be pleasantly surprised ? BF721 will take up the work of 2SB716 . My quest is low Cob and high gain ( 300V is not to be sniffed at either ) . 2N5551 and 5401 are workable and I am sure were the inspiration for the Hitachi devices . Some 756 and 716 I bought I suspect were 2N5551/5401 ( fakes , looked perfect ) .

Hopefully subjective verse measurements on this please ? John said to me we can do better with our designs than live in yesterdays world ( I paraphrase a bit ) ? With transistors dying like flies it is becoming difficult

Last edited by nigel pearson; 9th June 2012 at 11:34 PM.
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Old 10th June 2012, 12:38 AM   #6100
tvrgeek is offline tvrgeek  United States
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Quote:
Originally Posted by nigel pearson View Post
Resistors .

I agree with DVV .

I remember years a ago Tom Barron of Rotel telling me how Stan Curtice redesigned the RA820 numerous times to allow for the cost of 10 critical resistors . Although a budget amp it didn't sound like one . One must remember Stan's previous amp was Lecson . I always took resistors seriously although still to this day know little worth sharing .

About TV's . I recently bought a bottom of the range Panasonic to replace a Sony . I was very disappointing by how short a life the Sony had . I was equally disappointing by the Panasonic although for 350 what should I have expected ( the Sony cost double ) ? That was until this week . I brought a same make PVR at 130 reduction ( 160 ) . What a transformation and cheaper than a TV of this standard would be ( TV + PVR = 510 ) . Now SD is better then HD was . HD is excellent at times . 80 hours of HD recording and internet steaming ( BBC I player ) . Also a joy to use .

What this says as was always true is that source is important ( front end of the TV , front end of a hi fi ) . I was told the old NTSC master tapes were out of this world good . Somehow it never was true for the consumer . I hope one day I see some .
If you troll back to my earlier postings, you will find where I suggest the older Rotels sound much better than their price. ( I have an 840, as well as several RB951's) The build is generic. The circuit is generic, but they work. The thing they do, I think, is their compensation tends to limit their bandwidth so they don't excite tweeter breakup modes as much as higher performance amps to. My conclusion is they know exactly what they are doing, or were as the newer ones seem dull. I really hope my next speaker experiments prove this theory so I can take advantage of the detail of these better amps. Parts should get here Monday.

BTW, every single Sony product I ever bought failed prematurely. Every stinking one.
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