Blind Listening Tests & Amplifiers

[mefinnis]

So it was actually a bit of disappointment to see it was greeted with a hostile response from some members under a false premise that I try to advertise it here. .....

Not meant to be hostile Peter, if it was interpreted that way, my apology. My concern (primarily) was the thread was being taken away from it's original intent - which I think is an important topic. Your "meander from the path", however pales into insignificance as I read the last 48 hours worth

Re the "advertising" bit, I just thought we need to be consistent. Remember poor old AKSA (Hugh) coped a beating around the ears when he first appeared for a lesser indiscretion.

Regards
mark

[Fred Dieckmann]

Originally posted by mikek


....you just try to solve for the curent in a simple L-R series circuit resulting from applied excitation Vcos(wt)....(assuming zero initial conditions for simplicity), using trig. identities....tedious...tedious.....

Hmmmmmmm....... I believe that is why they invented Spice modeling,which is far from tedious and is easy..... easy..... easy.

Nobody's written about it in the AES journal?

[Christer]

Originally posted by Fred Dieckmann



Hmmmmmmm....... I believe that is why they invented Spice modeling,which is far from tedious and is easy..... easy..... easy.

Nobody's written about it in the AES journal?

Except that a Spice simulation is not the same thing as solving
the equations. Spice does a numerical simulation for particular
component values and does not give a symbolic solution, and
being a numerical simulation, a Spice result can never be
trusted unless an error analysis is done.

That said, I agree that Spice is an extremely useful tool. Being
a computer scientist, I do however find a lot of shortcomings
that make it quite tedious to use. That should be possible to
fix, though, by adding an abstraction layer on top of the Spice
engine.

[Christer]

Originally posted by Peter Daniel


You don't know me, then. I like to be practical and this is a simple setup for resistors sound comparison. It takes only few seconds to change resistor so you still have the memory of the sound of the previous one. Of course some will argue that this is not valid setup, because I don't solder resistors and it's outside of the amp so all kind of interferences come in effect. Yet it allowed me to hear repeted and consistant difference with few types of resistors and it was perfectly in line with other forum members. If you will continue to claim that resistors don't have specific sonic signature I simply refuse taking seriously anything you say.

And BTW, I never use inductive resistors.

I think your setup is reasonable, but to make any experiments
valid you must have somebody else to do the resistor swapping
for you, and this person must try to emulate a random
behaviour, sometimes swapping resistors, sometimes just putting
back the resistors he/she just removed. Preferrably, this person
should also not be visible for you, but if he/she is well aware of
the potential problems when visible, I think it is not necessary.

[Christer]

SY,

since I think it is relevant to this thread, has anything happened
to the experiment you and dorkus were planning before
Christmas?

[mefinnis]

I thought you guys had been busy a couple of days ago when I checked back in to see what was happening........ WOW!

For raising this topic in this forum, I recall referring to NW as borderline insane and blessed his naive & deluded socks! (Stated in a standard "taking the ****-out" kind of speak, given I'm from Oz, ie no offence intended)

Well, I was right ....... and we now have 20+ pages of proof (for those who like that sort of thing).

I'm not in a position to even remotely argue the "null-test" bit and actually this appears to have received some rational/educated debate.

The discussions around DBRCTs however have departed the realm of all rational scientific thought.

I have NOT stated any of the golden-eared ones will not be able to ascertain a difference between A & B. They may, they may not. However, failure to accept that phychological factors do alter perception seriously undermines the position taken by a number of people.

I am sure there are components which are better (or I certainly bloody hope so!). Reproducibly better and we should define these scientifically, so we may all be confident about what we are talking (and about to spend money on!).

People are (rightly or wrongly) perceiving this statement as an attack on their personal ability (hearing), their system, or their love of HiFi. The resulting slanging matches create images of 4yo children in a sand-pit.

cheers
mark

PS: That was a 2 glass of wine read ..... and opposed to those who say ETOH diminishes the appreciation of Hifi, I say ..... so be it, but it enhances the appreciation of the music

[Fred Dieckmann]

Originally posted by nw_avphile

Well... this is sort off topic, but you asked so I'll answer.

I'm open minded enough to think vibrations can possibly have an effect on other components as well, but I've never encountered it that I'm aware of. The amount of overall gain in a power amp is roughly 2 orders of magnitude less than in a phono pre-amp. So any tiny effects from microphonics would be much less likely to have an audible effect.

Yes unless they effected the differential pair that can cause gain variations outside the influence of the negative feedback loop. Before everybody decides that vibration effects in ICs are impossible, consider that silicon dioxide is commonly used as a passivation layer. The piezoelectric properties are known and put to use in crystal oscillators. Vibration could create noise voltages that are coupled into the semiconductors inside the IC. perhaps even the semiconductor material could have piezoelectric properties

http://www.wikipedia.org/wiki/Piezoelectric_effect

http://www.wikipedia.org/wiki/Quartz

http://www.batnet.com/enigmatics/sem...roperties.html

As for resistors, many of the ones recommended for delusional audiophiles have very low temperature coefficients and voltage coefficients. As the voltage signal changes across a resistor the power dissipated (V squared divided by R) changes the temperature and by proportion to the temperature coefficient; the resistor value. That is the resistor value is changing as a function of signal. This is also related to the thermal mass and thermal time constant of the resistor. A similar effect exist for the voltage coefficient.

It seems that two amplifiers identical expect for the resistors tempco will differ in output as a function of these resistor values dynamically changing with signal. Steady state sine waves are probably poor test signals to demonstrate this with and most of the test discussed may have insufficient resolution to test this effect. The mechanism for distortion is there and who is to say that we cannot hear it in a system of sufficient resolution and listeners with sufficient experience. I guess the guys at the AES have investigated all these effects though.

As for the Crown amp sounding wonderful, you must not have had the levels matched since we know it should sound no better than any other competently designed amp.

[SY]

Christer, no, nothing has moved much. The last I heard, there were some buffers that I was supposed to receive, but haven't yet. I've located and procured a rather massive multiposition switch for the box. If the "golden ears" think that something like a BUF-03 is an acceptable unit, I do have a few of those laying about which I'd donate to the cause.

I invite the participation of anyone who wants to help out. Specifically, I'm looking for the donation of some "approved" fashion plugs, resistors, and caps (they can even be painted with Tube-O-Later!); besides the switch and the box, I'll happily provide the Radio Shack grade comparison parts.

[Fred Dieckmann]

Originally posted by mefinnis
I have NOT stated any of the golden-eared ones will not be able to ascertain a difference between A & B. They may, they may not. However, failure to accept that phychological factors do alter perception seriously undermines the position taken by a number of people.

cheers
mark

I absolutely accept that psychological factors do alter perception!

This is a two edged sword that may cut even more sharply in the other direction.

Consider the factors that effect the converse stand.

1. Reliance on the viewpoints of someone whose experience, motivation, listening skills and test methods I have incomplete knowledge. Some of these factors can influence testing measurements even outside situations with subjective factors.

2. Design of a test who's particular outcome is desired to prove an existing exception This should be the biggest red flag for any objective test.

3. Anxiety, time pressure, social pressure, and unfamiliarity with system under test for the test precipitants.

4. Design and resolution of the test system.

I don't understand the assumption that audiophiles are presumed to expect improvements for a given change and that the results of these changes are always assume to be improvements. Doing R and D on audio designs will just as often result in the converse, i.e. It sound worse, it sounds different, it sounds the same. Many of these depend on break-in time, power line conditions and RFI background (very time of day dependent by the way and discussed in non audio literature), source material, add variations in equipment set up, cable and component interactions, and a number of other factors. Almost all of these have scientific and engineering principles behind them.

My biggest problem with a lot of these discussions are the cynical presumptions made about the methodology, motivations, techical abilities, and experience of those who claim to hear differences based on factors outside of mainsteam audio engineering . There are any number of even sharper engineers from other disiplines outside the audio community. I know it is hard to believe, but many other engineering fields even more challenging that audio design. There are contributions from other fields that will advance the art. Siegfried Linkwitz's background at H.P. designing RF and microwave test equipment and its influence on crossover and spearker design is a perfect example. John Dunlevy had a background in antenna design as another example. I believe there are many contributions from areas of science and engineering outside the audio engineering disipline that can make contridutions to the advancement of the art.

[Peter Daniel]

[i]Originally posted by mefinnis [i]
I have NOT stated any of the golden-eared ones will not be able to ascertain a difference
between A & B. They may, they may not. However, failure to accept that phychological
factors do alter perception seriously undermines the position taken by a number of
people.

cheers
mark

This indeed cand be two edge sword.

Let's assume that somebody takes part in one of those blind tests, yet for some reason it is not performed properly and the individual under test cannot identify the amps. This carries out a psychological effect on him and he starts to believe that all amps should sound the same (and indeed sound the same to him) and spreads the news to everybody he has a chance to. Most people are always on a look out for most convenient belief and this may appeal to many.

I mentioned it yesterday and this is certainly a possibility we cannot deny.