Revisiting "Psychoacoustics and amps" thread from '02/'03-Ken Kantor, are you there?

[kkantor]

http://www.neurophys.wisc.edu/h%26b/qtmovies/volley.mov

http://www.physiol.ucl.ac.uk/ashmore/ohc2-s.mpg

http://serous.med.buffalo.edu/hearing/auditory_nerve.html

[Guest Bret]

The problem with characterizing hearing as digital is perspective.

Of course a greyscale image IS made-up of black and white, but the *image* is not, it's a bunch of different greys.

Nothing remotely resembling a 1kHz hair-cell's 1 or 0 gets anywhere near the brain in a recognizable form. The hair cell may produce a 1 or 0, but that's the last time a 1kHz, 1 or 0 exists in the entire process.

Bret

[Guest postjob62]

Boy, This thread sure has veered off from my original post!

Not sure I've actually gotten a directly related answer yet...

Ed

[soundminded]

Exactly as expected, all of the pulses are exactly the same, only their number, rate of firing, and which bundles they are in vary with the stimulus. Once the resolution of a means to reproduce sensory stimuli exceeds the nervous system's ability to process it, further improvement is of no value. This is consistant with information theory and the design criteria for systems to capture, transmit, store, and reproduce sound and images. Psychoacoustics is at least in part, the science of determining the relevant parameters and the maximum resolving capability of human perception. I'll bet there is much less controversy among amateurs such as shutterbugs regarding the visual counterpart of this branch of psychology. OTOH, among professionals in the field, there is probably not much disagreement about psychoacoustics either because they have no emotionally based preconceptions about the differences between objective and subjective equipment performance.

[Wally]

Thanks Pete,

Interesting and relatively simple test. I'll bet the 'exotic' equipment and cable people say it's flawed!!! LOL :-)

>Hi Wally,

>

>Here are some links.

>The null test is shown on page 7:

> http://www.hafler.com/techsupport/pdf/XL-280_amp_man.pdf

>This references some earlier work by Baxandall:

> http://sound.westhost.com/sim.htm

>

>Good to hear that your in your new place.

>

>Pete B.

[Guest Bret]

>I'll bet there is much less controversy among amateurs such as shutterbugs regarding the visual counterpart of this branch of psychology.<

Honestly, I think the process of vision is understood better. I don't know if that's because of more time spent on it, or just why. Take the limitations, for instance; At 60fps we interpret a movie as smooth motion. Yet some people really seem to be able to see the blinking of a properly functioning flourescent tube and I've read reports that say we all react to it whether we see it or not. Take two flourescent tubes, one malfunctioning and blinking at 20Hz, and anyone would tell you that the broken one is broken. But not everyone would say the non-broken one is not blinking.

And lets not even get into glasses to focus an eye that's a little misshapen.

But a shutterbug friend of mine, who is also a professional artist, I swear sees things that aren't there concerning edge-to-edge clarity and grain. Maybe it IS there and I just don't see it.

Nobody doubts there is such a thing as colorblindness. The test for colorblindness has some people saying, "Huh? There's nothing on the page but squiggles," while others immediately say "Seventy-two." We accept that there is this difference in perception. Nobody asks "how clearly can you see the number "seventy-two" on that page? I mean, really clearly, or just sorta clearly?" If there is a scale of colorblindness at any given frequency, I'm unaware of it.

And in taste - there's a genetic basis for some people tasting the bitter part of some tastes and other people not. There's an experiment school children do in their classrooms to demostrate this. We accept that, also. 'Tis fact, the way it is, over and out.

We also agree generally about what hearing loss is, and have devices to fix it, but like glasses cannot fix colorblindness hearing aides fix some things and not others.

But for our purposes, for some reason, if the lab graph says "fall at 3db/octave" and that doesn't bother most people, we expect "all people" to hear it exactly the same and if they don't, then they are freaks. If they hear something I can't, they are "all emotional?"

Personally, I have trouble matching socks or telling if this shirt clashes with those pants and it isn't because they aren't in focus or because there isn't enough light. My wife looks at the same socks and says, "This one with this one, that one with that one, and change shirts before dinner, you're wearing two greens that clash, oh, and the socks you have on are blue, you know."

No. I didn't know.

Bret

[Guest Bret]

Ken - “You win” is a way for us commoners to bow-out of a debate in a non-rude way. I was not trying to identify you as having been in a contest or trying to force your admitting to a contest. I would get no pleasure whatsoever out of making you “cry uncle” and deny something you know to be true or having you prove that I’m an idiot. Risky business, that.

The problem I am having communicating is, in my opinion, that you aren’t leaving room for “all” the truth, or at least for me to experience it.

I concede that most amplifiers “sound” so close to one another that it would be extremely difficult for anyone to identify the amplifier they are listening to. I agree that the amplifier is probably the least problematic component in a system. I agree and acknowledge that it would be easy to fool someone in a “listening test.”

It is also true that A/Bing amplifiers can show minor performance anomalies. Are these important? That’s not for me to say as it is in the ears of the beholder. The following is real, only the names have been removed to prevent emotional attachments.

Take the case of amps A, B, and C. Amp A and amp B, neither are broken, use different output devices. I believe hear a difference in high frequency performance and “tightness” of bass. However, give me a few days (or hours) to forget, and I feel certain I could not identify one from the other just walking into the room and having someone turn one or the other on. That isn’t because they magically became identical, but because I don’t have the capacity to remember tiny variances that well.

However! Take amp A or B and play a really low pipe organ pedal tone and you can hear the bellows giving-up and the bass “throb” slowly. I even pointed-out the bellows “running out of breath” to a friend.

Take the new amp C and play the same note, same CD - the bellows have plenty of air. Uh oh. Now we have a readily identifiable “artifact” in amps A and B and can identify amp C out of the line-up of those three at any time.

Take amp C and compare it to amp D. Bass guitar note, sliding to almost subsonic depths. Amp C plays the note and falls-off into nothing. Amp D plays the note and as the frequency falls it first gets louder, then trails-off into nothing. Uh oh. Another “fingerprint.” Is amp D broken? We don’t have enough information to know that. Room interaction with the speakers could account for the hump. Maybe amp C that “sounds right” has a dip which is offset by room reinforcement.

But now between C and D we have another readily identifiable characteristic. I might not be able to tell you if it’s A, B, or D playing, but I can find C out of the bunch.

Assuming an amplifier cannot play a note that is not present, but can refuse to amplify a signal that is, I want to say that of non-broken amps A, B, and C, C is the “best” at playing pedal tones.

This is not like judging the translucency of pixie-wings.

I accept that these differences are minor and none would be responsible for my losing sleep or destroy my enjoyment of listening to music. (there are other differences in them, but they are the kind of differences that are easily lost even if not forgotten). Since most differences are easily lost, I’m more than happy to join you in saying that two amplifiers of like power should sound virtually the same.

When someone asks me what amplifier would match well with an AR-9, 3a, 10pi I want to tell them that they need an amplifier which is notoriously stable into low impedance loads. I want to say the bass is “better” in amp C and I want to tell them that all other things being equal the more powerful, the better.

It would do no good for me to tell them that “all amplifiers (working, unbroken, of equal power) sound pretty-much alike” when how well amps can handle a load, or how much overkill is in the power supply, or whatever it is, can make a pipe-organ bellows run out of wind - or not.

It’s also not necessarily the case that an amplifier which can be ridden out of power or driven to instability by an AR-9 or 10pi on a pipe organ pedal tone is broken; operating outside the anticipated or allowed parameters, maybe.

I’m done. I know what you mean and agree with my understanding of what you say. Now you know exactly what I mean when I say “one” can hear differences in amplifiers. I hope there is room in your world for us to value different aspects of the same experience and conclude that differences *can* be audible, but they may be relatively unimportant on average. (which is what I took you to say earlier in *this* thread)

If we can’t, well, its not that important to me, either. Regardless of studies and bets and listening tests I didn’t attend, even regardless of facts related to me by an experienced audio professional, I can’t ignore the repeatable result of a practical experiment, nor will I fib in order to gain acceptance.

Bob Carver is an audio professional, too, and taps his amps in two different places because each output sounds different. Mr. Carver, from all I hear, is quite a character and believes he can make any amplifier sound like any other by fooling with a few parameters - and demonstrates as much live (gutsy) - meaning you and he surely must agree and disagree.

On a more personal note, I need to ask you for a favor. . . please don’t imply that I try to get you to ignore what you know. It implies that I don’t respect the years of experience you have and identifies me as a fact-ignoring “audiophile” suffering from auditory hallucinations overlayed with delusions. If you want to think it privately, I cannot stop you and have no objection. I just hate the thought that someone else will get the idea I don’t respect you because *you* imply it. If it ever comes to that, let *me* imply it! ;-)

Personally, I think the back and forth is because you and I have difficulty communicating. Could it be that we think we understand the other better than we do? Is it that there are "two camps" and we try to force each other into one or the other?

How can I not-respect the experience of the man who first designed with an MTM arrangement because he did the measurements and concluded it was necessary for his purposes?

Bret

[Guest Bret]

>Not sure I've actually gotten a directly related answer yet..<

Yes, there is a difference in the way brands of receiver sounded years ago. The differences are almost certainly not-due to the amplifier section.

Do you care where the difference comes-from?

As far as I know there is no way to tell which receiver you would prefer or that your preference would remain constant.

Regardless of how loathed the analogy, like vintages or appelations of wine, different series (years) of receivers within the same brand and different "levels" (design) of receiver within the same series can also have different sonic signatures.

I have always chalked that mostly up to the preamplifier, and in "my day" usually attributed it to a change phono sections. I cannot say if I consistently preferred the "better" phono section or not. I suspect the differences are much smaller using AUX inputs from a CD player.

So. . . I'm sorry but I cannot say that there is a magical combination of any Marantz receiver and AR speaker that produces a superior result.

Maybe someone else's experience varies and they'll jump in here.

Bret

[Pete B]

Hi Soundminded,

I wondered why you spoke so highly of this amp, yes it tests fairly well, when it was new, but I have to wonder given that it has so many electrolytic interstage coupling caps and that huge output cap. The RCA quasi complementary reference design as a comparison was far more advanced and was very widely used. It is clear that the old Harman Kardon Citation 12 was a derivative of it. The regulated supply was interesting, it actually had a negative output impedance up to the current limit point, and I used it in one of my own scratch built amps. Amplifiers with regulated supplies have no dynamic headroom which is not an issue when very high power is available but is usually an issue with lower power amps.

The worst aspect was that the amp current limited into lower impedance loads, the power available into 4 ohms was actually lower (only about 40 watts) than into 8 ohms. I like high current amplifiers.

As far as the ForA-9 goes, as I said I have no plans to complete it perhaps I would under contract.

Pete B.

>Hi Pete, haven't heard from you in a long time. The Dynaco

>Stereo 120 had one huge advantage, the bias was fixed in the

>design, there were no pots to adjust ever. It was also pretty

>well protected. I once accidentally shorted the B+ to ground

>and sparks flew. It still worked perfectly for another 20

>years after that. It had a regulated power supply. That was

>the main difference between it and the Stereo 80, the 80s lack

>of regulation. It was also a very simple easily reproducible

>design as were all Dynaco circuits. My speaker arrangement

>has about a one ohm impedence at high frequencies by virtue of

>the three 8 ohm tweeters in parallel with the AR9. It never

>seemed to bother it. It finally died after 23 years of

>valliant service. Its left channel was taken out by Alexander

>Nevsky's battle on the ice. It was a casualty of war. I

>replaced the output transistors but they failed again and I

>decided to build a new kit which I've been very pleased with,

>the Mosfet 120 is no longer available sadly. I should have

>bought several of them. One my Dynaco SCA80Qs failed recently

>too. I haven't had a chance to look at it but I think it's

>got a power supply problem. There are some 5 watt resistors

>which have had a spotty record. I also had to replace one of

>the large electrolytics. Turned out Mallory makes exact

>replacements cheap.

>

>Any progress on your AR9 based speaker concept?

[Pete B]

Your welcome,

I think they try to avoid it because it disproves their claims, LOL, your right also they will find something wrong with it.

By the way, does the AR-LST manual you found have the later crossover schematic with the 2500 uF value?

Pete B.

>Thanks Pete,

>

>Interesting and relatively simple test. I'll bet the 'exotic'

>equipment and cable people say it's flawed!!! LOL :-)

>

>>Hi Wally,

>>

>>Here are some links.

>>The null test is shown on page 7:

>> http://www.hafler.com/techsupport/pdf/XL-280_amp_man.pdf

>>This references some earlier work by Baxandall:

>> http://sound.westhost.com/sim.htm

>>

>>Good to hear that your in your new place.

>>

>>Pete B.

>

[soundminded]

"Amplifiers with regulated supplies have no dynamic headroom which is not an issue when very high power is available but is usually an issue with lower power amps."

I consider lack of dynamic hearoom an asset, not a detriment. So called dynamic headroom is a measure of a power supply's inadequacy because the B+ output voltage drops when you deplete the filter capacitors. The Stereo 120 was more than adequate to drive my pair of AR9s to very loud levels including deep bass without any sign of audible distortion or distress in a room 13 x 17 x 8 with average acoustic liveness. IMO, sound systems should be "engineered" by keeping requirements of the entire system in mind. I am no longer of the usual opinion that the more power the better. Once the maximum power needed to achieve a specific loudness level is achieved, additional available power is of no practical use and a waste of money. For most home installations, probably a 100 wpc stereo amplifier is sufficient however, there are those rare cases as with electrostatic speakers and my original Bose 901 enhancement project where more power is useful and desirable. Fortunately, in this day and age, excellent monster power amps at reasonable cost like the Crown CE-1000 are availabe at very low cost, well under $500 including shipping.

"The regulated supply was interesting, it actually had a negative output impedance up to the current limit point, "

I think it had a kind of crowbar circuit which limited drive current by reducing B+ voltage to the output stage if overdriven as into a low impedence load.

Sorry you gave up on your ForA-9 project. I would have been interested to see how you would have approached it.

[soundminded]

While there are differences in the accuity of perception and preferences, this is a bogus arguement for judging the performance of sound reproducing equipment just as it is bogus for judging the performance of optical equipment like camera lenses. Everyone recognizes that a picture of a house is a house and not a cow and recognizes that red is not blue regardless of their preferences if they do not have visual impariment. There is a minimum threshold beyond which barrel and pincushion distortion of a lens cannot be detected with the naked eye and it can be objectively measured. So can the graininess of photographic film and the errors it presents in reproducing colors. It's not a matter of preference. Neither is the accuracy of an audio amplifier's ability to amplify an electrical signal without distortion or the ability of a loudspeaker to accurately reproduce the sound of musical instruments. Yes there are variables which skew the comparison such as the way a recording was made or the acoustics of the room the reproducing equipment is installed in. But manufacturers of expensive audio equipment like amplifiers and cables will not perform the obligatory double blind tests to prove the superiority of their product because they know that they can't. They therefore must rely on misleading advertising and the propagation of a culture of myths to convince their niche market that their products merrit their high price tags. Professionals don't buy it but merely shake their heads and laugh. You can bet your last dollar that when Bryston is bidding a contract against a specificaton to supply amplifiers which are nearly identical to their consumer versions for commercial sound systems they don't play any games and the prices are far far lower. If they pandered their hype to their professional customers the way they do to audiophiles, they'd get the door slammed in their faces.

[Guest Bret]

>While there are differences in the accuity of perception and preferences, this is a bogus arguement for judging the performance of sound reproducing equipment just as it is bogus for judging the performance of optical equipment like camera lenses.<

Yeah, it would be. I'm not sure why this came-up. You don't think I said or think such a thing, do you?

Bret

[ar_pro]

It's difficult not to get caught up in the mechanics of human auditory perception.

The crucial question is not how everyone *senses* sound waves, but rather, what technical *process* of sound reproduction would have the capacity to convince any and all that said reproduction is AUTHENTIC.

We all hear differently, but within the range of "normal" (a wide, wide range of capability, mind you) most people are able to separate the real-time *production* of sound from the attempted *reproduction* of that same sound.

In other words, fellas, at our current level of technology, you don't need to be a Golden Ear to know that it just ain't *real*.

[Guest Bret]

>http://www.physiol.ucl.ac.uk/ashmore/ohc2-s.mpg<

Now THAT'S entertainment.

Bret

[kkantor]

Ed,

I certainly have >tried< to answer your questions directly. Since I have failed at this, list them again, and I will try again! Thanks.

-k

[kkantor]

Methinks you doth protest too much!

The hair cell is analog.

The auditory nerve is digital.

Therefore the inner ear functions as an A/D converter.

The brain receives audio information as a digitally encoded bitstream. 1's and 0's. The major conceptual difference between the signal on the auditory nerve and the signal on SPDIF is that the former is only quantized in level, not time. This is widely recognized, and not controversial in the field of audio perception and hearing science. I don't understand why/how you would/could assert it is not true.

If you are saying that, within the brain, labels like "analog" and "digital" are far too simple, I agree. I also understand that the lack of temporal quantization in the ear allows a potentially more "analog" encoding of the signal than Redbook does. Never-the-less, it is a bit-wise encoding, and it has an information theoretical limit that is not that hard to determine.

[Guest Bret]

>Methinks you doth protest too much!<

Methinks you have much in common with my wife.

I understand, you understand, I'm too tired to tell you that I just would not have said "allows" a more analog interpretation; I would have said "forces an abandonment" of a digital interpretation.

Who cares? We communicated. Awesome.

Bret

[soundminded]

"It's difficult not to get caught up in the mechanics of human auditory perception."

If you are out to design a high fidelity sound system, it is not merely difficult but impossible not to. That is because the parameters of perception define the technical requirements of reproduction system. We don't need color photographic film to reproduce infrared and ultraviolet light reflected off objects because our eyes cannot perceive them. It is entirely possible that our understanding of auditory perception is still insufficient to define these requirements to the point where we can assure accurate sound systems are possible. The hearing mechanism must be linked to the way our brains interpret the signals they get and we must also recognize that the ability to detect the size and direction of a source of sound may also include the hearing/brain interaction when we turn our heads slightly using our direction finding ability as a dipole antenna direction finding tool does. This may explain why it is difficult or impossible for two channel stereo to consistantly reproduce the effect of large numbers of musicians at different locations such as spread across a performing stage. At the other end of the chain, our understanding of how sound equipment integrates as a system and how loudspeakers integrate with room acoustics may also be inadequate. Not only would it seem that using a resistive load to test amplifiers for predicting the way they perform connected to loudspeakers is overly simplistic but even more so using anechoic chamber frequency response measurements to predict how loudspeakers will sound in real rooms. The proof of that is for reasons most manufacturers can't explain, speakers which measure nearly identically can sound very different in the same room. Clearly as Peter Snell once pointed out, it's not the frequency response that the speaker eminates but the frequency response at the listener's location which matters. This has to do with the total energy not merely radiated but reachinng the listener after being absorbed by the room. As far as I can tell, no manufacturer has ever addressed this aspect of sound reproduction.

[Pete B]

Professionals would disagree with you and have performed rigorous tests to prove it:

http://www.bostonaudiosociety.org/bas_spea...bx_testing2.htm

>Given the inherent limitations of a DAC, I'll be surprised if

>they ever manage to build a digital system that sounds as

>fluid as an analog system. Our ears are analog after all and

>no amount of engineering will ever change that, and they

>unfortunately (coupled with our brains) can hear far more

>detail than we can easily explain. Consider the fact that with

>only two ears, we can identify whether a noise comes from in

>front or in back of us.

>

>The Denon DCM 560 CD player was even marketed as being almost

>as good as analog.

[Pete B]

The regulator output voltage went up, slightly, as the load current increased until the current limit was reached, this is a negative source impedance. Current limiting of this type is fold back current limiting not a crow bar. Crow bars are typically "across" elements that limit voltage not current.

Pete B.

>"The regulated supply was interesting, it actually had a

>negative output impedance up to the current limit point, "

>

>I think it had a kind of crowbar circuit which limited drive

>current by reducing B+ voltage to the output stage if

>overdriven as into a low impedence load.

[Pete B]

The the 1985 "Carver Challenge" is also required reading in this matter. I see several here refering to Carver's positions on the issue but not this event.

>As some of you have suggested, amplifiers are much closer to

>being "perfect" than loudspeakers. Most medium to high

>quality amplifiers perform with less than 0.1% distortion

>(harmonic and IM). Amplifiers are the most accurate component

>in nearly every audio system. Very few parameters of

>loudspeakers are accurate within 1%--distortion, transient

>response, etc.

>

>I agree with Ken Kantor about amplifiers sounding the same. I

>have not heard of even one blind listening test where the

>panel was able to, with any consistency, identify any specific

>amplifier when driving the same speaker(s). Those of you who

>don't believe that can test it for yourself. Use the same

>signal source for the two amps being tested. Use a DPDT

>switch to switch between two amplifiers driving the same

>loudspeaker. Carefully adjust the level of each amplifier to

>be equal and be sure there are no equalizers or tone controls

>active. If they are decent amplifiers, you will not be able

>to pick which one you're listening to once you lose track of

>which one is switched on.

>

>It would be refreshing to hear some feedback from those of you

>who have tried this. Anything else is just talk.

[Guest postjob62]

Ken,

Thanks for your kind offer. Much of this thread is admittedly way over my head, and beyond what I need to know to enjoy music at my level of (un)sophistication.

To reiterate:

"... am I to understand that *nothing* else about the amp matters? Output coupling, power supply, transformer size, damping factor, subjective "voicing", and all the things that make up a SS amp's architecture-none of these things matter, just the number of watts produced?? So the perceived "warmth" of an early Marantz, the smoothness of the HKx30 series, the brightness and articulation of '70's Pioneers- all this is simply that, just subjective perceptions based on, well, perceptions?"

As I followed up, I'm probably guilty of confusing some preamp functions with pure amplification, since I was talking about a receiver. Clearly you are just referencing the latter.

As well, perhaps I'm not understanding terms. Maybe your use of the term "broken" would encompass poor or inadequate design, or to stretch a bit maybe "broken" would also refer to differences in design among amps that are operationally OK.

Again, I'm very much a layman here so I'm not refuting your assertion-just trying to understand. As an example, I'm considering the purchase of an Adcom power amp for my AR's. There is a considerable difference (I think transistors vs. Mosfet's or something of that nature)in the design of the GFA-545 and the

GFA-545II, but their power ratings are exactly the same. Based on your statement, should I just ignore the design differences since they won't matter anyway, and get the cheaper of the two? Or to take it to an extreme, should I just purchase any old power amp with similar output specs and only consider cost vs. reliability?

I think you can see why this theory (or reality) is a troubling proposition to a someone like myself whose knowledge base is just sufficient to get him in trouble. I suppose it's difficult to ignore the effects of years of manufacturer's disinformation, if that's what it is. I'm just trying to learn here, not to challenge as I previously mentioned.

Also as questioned originally and in a related vein, what is your take on Aczel's "tube superiority is a myth" propostion?

Thanks,

Ed

[Wally]

Nope, the schematic is the same one as in the library.

Shows 4 caps in series parallel and specifies 5000ufd.

BTW, would AR speakers benefit from Baffle Step equalization? When would manufacturers have stsrted to design speakers with Baffle Steo Equalization built in? I have some well reviewed speakers like Paradigms and Celestion DL10 that are much bassier than AR's when against a wall for instance. The bass on these sounds about the same as my AR's when these (newer!) speakers are away from room boundaries.

Yesterday I lined The following up on a shelf on one wall and compared them with my LST's on the smame wall. They all had similar bass characteristics with the LST's, AR12's, DynacoA25XL's,AR4's having deepest to least deep in that order of course. Interestingly These speakers bass sounds excellent when against a wall (about 2/3 of the way up). The following had fat boomy sounding bass until they are brought into the middle of the room..

Paradigm Studio monitors, Paradigm Phantoms, Celestion DL10 seriesII,

Technics SB7000A.

Interestingly, all the AR's and the Dynacos had similar overall sound with the Dynacos having a bit more upper bass. All of these sound very good even when compared with the more modern Paradigms which are excellent performers. The Celestions and the Technics had their own sound characteristic, although very good also, it was markedly different from the former group.

I am now satisfied that the LST's are operating correctly and sound as designed given that I am using the newer Tonegen woofers as opposed to original woofers. I need a new 6 way switch for the LST's as one is defective and I have them hard wired in the '5' mode which replicates the AR3A sound according to the booklet. I don't think I can do them justice in the room I have and I believe that they would sound/perform much better in a larger room with the listener more than 8' away as in my listening room.

The driving equipment ( for the above comparison) is a NAD tuner/preamp, NAD CD, Kenwood M2A power amp rated at 200wpc into 8ohms and almost 400 into 4. I am not using the McIntosh stuff for comparisons because it saves me dealing with the impedance taps on the MC2105 power amp.

In line with this thread, I believe I hear differences between my Kenwood, McIntosh and Crown power amps but I have not done instant switching or double blind tests. The Mc sounds the 'fattest' and the Crown DC300A the leanest. Very subtle mind you. The preamps I have tried have a greater effect on the sound (I think). No interconnects or speaker cables from cheapest to mid priced exotics make any difference to my ear..... all cables are of at least decent quality construction....

Phono cartridges have sonic signatues as do speakers. Turntables, some but again, subtle.

Thes are my humble opinions and findings based on the above simple tests and years of messing with hifi equipment.

[Pete B]

I state over and over to people how important it is to have a lot of reserve power. In fact, I believe that one reason amps sound different to people is that they do not take any precautions to keep them out of clipping. Surely differnt topologies will sound different in clipping. I believe that one thing that system tweakers/tuners are doing is matching the clipping level of the amp to the overload characteristics of the speakers.

I mentioned this to one person at last years CT Audio Society summer meeting and this year he said he went to some audio event where a guy had a clipping indicator that he could use on different power amps, most of them were clipping. I have over 1000 W RMS in my main system.

Anyway, I like Art Ludwig's site and analysis where he calculates the peak power requirements for music as varied as the Talking Heads to Diana Krall:

http://www.silcom.com/~aludwig/EARS.htm

He writes about half way down that page:

"When I play the Talking Heads cut, my CLIO sound measurement system shows a peak sound level of 100 dB SPL in the room, and an average of around 95 dB. Judging from the oscilloscope connected to the amp outputs, the average amplifier output power appears to be about 17 watts. The ratio of peak power to RMS power was 40:1, 40:1 and 30:1 for the Talking Heads, Diana Krall, and Shostakovich cuts respectively. Therefore, for 17 watt RMS, the peak power demands are on the order of 700 Watts. This indicates that either my amps can put out peaks much higher than their rated power (possible, but I'm not sure), or they are clipping.

Jourdain (page 41) states that an orchestra produces 67 watts of acoustic power at full blast. Loudspeakers have efficiencies on the order of 0.5 to 2% converting electrical power to acoustic power. Even at 2% efficiency this implies that well over 3,000 watts of electrical power would be required to duplicate this sound level. Of course an orchestra plays in a large auditorium, and no doubt less power is needed for a small room. This still indicates that power requirements should not be underestimated."

Art Ludwig's main page: http://www.silcom.com/~aludwig/

Soundminded wrote:

>I consider lack of dynamic hearoom an asset, not a detriment.

>So called dynamic headroom is a measure of a power supply's

>inadequacy because the B+ output voltage drops when you

>deplete the filter capacitors. The Stereo 120 was more than

>adequate to drive my pair of AR9s to very loud levels

>including deep bass without any sign of audible distortion or

>distress in a room 13 x 17 x 8 with average acoustic liveness.

> IMO, sound systems should be "engineered" by keeping

>requirements of the entire system in mind. I am no longer of

>the usual opinion that the more power the better. Once the

>maximum power needed to achieve a specific loudness level is

>achieved, additional available power is of no practical use

>and a waste of money. For most home installations, probably a

>100 wpc stereo amplifier is sufficient however, there are

>those rare cases as with electrostatic speakers and my

>original Bose 901 enhancement project where more power is

>useful and desirable. Fortunately, in this day and age,

>excellent monster power amps at reasonable cost like the Crown

>CE-1000 are availabe at very low cost, well under $500

>including shipping.