Re phase and polarity, I believe the reason for the ambiguity and inconsistent use of the term "phase" is that a delay or phase shift mechanism can be either phase dispersive (affecting the phase of different frequencies differently), or phase non-dispersive (affecting the phase of all frequencies equally).
A polarity inversion is the same thing as a 180 degree non-dispersive phase shift. An arrival time difference caused by multiple drivers whose physical placement is not time-aligned relative to one another would be a dispersive phase shift.
Regards,
-- Al |
Herman: Take 2 equal signals consisting of a mix of 20 hertz and 100 Hz all the same amplitude in phase....
.... polarity invert one and sum the result you get complete cancellation.
.... phase shift one signal by 180 degrees...well... here is where you run into a problem. You can't phase shift them both by 180 degrees because the periods are different. a 180 degree shift of 20 Hz is 25 milliseconds and a 180 degree shift for 100 Hz is 5 milliseconds. You can't phase shift them both by 180 degrees. You can shift both by 180 degrees if you implement the phase shift via non-dispersive means, such as by inverting polarity! :) I am in agreement with what you have said about how the terms "phase" and "polarity" are best used, and should be used. My point was simply that it is understandable that the term "phase" is commonly used in a loose manner. Best regards, -- Al |
Prdprez & Herman,
I'm not particularly familiar with the BAT solid state amplifiers, but if indeed the only relevant difference between configurations that offer, for example, 300W into 8 ohms and 150W into 8 ohms is that output circuits are paralleled, then my guess is as follows:
I would guess that both configurations are either designed with the same internal voltage rails and output voltage swing capability, or are designed such that those parameters can be easily selected internally between two values corresponding to the two configurations. In the lower powered (non-paralleled) configuration, the 150W rating (which represents continuous MAXIMUM power delivery into 8 ohms, at a specified distortion level) is limited by either current capability or by heat dissipation considerations, or both.
In that situation, paralleling the output circuits would double the continuous MAXIMUM power rating. However, the amount of power delivered into a given load, for a given input signal and gain, would be identical for both amplifiers as long as the voltage, current, power, and thermal limits of the lower powered amp are not exceeded.
Regards,
-- Al |
Hi Herman, I, of course, agree with your technical statements about amplifier power, etc., as far as they go. And they are not inconsistent with my previous post. However, keep in mind that the amps we were discussing as examples are solid state amps. So rather than using higher taps on the output xfmrs, I would guess (as I indicated earlier) that either the voltage rails on the non-paralleled amp configurations are the same as on the otherwise similar paralleled configurations, or can be internally selected between voltage values appropriate to each configuration. As you will realize, the paralleled configuration simply provides the current capability and/or heat dissipation capability necessary to support the application of the higher voltage to the given 8 ohm or other load. And Prdprez has now agreed that we are talking about maximum power ratings, not about paralleled output stages forcing more current into a load without a voltage increase. Prdprez, All three of my examples have listed specs of 26dB gain. This equates to 400W, correct? (under ideal circumstances)
Yet the other specs are listed as 150W and 300W. The maximum wattage is not specified for paralleling the largest amp (VK-600m) So we can probably assume that it tops out at 400W maximum (still 26dB gain) with overkill ability on the current side. I don't think we can say how much power the VK-600m can supply, without more information than appears to be provided on their site. Besides there being no spec on maximum output power, unless I missed it there appears to be no spec on input sensitivity (i.e., how much input voltage is required to produce the rated output). 26db gain (the spec for the VK-600 and VK-255SE) simply means that the output voltage will be 20 times larger than the input voltage, provided that the output voltage, current, and power, and the corresponding heat dissipation, do not exceed the amp's capabilities. Thanks for the nice words. Best regards, -- Al |
We live in a neighborhhod with Victorian style homes including ours and the Grammophone like look appealed to her. We think alike in this way in that I think that is part of the appeal of horns to me, is that tie to the past. While the ancestral heritage of modern horns is most commonly associated with the gramophone and phonograph, for which the horn provided acoustical amplification without electrical signals being involved, it should be kept in mind that horns were also the leading speaker technology in the earliest days of commercial radio broadcasting. Those being the years between roughly 1920 and 1925. Rather than providing mechanical/acoustical amplification of the vibrations of a stylus and an associated diaphragm, in radio applications a headphone-like transducer was used to convert electrical signals to sound, which in turn was amplified by the horn. A nice collection of these things is shown here. My collection of antique radios includes a mahogany version of the Amplion Dragon (another example of which is shown at the upper right of that page), which to collectors is one of the more desirable models. I haven't yet tried it in my main audio system, though :-) Best regards, -- Al |
I read TAS religiously from the late 1970's until around the time the world wide web emerged in the mid-1990's. I also read pretty much all of the other major audio-related publications of the time, and a number of the minor ones, representing pretty much all of the points on the spectrum of audiophile ideologies. I found that I could glean useful information from all of them.
As a technically oriented person I certainly had issues with a lot of what I read in TAS, especially when the writers hypothesized technical explanations for their sonic perceptions. However, based on my listening experiences during that period and those of my audiophile friends, I don't think it can be denied that the listening impressions reported by HP and many of his writers tended to be more consistently spot on than those in any other contemporaneous publication. Albeit with matters of degree perhaps being somewhat exaggerated at times.
Concerning Harry's considerable power and influence, it seems to me that ultimately its most significant effect was promulgation of his fundamental underlying philosophy, the use of the sound of acoustic instruments in a real performing space as the ultimate reference. And promulgation of that philosophy was sorely needed at the time, and all to the good, IMO.
If some folks followed his recommendations blindly, and if he had great influence (which he did), that is not his fault. My perception has been that the net result of that influence during the roughly 20 year period in question was more beneficial to the evolution of quality audio reproduction than that of any other audio reviewer or journalist.
And btw, I've found Parker's wine ratings and books to be useful as well.
Regards,
-- Al
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Regarding Mr. Aczel, I think it is worth noting that there were vast differences in his views following and prior to the approximately seven year lapse in publication of "The Audio Critic" that occurred between early 1981 and late 1987, while he was involved with the Fourier loudspeaker company. The later Mr. Aczel, consistent with what has been said above, believed that all amplifiers meeting certain basic criteria (high input impedance, flat frequency response, low output impedance) sound the same. The low output impedance criterion, btw, excludes most tube amps. On the other hand, here are some quotes extracted at random from Volume 2 Number 3, published in 1980. These pertain to solid state amplifiers, which certainly meet those criteria: Re a revised version of the Bedini 25/25: The sound is, if anything, even better; the silkiness of the highs and the transparency of the midrange are unsurpassed in our experience, except possibly by some -- not all -- versions of the Futterman tube amplifier and one or two solid state prototypes. The bottom end of the Bedini is very impressive for a 25/25 watt stereo amplifier with a single power supply, but of course there are many large amplifiers with all-out dual power supplies that will give you firmer and subjectively deeper bass. Re The Leach Amp: We find it beautifully transparent in the midrange, very well controlled on the bottom end, but a bit overbright and glassy on top (our bench tests won't tell us why). And this comment in the preamplifier review section of the same issue: Regardless of your methodology, you can't escape from judging subjectively which one of two sounds appears to sound more like music. Or at least more like what you believe to be the true sound of the input. And such a belief can be formed only by listening first to the output of a familiar reference system driven by that input. Which is where we came in. Mr. Aczel was someone who's reviews and opinions I **wanted** to like and respect. He wrote in what was stylistically an extremely persuasive manner, and his writings always seemed to convey an impression of an intelligent and disciplined approach to component evaluation. Ultimately, though, I found it impossible to reconcile much of what he had to say with my own experiences, and those of others for whom I had respect. Especially in his later period. Which is not to say that I believe investing $10K in a pair of wires generally makes much sense. In audio, as with most things in life, IMO the truth usually lies somewhere in the middle ground between the extremes. Regards, -- Al |
Slight correction to my previous post: "who's" should be "whose" :-)
Regards,
-- Al |
Frogman & Tubegroover, thanks for your comments. Yes, I recall the saga of the Fourier Systems speakers quite well.
In fact I auditioned the substantially redesigned second version of the Fourier I at Lyric's White Plains store in 1983, as I was shopping for speakers at the time. In Aczel's own words (Issue 10, published in 1987 following the long hiatus), the redesign addressed "some driver-related problems that had eluded our attention in the laboratory, [which] made its interface with certain rooms unpredictable." Shortly after the release of the initial version a generally negative review in "The Sensible Sound" (not exactly the most hyper-critical of audio review publications) had cited a "silvery spacey effect" created by its subsequently replaced tweeter. The mid-range driver was also replaced in the redesign.
The version I heard sounded generally ok during my fairly brief audition, but left me unexcited.
Aczel's lengthy recounting in Issue 10 of the Fourier saga and his involvement in the company is persuasively written, as might be expected, and if taken at face value would dispel any cynicism about it all. But who knows?
One thing is certain. Both the timing and the degree of his ideological metamorphosis were striking, and, as you indicated, fascinating and mysterious.
Best regards,
-- Al
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03-06-14: Kiddman
Aczel criticism overblown? I don't know that this would be possible.
Here's a guy who never published a particular issue, but write a bogus review for Carver saying that Carver had exactly duplicated the sound of a well known, very expensive amplifier. Nice little arrangement, Carver reprinted the excerpt from the non-existent issue and supplied them by the load to Carver dealers. Nice little bit of fraud on both sides. The amp, by the way, was very poor sounding compared to one Aczel said it was identical to, and took out many a tweeter of relatively easy to drive speakers at way less than its stated output power. The aforesaid review was in fact eventually published, in Issue 10 in 1987. That was the first issue Aczel published following the nearly seven year hiatus I referred to earlier. The 1983 review "preprint" to which you refer was extracted from what Aczel indicated in Issue 10 had been an almost complete, mostly set in type issue which was not published due to the hiatus, which occurred for unrelated reasons. Carver requested and was granted permission to issue the preprint. Also, I recall some seemingly credible speculation that the close transfer function match between the aforesaid amplifier, the Carver M400t, and the transfer function of the Mark Levinson ML2 it was designed to emulate, may not have been maintained in production to anywhere close to the same degree as the match that was measured by Aczel on Carver's prototype. Also, I'll mention that I owned an M400t for about 20 years, alternating it with other much more expensive amplifiers. It sounded surprisingly good, driving 90 db speakers having easy to drive impedance characteristics. (Its predecessor model which I VERY briefly owned, the M400a, which pre-dated Carver's attempt to match the transfer function of the ML2, did sound very poor). The M400t had no trouble whatsoever cleanly producing 100 to 105 db peaks at my 12 foot listening distance playing classical symphonic music on labels such as Telarc, Sheffield, and Reference Recordings. It never clipped once in my extensive experience listening to those kinds recordings having exceptionally wide dynamic range. The amplifier, btw, is still going strong in the home of a relative, after 30 years. Regards, -- Al |
Correction to my previous post: Looking at Issue 10 of "The Audio Critic" I am reminded that the Carver amplifier which was the subject of the preprint was the M-1.5t. The M400t was released subsequently, and was claimed to have been similarly matched to emulate the transfer function of the ML2, but was not the subject of Aczel's preprint.
Regards,
-- Al |
Hi Unsound,
That was an emulation attempt that occurred a bit later during the 1980's, with a different Carver amplifier model, that was written up in Stereophile and therefore drew more widespread awareness. Remarkably (or perhaps not), Stereophile's writeup of Carver's effort to emulate the CJ tube amp made no mention and reflected no awareness of his earlier effort to emulate the solid state ML-2 with some of his other models.
Best regards,
-- Al |
