Owner`s manual

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complete surprise, not only was the gong much easier (no edginess) for my hearing to take, but it had more substance . . . more body. It was
more musical. I have to say that the PT experience is as close to having all the good qualities of our classic analog LPs as I can imagine. I say
good qualities, because the PT's sound lacks the pops, hisses, and clicks that plague phonograph records.
OK, the question is, "What the heck is going on here?" Upsampling means that you take the 44,100 samples per second and increase them to
96,000. This requires a lot of mathematics, and "interpolation" is used. This means that you look at a series of samples and try to interpolate
(calculate with an intelligent guess) what the curve would look like in between those samples, and generate the additional samples accordingly.
Oversampling is a different thing, but related, sort of. Oversampling creates new numbers too, but it is for the purpose of making it easier for
the filters to do their job. With oversampling, the new numbers can just be a string of 0s. Upsampling tries to actually calculate the values in
between the original samples. There is plenty of head scratching on how to do this, and once the calculations are made, an "algorithm" (a set
of mathematical formulas) is the result. This algorithm is built-into the upsampling chip, and the final set of samples includes new samples
generated by application of the algorithm.
Now, of course, Perpetual Technologies' algorithm is proprietary, because not all algorithms are the same. Whatever it is, it is certainly
spectacular in its result. My guess is that Fourier analysis has been applied to a number of sounds recorded at very high sampling rate and
word length, and then compared to a Fourier analysis of the sounds as they come out after down-conversion to 44.1/16 standard CD signals.
Fourier analysis is a way of breaking down a waveform into its various components, called frequency domains. You get number values of the
strength of the frequency components in the signal at the same time. The differences between the values in the original recorded signal vs.
those in the final 44.1/16 signal represent what is lost in the process. By analyzing different types of music, it seems to me an algorithm could
be designed that would put back in what is lost (the differences between the two Fourier analyses). The algorithm might say that if the
waveform looks like "A", then "A1" is added to it, and if "B", then "B1" is added, and so on. The definition of "A1" and "B1" would be based on
sitting down and listening to the effects of their addition, with tweaking here and there as to the relative amounts of the frequency domains. So,
as a result, the upsampling would not simply smooth out the curve, but actually enhance it with new detail, based on the algorithm's
mathematical assumptions. The bottom line is not so much as to whether or not the result is a perfect representation of the original instruments,
because no system can do that. It is, rather, does it sound good? Does it give me pleasure? The answer to this is yes on both counts.
To put it another way, the PTs move the sound quality closer to what an actual 96/24 recording would sound like than I have ever heard. It is
giving me the opportunity to hear my old CDs in a totally new, and thrilling situation, rather than having to wait until they are all redone as 96/24
discs (from analog tapes or high resolution digital tapes).
The P-1A has speaker correction and room correction as optional features. Depending on your speaker models, you will be able to download
the correction algorithm for a fee. The room correction algorithm will be based on having a laptop and microphone sent to you, and following
the instructions, you will gather room audio characteristics, and send them back to PT. They write the algorithm, and you install it into the P-1A
using the USB port on the P-1A's rear panel. The P-1A has 64 MB of static RAM, so there is plenty of space for complicated mathematics to
do their job.
For speaker correction, here is the scenario of how it might work. Just about every speaker on the market has at least two drivers. Two-way
speakers have a tweeter and a woofer, three-way speakers have a tweeter, midrange driver, and woofer, and so on. At the crossover points
between the drivers, the signal suffers phase shift. This means that, as the signal level declines at crossover, the phase is delayed. It is
specified in degrees, such as 10
0
, 90
0
(a quarter wavelength), or even 180
0
(a half wavelength). This results in a substantial part of the signal
not being time aligned with the rest of the signal, and deteriorates our "you are there" experience. What the P-1A might do is (I don't know for
sure, since the actual technique is proprietary), knowing the phase relationships of your particular speakers, slow down the rest of the signal
so that it is now in perfect alignment with the phase of the signal that has been slowed down by the crossover network in your speakers. This
will provide a very big improvement in the sound. Room correction will adjust the level of various parts of the spectrum that are overemphasized
or decreased as a result of the layout of your listening room
The P-1A and P-3A together represent one of the most innovative and important digital audio technologies to come along in several years.
They not only have superb sound quality rivaling equipment selling for thousands of dollars more, but have new concepts that no one else
offers. The beauty is that PT is just getting started on these products. The algorithms will be improved, and we can download them. They are
easily worth the money with no further additions, but the speaker correction and room correction options, coming shortly, make them a must
have.
- John E. Johnson, Jr. -
Notes by Paul Knutson
Stacey and John have covered the engineering, so I’ll focus on subjective listening
impressions, comparisons to other DACs, and finally, suggestions for setting up the P-1A/3A
to optimize performance.
P-3A DAC – Listening Impressions
Pardon my statement of the obvious, but the state-of-the-art is advancing exponentially more
quickly with digital-to-analog playback than with any other component in the history of home
audio reproduction. There’s more to come, too, and it’s happening fast. A number of
respected companies are in the game, but Perpetual Technologies is planning to re-write the