Sharing

August 13, 2015
 by Paul McGowan

Before we get started I just had to share something with you. One of our customers, Clarence, in Malaysia, just received his BHK stereo amplifier and dropped me a note from his iPhone. It touched my heart and helped me remember why I so enjoy going to work each and every day.

I am now a proud owner of this masterpiece of creation of a great sounding amp that will not make you bankrupt.

It is worth the wait and after reading and hearing from Bascom himself selling his beliefs, the performances so far keep up to his word than just his reputation.

I have just one word – awesome.

How many companies get to touch people’s hearts like this? For me, it really makes everything worthwhile. Thanks Clarence, and I hope the amp gives you many, many years of happiness.

I wrote yesterday of the Digital Lens, a regenerator that accepted bits of any quality and output perfect ones at the other end. It was a true accessory, having no purpose other than making things sound and perform better. We had created the device out of frustration. Transports and cables had such differences that it made our lives difficult finding just the right combination – and was that combo right or just a better set of compromises? The money people were spending on exotic transports and cables seemed a wrong headed approach when perhaps we could solve the basic problem they tried to address.

Our ultimate goal was to take any quality CD transport and have it sound close to our most expensive and hand picked versions. We came close but never achieved parity. Coming close was not too bad, and it took much work.

Our original plan was to build an interface that performed only one task: strip the clock from incoming data, place the cleaned bits in a holding tank, then output with a fixed and superior timing mechanism. When completed the results were certainly better, but not nearly as big as we had hoped. The difference between our $50 piece of crap (POC) CD player and reference Jadis transport remained too high. Something else was amiss, and this is where good engineering comes into play.

Every engineer I know speculates as to possible problems, then does their best to eliminate them one at a time until all that’s left is the answer. It’s how most science is done, though what we do cannot always be officially be called science because we rely on our personal sensors for meters; methodology that is often vilified in circles of learned people.

Our list of possible causes was long, but one seemed to stand out more than others. Electrical interference from grounds and power supplies unrelated to the bits. We reasoned that if contamination was the culprit, then we should be able to make the reference Jadis transport sound bad, where it once sounded good. So we performed a simple experiment by adding another input to the Digital Lens prototype. This input was electrically identical to its mate, though not active. While we played something on the Jadis we could simultaneously connect the output of the $50 POC to the Lens. If it was adding electrical garbage to our grounds then we should notice a decrease in quality of the Jadis. Success!

Next, we had to figure out what to do about this next problem.

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7 comments on “Sharing”

  1. Thanks, Paul. It is so valuable to hear about your discovery process. So many of the “conclusions” about digital vs. analog, this variable or that variable, don’t start by identifying the system’s fundamentals.

    For a listening test, to start with live music in an acoustic space gives us a perfect place for comparison. Only if you make a simply-miked recording of the
    concert through great mikes, on a fine recorder, in at least CD, hopefully higher quality, do you get the means of comparison. (I’m ignoring the inter-ear crosstalk issue for today.)

    A reviewer lost credibility by saying that his featured speakers flawlessly reproduced Stevie Nicks, because he heard her live twice. Does that mean his reviewed speakers sound like her voice through a squawky PA in a large venue? Does he assume that the commercial recording has captured her naturally, without processing?

    The point is that you identify the existence of the problem, break it down to identify the problem’s possible sources, and systematically proceed to isolate and correct. I wish more reviewers and self-proclaimed audio gurus were so careful. After all, once they put their conclusions in print, they must certainly be true…

  2. I did a little more research into jitter. Not my favorite subject. I was surprised that besides the clock jitter, noise and waveform distortion also contribute to jitter by altering the precise time a “1” value input will trigger the transistor to switch from “0” input. You’d think rise time would have been selected to be so fast and amplitude so high the change wouldn’t matter but evidently it does. You’d also think oversampling would average out jitter, that is null it out by a preponderance of right calls. Does it? The digital signal must be dejittered at some point in the transport since even the best mechanical transports can’t have anything like the speed accuracy or speed stability required for digital audio.

    According to Wikipedia the threshold of audibility of jitter for pure sine waves is;

    “Periodic jitter produces modulation noise and can be thought of as being the equivalent of analog flutter (Rumsey & Watkinson 1995). Random jitter alters the noise floor of the digital system. The sensitivity of the converter to jitter depends on the design of the converter. It has been shown that a random jitter of 5 ns (nanoseconds) may be significant for 16 bit digital systems (Rumsey & Watkinson 1995). For a more detailed description of jitter theory, refer to Dunn (2003).

    Jitter can degrade sound quality in digital audio systems. In 1998, Benjamin and Gannon researched the audibility of jitter using listening tests (Dunn 2003:34). They found that the lowest level of jitter to be audible was around 10 ns (rms). This was on a 17 kHz sine wave test signal. With music, no listeners found jitter audible at levels lower than 20 ns. A paper by Ashihara et al. (2005) attempted to determine the detection thresholds for random jitter in music signals. Their method involved ABX listening tests. When discussing their results, the authors of the paper commented that:

    ‘So far, actual jitter in consumer products seems to be too small to be detected at least for reproduction of music signals. It is not clear, however, if detection thresholds obtained in the present study would really represent the limit of auditory resolution or it would be limited by resolution of equipment. Distortions due to very small jitter may be smaller than distortions due to non-linear characteristics of loudspeakers. Ashihara and Kiryu [8] evaluated linearity of loudspeaker and headphones. According to their observation, headphones seem to be more preferable to produce sufficient sound pressure at the ear drums with smaller distortions than loudspeakers.”

    From Streophile’s measurements: “The RMS jitter level also dropped from 230ps to 160ps. ” [that’s from 0.230 ns to 0.160 ns]

    Comparing figures 1 and 2, most but not all spikes in the jitter frequency did drop but the overall curve remained unchanged. These spikes dropped from about 11 to 4.

    The result of jitter is described as comparable to analog flutter. I’ve never heard it from a CD myself.

    The Perfect wave DAC presumably drops jitter to below 0.2 nanoseconds. That level should be inaudible to anyone.

    Ya puts yer money down and ya takes yer choice.

  3. It says a lot about you and the philosophy of PS Audio when you can make one of the best amps. at a fraction of the cost of other top notch amps. Congratulations. This was the approach audio manufacturers used to take in the past before the High End monster was created. You have proven that world class products don’t have to cost an arm and a leg. Obviously very expensive products are just overpriced. Remember the venerable SHURE V15 cartridge ? Many felt and still feel that it sounded the most like master tapes and it’s cost was in hundreds not thousands of dollars. Go figure as they say. Regards.

      1. The Shure V15 series cartridges were among the best cartridges ever offered IMO. I’ve got both the V15 Type II improved and V15 Type V MR. That was the cartridge you listened to in listening Room 2 at my house Paul, the Type V.

        One of Shure’s highest priorities was trackability. This means that the cartridge will track even heavily modulated grooves without distortion and without flying out of the groove or losing contact eve at very low tracking forces. This not only sounds better but at the same time reduces record wear and stylus wear. MC cartridges can’t do this because of their high dynamic mass and low compliance. It also has much higher output than most MC cartridges.

        Others in the same league were manufactured by Empire. ADC and Stanton were excellent also. Empire was bought out by Benz.

        When Shure announced the discontinuance of the V15 Type V MR cartridge, The Library of Congress bought out all of their remaining stock. The hollow beryllium cantilever was just too expensive to manufacture.

        For those who accept that the output of a cartridge will be equalized anyway, the tonal balance can be adjusted to compensate for differences in sound systems and phonograph records. The FR of Shure cartridges is usually very flat without any resonant peak typical of many other cartridges when used with normal RIAA equalization.

  4. Seems to me I remember the Shure cartridges in the 60s as costing in the $15 to $20 range. Could be remembering wrong but the V15 was maybe $35.00? Seems impossible that pricing has escalated that much but, then, that was 50+ years ago! The McIntosh 275 was $444.00 at that time. Yes, I do remember that figure for sure. 😉

  5. The Shure V-15 IV was the king of trackability and sold for $150 in the late 70s. The V-15 V sold for @ $250 and was also a decent sounding cartridge.

    David Fletcher of Sumiko distributed the Grace G-707 tonearm and F-9E phono cartridge back in the late 70s and both were decent performers in their day. David personally introduced me to the Supex SD-900 moving coil cartridge and i fell in love with it’s musicality and romantic qualities. Shortly there after i was introduced to and smitten by the Koetsu Onyx.

    The Denon DL103, Sonus Blue, Grado Signature and countless others were also extremely popular back in the day and my assumption is that Paul has invested 1000s of hours listening to various phono cartridge & phono gain stage combinations in his lifetime.

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