CH Precision D1.5 SACD/CD player/transport

There's a school of thought that maintains that among all hi-fi components, the D/A converter is easiest to perfect or come close to perfecting. Just make sure that every sample is converted accurately, that there's little rolloff in the audioband, that aliased images are suppressed almost completely, and that background noise is extremely low, and you have a top-quality D/A processor. Use of a high-quality DAC chip is assumed.

The transport part of the player is even easier to nail, this thinking goes, because all it needs to do is extract the data accurately, something any box-store CD player can do. Jitter? No need to worry about that, or anything happening in the time domain, as long as the data are transferred to a decent DAC via an asynchronous isochronous interface and reclocked inside the converter. Reclocking salves all digital wounds, or so this thinking goes.

What's especially reassuring to like-minded audiophiles is that all this can be verified with a simple set of measurements that almost anyone can do; all you need is some affordable software and a $150 USB computer interface—or, at most, an Audio Precision analyzer, which isn't cheap but costs half as much as Michael Fremer's reference phono preamplifier.

Such an approach allows the manufacture of players and DACs that can be sold for perhaps $1000, or even several hundred less than that, assuming it's manufactured in a low-wage country. Manufacture it in the US or Europe and, even if it's built to an exceptionally high standard, the price can remain quite low.

A top-quality digital source, then, is a commodity, like gasoline, a dozen eggs, or flash drives. It's pointless to spend more, or so the thinking goes. Or perhaps not.

Digital is analog
The subject of this review—the CH Precision D1.5—is hardly a commodity. Fundamentally, it's a transport, built to a very high standard and equipped to read and output data from CDs, SACDs, and MQA CDs. But it's modular. It accepts add-in cards that turn it into a CD/SACD/MQA-CD player.

Equipped as a transport—with, of course, a digital output card—the D1.5 costs a formidable $41,000. Equipped as a player, with two mono DAC boards added in, the price rises to $46,000.

As I prepared to write this review, I spoke by Zoom with CH Precision's two principals: Florian Cossy, the "C" in CH Precision and also in "CEO," and Thierry Heeb, the "H" in CH Precision and a senior researcher at the University of Applied Sciences and Arts of Southern Switzerland specializing in audio/video DSP. Cossy and Heeb are both engineers, Cossy on the analog side and Heeb—obviously—digital.

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During our chat, both admitted the possibility, even the likelihood, that other, quite different approaches could be equally valid. Still, they have their own vision, their particular approach. Their job, as they see it, is to execute that vision to the best of their collaborative abilities. So, what is that vision?

"I would say that one very important point in digital products apart from the pure software part is that it's actually analog design," Heeb said at the start of our interview. If there was a broad theme, that was it. "Even if the signals or the electrical signals are supposed to be digital, basically just two levels, a zero and a one, as soon as you get into an electronic board, they are actually analog signals, current or voltage flowing through components. That is especially true, for instance, for clock signals. If you just consider clock signals as being a shift between two values between zero and one, you don't really get what clock is. The most important point in clocking is in the time domain, with finite resolution. Basically, it boils down to an analog signal again."

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Digital has two faces. On the one hand, it's symbolic; that's the "digital" part. Ones and zeros can be stored, read, and processed almost error-free (almost, because there can be computational errors due to the imprecision of digital data). But when you introduce time into the picture—as you must in audio—and anytime you require signals to be transmitted from place to place, it matters how those ones and zeros line up. Analog concepts like noise and distortion become important, not just for the analog part of the process but in the digital conversion itself. Those imperfections may be too small to cause inaccurate calculations, but that's not the point. The problem comes at transitions: Precisely when does zero become one, and vice versa?

This is hardly a new idea. The concept of jitter has been around as long as digital audio itself. (Longer, actually.) But isn't it a solved problem? Perhaps not. In an "on background" interview some months ago, a different well-known designer told me that even very small amounts of jitter can affect ultimate performance—much smaller than, eg, the results of the Miller-Dunn J-Test used by Stereophile. Indeed, many digital designers I've spoken to seem laser-focused (sorry) on timing accuracy.

Is that all it is then—just jitter? That's a big part of it, but no, not all. Also important is the timing precision of the digital conversion itself; Cossy and Heeb call it time-smearing. (So do Bob Stuart and the MQA folks.) More on this below.

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The D1.5
I'll be auditioning the D1.5 as a player, but, as I said near the beginning of the article, it is fundamentally a transport, so let's focus first on the transport part.

Transports are relatively simple things: They spin silver discs and read the data on them. Even inexpensive transports can read data just fine; in the absence of defects, damaged discs, and intense vibrations, reading errors are rare. But if you're a perfectionist and you're building a transport, you acknowledge the analog nature of digital and aim to produce a datastream that's as pure as it can be, as perfect as possible when it arrives at that last little bit of wire before the D/A conversion. To do that, you have to account for vibrations and electronic noise.

A CD rotates at midrange frequencies, in the 200–500rpm range. (The spinning frequency varies depending on which part of the disc is being read.) SACDs spin faster than that. Any eccentricity in the disc will cause vibrations at those frequencies. Especially inside an electric or magnetic field, vibrations can translate directly to electrical noise.

If you want to solve this problem, you start by leaving off components, such as ceramic capacitors, that translate vibrations directly into electrical noise. (As Heeb mentioned in our interview, a ceramic capacitor is essentially a microphone.) The other thing you must do is keep vibrations away from wires and other circuit elements.

"In the D1.5, we completely redesigned the optical unit," Cossy said in the interview. In the D1, which used a high-quality drive from another manufacturer, the optical units were "mounted on very thin steel plate and inverted rigid dampers. There is a resonant frequency of this block which is between 300 and 800Hz.

It is exactly where we don't want it to be"—right in the midrange and right in the range of the spinning CD.

So, in moving from the D1 to the D1.5, they redesigned the optical unit. The optical pickup and motor are now mounted on a brass "sled." The unit as a whole now "weighs 1.5kg instead of a few hundred grams." Resonant frequency is inversely proportional to mass, so that brings the resonant frequency way down. "We've been able to lower the resonant frequency to 25Hz," Cossy said.

Alpha GEL dampers (footnote 1) isolate the mechanism from the chassis and the chassis from the mechanism; these dampers are "fine-tuned to filter vibration down to AC mains frequencies," Cossy said. The chassis itself is reinforced with a rigid support frame made with more than 4lb of machined aluminum.

One reason some people—including me—are fond of turntables is that they're simple, mechanical devices. I like CD transports for the same reason: They employ principles of design that are easy to understand. As a transport, the D1.5 checks all the boxes.

Built in to the D1.5—after the transport but before the add-in DACs installed in the "card cage"—is a DSP unit that serves two main purposes. It decodes MQA CDs and upsamples CD data.

As a player, the D1.5 is capable of full MQA-CD decoding, which is followed by upsampling to DXD. Via its proprietary CH Link connection, the D1.5 can output "MQA core" data stored on disc, "unfolded" to 88.2kHz, equivalent to what Roon or Tidal output with MQA-encoded files if you don't have an MQA-capable DAC. MQA says this is better than CD but not as good as all-out, fully decoded MQA.

Conversion
Cossy: "The DAC chips we are using are the WM8742." It's a sigma-delta chip produced by Wolfson/Cirrus Logic. (Cirrus bought Wolfson in 2014.) It became clear to me during this interview that CH Precision uses these DAC chips only for their core conversion function, ignoring the chip's peripheral features that are performing other critical calculations in software. "These chips accept eight times base frequency, so it's DXD rate. What we do prior to conversion is to transform everything into DXD, so it can be DSD to DXD inside the DSP, it can be 44.1kHz from a regular CD to DXD, or it can be MQA CD to DXD." For MQA data, the MQA "black box" interpolation filter is used.

Early digital focused largely on the frequency domain. As a result, mistakes were made. The "Red Book" standard for CDs settled on a sampling frequency of 44.1kHz because that was the minimum rate needed to cover the full audible range (you must sample at twice the bandwidth in order to allow "perfect" recovery of the original time series, which gets us up to a sampling frequency of 40kHz) plus a narrow transition band to allow for bandwidth-limiting (footnote 2).

But the folks who defined the "Red Book" spec didn't allow enough room for optimal filters—just sharp, ones. Sharp and fast in the frequency domain equal broad and slow in the time domain. At CD resolution, you can get near-perfect frequency response or good time-domain performance, but you can't have both.

"Another point, which is very specific to CH, is that we don't believe that much in the necessity of achieving pure 20kHz, 0dB passband," Heeb said in our interview. "That almost never happens in nature. As soon as you go back from a sound source, you will have a high-frequency rolloff in any case."

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The D1.5's converter "has been designed on a set of principles that we recognize at CH as being important for proper digital audio reproduction or audio reproduction in general. One of the key points is to limit the time smearing of those filters—that is, limit basically the time dispersion that a sample would bring once it is passed through the filter."

Even ignoring jitter, and beyond the narrow transition band mentioned above, the traditional approach to digital conversion has some time slop in it due to the fact that the sampling "kernels" used—the mathematical functions used to divide audio into samples in ADCs and then to reassemble it into a continuous whole in DACs—are longer in the time domain than they need to be. They're too slow.

To address this issue, the CH Precision interpolation filter utilizes splines, an algorithm that carries the acronym PEtER. A spline is a certain kind of mathematical function, a smooth, piecewise polynomial.

"It's compact support," Heeb said. "This is exactly what I was talking about before when I told you we want to reduce the time smearing. Time smearing is basically if you put a single pulse through the system, if you have a filter with a very long impulse response, that single sample will extend over a large number of samples. We prefer to use splines, which have a much more compact support, which makes it so that when the sample goes in, what comes out has, in our case, [no more than] 100µs of pre-ringing and post-ringing." 100µs is the target because it's a level of timing precision where errors are thought to be audible. It's a conservative figure; I've seen estimates in the literature as low as 5–6µs.


Footnote 1: Alpha GEL is a trademark of the Taica corporation of Japan.

Footnote 2: Here's the first problem for those who believe that bits-is-bits: The perfection Shannon's theorem promises can be realized only for information that is strictly band-limited, to half the sample rate. Which, for real music, means that you must low-pass–filter the signal before you can convert it. You can argue that nothing matters if you can't directly hear it, but if your standard is to perfectly recreate what was captured on the recording—well, there goes "perfect."

COMPANY INFO
CH Precision
Switzerland
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ARTICLE CONTENTS

COMMENTS
volvic's picture

Great review; I would have been happy reading even more technical info and how these engineers think. Do the engineers at CH believe that 16 bits are good enough for Red Book replay?
It was nice to read their attention to the transport, a pet peeve of mine on expensive players. The best machines I ever heard and owned were in-house-built transports or heavily modified ones; Wadia, Linn, Luxman, Esoteric, and others used well-designed solid transports to minimize vibration.
I would love to hear CH products with SACD recordings. It is a shame that format never really took off. Its built-in copy-protection limited how it could be used and connected to other components.
Great review; I can’t wait to read about the other related CH products.

Glotz's picture

Perhaps an extra box with anti-theft lasers??

Zero mockery of CH Precision. If I had lottery money, these would be mine tomorrow.

volvic's picture

I would sit down and here these beauties the Goldmunds, and the Esoterics. I betcha it would be a really tough call.

Kal Rubinson's picture
Quote:

Its built-in copy-protection limited how it could be used and connected to other components.

Those problems were solved a long time ago. SACD failed because of marketing errors and the underlying issue that improvements in sound quality rarely have any impact in the mass market.

volvic's picture

Maybe, but I still can't bypass and use the digital out or hdmi out for better sound, and I paid a fortune for it in 2004. Only through the RCA jacks. Don't disagree with the sound improvements, goes without saying, most don't care, except for us subscribers and readers to Stereophile.

Kal Rubinson's picture

Of course, it depends on one's choice of machine but 2004 was probably just too early. HDMI 1.2 (released in August 2005) added DSD support for transmission of SACD content at up to 8 channels.

volvic's picture

The downside of being an early adopter. Maybe time to upgrade. Thanks for the info.

Kal Rubinson's picture

Yeah but now you may be too late. :-)

volvic's picture

You’re probably right, don’t see many sacd machines with hdmi outputs nowdays. Maybe source a used one.

Robin Landseadel's picture

Managed to find two Sony Blu-Ray players, used and crazy cheap, within the last 4 years. One for $20, the other $7. SACD capable, HDMI out, also digital coax out, which is what I use on those very rare occasions I play a CD. I suspect the coax out converts the DSD stream to PCM. In any case, single layer SACDs play just like the CDs with these players. Most of the time I rip the contents of the CD to a SSD, back that up on a Micro SD for a DAP, connect a USB out on the laptop to a Topping E30, use the I-Tunes playlist. Found remotes for the Blu-Ray players online, about $10 each.

"The CH Precision player featured very low levels of harmonic distortion, with the third harmonic the highest in level at –100dB with SACD data (fig.7)."

From the measurements I've seen, the Topping E30 [$150, give or take] beats that spec by -10db.

RH's picture

Inured as I thought I was to expensive items reviewed in Stereophile, when I came to this sentence:

-- "Equipped as a transport—with, of course, a digital output card—the D1.5 costs a formidable $41,000."

...I literally choked on my food. Actually gagged.

Ok, maybe it was partially due to my wife's occasionally clumsy attempts at Banana Bread. But still...that price seems at least as hard to swallow as my wife's banana bread.

Somewhere at Benchmark, someone is smiling. ;-)

Axiom05's picture

Is it April 1st already? A review of a pre-production unit, a $41K CD/SACD player? OMG, MQA-CD alone should be a joke. No disrespect for the designer but this one really makes my head spin. There are so many better options available at a fraction of this price.

tonykaz's picture

What happens if you scratch it up ?

I just did a small real estate deal involving a Bank and $150k. I needed to present something for them to hold onto of much greater value.

Hmm, is this how you lads secure loaner gear ?

Of course, for selfish reasons, I would encourage you to do a long term test, if it was my company's gear and I was certain that you would be THRILLED with it's performance enough to publish gushing accolades of greatness.

I personally would "OWN" great discovered Gear because outstanding is so rare and hard to come by. ( unless other factors (like $ cost) make it prohibitive )

That CH gear needs to hold 80% of it's MSRP and even then it's still too pricy. ( for me )

Tony in Florida

teched58's picture

The solution is to have one's butler stand next to this $̶5̶ ̶m̶i̶l̶l̶i̶o̶n̶
$41,000 CD player to make sure that the drawer does not get bumped or bent. Dunno what Jeeves can do about the fact that you're paying a very small portion of your Wall Street bonus for a player that has old firmware. Maybe if Jeeves is an ex-IT guy (e.g., he's over 40 so was laid off from his corporate gig) he'll be able to download it for you. Just make sure he remembers to close the CD drawer! Oh, and Jeeves is old enough to explain to you what a CD is and why they were once popular.

Archimago's picture

Wow, this sounds really fancy:

"It's compact support," Heeb said. "This is exactly what I was talking about before when I told you we want to reduce the time smearing. Time smearing is basically if you put a single pulse through the system, if you have a filter with a very long impulse response, that single sample will extend over a large number of samples. We prefer to use splines, which have a much more compact support, which makes it so that when the sample goes in, what comes out has, in our case, [no more than] 100µs of pre-ringing and post-ringing." 100µs is the target because it's a level of timing precision where errors are thought to be audible. It's a conservative figure; I've seen estimates in the literature as low as 5–6µs.

Come on guys, it's just a minimum phase, moderately steep, digital filter that rolls off quite early around 15kHz with a stopband frequency below Nyquist.

Nothing all that fancy about this at all. Nothing requiring thousands of dollars to perform.

In 2022, looking at an impulse response and talking about "blurring" as if this is even a "timing precision" issue as if audiophiles haven't maybe thought about this already is looking really, really silly! This is the kind of misinformation that MQA has been trying to perpetuate for years.

Come on Stereophile, time to move on. Enough with nonsense! Minimum phase filters introduce timing/phase shifts whether it's with this device or the MQA filters.

supamark's picture

You should read them. Turns out the item under review had old firmware and was using an incorrect filter. They're going to do a follow up with the correct filter/software. The filter makes a huge difference to the sound, so I'm curious what Jim will hear and hopefully some add'l measurements too.

Mark Phillips
Contributor, Soundstage! Network

Kal Rubinson's picture
Quote:

I suspect the coax out converts the DSD stream to PCM.

That or you are playing the CD tracks.

Robin Landseadel's picture

Again, a single-layer SACD doesn't have a Redbook layer, at least that's what I've read elsewhere.

This [obviously cheap] Sony BDP-BX57 Blu-Ray player I'm now using is nearly "Universal". When I had a 5.1 system, it would play back 5.1 DVD-A discs via the plainwrap DVD layer, surround courtesy Dolby. I thought I heard a difference between that and true DVD-A, but not enough to really care. I once had an OPPO DVD-era player, great with DVD-A, but would hang like the other DVD-A players I've used. However, the Sony would play my copy of Beck's Guero all the way through as a DVD. As DVD-A, it would regularly hang, probably because of that disc's amazing, constantly fluctuating visual presentation rendered on the fly.

Kal Rubinson's picture
Quote:

Again, a single-layer SACD doesn't have a Redbook layer, at least that's what I've read elsewhere.

Yup but some people mis-use that term.

The "hang" problem you describe is not something I have come across with any of the Oppos (or, for that matter, with any player I've owned) except with a rare faulty disc. That includes DVD-As and single-layer SACDs.

Robin Landseadel's picture

I had no issues with DVDs in my OPPO otherwise, I suspect "Guero" may have bitten off more can it can chew.

jtshaw's picture

My Bryston BCD-3 feeds a balanced input on a Luxman L-509x integrated amplifier, which in turn sends the music to a pair of Joseph Audio Pulsars. My entire system comes in at much less money than this CH Precision transport/player.

I would not be surprised if the CH Precision provides superior performance, but how much better? In my actual listening experience, the Bryston BCD-3 comes very close to a dCS Puccini. I suspect performance improvements are truly at the outer margins.

I don't begrudge anyone their purchase if they can afford to buy and enjoy the CH Precision, but in this case they are likely buying at a point where the curve of diminishing returns has already long gone nearly vertical. Much of my pleasure in audiophilia has been putting together systems that to my ears hit that point where curve starts its nearly vertical climb.

volvic's picture

The BCD-3 is one of the finest DAC's I have ever heard and agree. However, done right on some of the best machines, SACD can sound revelatory. While SACD may be on life support in North America, I suspect it is still going strong in other places, most notably Japan. Hence why these machines exist. I wish it had thrived, it has this clarity and hyper-detail that even my SME and Roksan vinyl rigs can't sometimes match. It can get fatiguing over long listening with some of my limited discs but, other times, it is very impressive.

HighEndOne's picture

Why?

Because I would think that some form of “control” or “standard” might be helpful in forming a good and valid review, and those constraints seems to be missing here. But then again, we are mostly talking about a subjective critique, not a scientific evaluation.

The reviewer is moving (or has moved) so he has no access to his reference music material. OK, yes you can stream files. Do you really know what is coming down that ethernet line at that moment? To my mind, it is a variable.

This may also mean he is in a new, or newer, listening room. I, for one, do believe that the room is a particularly important component to the results one hears.

Likewise, some of his associated reference equipment may also be unavailable. I will gladly stand corrected on this point if needed.

Perhaps unknown to the reviewer at the time, the unit being evaluated is a pre-production unit. I could say it is a possible "ringer" if were not for the JA (John Atkinson) measurement failure listed below.
The unit in question measures poorly in the frequency response area (Per JA -Redbook). Did the listening tests miss this? And what about the frequency response of the reviewer’s ears? Can we measure those as well?

After JA measures the sample, the manufacturer now admits that this pre-production unit was released with down-rev software and that the settings for some functions are less than clear. But of course, CH says they can send you the updated code that YOU can install. (BTW, since my technical time is worth $500 per hour, is CH going to reimburse me?) And I guess I can download, and then print, the new, revised operator’s guide too.

Now let me say that CH gear is likely built to an extremely high “Swiss” standard overall, and that the intent at CH is to surpass the competition. Of this I have no doubt (my father was a watchmaker, so I know a little about the Swiss approach). And I also must admit that I have never seen, nor heard, CH gear in action. I can only say that my exposure to decent gear (my older Levinson stack: 38S – 37 – 360S) gives me a taste of what can and should be possible at the even-higher price echelons that CH inhabits.

Nonetheless, CD audio nirvana is just $40K away, right? Maybe for some. Not for my money, thank you. Why? How will I know that MY $40K unit is meeting specifications or not? Do I need to ship it to JA to confirm that MY unit is working correctly?

Over the many years I have read this magazine, there have been instances of expensive gear getting rave reviews, only to be found to have, shall we say, less-than-stellar measurements. Then we will see the associated manufacturer’s comment that the unit was either defective, mishandled in shipping or “fill-in-the-blank”. Is this is supposed to make it all better? And please do not recite the banner statement that all that really counts is the sound of the item under review. If MY new Corvette, for example, looks great but (unbeknownst to me) will not break 120 MPH, what is the point? I paid $75K or $100K for what?

And on a loosely related topic, how can Michael Fremer stand behind years of review work, when by his own admission, until recently, the AC power quality to his reference rig was, to be charitable, quite questionable, and a long-term problem? It is great that he documented all the effort taken to rectify (no pun intended) his AC issues; it just makes me very uneasy when five and six figure gear is placed on a pedestal that might be made of sand (bad power).

In closing, despite my ranting and raving here, please keep up the excellent work you folks do. You should know that the first thing I look for in your reviews is the JA measurements section. Once I am past that, then I will read the “opinion” portion of the article.

And this also keeps me from “absolutely” investing in that other magazine. There are no independent measurements to back up anything said there.

All the best… HighEndOne

David Harper's picture

So then I take it this thing is better than my OPPO 203?

shawnwes's picture

It's one thing to have a news blurb about a soon to be released product but to do a review on a non-production sample goes against the standards your readers expect from Stereophile. Readers have no idea how this unit might be different from an actual production unit. The fact they had "incorrect software" loaded in a $40k unit under review is a very bush league answer even if it is true.

Andrei's picture

"Reclocking salves all digital wounds, or so this thinking goes." I am in in this camp. The errors in clocking would have to be huge for the re-clocking to to work, I doubt there is a transport that would be that bad.

But it is worse than that. These days the transport can be PCM or DSD files held on a SS hard drive. It is not difficult to get an unpolluted USB or a I2S or other method to get to a DAC that will equal this unit. So in effect this vast sum is being paid for a transport that is not needed. I guess you would have to be invested in (SA)CDs, like the idea of the physical media, and be well heeled. Maybe there is some cachet in just owning such a piece.

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