CH Precision I1 Universal integrated amplifier Measurements

Sidebar 3: Measurements

I measured the CH Precision I1 Universal amplifier with my Audio Precision SYS2722 system (see the January 2008 "As We See It"). Before performing any testing, I connected the amplifier's Ethernet port to my network, then ran it at one-third power into 8 ohms. At the end of that period its top panel was warm, at 107.8°F (42.1°C), and the front-panel display indicated that the internal temperature was 63°C (145.4°F). (This panel is very useful—as well as temperature, it indicates volume, the input settings, and when the amplifier is clipping. It also allows the menu to be navigated, as does the CH Android app.)

I wasn't able to test the CH I1's phono stage because its current-mode input didn't appear to be compatible with the Audio Precision's voltage-mode output. Looking first at the line-level analog inputs: With the volume control at its maximum setting—the default setting is "0dB," though additional gain up to 24dB can be selected for each input via the menu—the voltage gain at 1kHz into 8 ohms from the speaker terminals measured a low 22.53dB for the balanced input but 29dB for the unbalanced inputs. (Usually, a balanced input offers 6dB more gain than an unbalanced input, not 6dB less.) The line inputs preserved absolute polarity (ie, were non-inverting) from all outputs. The unbalanced input impedance was 44k ohms at low and middle frequencies, dropping to 23k ohms at 20kHz. As expected, the balanced input impedance was twice the unbalanced value. The preamplifier output offered an insertion loss of 0.7dB, with an appropriately low output impedance of 72 ohms across the audioband.

The output impedance at the speaker terminals (including cables) varied according to the amount of global negative feedback selected with the menu. With global negative feedback set to 100%, the output impedance was 0.11 ohm at 20Hz and 1kHz, rising slightly to 0.15 ohm at 20kHz. As a result, the modulation of the I1's frequency response with our standard simulated loudspeaker was just ±0.1dB (fig.1, gray trace). Reducing the feedback level to 60% increased the impedance to 0.23 ohm at 20Hz and 1kHz, 0.27 ohm at 20kHz. With 40% feedback, the respective impedances were 0.3 and 0.32 ohm. With no global feedback, the impedance was 0.40 ohm at 20Hz and 1kHz, 0.44 ohm at 20kHz, and the modulation of the frequency response was now ±0.2dB (fig.2, gray trace).

119CHI1fig01.jpg

Fig.1 CH Precision I1, analog input, 100% feedback, volume control at max, digitized frequency response at 2.83V into: simulated loudspeaker load (gray), 8 ohms (left channel blue, right red), 4 ohms (left cyan, right magenta), 2 ohms (green); Bypass frequency response at 2.83V into 8 ohms (left blue, right, yellow) (1dB/vertical div.).

119CHI1fig02.jpg

Fig.2 CH Precision I1, analog input, 0% feedback, volume control at max, digitized frequency response at 2.83V into: simulated loudspeaker load (gray), 8 ohms (left channel blue, right red), 4 ohms (left cyan, right magenta), 2 ohms (green) (1dB/vertical div.).

An unusual aspect of these two response graphs is that the amplifier's output drops sharply above 35kHz. I had understood that in Normal mode, the I1 digitizes its analog line inputs at 384kHz—but figs. 1 and 2 suggest that the sample rate is actually 88.2 or 96kHz. There is nothing in the manual about changing the sample rate for the analog inputs, nor do the front-panel or Android-tablet setup menus offer options for this. I did wonder if the sample rate was somehow affected by that of the data present at the digital inputs; however, even with, for example, the AES/EBU input receiving 192kHz data, the analog digitizing sampling remained at the lower rate. When I set the balanced input to Bypass, which eliminates the digitizing (and the volume control), I got the frequency response shown as the blue and yellow traces in fig.1. It extends significantly higher in frequency, not reaching –3dB until 100kHz. (Fortunately, Jason's comparisons with the dCS Rossini were performed with the I1 in Bypass mode.) In Normal mode, the digitization affects the shapes of 1kHz (fig.3) and 10kHz (fig.4) squarewaves.

119CHI1fig03.jpg

Fig.3 CH Precision I1, analog input, small-signal, 1kHz squarewave into 8 ohms.

119CHI1fig04.jpg

Fig.4 CH Precision I1, analog input, small-signal, 10kHz squarewave into 8 ohms.

Channel separation was excellent, at >110dB in both directions below 2kHz, decreasing to 80dB at 20kHz. With the analog inputs shorted to ground and the volume control set to its maximum, the wideband, unweighted signal/noise ratio (ref. 2.83V into 8 ohms) measured 62.6dB in both channels. Restricting the measurement bandwidth to 22kHz increased the ratio to 83.3dB, and an A-weighting filter increased it further, to 86.0dB. Levels of residual spuriae at the AC power-line frequency and its odd-order harmonics, presumably due to magnetic coupling from the massive power transformer, were very low (fig.5).

119CHI1fig05.jpg

Fig.5 CH Precision I1, analog input, spectrum of 1kHz sinewave, DC–1kHz, at 1W into 8 ohms (left channel blue, right red; linear frequency scale).

CH Precision specifies the I1 as delivering a maximum continuous output power of 100Wpc into 8 ohms (20dBW). At our usual definition of clipping (ie, when the percentage of THD+noise in the amplifier's output reaches 1%), with continuous drive in both channels, the CH exceeded that spec, delivering 120Wpc into 8 ohms (fig.6, 20.8dBW). With both channels driven into 4 ohms (fig.7), the I1 clipped at 210W (20.2dBW), compared with the specified power into this load of 175Wpc (19.4dBW). Fig.6 was taken with 100% global feedback; the actual distortion is below the noise floor until the power reaches 50W or so. Repeating the 8 and 4 ohm tests with 0% feedback gave the same clipping power, but with about 20 times higher distortion below clipping (figs.8 & 9).

119CHI1fig06.jpg

Fig.6 CH Precision I1, analog input, 100% feedback, distortion (%) vs 1kHz continuous output power into 8 ohms, both channels driven.

119CHI1fig07.jpg

Fig.7 CH Precision I1, analog input, 100% feedback, distortion (%) vs 1kHz continuous output power into 4 ohms, both channels driven.

119CHI1fig08.jpg

Fig.8 CH Precision I1, analog input, 0% feedback, distortion (%) vs 1kHz continuous output power into 8 ohms, both channels driven.

119CHI1fig09.jpg

Fig.9 CH Precision I1, analog input, 0% feedback, distortion (%) vs 1kHz continuous output power into 4 ohms, both channels driven.

With the amplifier set to 100% feedback, I measured its THD+N percentage against frequency at a level of 12.65V, which is equivalent to 20W into 8 ohms, 40W into 4 ohms, and 80W into 2 ohms. The distortion levels were low even into 2 ohms (fig.10, gray trace), and, perhaps more important, didn't rise by much at higher frequencies. This was also true when the I1 was set to 0% feedback, though the distortion levels were again around 20 times higher (fig.11).

119CHI1fig10.jpg

Fig.10 CH Precision I1, analog input, 100% feedback, distortion (%) vs frequency at 12.65V into: 8 ohms (left channel blue, right red), 4 ohms (left cyan, right magenta), 2 ohms (gray).

119CHI1fig11.jpg

Fig.11 CH Precision I1, analog input, 0% feedback, distortion (%) vs frequency at 12.65V into: 8 ohms (left channel blue, right red), 4 ohms (left cyan, right magenta), 2 ohms (gray).

The shapes of the distortion-spuriae waveforms (fig.12, 100% feedback; fig.13, 0% feedback) suggest that the third harmonic was the highest in level, but with higher-order harmonics present with zero feedback. Spectral analysis indicated that with 100% feedback the second and third harmonics were equal in level, though at –104dB (0.0006%) both are negligible (fig.14). With 0% feedback, the higher-order harmonics are present at much higher levels (fig.15). Both second-order and higher-order intermodulation products at 20Wpc into 8 ohms with 100% feedback were negligible (fig.16). All the IM products increased as I reduced the feedback level, and with 0% feedback the second-order product reached a still-low –80dB (0.01%) (fig.17).

119CHI1fig12.jpg

Fig.12 CH Precision I1, analog input, 100% feedback, 1kHz waveform at 40W into 8 ohms, 0.0024% THD+N (top); distortion and noise waveform with fundamental notched out (bottom, not to scale).

119CHI1fig13.jpg

Fig.13 CH Precision I1, analog input, 0% feedback, 1kHz waveform at 40W into 8 ohms, 0.048% THD+N (top); distortion and noise waveform with fundamental notched out (bottom, not to scale).

119CHI1fig14.jpg

Fig.14 CH Precision I1, analog input, 100% feedback, spectrum of 50Hz sinewave, DC–1kHz, at 20Wpc into 8 ohms (left channel blue, right red; linear frequency scale).

119CHI1fig15.jpg

Fig.15 CH Precision I1, analog input, 0% feedback, spectrum of 50Hz sinewave, DC–1kHz, at 20Wpc into 8 ohms (left channel blue, right red; linear frequency scale).

119CHI1fig16.jpg

Fig.16 CH Precision I1, analog input, 100% feedback, HF intermodulation spectrum, DC–30kHz, 19+20kHz at 20Wpc peak into 8 ohms (left channel blue, right red; linear frequency scale).

119CHI1fig17.jpg

Fig.17 CH Precision I1, analog input, 0% feedback, HF intermodulation spectrum, DC–30kHz, 19+20kHz at 20Wpc peak into 8 ohms (left channel blue, right red; linear frequency scale).

Turning to the digital inputs, the I1's's AES/EBU and coaxial S/PDIF inputs locked to datastreams with all sample rates up to 192kHz. The optical input topped out at 96kHz. All digital inputs preserved absolute polarity. Apple's USB Prober utility identified the I1 as "CH Precision USB Audio 2.0" from "CH Precision," and confirmed that its USB port operated in the optimal isochronous asynchronous mode. The AudioMIDI utility revealed that the I1's USB port could handle 16- and 24-bit integer data at all sample rates up to 384kHz. With the volume control set to its normal maximum of "0dB," a 1kHz digital signal at –12dBFS resulted in output levels of 1.36V at the balanced preamp outputs and 20.55V into 8 ohms at the speaker outputs. The front-panel display indicated that the amplifier was clipping with digital data higher in level than –11dBFS. Therefore, I continued testing the digital inputs from the balanced preamplifier outputs with the volume control set to "–12dB."

The CH's impulse response with 44.1kHz data (fig.18) indicates that its reconstruction filter is a very short linear-phase type, with just a couple of cycles of ringing to either side of the single sample at 0dBFS. The manual says that the I1's reconstruction filter can be set to linear phase or minimum phase. However, neither the front-panel display nor the Android app offered a menu item for switching between the two reconstruction filters. Perhaps this choice will be the subject of a firmware update.

119CHI1fig18.jpg

Fig.18 CH Precision I1, digital input, impulse response (one sample at 0dBFS, 44.1kHz sampling, 4ms time window).

With 44.1kHz-sampled white noise upsampled to 352.8kHz (fig.19, red and magenta traces), the I1's response rolled off slowly above the audioband, not reaching full stop-band suppression until an octave above the Nyquist frequency of 22.05kHz (vertical green line). The aliased image at 25kHz of a full-scale tone at 19.1kHz (blue and cyan traces) is suppressed by only 10dB, though almost no other aliasing products are present. The CH Precision's digital frequency response with AES/EBU data at 44.1, 96, and 192kHz followed the same basic shape at each sample rate, with a slow rolloff that reached –3dB at 20kHz with 44.1kHz data (fig.20, green and gray traces). Some passband ripples present in the top audio octave with 44.1kHz data are absent at the higher sample rates.

119CHI1fig19.jpg

Fig.19 CH Precision I1, digital input, wideband spectrum of white noise at –4dBFS (left channel red, right magenta) and 19.1kHz tone at 0dBFS (left blue, right cyan), with data sampled at 44.1kHz (20dB/vertical div.).

119CHI1fig20.jpg

Fig.20 CH Precision I1, digital input, frequency response at –12dBFS into 100k ohms with data sampled at: 44.1kHz (left channel green, right gray), 96kHz (left cyan, right magenta), 192kHz (left blue, right red) (1dB/vertical div.).

When I increased the bit depth from 16 to 24 with a dithered 1kHz tone at –90dBFS (fig.21), the noise floor dropped by about 15dB, meaning that the I1 offers between 17 and 18 bits' worth of resolution. With undithered data representing a tone at exactly –90.31dBFS (fig.22), the three DC voltage levels described by the data were well resolved and the waveform was perfectly symmetrical, though some HF noise was present. With undithered 24-bit data, the result was a slightly noisy sinewave (fig.23).

119CHI1fig21.jpg

Fig.21 CH Precision I1, digital input, spectrum with noise and spuriae of dithered 1kHz tone at –90dBFS with: 16-bit data (left channel cyan, right magenta), 24-bit data (left blue, right red) (20dB/vertical div.).

119CHI1fig22.jpg

Fig.22 CH Precision I1, digital input, waveform of undithered 1kHz sinewave at –90.31dBFS, 16-bit data (left channel blue, right red).

119CHI1fig23.jpg

Fig.23 CH Precision I1, digital input, waveform of undithered 1kHz sinewave at –90.31dBFS, 24-bit data (left channel blue, right red).

Intermodulation distortion via the I1s' digital inputs was extremely low (fig.24). When I tested the digital inputs' rejection of word-clock jitter with 16-bit J-Test data, the odd-order harmonics of the LSB-level, low-frequency squarewave were all at the correct levels (fig.25, sloping green line), with no other sidebands visible. There were no sidebands visible with 24-bit J-Test data (fig.26).

119CHI1fig24.jpg

Fig.24 CH Precision I1, digital input, HF intermodulation spectrum, DC–30kHz, 19+20kHz at 0dBFS, 44.1kHz data (left channel blue, right red; linear frequency scale).

119CHI1fig25.jpg

Fig.25 CH Precision I1, digital input, high-resolution jitter spectrum of analog output signal, 11.025kHz at –6dBFS, sampled at 44.1kHz with LSB toggled at 229Hz: 16-bit AES3 data (left channel blue, right red). Center frequency of trace, 11.025kHz; frequency range, ±3.5kHz.

119CHI1fig26.jpg

Fig.26 CH Precision I1, digital input, high-resolution jitter spectrum of analog output signal, 11.025kHz at –6dBFS, sampled at 44.1kHz with LSB toggled at 229Hz: 24-bit AES3 data (left channel blue, right red). Center frequency of trace, 11.025kHz; frequency range, ±3.5kHz.

CH Precision's I1 Universal integrated amplifier offers excellent measured performance, and its variable negative-feedback control allows the addition of distortion to suit its owner's taste!—John Atkinson

COMPANY INFO
CH Precision Sàrl
ZI Le Trési 6D
1028 Préverenges
Switzerland
(41) (0)21-701-9040
ARTICLE CONTENTS

COMMENTS
RobertSlavin's picture

For an integrated amplifier with a base price of $38,000, I'd say the square wave at 10 kHz is poor.

I'm not sure how many phonograph listeners would be fans of having the amplifier transform the signal into a digital stream and then having the amp transform it again back to an analog signal.

tonykaz's picture

That's how Vinyl Records are made, isn't it?

Tony in Michigan

Bogolu Haranath's picture

These days the vinyl records are made from D to A ....... This integrated amp takes A to D to A ........ So, eventually what happens is, from recording A to D to A to D to A ........ Hope you are following this :-) ........

tonykaz's picture

Ada boy, good catch.

So, Vinyl people double down on digital "DDD".

Tony in Michigan

Ortofan's picture

... the Parasound HINT 6 - along with your choice of an Audi A4 or a BMW 330i.

Bogolu Haranath's picture

Come on ........ You should also include, Lexus ES 350, Acura TLX. Infinity lower priced models, Cadillac and Lincoln lower priced models, Mercedes C-class ...... also Volvo and Genesis :-) ........

tonykaz's picture

I was once in a large building where a NEW Audi 4 Series was dismantled down to it's smallest fasteners.

It's impossible to conclude that all the Engineering that went into all those Automotive Systems could in any way equate to an Amplifier. Every part of that Car is designed for and performs at a much higher level then a simple piece of audio Amplification.

Finding ways to defend Audio Gear's False Equivalencies has yet to be done by any Reviewer including the outrageous HP digging to his deepest depths of writing skills.

The Important ( missing ) detail from this Review is where this piece of gear should "Place" on this Reviewers "personal" sliding scale of Value/Price, just like anyone would do with any purchase.

We look to our Reviewers for their Subjective opinions. If they recommend, it should be reflected in their actual purchase ( or long term loan ) because their action is far more revealing than the structure of the concluding comment paragraph. ( isn't it? )

Reviewers are writers on a journey of building an "always better" performing music system, we readership follow along because we admire and approve. Reviews are candid appraisals from trusted authorities. ( or should be )

Tony in Michigan

Jason Victor Serinus's picture

Some reviewers are comfortable assessing price vs. performance and declaring whether something is a good value. I am not. I do not feel it my business to weigh in on anyone else's financial decisions. Nor do I believe that a reviewer has a responsibility to share their personal sliding scale of value/price, assuming they even have one, let alone suggest that others adopt it.

How a reviewer chooses to handle their money is their business, period. When I'm elected President, I'll share my tax returns.

The statement that reviewers "should" only recommend products that they either purchase or borrow long-term makes no sense to me.

tonykaz's picture

Please explain, if you can, what purpose a Review should have.

It seems a Review without judgements is what J.Gordon Holt railed against.

David in today's Audiophiliac Vlog gives his opinion of what a Review should be ( and include ) along with his judgement of the Reviewer's Credibility. ( I've felt Cordesman's many Audio related assessments to be unreliable or completely erroneous, from actually buying his product endorsements. )

Perhaps you feel yourself a Product Presenter, not a Reviewer. No harm in that, my industry employs Presenters to do all our Auto Shows.

The Auto Industry Reviewer Alex Dykes goes Deep into a Car, puts it into Context: tests, evaluates and describes all it's features, places it's price performance ratio. Audio's closest Dykes equivalent have been Tyll, HR & Steve G.

Reviewing is a Responsibility & Commitment, isn't it?

Stereophile is a Jury of 12 Reporting, Reviewing and bringing clarity to all things Audiophile.

Tony in Michigan

spacehound's picture

'Value' is a personal choice. Though I assume those who have made sufficient money to afford such things as this amplifier have not done so by making poor financial decisions.

The 'car' comparison does have a point though. A car is much bigger, which equals more materials, and contains far more components.
Also the car company, usually being large, has to financially support its sport clubs, cafeteria, health schemes, etc. A small company does not have these expenses.

tonykaz's picture

Are you hinting that there is some pathway of rationalization for this little gem to be considered a good financial decision?

More likely, the eventual buyer of this little Amp will be an inheritor of some Captain of Industry's Stock Portfolio & Estate. This thing is destined for a NEW Yacht with a Half Million$ Music System.

Some Audio Gear is designed to be Huberistic.

Hubris is the new and up & coming Class.

Tony in Michigan

spacehound's picture

The whole thing is irrational and still would be even if it was a 'budget' amp.

Because every input goes to the DAC. So the analog inputs have to go through an ADC to be changed to digital first. That's nuts, a sane designer would simply feed the analog inputs direct to the amp circuitry, which is analog.

As for 'rationalisation', we all know that many 'rich' people are rich because they had rich parents. But I didn't want to get into that stuff so I left it at "not making bad financial decisions".

Value.
There sometimes comes a point in some people's lives where cost simply no longer matters, so 'value' doesn't either.

This is what allows manufacturers such as CH to survive. Their customers may have money but there is no evidence that they have more 'discrimination' than anyone else. So they tend to automatically equate high price with high quality.

Meridian do the same. They are tiny to the point of invisibility in the genuine hi-fi world. So they make their money by supplying the 'not quite top flight' car manufacturers with their 'not quite top flight' car audio systems as an extra cost option. Jaguar/Land Rover is an example.

tonykaz's picture

...is showing us Audio gear that the Super Rich choose from.

From me, I'd describe this thing as Mid-Fi for the children of the top 1% and even then I still can't grasp a concept understanding, I'm feeling like Alice in Wonderland.

It must be good, it got 4 pages.

Tony in Michigan

tonykaz's picture

...equates to Smugnorant.

Tony in Michigan

ps. the construct "smugnorant" is Open Sourced, as far as I know.

tonykaz's picture

"Down Memory Lane"
Another piece of superb Journalism that captures our entire Audio Hobby Trajectory with accurate insights and correlations.

One hell-of-a-piece of Storytelling.

Tony in Michigan

ps. I met him and Tyll in 2011 fully well realizing that I'd met two Greats, you only meet guys like this once in a Decade or so.

Ortofan's picture

... Empire turntable - and bought records instead of speakers at E. J. Korvette.

Speaking of XAM speakers, that must be where the concept for the first WAMM speaker originated:
https://www.youtube.com/watch?v=d36gtE7DOlg

Bogolu Haranath's picture

Mark Levinson HQD loudspeaker system is somewhat similar ....... They were kinda reviewed in Stereophile by JGH :-) ..........

es347's picture

..may attract some folks but for that amount of moolah one can own some very good separates. Re comments relating to cost comparisons between cars and audio equipment, it’s tough sledding to justify say a $150K amplifier or something like the MSB DAC to goes for $90K. Do I chastise the guy who buys one...not at all. How someone spends their $$ is their business. But if I’m forced to choose between a D’Agostino amplifier and the BMW i8 I’m going with the car..

spacehound's picture

$38,000 'base' then another $3,000 for a USB port and another $5,000 for an ethernet port.

That's approaching the price of my Mercedes SLK55, made by a company with a 130 year 'provenance', a known good reputation (though maybe not entirely justified), and the car has the world's most efficient V8 (and excluding $100,000 plus 'supercars', one of the most powerful).

These two guys are just 'serial company founders'. No provenance at all, and their several companies are almost unknown in the hi-fi world.

On top of that, it's a stereo amplifier, which is hardly rocket science, but it won't work at all unless you have the Android app, Android being known for its 'stability', they say. In near 40 years of writing operating systems (and a few other things) I have never known anything LESS stable than Android, and even worse, Google are talking of discontinuing it and replacing it with something else.

And just HOW many are born every minute? :)

tonykaz's picture

Our Man in Europe.

Our insightful Corresponding Journalist.

'serial company founders' bringing us another, Gift ? , keep us in suspense no longer.

Who are these CH people? What success have they enjoyed and who are the intended owners of their products?

Should we anticipate the Curtain being pulled back?

Tony in Michigan

ok's picture

..save for electronics modern cars have not actually been evolved any more than amplifiers or speakers have done for the past seventy years or so. Any preposterous vice that applies to hi-end audio applies also to luxury cars minus the plus that the former are for the most part aftermarket consuming- maintenance- tax- free and thus of considerable resale value. It is hard for big money to be spent in a meaningful way, but big money has to be spent one way or another anyway.

georgehifi's picture

"For an integrated amplifier with a base price of $38,000, I'd say the square wave at 10 kHz is poor."

If that's the output section of a linear class-A/B there is something not right, as it looks much more like the output of a dac's test square wave, not a linear amp, as I've never seen ringing on square waves of the leading and trailing edge of a linear amp!!! (somethings doesn't seem right)

Cheers George

John Atkinson's picture
georgehifi wrote:
If that's the output section of a linear class-A/B there is something not right, as it looks much more like the output of a dac's test square wave, not a linear amp . . .

As I explain in the measurements, the shape of the squarewave is due to the CH I1 in its default mode digitizing its inputs.

John Atkinson
Editor, Stereophile

spacehound's picture

It leads me to wonder if measuring with 'square' waves on a box that digitizes its inputs is worth doing at all.

A square wave, by definition, has rise and fall times of zero and so includes all frequencies. This of course is impossible in practice.

And in actual practice the 'almost a square wave' which is as close as we can get will break the Shannon/Nyquist sample rate theorem (it's not a theory, being a theorem it's actually true).

So all such a measurement can do is show the shape of the inbuilt DAC's output filter. So what's the point?

georgehifi's picture

Thanks JA, sorry didn't read that bit.

So it can be fed an analog signal without digitizing it when not in default mode? Did the 1k and 10k square waves look normal then?

Cheers George

John Atkinson's picture
georgehifi wrote:
So it can be fed an analog signal without digitizing it when not in default mode? Did the 1k and 10k square waves look normal then?

Yes, in bypass mode, which is how JVS compared the I1's digital performance with that of the dCS Rossini fed into one of the CH's analog inputs.

John Atkinson
Editor, Stereophile

RobertSlavin's picture

I have a few concerns with this review and with this product.

Concerning the product: Not only is the phono input signal digitized by the integrated amp but all analog signals are digitized. This is indicated in the Analog Inputs section of the Specifications section on the amplifier on the company's web site. Also, Mr. Atkinson indicates it by saying in the measurement section when he says that the digitization affects the "analog input" squarewaves.

I am skeptical of the wisdom of this approach to amplification.

I could not find in Mr. Serinus' review the fundamental point that ALL analog signals are digitized by the l1. The digitization means that any signal from a phonograph, tuner, reel-to-reel, cassette deck, or even CD player without a digital signal will be digitized. This should have been made clear in the review.

Maybe I missed the point in a review of a complicated product but surely this is one of the most fundamental things to say about this amplifier and, at best, the point is not prominent.

In the review we learn of the amp's abilities to handle phonographic signals only through Mr. Serinus' friend Gary Forbes. Mr. Forbes only listens for one day. The last sentence of the second paragraph of the section on the phono amplification performance suggests to me that Forbes prefers the sound with the l1's internal clock to that with the Scarlatti clock. However, the last sentence of the third paragraph says the reverse. I wish this could be clarified.

Mr. Atkinson says Serinus compared the l1 with the Rossini using a bypass mode. Maybe I missed it in this review of an admittedly complicated product, but I failed to see this explanation in the review.

The fact that this poor squarewave was an artifact of the digitization of the signal doesn't change my concern about it.

Jason Victor Serinus's picture

Some writers repeat their statements over and over to ensure that readers don't miss them; I prefer to state what I have to say once, as clearly as possible, and trust that readers who care about a product as complex as this will take the time to absorb everything in what, online, amounts to an unusually long four-page review. Note that the copy was actually considerably longer than this before editing.

What you believe is missing is definitely in the review. Here are four quotes that address your points:

1. Nonetheless, the I1's optional phono stage operates mostly in the digital domain—as is not the case in CH's P1 phono preamplifier ($31,000), which operates exclusively in the analog domain, and which our Michael Fremer uses with CH's X1 power supply ($17,000).

The analog gain stage that the I1 dedicates to its phono section is identical to the analog gain stage in the P1. "The I1 has a digital heart, including the phono stage," Pasche said. "The phono stage is also current-based rather than voltage-based, and is far more suitable to lower-resistance MC cartridges that deliver a lot of current." The I1's phono signal path is: input connector->analog gain stage (the most important stage of the signal path, which raises the signal from cartridge level to line level)>A-to-D conversion to 384kHz>digital signal processing via a choice of RIAA, eRIAA, EMI, Columbia , Teldec, and Decca EQ curves>DAC and power amp.

2a. Although neither manual nor website offers instruction in how to operate the Control app, it's extremely easy to use once someone's shown you how. (Bless you, Ralph Sorrentino.) Whenever I wanted to reconfigure the I1 to connect an external clock, switch between the I1's internal DAC and my Rossini DAC, or activate volume bypass to let the Rossini control volume, change inputs, etc., I grabbed the Android tablet and succeeded, without pain.

2b. To switch between the I1's DAC and the Rossini DAC, I had to move an Ethernet link from the MacBook Pro to the Rossini DAC, then switch inputs on the I1 from USB to Analog In XLR, ensure that the I1's volume control was set to Bypass, and select the appropriate audio zone in Roon. I did this so many times that I got the entire procedure down to under 90 seconds.

2c. Once everything was correct . . .
Ultimately, I found that the best way to get a handle on the CH I1's sound was to compare the sound of its DAC to that of the dCS Rossini DAC, using the I1 for amplification, bypassing the amplifier's A/D converter. Note, however, that by the time you read this, the Rossini's software will have been upgraded to v.2. If the difference between Rossini v.1 and v.2 is anywhere near as great as that between v.1 and v.2 of dCS's Vivaldi DAC, some of the conclusions that follow will no longer apply. Then again, CH Precision might also issue a downloadable software update by publication time. Meanwhile, I had to start somewhere.
---

Questions have been raised about my failure to make a judgment call about digitizing analog signals. I was 100% certain that readers who object to such a process would make the judgment call on their own, without even hearing the product. Multiple comments have now demonstrated that I was correct.

jason

RobertSlavin's picture

The passages Mr. Serinus quotes do not address my concerns.

1. None of them make clear that ALL analog signals, not just phono signals, coming into the l1 are normally digitized. This is a fundamental point about the l1 and should have been made clearly and early on in the review. There is a lot of discussion of the technical features of this amplifier but what is perhaps the most important thing isn't mentioned.

2. Mr. Serinus does not make clear what the "bypass mode" is. Does it just leave an analog power amp section? Or does it introduce an analog pre-amp line stage?

3. Which mode did Mr. Forbes prefer when listening to a phonograph -- the 1l with internal clock or with the Scarlatti external clock? The passage in the review suggest one and than the other.

John Atkinson's picture
RobertSlavin wrote:
The passages Mr. Serinus quotes do not address my concerns. . . None of them make clear that ALL analog signals, not just phono signals, coming into the l1 are normally digitized.

This was addressed in the review when I wrote "There is nothing in the manual about changing the sample rate for the analog inputs, nor do the front-panel or Android-tablet setup menus offer options for this."

RobertSlavin wrote:
This is a fundamental point about the l1 and should have been made clearly and early on in the review.

With such a ridiculously complex product, yes, this should have been emphasized but it was discussed in the review, as was the fact that Bypass avoids the digitizing of line-level input signals.

John Atkinson
Editor, Stereophile

Bogolu Haranath's picture

Pass labs INT-250 integrated amp, 250 WPC/8 Ohms ........ Weighs 105 pounds ...... All analog ...... $12,000 :-) .........

spacehound's picture

...buy an amplifier. If you want a DAC buy a DAC.

Don't buy a box that mixes the two. DAC technology changes much more often than amplifier technology does and how often do you hear this BS about "We will supply improved DAC modules as the technology improves". It rarely happens and if it does it still locks you in to that manufacturer. Also you are left with the original module which, unlike an older separate DAC, won't be any use for anything else.

And anyway, taking an analogue input, such as phono, using an ADC to digitize it, then feeding it into the DAC section to get it back to analogue for the amplifier section is moronic.

Bogolu Haranath's picture

$52,000 integrated amp, which can do soo many things may be a better value than, $48,000 phono stage :-) .........

spacehound's picture

$48,000 for a phone stage, $100,000 plus for a pair of their monoblocks.

It's complete nonsense.

dial's picture

At last a competitor for Dartzeel, ah but no, wait, this is more than double the price. Hope the sound is far better.

spacehound's picture

Or Soulution.

What is it with Swiss audio? It is all extremely high-priced yet although Switzerland is a wealthy country the labour costs and the overall cost of living, though high, are not vastly higher than the rest of northern Europe (including the UK) or the USA.

Are they in a price cartel (which I believe is not illegal, or maybe not policed, in Switzerland) to con the rest of the world into thinking there is something 'special' about their audio products so they can make their ludicrous prices acceptable "because they are from Switzerland"?

And leaving aside the digital inputs on this particular amplifier, amplifier design has been extremely well-understood for a long time, and achieving near-perfection in amplifiers is not especially demanding. So much so that you quickly come to a point where not just the 'law of diminishing returns' kicks in, but where you get no extra returns at all for the price you have paid.

I suggest that had the reviewer been 'blind' to the amplifier (just put it behind a small screen, such as a coffee table on its side, no need for anything more sophisticated), he would not have been honestly able to say it was 'better' than a 5,000 - 10,000 dollar Naim or Pass. (Note that I am not suggesting an 'immediate' and direct blind comparison here as done in a 'formal' blind test with swap-overs and such, just hiding what amplifier it is.)

Ortofan's picture

... you should look at even lower priced units.

An Absolute Sound reviewer summed up his evaluation of the $900 Yamaha A-S801 with the statement that "for lots of people who just want a good hi-fi to play their music on, a hi-fi may be a once-in-a-lifetime purchase. For those people, or for anyone who wants good sound with lots of flexibility at a reasonable price, the Yamaha A-S801 integrated amplifier would be my top recommendation. It may be the only hi-fi electronics purchase they will ever need."
http://www.theabsolutesound.com/articles/yamaha-a-s801-integrated-amplifier-and-yba-11-bluetooth-wireless-adapter/?page=3

At $1,600, the Denon PMA-1600NE won a Hi-Fi Choice comparison test by surpassing amps from Arcam, Hegel, NAD, Technics and Yamaha.
https://files.hifiklubben.com/4a500a/globalassets/tester/denon/2017/pma-1600ne-hfc-group-test-verdict.pdf

Why hasn't Stereophile tested these amps?

funambulistic's picture

The Yamaha A-S801 has excellent test results ( https://www.audioholics.com/amplifier-reviews/yamaha-a-s801-amplifier-review/yamaha-a-s801-measurements ) and sounds fantastic to my ears. A while back, another reader and I suggested the Yamaha R-N803 receiver for review, but JA said Stereophile does not review receivers (which is not true: https://www.stereophile.com/content/outlaw-audio-rr2160-stereo-receiver for example) and directed readers to Sound & Vision. Perhaps he thought we were referring to a HT receiver...

dial's picture

Well, I must admit that life in the land of banks is pretty expensive. For everything you buy : food, all gears, clothes and of course houses. That's why people there are well paid, but all vanishes when you need electricity, water, clothes etc etc Everything is imported, so Nagra, Goldmund, Piega, Swiss Physics (remember them ?) are so high priced, but it's the same in France and hifi there (also in England or Germany) isn't so expensive. So I cannot really answer your questions, sorry. Perhaps is this a choice ?
For ABX, I've made many, the latest one for several speakers, all modern productions from recent years, tend to sound the same, I Think because everyone (even for tubery) wants a flat response...

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