Dan D'Agostino Progression Mono monoblock power amplifier Measurements

Sidebar 3: Measurements

I initially measured one of the Dan D'Agostino Master Audio Systems Progression Mono monoblocks (serial no. PMO26P) with my Audio Precision SYS2722 system (see the January 2008 "As We See It"). Before doing any testing of a power amplifier, I precondition it by running it at one-third its specified power into 8 ohms for 60 minutes. This power level results in the highest thermal stress on the output devices of an amplifier having a class-B or -AB output stage. After an hour driving 167W into 8 ohms, the temperature of the Progression's top panel and heatsinks was fairly high, at 109.8¯F (41.3¯C). With the amplifier cold, the THD+noise at this power level was 0.04%; after the hour, it had dropped to 0.025%.

The voltage gain into 8 ohms for the balanced input was 29.7dB, and the input preserved absolute polarity, the XLR jack being wired with pin 2 hot. The input impedance at low and middle frequencies was as specified, at 100k ohms, though it dropped inconsequentially at 20kHz, to 70k ohms. The output impedance was high for a solid-state design, at 0.44 ohm at 20Hz and 1kHz, rising slightly to 0.49 ohm at 20kHz. Consequently, the response with our standard simulated loudspeaker varied by ±0.3dB (fig.1, gray trace). The amplifier offered a wide small-signal bandwidth, the output into 8 ohms (blue trace) not reaching –3dB until 180kHz. Consequently, the Progression's reproduction of a 10kHz squarewave (fig.2) featured very short risetimes with, commendably, no overshoot or ringing apparent.

1017DagProfig01.jpg

Fig.1 Dan D'Agostino Progression Mono, frequency response at 2.83V into: simulated loudspeaker load (gray), 8 ohms (blue), 4 ohms (magenta), 2 ohms (red) (0.5dB/vertical div.).

1017DagProfig02.jpg

Fig.2 Dan D'Agostino Progression Mono, small-signal, 10kHz squarewave into 8 ohms.

1017DagProfig03.jpg

Fig.3 Dan D'Agostino Progression Mono, spectrum of 1kHz sinewave, DC–1kHz, at 1W (blue) and at 100W (red) into 8 ohms (linear frequency scale).

Measured with the input shorted to ground, the Progression offered a wideband, unweighted signal/noise ratio of 57.5dB, ref. 1W into 8 ohms. This was primarily due to the presence of noise with a center frequency of 923kHz. Concerned that the amplifier was picking up some RF interference that was being demodulated, I turned off all the CFC and LED lights in my test lab, but the noise persisted. The ratio improved to 80.1dB when the measurement bandwidth was restricted to 22Hz–22kHz, and to 87dB when the reading was A-weighted. The blue trace in fig.3, taken at 1W into 8 ohms, reveals that the primary source of noise is magnetic interference at 60Hz and its odd-order harmonics, presumably stemming from that massive toroidal transformer. However, at higher powers (red trace), the spuriae at 120Hz and its harmonics increase in level.

When I measured how the percentage of THD+N varies with output power into 8 ohms and 4 ohms, I got lower power than specified. With "clipping" defined as when the THD+N reaches 1%, the Progression clipped at 460W into 8 ohms (26.6dBW), which is 0.4dB lower than the specified 500W, and 690W into 4 ohms (25.4dBW), this 1.6dB lower than the specified 1kW into this load. When I tried to test the clipping power into 2 ohms, the amplifier turned itself off at 750W and just before then, I could hear the amplifier acoustically buzzing, and a burst of static through the FM radio I keep tuned to NPR in the test lab.

When Dan D'Agostino received the initial preprint of this review, he was concerned that this behavior indicated that the amplifier had suffered some sort of damage on its way to me from Jason Serinus. (After it had been picked up from Jason, the amplifier had been shipped to a dealer before it eventually found its way to me.) I was therefore sent a new sample of the Progression Mono (serial no. PMO100P), which had been fully checked out on the test bench, to test.

The voltage gain, input impedance, and frequency response of this sample were identical to those of the first, though the output impedance was slightly lower, at 0.32 ohms, and there was no RF noise present at the amplifier's output. And when I examined how the percentage of THD+N varies with output power, this sample clipped at 595W into 8 ohms (fig.4), which is 0.8dB higher than the 500W specification. Into 4 ohms, the clipping power was 934W (fig.5); though this is 0.3dB lower than the specification, I don't hold the wall voltage constant during these tests, feeling that this is more representative of an amplifier's behavior in a typical system. The wall voltage was 120.1V with the amplifier idling, but had dropped to 115.4V at 934W into 4 ohms.

1017DagProfig04.jpg

Fig.4 Dan D'Agostino Progression Mono, distortion (%) vs 1kHz continuous output power into 8 ohms.

1017DagProfig05.jpg

Fig.5 Dan D'Agostino Progression Mono, distortion (%) vs 1kHz continuous output power into 4 ohms.

I examined how the THD+N percentage varied with frequency at a fairly high level, 28.3V, which is equivalent to 100W into 8 ohms and 200W into 4 ohms. (The front-panel meter's needle lay halfway between 100W and 500W at this level.) The results are shown in fig.6: the distortion and noise remain low over most of the audioband, with only relatively small rises in the top octave and into lower impedances. However, when I examined the waveform of the THD+N after notching out the fundamental (fig.7), I was surprised. Although the THD+N is low in this graph, at 0.027%, you can see a double spike in the residual waveform (red trace) that coincides with every zero-crossing point in the signal's waveform (blue). This behavior suggests that the Progression's output stage lacks sufficient bias current, something that I find surprising given Dan D'Agostino's history of designing amplifiers with high, even class-A bias.

1017DagProfig06.jpg

Fig.6 Dan D'Agostino Progression, THD+N (%) vs frequency at 28.3V into: 8 ohms (blue), 4 ohms (magenta), 2 ohms (red).

1017DagProfig07.jpg

Fig.7 Dan D'Agostino Progression Mono, 1kHz waveform at 100W into 8 ohms, 0.027% THD+N (top); distortion and noise waveform with fundamental notched out (bottom, not to scale).

Fig.8 shows the spectrum of the amplifier's output while it drove 50Hz at 100W into 8 ohms; a regular series of high-order harmonics can be seen, correlating with the waveform of the spuriae shown in fig.7. The second and third harmonics are similar in strength in this graph, respectively lying at –76dB (0.015%) and –80dB (0.01%). The harmonic spectrum was almost identical with the amplifier driving 50Hz into 4 ohms (not shown).

1017DagProfig08.jpg

Fig.8 Dan D'Agostino Progression Mono, spectrum of 50Hz sinewave, DC–1kHz, at 100W into 8 ohms (linear frequency scale).

Although the THD+N percentage didn't rise by a great deal at high frequencies, the Progression performed relatively poorly when I examined the spectrum of its output as it drove an equal mix of 19 and 20kHz tones into 8 ohms at a peak level of 100W (fig.9). While it is true that none of the intermodulation products is particularly high in level—the difference product at 1kHz lies at a respectable –80dB (0.01%)—an alarming number of higher-order intermodulation products is visible in this graph. These all disappeared, however, when I reduced the peak level to 1W (fig.10).

1017DagProfig09.jpg

Fig.9 Dan D'Agostino Progression Mono, HF intermodulation spectrum, DC–30kHz, 19+20kHz at 100W peak into 8 ohms (linear frequency scale).

1017DagProfig10.jpg

Fig.10 Dan D'Agostino Progression Mono, HF intermodulation spectrum, DC–30kHz, 19+20kHz at 1W peak into 8 ohms (linear frequency scale).

The Dan D'Agostino Master Audio Systems Progression Mono is a powerful amplifier indeed, and the measured performance of the second sample does suggest that the first sample I received had somehow suffered during its travels. I was still puzzled by what appeared to be crossover distortion. However, it is fair to note that the Progression Mono measured very similarly to Dan D'Agostino's more expensive Momentum monoblock, which Michael Fremer very favorably reviewed in February 2013 and which I declared to be "well-engineered."—John Atkinson

COMPANY INFO
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PO Box 89, 7171 E. Cave Creek Road, Unit K
Carefree, AZ 85377
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COMMENTS
georgehifi's picture

Agostino Progression Mono monoblock:
"Consequently, the Progression's reproduction of a 10kHz squarewave (fig.2) featured very short risetimes with, commendably, no overshoot or ringing apparent."

Linear Tube Audio ZOTL40 Mk.II power amplifier:
Read more at https://www.stereophile.com/content/linear-tube-audio-zotl40-mkii-power-amplifier-measurements#dF5kOX8x0c8mEESx.99
"the response extended very high, not reaching –3dB until 120kHz, this correlating with the superbly defined shape of a 10kHz squarewave into this load (fig.2). A slight amount of overshoot is visible in this graph, though there is no ringing."

These are great to see, and it's great that from the comments they're appreciated by the measurement team and readers alike.

Though when Class-D amps are measured, they normally have horrendous looking square waves, but these days Stereophile use low power special bench test filters to filter them so they look good to the readers. This is not representative of what's being sent to the speaker in normal everyday use.
This is from the days when Stereophile didn't use the "special" filters, to show what's really coming out the speaker terminals. I believe it should go back to this.
https://www.stereophile.com/images/archivesart/805CIAfig2.jpg

Cheers George

a.wayne's picture

John, NPR ! not surprised all that RF hash did you in ... :)

Ortofan's picture

... "musical"? Is it the non-flat frequency response into a typical loudspeaker load? Is it the series of distortion products that are up to 20dB above the noise floor of a CD, let alone that of a higher bit-rate recording?

Why not perform a Hafler type straight wire differential test test on every amp that comes in for review?
https://www.stereophile.com/content/manufacturers-comment-0

Or a level-matched A/B comparison as demonstrated by Harbeth's Alan Shaw: https://vimeo.com/137001237

Perhaps a direct comparison with the Rotel RB-1590?
http://www.bwgroup.ch/wp-content/uploads/2016/11/Hi-Fi-News-11-2015-Test-Rotel-RC-1590-RB-1590.pdf

John Atkinson's picture
Ortofan wrote:
Why not perform . . . a level-matched A/B comparison as demonstrated by Harbeth's Alan Shaw: https://vimeo.com/137001237

See my fairly recent writing on such tests at www.stereophile.com/content/simple-everything-appears-simple.

John Atkinson
Editor, Stereophile

Ortofan's picture

... exceedingly straightforward.
Match the input sensitivity of the two amps being compared using a test tone and a voltmeter; find the clipping point of the lower powered amp (and then keep the input volume for both amps below that level); then switch back-and-forth between amps at will.
Is there something he's missing?

Have you considered acquiring one of the Audio by Van Alstine ABX Comparator units and having the Stereophile reviewers give it a try?
https://www.dagogo.com/audio-by-van-alstine-abx-comparator-review-part-1-audio-store-wiring/
https://www.dagogo.com/audio-by-van-alstine-abx-comparator-review-part-2-trials/
https://www.dagogo.com/audio-by-van-alstine-abx-comparator-review-part-3-new-twists-conclusion/

John Atkinson's picture
Ortofan wrote:
Mr. Shaw makes the comparison testing seem exceedingly straightforward. Match the input sensitivity of the two amps being compared using a test tone and a voltmeter; find the clipping point of the lower powered amp (and then keep the input volume for both amps below that level); then switch back-and-forth between amps at will. Is there something he's missing?

Yes, such testing tend to produce false negatives, ie, not detecting a difference when one actually exists. So unless you want to "prove" that no differences exist, they are no more useful than sighted listening. I do admit, however, that the latter tend to produce false positives.

Ortofan wrote:
Have you considered acquiring one of the Audio by Van Alstine ABX Comparator units and having the Stereophile reviewers give it a try?

I tried out the original ABX box 30 years ago and found, for example, that I could identify absolute polarity with statistical significant certainty. I have also identified amplifier differences under blind conditions, even differences between series capacitors of different types. Yet those results were all dismissed by the proponents of blind testing. So what would be the point in repeating all that work? No-one would be convinced by the results, on both sides of the debate.

John Atkinson
Editor, Stereophile

Ortofan's picture

... determined to be statistically significant, then on what basis were they dismissed?

Would no one at all be convinced by the results of blind/level-matched comparisons? There are probably those readers who pay no heed to the test measurements you publish, yet you expend the time and effort to make them. Results of an AB(X) test would provide additional input to the evaluation/decision process for those who might place some value on the outcome.

Lastly, Harbeth's Mr. Shaw has a standing offer of a free pair of his speakers to anyone who can distinguish between two amplifiers in a blind/level-matched comparison. Have either you or one of the reviewers on your staff considered taking him up on his challenge?

John Atkinson's picture
Ortofan wrote:
If the results of your ABX comparison trials were determined to be statistically significant, then on what basis were they dismissed?

Because the results were contrary to what so-called "objectivists" believed. Demands for reviewers to participate in blind testing come from those who want such tests to "prove" there are no audible differences.

Ortofan wrote:
Results of an AB(X) test would provide additional input to the evaluation/decision process for those who might place some value on the outcome.

Did you not read the article linked in an earlier posting of mine? Performing a blind test that produces legitimate results when there are small but real audible differences is not a simple matter. And if no-one takes any notice of the results if they conflict with their beliefs, what would be the point?

BTW, my opinion is formed by having taken part in more than 100 such tests as organizer, proctor, and test subject since my first in 1977. I think it fair, therefore, to ask how many tests you have taken part in to be so sure of their efficacy?

Ortofan wrote:
Lastly, Harbeth's Mr. Shaw has a standing offer of a free pair of his speakers to anyone who can distinguish between two amplifiers in a blind/level-matched comparison. Have either you or one of the reviewers on your staff considered taking him up on his challenge?

I don't see any benefit in participating in Mr. Shaw's marketing.

John Atkinson
Editor, Stereophile

John Atkinson's picture
John Atkinson wrote:
Ortofan wrote:
If the results of your ABX comparison trials were determined to be statistically significant, then on what basis were they dismissed?

Because the results were contrary to what so-called "objectivists" believed. Demands for reviewers to participate in blind testing come from those who want such tests to "prove" there are no audible differences.

For more on this denial of facts by believers in "scientism," see this essay I wrote 23 years ago: www.stereophile.com/asweseeit/894awsi/index.html.

John Atkinson
Editor, Stereophile

Ortofan's picture

... I've been involved with approximately one blind/masked test per year - though never with consumer grade audio equipment. Whether the outcome is as expected or not, the methodology has proven useful as a means to preclude certain factors from influencing the results of a comparison test. If you doubt the validity of such a testing protocol, by what other means might you suggest eliminating such factors as unmatched levels, knowledge of the brand identity and product appearance from potentially influencing the outcome of a comparison test?

John Atkinson's picture
Ortofan wrote:
On average, during the past four decades I've been involved with approximately one blind/masked test per year - though never with consumer grade audio equipment.

Thank you. My experience of those who demand blind tests of reviewers is that they have never taken part in such tests so have an uncritical belief in the results of such tests. You are a rare exception.

Ortofan wrote:
Whether the outcome is as expected or not, the methodology has proven useful as a means to preclude certain factors from influencing the results of a comparison test.

Of course. But without additional testing you have no idea if your blind test protocol is sufficiently sensitive to detect small but real differences. If, for example, your test cannot detect something that is known to be audible, such as a 1dB difference in level, then any results it produces will be meaningless. There must have been interfering variables that you have not accounted for. One such is even the fact that the listener's mental state in a test is different from what it is in conventional listening. I mentioned this in the articles of mine that I have linked in earlier responses, which I assume you have read. If you have not, then please do so.

Ortofan wrote:
If you doubt the validity of such a testing protocol, by what other means might you suggest eliminating such factors as unmatched levels, knowledge of the brand identity and product appearance from potentially influencing the outcome of a comparison test?

Level matching is trivially easy. Knowledge of the brand is not that important for professional reviewers because they audition so many products over so many years that they don't have a horse in the race. If you doubt that, then I have to ask why you subscribe to Stereophile at all?

John Atkinson
Editor, Stereophile

Ortofan's picture

... is a key gating factor in the process of developing a new product and the decision of whether or not to release it to production. If the test panel determines that the new product is in some manner better/preferable to (or at least discernibly different from) an existing one, then the product is more likely to get approved for production. If the test panel cannot make a statistically significant distinction, then its future might hinge on whether or not it can be made more reliable or brought to market at a lower cost than the competition.

Also, certain individuals are more or less amenable to participating in blind/masked comparison testing, so you use multiple subjects. Likewise, their mental state can vary from day to day, so you conduct multiple trials.

Agreed that level matching (of electronics at least) is a simple process - but do your reviewers always (or ever) do it? With digital disc players and DACs it's not uncommon for the output from a 0dBFS input to exceed a nominal 2.0V level.

Continued interest in Stereophile is because you still conduct and publish the results of objective tests. For example, I'd prefer to spend $3K (or $6K for a bridged pair) for an amp that measures like the Benchmark AHB-2 rather than an order of magnitude more for this particular one, whose measurements, IMO, leave significant room for improvement.

mauidj's picture

when I read stuff like this...

"I also began to realize that while my reference Pass Labs XA 200.8 monoblocks sound gorgeous, and convey a special glow around the edges of each note, the Progressions illuminated each note from within."

Is it just me?

JoeinNC's picture

No, it’s not just you.

supamark's picture

he has synesthesia. I do, and sounds have palpable textures to me with some visual as well. For example, in a nice live hall, reverb tends to have an enveloping syrupy quality to me (denser reverb, thicker syrup) with a bit of visual glow (color and intensity dependant on how bright and dense respectively the reverb is).

Maybe you're simply mocking what you don't understand, and that's really not a good look.

tonykaz's picture

The Electro stuff was gorgeous sounding, I don't know why, I'm an engineer, my partner was an engineer.

But that Electrocompaniet could make our big Thiel CS3 play beautifully, much more beautifully than any other gear we ever got our hands on.
We couldn't get the Krell stuff but I had access to the Krell people who supplied me with the Koetsu Phono Cartridges. The only Electro Sales I lost were to Krell Amps.
Even Michael Jackson and Quincy Jones were Electocompaniet lovers.

Gosh darn it, some electronics make your music system sound superb. Now, we are realizing PrimaLuna stuff is like that. Go figure.

There's mediocre ho-hum stuff and there's certain pieces that are way too good to be true but true they are.

A good way to tell which is which is to look at eBay used prices for gear. The Krell stuff holds it's price well, so does Schiit stuff.

Tony in Michigan

ps. I'm waiting to learn if Jason decides to have this pair of Amps or keeps his Pass

foxhall's picture

My very first exposure to high end audio was in the mid 1990's and the system a very popular combination of Apogee, Krell and Wadia. I remember the owner remarking he preferred 3 hours of warm up for his Krell amplifiers.

Has the optimal warm up time decreased with innovation? Do you think there will ever be a time when A/B amplifiers won't need warm up time?

Do some manufacturers include warm up best practices in their manuals? My Parasound Halo gear manuals don't include this type of information so I was just wondering.

Johnny2Bad's picture

Thank you, thank you, thank you Jason for your written words "...The Progression's enclosure and chassis—in this case, the same thing—is machined from a solid billet of aluminum. ..."

Finally, a journalist who gets it ... I tire of reading, in audio and other pursuits, of a product described as "billet aluminum". A billet of aluminum is a lump of metal. There is no reason to purchase one unless a lump of metal was what you wanted in the first place, versus a functional, machined device, and they can be had at much lower cost at your metal supplier versus your audio vendor or automotive performance parts reseller.

Now, if we can only banish the fictitious product, "aircraft grade aluminum" (or it's sister, the Ford Motor Company's "military grade aluminum", another product that does not actually exist), the world will be much improved.

Of course, strictly speaking, you could have left out the "solid" part, as it's redundant (by definition, all billets are solid) but I'm still going to thank you for getting it mostly right.

tonykaz's picture

This Amp chassis is made up of multiple pieces.

It's CNC machined , no big deal considering the tooling we have today. It does not have all that exotic & beautiful a surface finish on the inside.

These aluminum pieces are not heavy, making me wonder about the power transformer.

and

making me wonder if the power supply benefits from one of those $10,000+ Power Conditioners -- or -- has Mr.D'Augostino figured out how to make a power supply that's not susceptible to what ever those Power Conditioners are supposed to filter out.

And

Does this amp need one of those aftermarket Power Cords for $5,000 to help it realize it's full potential ?

And

Of course: will these Amps replace the Pass 'house' reference Amps?

Way back in 1985ish, one of my customers went and purchased a 200W. Krell Stereo Amp that took two people to carry into the guy's house. phew

I was there to see the unboxing of the Beautiful Amp but couldn't see myself carrying the Krell line, the stuff is sooooooo darn heavy and with sharp edges. ouch.

I must say that I've admired Krell but it always seemed to be "Over-kill" type of gear.

The big Chord stuff is even greater Eye Candy.

Tony in Michigan

Allen Fant's picture

J.A.

recently you had mentioned using a disc of tracks from HiFi News-
where can I get this disc? If it not avail for purchase, is it possible to get a copy that you use? I can send a blank CD-r.
Thank You

John Atkinson's picture
Allen Fant wrote:
J.A. recently you had mentioned using a disc of tracks from HiFi News-where can I get this disc?

This was in a reprint of a review first published in 1987 and the CD is long out of print. Send me an email at JAtkinson at enthusiastnetwork dot com.

John Atkinson
Editor, Stereophile

pma's picture

From JA measurements we can see that
A) there is quite high crossover distortion in this amplifier which has not been corrected by appropriate global negative feedback. IMO the level of this crossover distortion is somewhere at the limit of audibility, so it might be audible or not. However, well engineered power amplifier should NOT exhibit such high level of crossover distortion.
B) We can see modulation of amplitude response into dummy speaker load that is quite high and we may say it would be audible. Again, not enough feedback.

Though it may be a nice piece of equipment, the engineering result is disappointing and I am sure that this is not the way how to design for highest sound accuracy. On the other hand, I understand that many listeners will appreciate the amp just for its inaccuracies.

Ali's picture

A good practice for reviewers is to put album screen shot cover here so we know exactly which album should we listen to: in this case, I could not recognize which Maria Callas album Jason refers to. Because they are many versions and I have the same problems in many other reviews too. Thanks.

Ali's picture

Thanks Jason for review, have you tried progression with its preamp?

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