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Review and Measurements of Accuphase E-270 Amplifier

JJB70

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#41
Parts and performance are Japanese-standard and mediocre.
Notwithstanding the surprising measurements of this amplifier I'm not sure I'd agree that products designed to Japanese standards parts and performance are mediocre. In terms of general build and product quality the Japanese manufacturers (even if no longer made in Japan) remain market leading IMO. I've found that mid-range Yamaha, Rotel, Marantz etc equipment is often built to standards that shame high end exotica (in some cases entry level Japanese gear displays fit and finish and general build standards to shame high end exotica). In terms of performance Japanese gear varies in the same way as other sources but the major Japanese brands are capable of making seriously well performing gear and in their pomp could engineer stuff that left most other gear behind regardless of price.
 
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#42
Notwithstanding the surprising measurements of this amplifier I'm not sure I'd agree that products designed to Japanese standards parts and performance are mediocre. In terms of general build and product quality the Japanese manufacturers (even if no longer made in Japan) remain market leading IMO. I've found that mid-range Yamaha, Rotel, Marantz etc equipment is often built to standards that shame high end exotica (in some cases entry level Japanese gear displays fit and finish and general build standards to shame high end exotica). In terms of performance Japanese gear varies in the same way as other sources but the major Japanese brands are capable of making seriously well performing gear and in their pomp could engineer stuff that left most other gear behind regardless of price.
Agreed. A lot of the premium Japanese electronics are sold in Japanese & Asian markets only. Both from boutique brands and mass-marketers like Sony. The concentration of extreme wealth in very densely populated ares of say Tokyo, Hong Kong, Shanghai probably make it easier for them to market premium products in these countries.

My sense is that Japanese companies generally market lower-end electronics to Europe and the Americas.
 

RayDunzl

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#43
General Jack D. Ripper: Were you ever a prisoner of war?

Group Capt. Lionel Mandrake: Well... yes I was, matter of fact, Jack. I was.

General Jack D. Ripper: Did they torture you?

Group Capt. Lionel Mandrake: Uh, yes they did. I was tortured by the Japanese. Jack, if you must know; not a pretty story.

General Jack D. Ripper: Well, what happened?

Group Capt. Lionel Mandrake: Oh, well, I don't know, Jack, difficult to think of under these conditions; but, well... what happened was they got me on the old Rangoon-Ichinawa railway. I was laying train lines for the bloody Japanese puff-puff's.

General Jack D. Ripper: No, I mean when they tortured you. Did you talk?

Group Capt. Lionel Mandrake: Ah, oh, no... well, I don't think they wanted me to talk really. I don't think they wanted me to say anything. It was just their way of having a bit of fun, the swines. Strange thing is they make such bloody good cameras.
 
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#44
once more this shows that usually you have to look for the limiting factor at the amplifier.
most amplifiers under 1000$ dream about 16bit resolution.

long live DSD :D
 

Arnandsway

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#45
The search for a benchmark continues :).
What would be the most likely well performing A/B amplifier? And what would it have to cost?

Also, would new Class D-amps (like the Hypex modules) have the best specs per dollar? Ofcourse we don't have a large dataset to confirm/dismiss this, but we could speculate.
 
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pierre

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#46
This is a review and detailed measurements of Accuphase E-270 Integrated Amplifier. It is on kind loan from our friends at Gig Harbor Audio. It is their demo unit so I have to return it on Tuesday. So if you need something else to be measured, ask right away! The E-270 was released in 2017 I think and retails for USD $4,500. This is not cheap by our normal standards but in high-end audio, this is a pretty reasonable price.

The industrial design of the unit seemingly has not changed from 1980s era with beautiful VU meters (with acceleration):


At 44 pounds, the unit is quite heavy for its capabilities. There is a massive transformer in the middle of the unit and the power amplifier modules with beefy heatsinks sit on either side. During my testing, I could not even get the unit to become warm let alone hot! It runs so comfortably that one thinks it is never going to stress out.

The front has a slick finish that is lovely to touch. Volume control is implemented through resistor ladders and hence has electronic control. Accuphase says it has 6,500 steps which should be plenty for listening although was a bit difficult to dial in the exact value for measurements.

There are slots in the back for optional DAC and phono stage (?) which mine did not have.

All in all this is the type of construction, look and feel that would justify paying good bit of premium over a budget product. Given the likely reliability that comes from a high-end product from Japan, I say the stage is set for a good impression.

Note: seeing how this is a demo unit to be sold, I did NOT attempt to stress the unit. No long term warm up and certainly no stress test. Given the overdesigned thermal design here though, I am not worried about the measurements holding under thermal stress.

Measurements
For reasons that will become clear later, I decided to test the power amplifier section first. Accuphase makes this dead easy with a front-panel button "MAIN IN" that decouples the power amp input from pre-amp output. This allowed me to test the power amplifier separately and compare its performance to recently tested power amps. So let's start with our 5 watt dashboard into 4 ohm:

View attachment 20307

I have added two more panels here: gain and dc output. Have not verified the latter but should be correct. As we see there is a 0.4 dB gain error and variation in distortion level. The loads I use are not precision types (none are at these high power levels) so some of this may be instrumentation. I did match levels (not shown) and distortion levels and differentials remained the same.

At 92 to 95 dB SINAD, we are getting in territory of transparency for CD music. The two distortion products are second and third harmonic at around -100 dB.

Signal to Noise ratio is very good at 116 dB+:
View attachment 20308

The E-270 is rated at 120 watts and it blows way past that to the tune of 155 watts prior to clipping (green pair):

View attachment 20311

You can see the comparison to recently reviewed Onkyo M-282. The E-270 outperforms it in every category from lower noise floor and distortion to more power prior to clipping. The Onkyo of course is a budget product at $300.

On not so good news, the Hypex based NC400 amplifier way outshines the Accuphase E-270. It has far less noise, distortion and much more power. Whoever thinks class AB amplifiers are better than switching ones like NC400, this is the time to cry! :)

Pre-amplifier
Let's isolate the pre-amplifier and measure it at unity gain (same level output that is input):
View attachment 20312

Wow, that is quite a bit better than the power amplifier with much lower noise floor and distortion. Don't get too excited though. There are some really odd things going on here. Let's switch inputs to XLR:

View attachment 20313

What the heck??? We lost 10 dB of performance.

What is really, really strange is that if I measure RCA but leave the XLR cables connected, performance drops way down just the same! You can see it easily in signal to noise ratio measurements:
View attachment 20314

Accuphase hints at much lower performance of XLR input in the specs for the product:

View attachment 20315

This aside, note as I have shown on the FFT chart above how we have lots and lots of power supply related spikes. This is evident in an FFT of the spectrum (power amp only):
View attachment 20316

Switching power supplies like used in Hypex NC400 amplifier shown in the inset in blue convert mains to DC and then convert it back to AC at hundreds much higher frequency (above audible frequencies). As a result, you are free of mains related noise in good implementations. There is no denying how clean the Hypex NC400 amplifier is in the audible band. The Accuphase E-270 in contrast while cleaner than budget Onkyo M-282, has a ton of noise spikes.

The problematic area for switching amplifiers is in the high frequencies so let's look at that:
View attachment 20317

The levels of noise and spurious tones is of course quite a bit lower than switching amplifiers. We once again see that XLR input has worse performance (see zoomed inset).

Let's now re-measure the power versus distortion using the E-270's pre-amp:

View attachment 20319

We have a repeat of issues with XLR input again. Notice the performance of RCA input with (red) and without XLR (blue) cable connected but not used. And of course we leave fair amount of performance on the table with respect to the power amplifier alone.

It seems that loading the pre-amp with the power amp reduces its performance substantially. I traced this to pre-amp getting severely distorted when the power amp is under stress. There is lack of isolation/independent power supply for the pre-amp.

Story is the same with intermodulation distortion versus level:
View attachment 20321

Interestingly enough the level sensitivity for XLR is the same as RCA. I should be able to swing that to 4 volts for the same output with RCA at 2 volts.

Frequency response falls in the category of very good news:

View attachment 20320

I left the levels different for each input so that the graphs don't fall on top of each other. The power amplifier (blue) has the flattest response but by just a bit. There is really no issue in the audible band to 20 kHz.

Conclusions
On fit and finish, the Accuphase E-270 integrated Amplifier delivers for a product in low thousands of dollars. It has the nostalgic look of 1980s product which is popular now and certainly different than common mass market products. Its power amplifier has respectable and conservative specifications. Measurements show it to produce far more power than stated with massive thermal capacity which should spell long service life.

Unfortunately I think there are some serious engineering issues in the pre-amplifier. The XLR input not only generates much worse performance on its own, but also serves to pollute the performance of RCA input! There is not sufficient power/isolation for the pre-amp causing its performance to sag when the unit is asked to produce a lot of power. These are faults that I don't tolerate in mass market products, let alone higher end ones.

I would say if you want to get an Accuphase product, get a power amplifier. The integrated unit as tested just doesn't do that job so sadly, I cannot recommend it.

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Did you test the headphone out?

I guess I need to sell my e360 now ....
 
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#47

DonH56

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#48
I'll put some numbers on it (that's what I do ;) ). For a single sinusoid the max slew rate is SR = 2*pi*f*A where pi = 3.141592653..., f = frequency, and A = amplitude (V). So a 100 W (28.28 Vrms, 40 Vpk) amplifier driving an 8-ohm load at 20 kHz needs a slew rate of about 5 V/us. Double the power to 200 W and you need about 7 V/us. If I did the math right (check it).
 

dc655321

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#49
I'll put some numbers on it (that's what I do ;) ). For a single sinusoid the max slew rate is SR = 2*pi*f*A where pi = 3.141592653..., f = frequency, and A = amplitude (V). So a 100 W (28.28 Vrms, 40 Vpk) amplifier driving an 8-ohm load at 20 kHz needs a slew rate of about 5 V/us. Double the power to 200 W and you need about 7 V/us. If I did the math right (check it).
Your math is fine (as usual!).
 

maty

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#50
In addition, it should be necessary to leave a safety margin and not stick to the theoretical one, I think.

But the question is if with higher slew rate the sound is better, specially complex music very good recorded.

It is like the amp bandwith, many designers believe that up to 350 kHz is better. No more to avoid RF/EMI problems.

These are two issues of which I have no certainty. :(
 

svart-hvitt

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#51
In back issues of The Audio Critic, you will see that the Technical Editor, Dr David Rich, notes that Accuphase below flagship level is quite ordinary except for the price. Parts and performance are Japanese-standard and mediocre. However, if for example you were to measure their E-650 model and look under the hood, you would find a superior product. Below flagship level there are many better choices available, usually for much less money.
Do you write that Accuphase are not able (or willing?) to build an adequte amplifier for USD 4500?
 

DonH56

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#52
In addition, it should be necessary to leave a safety margin and not stick to the theoretical one, I think.

But the question is if with higher slew rate the sound is better, specially complex music very good recorded.

It is like the amp bandwith, many designers believe that up to 350 kHz is better. No more to avoid RF/EMI problems.

These are two issues of which I have no certainty. :(
It is true that live music can have content well above 20 kHz. Whether we can hear, it, meh. I can't. The argument for ultrasonic performance usually hinges upon mixing those signals back down into the audio band at a level loud enough to hear. I do not know, not something I've researched, but I have doubts.

It is always good to have margin, but also remember it is unlikely to see a full-power signal at 20 kHz. At least and have your tweeters survive... As the output voltage decreases slew rate falls directly. That said, 10 V/us would sustain about 80 Vpk or 56 Vrms, good for about 400 W into 8 ohms at 20 kHz. That seems sufficient... Higher slew rate means wider bandwidth and thus more noise, albeit mostly ultrasonic, and potentially reduced stability. In my world too much bandwidth can be as bad as too little. Always trades...

There was a big push for ultrawideband designs years ago but that seems to have died out (except for Spectral).
 
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sergeauckland

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#54
It is true that live music can have content well above 20 kHz. Whether we can hear, it, meh. I can't. The argument for ultrasonic performance usually hinges upon mixing those signals back down into the audio band at a level loud enough to hear. I do not know, not something I've researched, but I have doubts.

It is always good to have margin, but also remember it is unlikely to see a full-power signal at 20 kHz. At least and have your tweeters survive... As the output voltage decreases slew rate falls directly. That said, 10 V/us would sustain about 80 Vpk or 56 Vrms, good for about 400 W into 8 ohms at 20 kHz. That seems sufficient... Higher slew rate means wider bandwidth and thus more noise, albeit mostly ultrasonic, and potentially reduced stability. In my world too much bandwidth can be as bad as too little. Always trades...

There was a big push for ultrawideband designs years ago but that seems to have died out (except for Spectral).
I think it was Cecil Watts who said 'The wider you open the window, the more muck blows in' It applies very much to bandwidth. It should be as wide as necessary, with a little in hand, but not too much. For example, bandwidth was defined as +-3dB, and 20Hz-20kHz was considered good. Now, we might prefer +-1dB 20Hz-20kHz, which gives a 3dB bandwidth (assuming 6dB/octave) of 10Hz-40kHz. That, I suggest, is quite enough. More, and a lot of muck does blow in, especially from noise-shaped digital sources, RF pollution and reduces stability margins. An audio amplifier that can output into the medium wave band is a poor design in my view.

S
 

restorer-john

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#55
In back issues of The Audio Critic, you will see that the Technical Editor, Dr David Rich, notes that Accuphase below flagship level is quite ordinary except for the price. Parts and performance are Japanese-standard and mediocre.
That's absolute rubbish I'm afraid. I've worked on Accuphase gear from their very first products to recent models over the last 4 decades and they were and are, a considerable step up from day one.

Even their very first integrated, the E-202, produced in 1974, had construction, performance and component quality far in excess of anything else out of Japan at the time. It garnered amazing reviews and many, if not most of them, are still out there, playing tunes.

1547500121915.png


Edge connector sockets for serviceability, careful routing of cables, absolute premium components for the time and a superb range of facilities and functions, all in a rock solid 20kg unit.

1547500442171.png


1547500537465.png


All boards are socketed on edge connectors for easy service. Every part is overspecified for the job. Go have a look at some internet images of the internals and tell me what you see.

To give you an idea, the last one I worked on needed a volume knob (its original was missing) and Accuphase supplied me one. Yes, they still had spare parts, 35 years after producing the amplifier! And cosmetic parts are usually the first to dry up. Try that with any other company.
 
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NTomokawa

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#56
But the most important part is: How does (or did) it measure?
 

svart-hvitt

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#57
That's absolute rubbish I'm afraid. I've worked on Accuphase gear from their very first products to recent models over the last 4 decades and they were and are, a considerable step up from day one.

Even their very first integrated, the E-202, produced in 1974, had construction, performance and component quality far in excess of anything else out of Japan at the time. It garnered amazing reviews and many, if not most of them, are still out there, playing tunes.

View attachment 20341

Edge connector sockets for serviceability, careful routing of cables, absolute premium components for the time and a superb range of facilities and functions, all in a rock solid 20kg unit.

View attachment 20345

View attachment 20346

All boards are socketed on edge connectors for easy service. Every part is overspecified for the job. Go have a look at some internet images of the internals and tell me what you see.

To give you an idea, the last one I worked on needed a volume knob (its original was missing) and Accuphase supplied me one. Yes, they still had spare parts, 35 years after producing the amplifier! And cosmetic parts are usually the first to dry up. Try that with any other company.
@restorer-john , how do you read and interpret @amirm ’s measurements on this Accuphase USD 4.500 amplifier?
 
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#58
Some of the findings are not nearly as bad as they are being made out to be. In fact, that are not unexpected at all--.01% THD+N at 1W is exceptional for an integrated amplifier driving 4 ohms. All you're looking at here is the noise floor, and since you've switched in a bunch more active circuitry, more noise than you see with the power amplifier bypassed is expected. Noise is a cumulative problem. The noise floor here is more than low enough not to be audible under most listening conditions. In fact, it's quite a bit better than this particular integrated nCore amplifier: https://www.stereophile.com/content/bel-canto-design-black-aci-600-integrated-amplifier-measurements.

As for the claim this isn't as good Hypex... well, the measurements don't really show that other than the noise floor and THD at 1kHz.. See the other comment here regarding Hypex and the request for measurements: https://www.audiosciencereview.com/...f-hypex-nc400-diy-amp.5907/page-2#post-132130. Those are supremely useful, and show where the Hypex falls short. Until you see how the amplifier performs at high power at higher frequencies, you aren't really testing for much of anything that will be audible as long as it is reasonably low. The reason for the higher frequency measurement is to give you an idea how how the amplifier will perform with regarding to intermodulation distortion, which can be quite nasty. Still, even that test isn't the end of the line: The Hypex performs (relatively) badly at higher frequencies (apparently with or without the AP AUX-0025 filter being used, which I assume is not being used here). Yet, it still performs very well on a 19kHz+20kHz IMD test. That usually does not happen with a Class AB amplifier. Class D apparently does not always follow the same rules. What would happen if you tested a Hypex at 19+20kHz full scale tones just below the knee of the distortion curve? That would be interesting.

The only conclusion it's possible to draw from the data posted is that the Accuphase is an exemplary piece of audio equipment with inaudible levels of distortion at 1Khz, but that their balanced input is not very good. That's was a very fair conclusion. If I had to guess, it's probably not actually a balanced circuit--they're probably taking the balanced signal and converting it to unbalanced internally, which is causing more noise from more resistors and more components getting switched in.

Measurements are wonderful things and you can draw some pretty good conclusions from them about how transparent a piece of equipment is, and how it will perform. However, you have to understand what they mean and measure the right thing. Else, you can be drawn astray. I think that may have happened here, since this really is an exceptional set of measurements... at 1kHz.
 
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restorer-john

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#59
@restorer-john , how do you read and interpret @amirm ’s measurements on this Accuphase USD 4.500 amplifier?
The measurements Amir performed are extremely limited. (no doubt due to time constraints). I certainly feel a categorical recommendation or lack thereof is a very unwise position to take.

What we can see, is the performance exceeded rated specifications by a wide margin (factors of 10+) for the parameters Amir tested. This was as expected and as I predicted. Frequency response tests appear to exceed spec also, but Amir has not specified the power output level he tested FR at. The standard and the spec is 1W. We can only guess what he used.

The high level preamplifer inputs were driven with a signal to give the same level out as in (2V). There is absolutely no point using a preamplifier that is specified with an 18dB gain and then winding back the attenuator to give unity gain for testing purposes. All preamplifiers are tested and specified at the wide open position and have been forever. The rated output of the preamplifier is 1.07V from a 134mV input. He fed it 2V and wound back the attenuator. You test a preamplifier at its rated input and output, not some made up number that suits you. We may be merely seeing non-linearities and noise (hum) etc, from being buried in the multiple stages of the AAVA volume control (see below).

1547505143761.png

I had hoped Amir would investigate this unusual implementation and test it at various increments/levels to give some insight into its performance or lack thereof. I'm not convinced piling VI buffers in line is a good idea, but who knows. Accuphase have been touting their AAVA for several years now.

1547503537316.png


One cannot characterize the performance of an amplifier with only one resistive load test (4 ohms), which is half the standard, and make no comparisons between different loads and different numbers of channels driven. There is no reactive testing, transient (IHF/EIA) testing, power bandwidth, shorted input residual, comparisons of various inputs, crosstalk measurements, etc.

There is zero discussion on the topology as the cover was likely not removed (understandable if it was on loan) and therefore we can only surmise as to the reasons for the burst of HF hash on the FFT. I have offered a possible reason in a previous post, but Accuphase is unlikely to have released a product into the wild with such an issue. It may be operator influenced perhaps.

The power amplifier stage is conventional and of a decent standard according to what I see on Accuphase's brochure.

1547505394000.png


What we can see is Accuphase appear to have decoupled supplies for the VA, the driver stage and the output stage and we know they will have high quality regulated supplies for the preamplifier stages. Amir makes the statement the preamplifier supplies are being affected by the output. This is perfectly normal in integrated amplifers with single transformers when operated at high powers into low impedances.

Comparisions to the Hypex are flawed. The Hypex units have not demonstrated they can even hit their specifications. Nor have they demonstrated they can be trusted not to shut down at inopportune times. Their power supplies overheat and are failing in the marketplace. The Accuphase wasn't pre-conditioned, or tested for 5 minutes at full rated power either.

I take the whole review with a grain of salt.

That said, further investigation would clear up a whole lot of the above. Time contraints are a b#tch.
 
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