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Review and Measurements of Accuphase E-270 Amplifier

amirm

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#1
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 $5,000. 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):

Accuphase E-270 Integrated Amplifier Review.jpg

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:

Accuphase E-270 Integrated Amplifier Power Amp Measurements.png


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+:
Accuphase E-270 Integrated Amplifier Power Amp SNR.png


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):

Accuphase E-270 Integrated Amplifier Power Into 4 Ohm comparison.png


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):
Accuphase E-270 Integrated Amplifier Power Amp Pre-amp with power amp disengaged Measurements.png


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:

Accuphase E-270 Integrated Amplifier Power Amp Pre-amp with power amp disengaged XLR Measureme...png


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:
Accuphase E-270 Integrated Amplifier Power Full Amp SNR Measurements.png


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

1547442685464.png


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):
Accuphase E-270 Integrated Amplifier Power FFT Measurements.png


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:
Accuphase E-270 Integrated Amplifier Power Broadband FFT Measurements.png


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:

Accuphase E-270 Integrated Amplifier Power Into 4 Ohm with and without pre-amp.png


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:
Accuphase E-270 Integrated Amplifier Power Intermodulation Distortion Measurements.png


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:

Accuphase E-270 Integrated Amplifier Power Frequency Response Measurements.png


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.

EDIT: update the price to the correct one ($5,000 instead of $4,500).
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RayDunzl

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#2
Certainly an unexpected result with the balanced input.

I wouldn't think Accuphase would be so negligent with the implementation.

Oh well.

More product info: http://www.accuphase.com/cat/e-270_e.pdf
 
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#3
In Tokyo, Accuphase is all over the place. Even in the huge electronics retail chains. I didn't see many integrated amplifiers, however.

Interestingly, in 2011, Accuphase launched the wonderful T-1100 FM tuner. A follow up to the excellent T-1000 tuner. Some consider the T-1100 to be the very best tuner ever made. Sounds absolutely wonderful.

http://www.fmtunerinfo.com/ricochets.html#T-1100
http://accuphase.com/model/t-1100.html

US new price is probably north of $5k now but I have no idea. A couple of years ago, used Japanese T-1100 and T-1000 sold pretty cheap but prices seem to have risen. Grey market units can be imported from Japan to Europe & the US. However, you would be stuck with Japanese tuning scheme (Accuphase told me a few years ago that they will not modify JDM units, although maybe that has changed or someone has figured out how to do that).

There are still some fantastic classical and college FM radio stations in Japan, Europe and the US. If a $5k Accuphase is a bit out of the budget, there are plenty of 1970s FM tuners that can be purchased and aligned by a good tech for less than $500.

Apologies for the tangent.
 

amirm

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#5
Certainly an unexpected result with the balanced input.
It confused the heck out of me initially. When a device has balanced input, I always start with that and in this case, I was amazed at the poor performance. I slept overnight and this morning thought of testing RCA and separating power amp/pre-amp from each other. Only then I figured out the issue with balanced input.
 

amirm

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#6
Looks like the budget ran out before the engineers finalized the XLR work.
Yeh, or a junior engineer was given the task of implementing it.....
 

restorer-john

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#10
The cluster of noise may be from the uP and/or the multiplexing of the LED display. Most of Accuphase's gear shuts down the uP and goes to static (non-scanning) of the key inputs after a second or so of no input (knobs/switches).

That is the only logical place where noise of that characteristic could come from as the power amp is completely conventional.

The XLR board appears to contain its own balanced receiver IC. I would expect it turns that on in the presence of a physical XLR plug and raises the combined noisefloor even though you are using the RCAs.

The THD is impressive and the power is well over spec. The frequency response is excellent as expected.

No output impedance testing was done and no other loads than 4 ohms?
 

amirm

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#11
No output impedance testing was done and no other loads than 4 ohms?
I have 8 ohm load but have not had time to connect it up. I also worry about length of testing when I start to include another load.
 

maty

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#14
@amirm, can yo measure the slew rate? Power amp and integrated.

https://en.wikipedia.org/wiki/Slew_rate

For years I have doubts about how much we need to reproduce in its fullness an orchestral mass. With class D it is clear that this is not a problem.

Is it enough with only 14 V/μs (like chipamp LM3886) or do we need twice as much? How much? I do not know the answer.

Tubes, I think the sr is about 10 V/μs.
 
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RayDunzl

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#15
Is it enough with only 14 V/μs (like chipamp LM3886) or do we need twice as much? How much? I do not know the answer.
All things being equal, which they never are, I should think the slew rate for a power amplifier, because it must slew across greater range of voltage, would need a higher minimum slew rate than for something handling a small signal.

What are the rates? I do not know the answer.

My amp is rated for 240kHz at -3dB, so, let's guestimate...

1547455493019.png


If 20khz is the goal... with 50V out:

1547455693108.png
 

maty

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#17
Then, with the usual BW of 100 kHz at -3dB -> 31 V/μs, a typical value in commercial class AB.

But some say that half is enough (LM3886), hence my doubts. The key must be the word fullness.

-> I listen to very good recordings with high DR (15 dB or more). Music with low DR must be need less slew rate, am I right?
 

maty

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#19
With 24 Vdc and 100 kHz at -3dB, 14 V/μs maybe is enough.

And one thing is the SR of the chipamp and other the SR of the power amp. They should be very similar.
 

maty

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#20
To finish, orchestral music needs more peak power (more Vpp)<- high DR. But it has very fast transients (or as it is said in English) too <- SR.

Maybe a new thread is better idea.
 
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