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Review and Measurements of Accuphase E-270 Amplifier

Jaimo

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There’s a fascinating discussion going on in the Hypex discussion thread about embracing FTC standards for amplifier testing. This includes warming up an amp for something like 30 mins at a reduced load before taking rated output distortion measurements. The only issue is that the test is done into a resistive load and even then, there’s opposition to running this test.

To me it seems that the industry opted for convenience rather than attempting to do a proper test and there’s no easy way to determine from the specs how an amplifier will measure or perform when driving a real loudspeaker. To make matters worse, there are loads of poorly designed “audiophile” speakers in the market that present awful loads to amplifiers and the unsuspecting public is trapped into the never ending upgrade cycle. Naturally this serves a somewhat unethical hi-if business well and leaves people frustrated with trying to get good sound.

My solution has been to use active speakers from reputable (science based) manufacturers. This deals with one aspect of system matching.

In truth, after messing with audio for close to thirty years, I am finally satisfied with my current system and confident that my next upgrade will produce real improvements over what I currently have.
 
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It is the classic ebay special type loads:



For 4 ohm I have two of the 2 om versions in parallel. I will characterize it when I get a chance.
Just stumbled over here - 2Ohm in parallel makes 1Ohm - so I guess its an type and you didnt load the amp with actually 1Ohm !?
 
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amirm

amirm

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Thread Starter #146
Just stumbled over here - 2Ohm in parallel makes 1Ohm - so I guess its an type and you didnt load the amp with actually 1Ohm !?
Sorry it was a typo. They were in series. FYI I no longer use those loads.
 

veeceem

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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).

View attachment 20348
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.

View attachment 20347

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.

View attachment 20349

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.
So this e270 uses the same preamp-section as the new e650? Which means the preamp-section of e650 will be just as bad???
 
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Quote ; 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;

But most sources today gives 2V to the amplifier , should not that be a relevant test point then? It will be the true input at full CD signal
 

restorer-john

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But most sources today gives 2V to the amplifier , should not that be a relevant test point then? It will be the true input at full CD signal
Most sources huh? Consider most people don't even use a standalone CD player anymore, but even if they did, 2V could be 2.2V or 1.8V and only @0dBFS (full level). Most music and content sits well below that.

As for "relevant test points", one tests against rated specifications, not arbitrary numbers you've dreamed up. 150mV was a de-facto standard for line inputs for many decades. Accuphase is a company which respects and adheres to established standards and testing protocols.
 
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My best manager had a mother that was an English teacher. So every time I wrote something, he would go after the English before even paying attention to what I had written. I would go multiple rounds just to get through that, only to be told at the end what he thought of the message. He gave me an excellent advice on this: "it is easier to critique than to create." So I learned to not worry about such things. Folks can provide the critique.
Peer review and critique is always important. Critique done right always fosters growth. Just my two cents.
 
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JohnYang1997

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The issue is caused by the introduced earth connection from the AP's balanced output. So I am pretty sure the XLR input GND is wired to signal GND internally. The issue maybe not be present when using the balanced BNC input of AP.
This is very tricky because this is a preamp and poweramp in one unit which is uncommon. If downstream devices are earthed it is likely to recreate this issue.
Alternatively, the same issue can come the other way around (more commonly). When introducing the earth return to devices using SMPS, the leakage current will have a return path at secondary side to earth. This is the exact reason that SP200, 887, 789 measure very well with no mains hum. If using RCA input the noise performance is going to be much worse. However thankfully these three are headphone amps. The correct way to measure headphone output is to use balanced input terminal of AP instead of the BNC connecter regardless of balanced or unbalanced output. The reason is that the AP's input gnd is earthed through a resistor, 470ohm measured, yet this is not input impedance since the signal is not earth referenced. The result will be there are some mains hum for both balanced and unbalanced output for these devices.
Hence coming back to the statement that having preamp and power amp in one unit is tricky. If there is this issue, the outcome is depending on the downstream component.
What's the cure? Well, for headphone amp, it's easy just to isolate the gnd completely from earth and use external transformer, or use SMPS that measured perfectly like Geshelli. For power amp, it's very difficult to make this a none issue. It's present here is because XLR connection has the issue instead of RCA which is normally accepted. Accuphase could have done something to make XLR worse than RCA. But the reason is the same as the other way around.
 

anmpr1

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Any thoughts on whether the measurable defects in this unit can be heard?
It depends. If you match the levels and hide the brands, probably not. If you know the brands and don't match levels, you'll hear all sorts of differences.

Generally, the more expensive the item, and the one with the rosewood sleeve and meters, will have better rhythm and pace, timing, soundstage, bloom, air between the instruments, and plankton. The sure way to tell is to secretly make a substitution and then wait to see if your waifu in the kitchen immediately notices the change. :)
 
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No nothing better than -80 dB pollution can be heard under any realistic home circumstance, and you will not notice any wrongdoings better than -60dB
Anything better than -100dB is purely of technical interest an not an aural problem
 

anmpr1

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I am aware of confirmation bias - my question is a serious one, and reality based.
There is no need to ponder such a question. Especially if you are serious and reality based. Once a thing is established beyond uncertainty, you don't have to keep reestablishing it, over and over, in order to prove that it remains the case.
 

anmpr1

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what exactly do you feel is established?
It has nothing to do with 'feeling'. What I meant to say, and what others have stated, was that it has been demonstrated time and time again that if you match levels and don't overdrive the gear then you will not be able to reliably tell any sonic differences.

However, if you don't do that, if you don't match the levels and if you know the brands and which device is playing at any given time, you will discover all sorts of 'differences'.

With this in mind, there is no reason to presume that the Accuphase will be any different.
 

Wes

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Where are the DBTs showing that your claim has been demonstrated time and time again ??

What we actually have is gap-filling based on engineering judgement. While I am inclined to agree that one has to go down scale in the measured factors to get a JND, that can only be regarded as a working hypothesis.

As a scientist, I will point out to you that experimental proof cuts both ways.

Now, we do not have measurements on every possible factor that might cause a JND, and we do not have proof of what levels could cause that on all the measurements we DO have as comparators.

so.... Any thoughts on whether the measurable defects in this unit can be heard?
 
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