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- #81
Correct. I left the other end connected to the Accuphase.For the record: XLR cable plugged or unplugged at source end for this test?
Correct. I left the other end connected to the Accuphase.For the record: XLR cable plugged or unplugged at source end for this test?
... and they have invented perpetuum mobile....
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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.
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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.
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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.
No one can reasonably contest the view that Accuphase gear looks nice internally and externally and is constructed with quality components with long-term spares availability. But Amir's measurements indicate performance deficiencies in the E-270 that should not be present in a $4,500 integrated 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).
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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.
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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.
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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.
No one contests that Accuphase gear looks nice internally and externally and is constructed with quality components with long-term spares availability. But Amir's measurements indicate deficiencies in the E-270 that should not be present in a $4,500 integrated amplifier.
I think you are being a bit harsh on the review. There is clearly an issue with mains pickup and other spuria on this unit which wrecks a lot of the numbers. Perhaps that isn't typical of Accuphase products but there is no doubt the NC400 is significantly cleaner than this particular example. More / different tests won't change that, unless it is considered faulty.
BTW the replacement power resistor arrived so I will be doing the 5 min test later on at least one of the hypex amps. Also I think one person replied to the forum about failed psus
But Amir's measurements indicate performance deficiencies in the E-270 that should not be present in a $4,500 integrated amplifier.
While I agree with the complaints about Hypex's power supply, I'm not sure it's fair to discount the whole amplifier's performance because of an underpowered, underheatsinked power supply
With equal respect the plots from the Accuphase test show some obvious problems yet you are seemingly very keen to defend it.
We've addressed all that in the DIY hypex amp thread. I don't think you can however use a product that only functioned part of the time during soak/full power testing, overheated, shutdown and failed to reach its specifications as a reference point to compare commercial offerings to.
I'm not defending it, I'm saying due to the unusual nature of the noise, I would be investigating it further and ruling out whatever I could before pointing the finger at Accuphase's design. The remainder of the test results show a very competent design.
And, for the record, I wouldn't be buying the Accuphase at USD$3500 in any case, with or without the 'problems', I don't believe it fits my value requirements. I think it is way too much money for what is essentially an 'entry level' Accuphase in real terms. I have a 1990 C-11 Accuphase preamplifier that was AU$3500 when new and probably when paired with its matching power amp (P-11) was a step up over the modern integrated reviewed here. I also have some older integrated Accuphase amps, but they are stored.
This is what it is doing with my analyzer hooked up to its power amp (pre-amp isolated) but not turned on:There is a cluster of noise which is atypical of any spectrum I've ever seen on an analog Class AB amplifier. T
This is what it is doing with my analyzer hooked up to its power amp (pre-amp isolated) but not turned on:
Here is a comparison of 1 to 50 watts in 5 steps with a 4 ohm load with a 2.3 uF capacitor in parallel. Bandwidth is 45 kHz so it includes some of the high frequency harmonics and AES-17 40 kHz filter is there for both devices: (click on image for large size)At very least, amplifiers should be tested at their permitted loads, 2,4,8 ohms both channels operating, and with 2uF in parallel to simulate a reactive load.
No, the amp is fully on but the analyzer output was off. The pulses come after a few seconds after power on which I suspect is when the output is turned on.The amplifier is not turned on? As in live power, but in standby?
No, it means I bypassed the pre-amp, driving the power amp by itself.So 'hooked up to its power amp' meaning the speaker terminals?
The pulses come after a few seconds after power on which I suspect is when the output is turned on.