I performed a complete set of measurements on one of the Accuphase A-300s (serial number L2Y188) in its Normal mode with my Audio Precision SYS2722 system. I preconditioned the A-300 by following the CEA's recommendation of running it at one-eighth the specified power into 8 ohms for 30 minutes. At the end of that time, the temperature of the top panel was 97.6°F (36.4°C) and that of the side-mounted heatsinks 120.4°F (49.1°C).
As auditioned by JVS, the balanced input was wired with pin 2 negative, the opposite of the AES standard. (A rear-panel switch allows it to be changed to pin 2 positive.) In the default position, therefore, the Accuphase's balanced input inverted absolute polarity, though this is easily changed. The single-ended Line input was noninverting. The A-300's balanced input impedance is specified as 40k ohms. I measured 39.6k ohms at 20Hz and 1kHz, 14.8k ohms at 20kHz. The single-ended input impedance, specified as 20k ohms, was 19.3k ohms at 20Hz and 1kHz but 5k ohms at 20kHz. With the gain set to MAX, the voltage gain at 1kHz into 8 ohms with both input types was close to the specified 28dB, at 27.83dB. The three lower gain settings lowered the voltage gain by 3dB, 6dB, and 12dB, respectively.
The output impedance, including the series impedance of 6' of spaced-pair cable, was a relatively low 0.14 ohms at 20Hz and 1kHz, 0.18 ohms at 20kHz. As a result, the variation in the frequency response with our standard simulated loudspeaker (fig.1, gray trace) was minimal, at ±0.15dB. The response into resistive loads was flat in the audioband, not reaching –3dB until 180kHz into 8 ohms (blue) and 130kHz into 4 ohms (magenta). With its wide small-signal bandwidth, the Accuphase's reproduction of a 10kHz squarewave into 8 ohms featured with very short risetimes in both modes (fig.2), with no overshoot or ringing.
The unweighted, wideband signal/noise ratio (ref. 1W into 8 ohms), taken with the single-ended input shorted to ground and the gain set to MAX, was a superb 88.9dB. This ratio improved to 103.6dB when the measurement bandwidth was restricted to 22Hz–22kHz and to 106.3dB when A-weighted. The ratios were 2–3dB greater with the gain to set to –12dB. Spectral analysis of the low-frequency noisefloor while the Accuphase drove a 1kHz tone at 1W into 8 ohms revealed a low random noisefloor, and while even-order harmonics of 60Hz were present, these all lay at or below –114dB (fig.3).
Accuphase specifies the A-300's maximum power in Normal mode as 125W into 8 ohms, 250W into 4 ohms, 500W into 2 ohms, and 1000W into 1 ohm, all of which are equivalent to 21dBW. We define an amplifier's clipping power as being when the THD+noise reaches 1%. With that criterion, the A-300 exceeded its specified powers. I measured 210W into 8 ohms (23.2dBW, fig.4), 385W into 4 ohms (22.8dBW, fig.5), and 610W into 2 ohms (21.8dBW, fig.6). I didn't examine the clipping power into 1 ohm, as I don't have a high-power test load with that value.
I examined how the percentage of THD+N varied with frequency at 20V, equivalent to 50W into 8 ohms, 100W into 4 ohms, and 200W into 2 ohms (fig.7). The THD+N percentage was extremely low into 8 ohms (blue trace) but rose into 4 ohms (magenta trace) and 2 ohms (red trace). It was still low in absolute terms, however.
The distortion waveform was predominantly the third harmonic (fig.8), though the second harmonic was present at a lower level (fig.9). Commendably, higher-order harmonics were absent. This graph was taken at 30W into 8 ohms, which is below the power where the Accuphase's output stage transitions from class-A to class-AB. Performing the spectral analysis at 75W into 8 ohms, which is closer to the transition power, the third harmonic rose by 8dB (fig.10) compared with fig.9 but was still very low at –99dB (0.001%). With the amplifier driving 60W into 4 ohms (not shown), the third harmonic lay at –80dB (0.01%), the second at –93dB (0.002%).
Intermodulation distortion with an equal mix of 19 and 20kHz tones was also very low in level, even above the transition power at 4 ohms (fig.11).
The Accuphase A-300's measured performance indicates that it has no problem driving low impedances, and it offers very low distortion, especially into 8 ohms. It is also a very quiet amplifier, even at the highest gain setting.—John Atkinson
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COMMENTS
How nice it is to see real audio amplifier measurements/pics/graphs that don't need to use "cloaking test gear devices" to hide the faults that other classes need to look respectable, and have wattage "load tests" that go well below 4ohm also
Cheers George
record still stuck , I see
that a component that costs $50,000, has the rear panel look of a $300 receiver. this is all too common with so called high end gear. cheapo gauge black anodized steel plate, t-shirt type silkscreening, visible fasteners. this happens on even cost no object components. and the reviewers are fine with it because mention is not made. hahahahahaha
... the output power from the Accuphase A-300 rarely exceeded 62.5W.
Yet, in a previous review he claimed that a D'Agostino Progression Mono amp excelled in dynamic contrast in comparison with a Pass Labs XA200.8's because the D'Agostino amp was capable of a 1,000W output versus only 400W for the Pass Labs amp.
semi fact checker, explain to us what difference this makes.
"Accuphase is expensive, but at least you know you're buying something that's well engineered and well built."
For $52kusd!!!!, not quite as good as you think even though it looks impressive.
Instead of just 2 massive "can" type caps, I would have been far more impressed to see 2 banks of 24 or so smaller ones to equal the same value, this improves the ESR of the power supply to a much better figure and therefore the bass slam and dynamic speed performance.
Cheers George
you know so much more about audio engineering than the heads of Accuphase! I mean they would be so grateful because your "army of smaller caps" idea obviously eluded them. Maybe Accuphase engineered this amp exactly like they wanted to and liked the way it sounded without your suggestions. Based on how JVS described the sound of Accuphase vs. the D'agostino, I'd take the Accuphase in a heartbeat.
You should'nt be naive about it, read up about "Low ESR" in solid state power supplies.
And how capacitors effect this greatly.
If arrays of smaller caps can do better, why Accuphase special made those huge ones assuming smaller ones also cost less?
I did measured the runtime (after 30 minutes, at low output level around 65-70dB to a pair of Harbeth 40.3 XD) temperatures on the left side middle spot of their heatsinks of a pair of A-300 (earlier production units than this L2Y188), found they are around 96F and 102F, not even, but much lower than 120F. Runtime/idle wattage of these 2 amps are not even also, so they are going back to Accuphase Lab for inspection/repair.
Always curious
Please that's being naive, they don't make their own caps, they are re-badged from a major cap maker, and far easier for production to have in a production amp, than 50 odd smaller ones and more pcb's and labor that has to go with them.
Like these 2 story, double stack ones in this amp, https://ibb.co/74YDFn3
And Gryphon and other amps use the same philosophy https://ibb.co/ynCd0Ms
https://ibb.co/9gtCCr9
Naive?? No one said special made means in house. For a system house like Accuphase, unlikely. Given the limited quantity and high price per unit, hard to imagine production/assembly cost be a major factor for consideration by any stretch. We don't know if there are other factors such as error margin of different sizes of caps, etc.
Note nearly all Accuphase amps of recent decades, class A or AB, all using 2 large caps for some reasons. So you can be their new Chief design/production engineer to bring in revolution.
Accuphase is not a cost-no-object ultra-hifi manufacturer. Their market segment is not the One Percent, it's well-to-do audiophiles who are prepared to invest a good chunk of money in their stereo system. When they design a product, Accuphase certainly have to make several engineering decisions based on their cost. Perhaps they could have chosen different capacitors, but that might have taken the amplifier beyond the maximum price they were aiming for. I trust they strive to maximize the sonic value they can get, given the cost and pricing decisions they have to make.
"Perhaps they could have chosen different capacitors, but that might have taken the amplifier beyond the maximum price they were aiming for."
Auditor is correct, everything is built to a price, including this amp as good as it is, others here that think that it's the best they can do, are living in a dreamworld and being very naive.
Cheers George
with the design philosophy of this amp. I know full well that Gryphon uses a lot of caps and Luxman uses two more than the Accuphase. I have a circa 1982 Luxman integrated - 100wpc class AB - and it has 2 large caps. So what are your credentials as an audio engineer/cirucit designer? Or do you just like to pick apart things that don't adhere to your Taliban-like rigid view of what constitutes good equipment? Or are you a bargain hunter like Ortofan ? Do you read ASR and get goosebumps when the science nerds measure their music instead of listening to it and feeling it ? Sheesh. You guys are really something else. I'm not sure what psychological classification you fall into...
I've done the A/B's between what's being discussed here.
Same amp 2 x massive HQ caps vs many smaller HQ caps
Those with any good tech knowledge of power supply "ESR" know (speed of stored capacitance release when called for) "equivalent series resistance".
In "bass control and speed of dynamic swing", the many smaller ones same combined value win out every time, due to their "lower combined ESR" than the slower release of the 2 x massive size caps.
Just read and educate yourselves about "capacitor ESR" if you can, instead of just foaming at the mouth without any posted technical knowledge to back it?
Cheers George
I'm not looking for brawn. I'm looking for grace. I don't need an amp for massive home theater like 100 db outbursts. I'm not trying replicate at home the sound levels of the Ramones at CBGB's in 1976/7. What you are mandating is not a requirement but a question of design philosophies and as we all know there isn't only one.
"I'm not looking for brawn. I'm looking for grace. I don't need an amp for massive home theater like 100 db outbursts."
Now your trying to twist things, lowering the ESR in a powersupply does not mean loosing grace or going for home theater/disco crap sound.
It's just a small part of getting the "very best" out of everything in poweramp design even in a 50w poweramp, having low ESR has the same effect in them as it would do in these beasts.
But there are those here seem to think that these Accuphase mono's are the end game, they're not.
you aren't going to change minds. I dont want my mind changed. I'm not buying an Accuphase. The review is written. It's JVS's opinion. If you don't agree based on some empirical data that seems corrupt feel free to write to Accuphase. Other than that, no one really gives an s about what you think. What I object to you is you and others lecturing us about what we SHOULD be listening to. A dictatorship w lots of caps and low price tag (because I doubt you own a Gryphon. Im also sure that by the time the next review of a high priced Gryphon integrated appears, Ortofan or you will point out that the Parasound measures better at 100th the cost.
Whatever, like I said "can't see the forest for the trees".
about the caps still makes no sense in the design of this amp. Look at the photo of it. more caps or smaller transformer? smaller heat sinks. this amp looks put together w surgical precision ! more caps is more labor to match them all. more things to go wrong. silly really. it's a thing of stunning beauty. why criticize it at all when YOU HAVENT LISTENED TO IT. You're just reacting to the observations of a different human in the Pacific Northwest.
Like I said, "can't see the forest for the trees"!
about an imaginary issue. They're only audio amplifiers guys. It's not rocket science. These amps (minus the placebo effect) will "sound" the same.
Every time I start reading these comments the same negativity is always followed by the usual suspects.
Why do such people feel a need to dissect every component that they will never be able to afford and feel a need shed their negativity upon others?
The only expertise they seem to have is in the area of jealousy, negativity and the need to share it with others every month!
Hey, hiendmomo, when you complain about people making the same old comments, you must be talking about yourself and the late johnnythunders.
Can't you shills for expensive equipment come up with a better insult than your go-to of "oooh, you're just jealous you can't afford it"?
When someone says this, they are actually voicing their own economic insecurity.
I think it's more the case that most of us with $50k would prefer to spend it on something that delivers a superior price-value proposition. That doesn't mean this particular amp isn't a good purchase for those who want it. It just means it's not for all of us.
Because of price/value, and dreamers and their followers (shills maybe) that post up that it's the end game for amp design. (it's not)
Cheers George
"Amusing to watch grown men having a fistfight over capacitors"
To quote you Auditor: "Accuphase is NOT a cost-no-object ultra-hifi manufacturer."
But other uneducated ones here think they are. https://ibb.co/BqBwV8k
And it shows that Accuphase didn't go the extra mile by using those 2 x massive far (slower dynamic release caps into low impedances) that have higher esr, compared to same value of many good much faster low esr smaller ones.
Cheers George
result in lower ESR, and sonically, can more quickly adapt to fast transients with lower stress (if well-implemented). It's an expensive consideration for any mfg, obviously.
Those things are friggin' HUGE! That's a ton of stored energy.
..BIG capacitors look like:
https://www.theaudiobeat.com/visits/ch_precision_l10_m10.htm
"Those things are friggin' HUGE! That's a ton of stored energy."
Granted that is a massive amount of stored energy, but it comes down to how fast it can be released instantly to the output stage ("flow rate" for want of a better word), to get the best dynamic range/tightest bass especially into low impedances bass speakers.
This is from an article on stored capacitance and it's dynamic release.
https://ibb.co/N1ZW4hq
Cheers George
That is the bottom line.
jason
It must be because it costs so much. We all know that price determines sound quality. Especially when it comes to amplifiers. And wires. And anything else that we can imagine. Which includes pretty much everything in "high end" audio. The key to understanding this is "imagine".
Nothing Accuphase makes has ever disappointed.
Nice review Jason. I am considering this amp for my Alexx V's. I know your reference amps are the Momentum M400 MxV. Which of these amps would be the best match. Thanks
I've done my best to describe their differences. They're both superb amplifiers. It's a matter of preference and system synergy (which includes room interaction). This is something no reviewer can predict.
...eyes, stop reading.
These aren't the amps you are looking for.
Go back to the 99cent store.
All will be well.
Someday, Chris, we must meet. Until then, long may you post.
jason
Meanwhile, keep up the great reviews!
The comment section will always be rife with "material"...
Yep at nearly all our A/Bing listening sessions, a philomath will keep the romantics inline with measurement/specs etc, and the romantics will supply the philomaths with https://ibb.co/jWx6Xgy whatever it is they're using to sway them.
Cheers George
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