Solid State Power Amp Reviews

Accustic Arts Audio Mono II monoblock power amplifier Specifications

Sidebar 1: Specifications

Description: Solid-state fully balanced class-AB monoblock power amplifier Inputs: 1 unbalanced (RCA), 1 balanced (XLR). Outputs: 2 pairs speaker binding posts. Power output: 300W into 8 ohms (24.8dBW), 500W into 4 ohms (24.0dBW), and 700W into 2 ohms (22.4dBW). Frequency response: 2.6Hz–105kHz, –3dB. Voltage gain: 31dB. Intermodulation distortion: 0.007% at 10W into 4 ohms. Signal/noise: 104dB A-weighted (ref. 6.325V). Damping factor: >300 at 1kHz and 4 ohms. Input impedance: Balanced (XLR): 2 x 20k ohm, Unbalanced (RCA): 100k ohms. Output impedance: <10 milliohms. Total transformer capacity: max. 1200VA. Power supply capacitance: more than 80,000µF. Rise time/fall time: 3.0µs with 4 ohm load (squarewave 20kHz, 12Vp–p). THD+N: 0.0012% into 4 ohm load at 1kHz and 10W.
Dimensions: 13.8" (350mm) H by 9.4" (240mm) W by 16.9" (430mm) D. Weight: Approx. 55lb (25kg).
Finish: Silver or black case with chrome front inlay.
Serial numbers of units reviewed: M2-1JB1258 & 1259.
Price: $24,900/pair. Approximate number of dealers: 5. Warranty: 3 years.
Manufacturer: Accustic Arts Audio GmbH, Hoher Steg 7, 74348 Lauffen, Germany. Web: accusticarts.com. US representative: Finest Fidelity, 3 Sagebrook Drive, Bluffton, SC 29910. Tel: (386) 341-9103. finestfidelity.net.

COMPANY INFO
Accustic Arts Audio GmbH
US representative: Finest Fidelity
3 Sagebrook Drive
Bluffton, SC 29910
(386) 341-9103
finestfidelity.net
ARTICLE CONTENTS

COMMENTS
JRT's picture
Submitted by JRT on October 1, 2019 - 2:54pm

I would like to see Stereophile subjectively and objectively review and test a ~$3k Rotel RB-1590 stereo amplifier, claimed to be two separate monoblocks in one enclosure. Rotel rates it at 350W/channel into 8_Ohms, 4_Ohm min load, 120_dB s/n A-weighted (presumably referenced to full power), 0.03%_THD over the range of 20_Hz to 20_kHz, frequency response 10_Hz to 100_kHz ±0.5dB.

It would have been interesting to know how that $3k Rotel subjectively and objectively compares to this $25k/pair Accustic Arts Audio Mono II monoblock power amplifier, after being rebuilt with proper power supply transformer (these big mistakes are not confidence building). More than 8x the price should buy some nontrivial improvement, else the opportunity costs need further consideration.

Bogolu Haranath's picture
Submitted by Bogolu Haranath on October 1, 2019 - 4:39pm

For $3,000, we can also get PS Audio Stellar mono-blocks (Stereophile Class-A) 350 WPC 8 Ohms and 700 WPC 4 Ohms :-) ...........

Ortofan's picture
Submitted by Ortofan on October 1, 2019 - 5:13pm

... following are a couple of other subjective and objective reviews to tide you over:

https://www.bwgroup.ch/wp-content/uploads/2016/11/Hi-Fi-News-11-2015-Test-Rotel-RC-1590-RB-1590.pdf

https://hometheaterhifi.com/reviews/amplifier/preamplifier/rotel-rb1590-rc1590-preamplifier-power-amplifier-review/

JRT's picture
Submitted by JRT on October 1, 2019 - 7:14pm

I had not seen those.

Ortofan's picture
Submitted by Ortofan on October 2, 2019 - 7:37am

... in the Mono II's price range, you know what to do next."

Permit me to finish that thought.
Buy a pair McIntosh MC1.25KW or a pair of Pass Labs X600.8 amps.
Or, if you can live with a two-channel amp, then a Pass Labs X350.8 or a D'Agostino Classic 2 will save you about $10K.
Better yet, save another $10K with a Parasound JC5.

Bogolu Haranath's picture
Submitted by Bogolu Haranath on October 2, 2019 - 8:07am

You could also consider the new Krell Duo 300-XD stereo-amp ($10,500), 300 WPC into 8 Ohms :-) ........

Ortofan's picture
Submitted by Ortofan on October 2, 2019 - 6:02pm

... four fans. No thank you.

Bogolu Haranath's picture
Submitted by Bogolu Haranath on October 3, 2019 - 7:35am

For most of the listening levels those fans probably won't turn on ........ Even if they did, the noise levels would be low enough, not to interfere with the listening to music ......... See Stereophile review of albeit more powerful older model Krell Solo 575 mono-blocks .......... MF did not mention any thing about fan noise interfering with his listening :-) ..........

Bogolu Haranath's picture
Submitted by Bogolu Haranath on October 2, 2019 - 8:37am

Or, you could also consider McIntosh MC462 stereo-amp ($9,000, Stereophile Class-A), 450 WPC 2, 4 or 8 Ohms :-) ..........

Ortofan's picture
Submitted by Ortofan on October 2, 2019 - 6:04pm

... high enough into lower impedances. Good try, though.

Bogolu Haranath's picture
Submitted by Bogolu Haranath on October 3, 2019 - 7:42am

450 WPC 2, 4 or 8 Ohms ....... For most of the music, for most listeners, for most of the listening levels, with sensitive speakers, we probably don't need more than 450 WPC :-) .........

Bogolu Haranath's picture
Submitted by Bogolu Haranath on October 3, 2019 - 7:48am

McIntosh MC462 can deliver more power than specified 450 WPC ........ See Stereophile measurements :-) ..........

Bogolu Haranath's picture
Submitted by Bogolu Haranath on October 2, 2019 - 8:53am

Or, you could also consider Bel Canto REF600M mono-blocks ($4,990, Stereophile Class-A), 300 WPC into 8 Ohms :-) ..........

Ortofan's picture
Submitted by Ortofan on October 2, 2019 - 6:08pm

... emits ultrasonic switching noise. Strike three.

Bogolu Haranath's picture
Submitted by Bogolu Haranath on October 3, 2019 - 9:26am

No human being can hear that high ultrasonic switching noise ......... No tweeter can reproduce that high ultrasonic switching noise ........ No music extends into that high ultrasonic switching noise ........ See Stereophile measurements of Bel Canto REF600M :-) .........

Ortofan's picture
Submitted by Ortofan on October 3, 2019 - 9:34am

... what we can or cannot hear. No audio amp should be radiating RFI.

Bogolu Haranath's picture
Submitted by Bogolu Haranath on October 3, 2019 - 9:42am

Ok ..... Don't use your smartphone or AM/FM radio or turn on your TV, while listening to music :-) .......

Bogolu Haranath's picture
Submitted by Bogolu Haranath on October 3, 2019 - 8:07am

If you insist on high power, in addition to the amplifiers you mentioned above, we can also consider the Bryston 28-B/3 ......... 1000 Watts into 8 Ohms and 1800 Watts into 4 Ohms ....... $24,000/pair ....... See Stereophile review of older model Bryston 28-B :-) ..........

Ortofan's picture
Submitted by Ortofan on October 3, 2019 - 9:48am

... suggestion. Even the 7B³ would be sufficient to far exceed the power ratings of the Accustic Arts amp, plus the Bryston 20-year warranty is not to be sneezed at, unless you're afflicted with upgrade-itis.

Bogolu Haranath's picture
Submitted by Bogolu Haranath on October 3, 2019 - 9:58am

Thank you ....... I could finally appease you :-) .......

Bogolu Haranath's picture
Submitted by Bogolu Haranath on October 3, 2019 - 10:04am

I think that 20 year warranty is also transferable :-) ........

georgehifi's picture
Submitted by georgehifi on October 6, 2019 - 2:20pm

"Manufacturer's Comment
Editor: The lack of performance of the Accustic Arts Mono II power amplifiers was caused by the fact that we unfortunately installed wrong transformers."

When sending a product sample to be reviewed and thoroughly bench tested to Stereophile, one would think that a company would give it's very best sample, (even "cough" better spec'd) than a production one, to be showcased in a magazine that will make or break that product.

this sort of answer happens way to much for my liking
Cheers "cynical" George

w1000i's picture
Submitted by w1000i on January 26, 2020 - 3:16am

For $24,900/pair and transformer issue. Is poor qulaity abd flag to avoid such product.

If as big as transformer than what about small transistor value?!!!

georgehifi's picture
Submitted by georgehifi on October 6, 2019 - 2:38pm

"Bel Canto REF600M .........
Submitted by Bogolu Haranath on October 4, 2019 - 2:26am
No human being can hear that high ultrasonic switching noise ......... No tweeter can reproduce that high ultrasonic switching noise ........"

You are correct, but you can hear the effects of the Class-D's output filter that has to get rid of that switching noise, with phase shifts that are large (up to 70 degrees!!!) that reach down to 1khz. That's why many complain about the upper mids and highs with class-D.

(copy and paste this link to your browser)
https://ibb.co/hd9qNC7

Cheers George

Bogolu Haranath's picture
Submitted by Bogolu Haranath on October 6, 2019 - 4:58pm

There are/were several Class-D amps and integrated amps included in the Stereophile recommended component lists ....... Many of of them earned Class-A distinction in sound quality and in measurements ....... Bel Canto models are one among them ....... Why is that? ........ Heaven forbid, you are not questioning the hearing ability of the Stereophile reviewers, are you? :-) .......

georgehifi's picture
Submitted by georgehifi on October 6, 2019 - 5:26pm

Reviewers have subjective outlooks, each to his own, but surely no one would turn a blind eye to the phase graph linked in my last post above?

Cheers George

Bogolu Haranath's picture
Submitted by Bogolu Haranath on October 7, 2019 - 8:36am

That one is above my pay-grade ........ May be JA1 with his technical expertise could shed some light on that particular topic :-) ..........

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