Wednesday, September 9, 2015

Acoustic Imagery Atsah 500 Mono Amplifier Review

Acoustic Imagery NC 500

The Class D revolution has been anything but. I was around back when the first "audiophile" class D amps from Nuforce were introduced. The buzz at the time reminded me of the "perfect sound forever" buzz (and disappointment) of CD. Class D amps were supposed to be super quiet, lightweight, low distortion, and very power efficient. It all looked good on paper, but to our ears they left much to be desired. They sounded dry, with a harsh midrange and ragged highs. Much of the harshness and raggedness was due to the switching power supply that the Class D amps made use of. The power supplies were noisy and injected all kinds of grunge into the AC lines. This grunge was supposedly out of the audible bandwidth, but anyone who has good ears knows, there are lower harmonics of that noise that trickle into the audible range...

Enter NCore

A few years ago Hypex (or rather Bruno Putzeys) introduced their NCore series of Class D amplifiers. The NCore was the first class D amplifier that could actually compete with Class A, AB amplifier designs and not make one want to run out of a room.  They retained all of the advantages of Class D, but the dryness, harshness, and raggedness were gone. In fact not only were they gone but the NCore amplifiers improved upon distortion and signal to noise ratios. To my ears, a well designed NCore amp could best a very good solid state Class A amplifier. Not quite Pass Labs, but Luxman and others of their caliber sounded broken by comparison.
With nCore, Hypex has refined their UcD concept to new levels of perfection by improving the modulator for more accurate feedback subtraction and PWM generation. The all-discrete driver and output stage have also been improved for lower open-loop THD as well as lower idling losses, normally conflicting requirements with conventional IC driver circuitry. An added control loop incorporating an integrator with adaptive clipping enables 20dB more feedback to be used across the audio band because of its extremely low-phase shift resulting in a dramatic reduction in distortion across the audio band. - NAD Web Site

Several amplifier manufacturers started buying the NCore amp boards and power supplies, coming out with their own versions of this amplifier at widely ranging prices. 

More recently, a smaller version of the original NCore NC1200 powerhouse OEM board became available, and were put to use by audio giants NAD, with more to follow.  While not quite as powerful, the newer NC500 amp modules were far less expensive than the NC1200. Now you could have an NCore powered amp from a reputable manufacturer starting at $3000 instead of $10,000.

Enter The Atsah 500

Acoustic Imagery was one of the original manufacturers of NCore based amps using the NC1200 modules. They were the least expensive NC1200 amp on the market at $9995 per stereo pair of monoblock amps, setting the bar for audiophile amplifier performance quite high, while keeping the price comparatively low.

Their new NC500 based amplifiers have set the price to performance bar very high once again. In fact, I think they have set a new standard for the industry.

The new Atsah 500 is a monoblock design, with each amp utilizing the same power supply used for  NC1200 amplifiers. That's right, each amp has it's own power supply. Unlike the NAD M22 where both amplifier boards share an NC1200 supply. They are rated at 400 watts into 8 ohms, and 700 into 4 ohms. Leaving plenty of power to drive nearly any loudspeaker, and losing out to the NC 1200's only at low impedence loads (the Atsah 1200 will do 1200 watts into 2 ohms). They have the same low distortion, low phase shift and low noise however. Making them a very formidable amplifier. They have a gain of gain of 26 dB, making them relatively easy to match to any preamp. They are a balanced design, and as such only have one XLR input. One can use RCA to XLR adapters if one's preamp has an unbalanced output. But fully balanced provides the best performance. Along with the balanced input on the rear is one set of binding posts, and a fused iec input connector. The dimensions are 200mm wide (7.87 in.) x 220mm deep (8.66 in.) x 65mm (2.55 in.) high. The weight of each amp is 2kg (4.4 lb.).

The finishes are a carbon fiber or silver finish composite case. The power supply and amp modules are mounted to grounded metal plates.

They are packaged quite nicely in individually fitted boxes that are then placed in a sturdy outer box for shipping. An owner's manual and power cord are included in each box.

The price you are wondering?  What would you expect to pay for monoblock amps utilizing the NC500 module? Considering the NAD retails at $3000 and has one less power supply, you might expect to pay around $4000 per pair, correct? Cut that in half. A pair of Atsah 500's will set you back $1995.


I am going to compare the Atsah NC500 with my tweaked out  Atsah1200's.  The Atsah 1200's have upgraded power and speaker wiring harnesses, fuses and a few other goodies. :)

I have had the Atsah 1200's in my system for the last 2 years, and am very familiar with their sound. When I put the Atsah 500's in the system fresh out of the box they sounded...Good but not near what the 1200's were. To put it bluntly they were dark. The highs were distinctly softer and less present. John Young of AcousticImagery told me his impressions were the amps were warmer in their character than the 1200. But this wasn't warm, this was rolled off.

Flash forward 24 hours and the amps had opened up considerably. They still weren't as airy as the 1200's. But it wasn't a bad thing. It gave the 500's a warm, rich, musical and forgiving nature. This was especially noticeable when streaming Tidal, Spotify, Pandora etc. It made the whole experience of listening to streaming audio much more pleasurable. A very good thing. Streaming high resolution music from my collection, I had slightly less air and extension of the 1200's, but as far as pace, dynamics, slam and low end growl I could not tell much difference at all. I would say the NC500's had a balance and sound similar to the Modwright KWI 200. Very listenable.

Then it occurred to me. I had been listening to my system as optimized for the Atsah 1200s. Meaning the cables I was using were a very nice compliment to the 1200s.  I had been auditioning Audience's latest balanced interconnect, the Ohno, and it was a great fit for the Atsah 1200's. The Ohno is a stunningly good interconnect in the $400 range. Dare I say I liked it better than the AU24SE unbalanced that I had in my system earlier.  The Ohno has body and presence like no interconnect at it's price point should.  It's only perceived weakness was the typical copper top end. It was a wee bit softer than my MG Audio Planus AG interconnects. The Planus AG's had the extension, but lacked the body, presence and a wee bit of the dynamics that the Audience had. With the Atsah 1200's I was using a pair of the Audience Ohno's from source to the Jay-Sho preamp, and from the preamp to the Amps. It was a little too much warmth for the 500's. In went the MG Planus AG from source to preamp. The high frequencies reproduced from the Atsah 500's had more extension, ambiance and decay. The system also maintained the warmth and presence in the lower and mid frequencies. The tradeoff of this combination being there was a slight tradeoff in dynamics. I found this a more listenable combination with the 500's long term than using all Audience Ohno interconnects. 

With all that in place, I continued with my listening. The sound was still warmer, rich and sounding way better than a $2000 pair of amps should.  It had a clarity and quietness that no amp I have heard at or near this price. If you are looking for a musically satisfying amp that will give you 90% of what the big buck solid state Class A amps deliver, without the heat, weight and price of a Class A amp, look no further. The AcousticImagery Atsah 500 sets the bar exceedingly high for the sub-$5000 amplifier category at a price of $1995 per pair. Highly recommended.