Of course amplification that is intended to be paired with very expensive speakers tends to be fairly highly priced itself, all this I knew.

What I did not know was that Classé had developed a more affordable series of components, the Sigma range, and that the power amplifiers were based on a class D design.

Background

With the 2200i arrival imminent, I did a little background research. I found that while this Integrated model of the Sigma range was indeed a merging of the power and preamp components within the line, it was also completely different at the same time.

The front-end consists of the stereo portion of the Sigma SSP, including inputs for USB types A and B, Ethernet for streaming AirPlay and DLNA, coax, optical, analogue inputs for XLR and RCA and an optional phono (as in the CP-800 and Sigma SSP). There's also 4 HDMI inputs for users with AV sources.

Any analogue inputs connected to the Sigma are converted to digital at 24bit/96kHz resolution in order to be fed directly to the power amp section.

Many of the physical components may well be the same but the design philosophy is not, for you see the 2200i does not include a DAC chip. This is actually an area that I have some experience with, albeit mostly at a lower price point. I have heard several “Direct Digital Amps” as they have come to be called, and found them to be one of the more interesting developments in audio over the last few years.

A DDA, for those unfamiliar with the term, is an amplifier that takes a digital signal, throws it through a quick conversion (from PCM to PWM*) and then uses it to drive a switching amp directly. In this way the conventional DAC which is present in most designs is omitted, and the pre and post DAC filters are omitted as well. In theory this should lead to a musical signal that is closer to that on the digital storage media than one which has travelled through a DAC chip and analogue post-DAC board. The reality is a little more complicated than that of course but that is the main gist of the theory.

* Pulse Code Modulation and Pulse Width Modulation respectively, for those curious about what these codes actually mean, remember, both Google and Wikipedia are your friends.

I have been fortunate enough to have heard several DDAs over the past 5 years. Four were at much lower price points, all at or below the $1K mark. While they sounded rather good considering their price point, the Wadia 151 being the stand out performer of those, none of them really set my world on fire. NAD’s 390DD was quite a memorable amp and I know of several owners who thought it was truly something special but the Classé sits at a price point well above the 390DD, more aligned with the now discontinued M2.

For those of us who love to fiddle, this new offering from Classé provides touch screen access to several features. Source names are customisable; each input can be assigned a volume increase or decrease in order to avoid large changes in volume level when switching between sources. EQ, tone and balance controls are all included, treble and bass cut offs (and subwoofer crossovers) are adjustable as well as a tilt function. Maximum, minimum and start up volumes are all adjustable.

The EQ possibilities seem rather interesting and I was tempted to play with them, but in the end I left the Sigma in full range mode for my listening. Since I don’t use a subwoofer, full range is the only range I am interested in.

The Sigma boasts 200wpc into 8 Ohms and 400wpc into 4 Ohms and generates very little heat in the process thanks to those extremely efficient class D modules.

For the gear enthusiasts amongst us the Classé Sigma 2200i was tested using a YBA Heritage cd100 as a transport with digital signals sent from transport to amp across an Aurealis coax cable. Speaker cables were of generic nature, which proved a better match than others I tested. The Classé Sigma 2200i would be powering Lenehan Audio S2R stand mount speakers.

Listening Impressions

The top end is beautifully rendered with excellent resolution, the highs have a very natural feel to them and they are very easy on the ear, no traces of hardness, harshness or glare.

Trumpets are a touch soft and yet still maintain their full brassy stature. Triangle is a delight, it sounds very much like the instrument that little silver bells want to be when they grow up. Softly played piano is even more pleasing than usual. The top end is very, very nice and yet, even having said that, it doesn’t feel particularly extended. It sounds extremely good but it doesn’t seem to be trying to stretch its performance, almost as if Classé are playing it safe and sticking with the range they know the Sigma can do properly.

It isn’t really necessary as the upper treble is, as I said, very, very nice but I can’t help but feel that it could be just that bit better with just a little more effort. I really hope Classé push the envelope in this area when it comes time for a revised model to arrive.

The Midrange is where the magic starts to happen in earnest. The lead instrument mids are some of the best I have heard. The Sigma just brings out the most in every instrument in every tune I could throw at it. Electric guitars seem just slightly more electric, acoustic guitars hold on to that note decay for an extra few tenths of a second, while violins come across with more flair and piano down here is even better than it is in the top end. Truly excellent. Even music that I know has been seriously compressed comes across better in the mids than I was expecting.