Product Review

Classé CAP-2100 Stereo Integrated Amplifier

Part II

October, 2005

Chris Groppi


Build Quality

The quality of the CAP-2100 is absolutely superb, both inside and out. As electrical engineering is an everyday part of my work, I regularly compare the build quality of high-end audio components to the Agilent/Hewlett-Packard microwave test equipment I use in my work. The hope is that the internal build quality and engineering that I see in our $75,000 Agilent PNA Vector Network Analyzer is repeated inside a high-end audio component, even if the audio component need only operate to 100 kHz rather than 20 GHz.

The chassis of the CAP-2100 is very attractive and massively over-engineered. Most high-end audio chassis are far more elaborate than professional test equipment costing ten times more. The CAP-2100 chassis is built around a massive front panel extrusion more than 5mm thick, mated to equally serious extruded aluminum heat sinks, and a main chassis frame made from aluminum extrusions and machined components all securely bolted together. A huge machined cross-member stiffens the chassis. There is no sheet metal in the CAP-2100. Even the top panel is an aluminum panel 1/8” thick, with vibration damping on the inside face, secured with no less than 12 countersunk hex head bolts.

The internal engineering is also impressive. As shown in the photograph on the right, a circuit board at the rear of the unit contains the preamplifier circuitry. This board is physically separated from the other boards. RCA and XLR inputs are directly mounted to the board, and switching is provided by high quality digitally controlled relays.

The preamp circuit is based on the Texas Instruments OPA-2134 audio op-amp, and the PGA-2310 digital audio volume control (a single IC containing op-amps and digital potentiometers).

The preamp circuit is fully differential to take advantage of the balanced input. A mix of surface mount and traditional through-hole components are used where justified. The circuit boards themselves are low dielectric FR-4 multilayer boards with especially thick plating. Traces are wide and have radiused corners. The low dielectric constant of the board minimizes crosstalk and potential phase errors due to unequal length signal paths. All unused board real-estate is covered with a ground layer, minimizing the infiltration of noise.

Amplifier transistors are heat sunk directly to the extruded heat sinks, with amplifier circuit boards mounted above. As usual with Classé designs, a combination of MOSFET, J-FET and bipolar transistors are used for the best performance.

The two amplifier channels share a minimum of circuitry. The center of the amp contains the massive, custom-made toroidal transformer and power supply circuit boards. A control board with voltage regulation and a PIC microcontroller sits above the main power supply board behind the transformer. The digital control board containing an ARM microcontroller (really a tiny CPU as used in PDAs) is mounted directly behind the front panel, and communicates with the LCD touch-screen and the optical volume encoder. Control signals are conveyed from one board to the next with ribbon cables, while power is supplied with discrete wires and Molex-style connectors.

The preamp and amp boards are connected with shielded, balanced cable of suitable audiophile quality. The amplifier stages are connected to the binding posts by gold-plated solid copper bus-bars that can only be described as incredible. One of these is pointed out by the white arrow in the photo above. I’ve poked around my share of high end audio equipment and lots of high-dollar test equipment. Short of the glory days of Hewlett-Packard microwave test equipment built in the early ‘80s, this is one of the finest examples of electromechanical engineering I have ever seen.


I have only three reservations about the design of the CAP-2100, relating to the choice of a microcontroller based interface. It is my gut-feeling that if a more traditional interface were chosen, the CAP-2100’s $4,900 price tag would be lower. While this is a fantastic product, the price will push it out of the reach of most audiophiles. A quaint set of mechanical knobs could have been substituted for the fancy interface, possibly cutting the cost.

According to Classé, a more traditional interface could reduce the cost, but only by a small amount. By using the same interface system for all of their Delta series components, development costs are spread out. Another annoying offshoot of the Classé interface implementation is that the CAP-2100 loses all custom settings when the power is interrupted, even for a split second.  I had to rename my inputs several times when the Arizona monsoon  season's lightning forced me to unplug my system. Classé told me this should not be so. After putting the unit into standby once, the settings should be saved, so my unit's firmware could have a small problem. The third reservation concerns reliability. The first CAP-2100 I received had a non-functional volume knob. Any electronic component can have a problem, and this failure was likely not the fault of a design issue. Classé says they actually have fewer problems with the optical encoder setup than they did with earlier, mechanical potentiometer designs.

The Sound

After installing the CAP-2100 in my system and allowing a couple of weeks of everyday TV-watching for break-in, the Classé did not disappoint me. The CAP-2100 was the first component to live in my system that completely transformed every area of performance. It dramatically improved shortcomings I thought were the fault of other components, and improved others I didn’t even think needed improvement. The change was so overwhelming and complete, it was like I had a whole new system, with every area of performance improved.

The first thing I noticed (or more precisely felt) was the bass extension, impact, and weight. I have a REL Strata II subwoofer, so you might think that there’s no way the amplifier could change the low bass performance. I didn’t think so either, but I was wrong. The transformation was spectacular. The bass with the Plinius 8150i was plenty good before. But the bass with the CAP-2100 was in another league. The extension seemed to go another half octave deeper. The power and weight were stunning. The bass didn’t just seem to fill the room, it felt like it was coming directly from inside me, like my heart was replaced with the subwoofer driver. Bass transients and timbre were in another league. And I thought I had no issues with the bass performance of my previous system.

The REL uses the high level speaker outputs of the amp as the input signal (with very high input impedance, so there’s no current siphoned off, and no load to interfere with driving the satellite speakers). This preserves the character of the amplifier stage as well as the preamp, improving sub-speaker integration. Somewhere in the CAP-2100, either in the preamp, the amp or both, there is some serious bass mojo. It’s clear the bass performance is still there when driving speakers. With the REL turned off, the lowest octave was missing, but the weight, impact and tightness of the remaining bass was still there. It has always been said that the Platinum Audio Solos have great bass for a little speaker, but this amplifier really brought out the best I have heard from them. And all this with “only” 100 watts per channel. The Plinius has 50% more rated power, but the Classé paddled its backside in the bass department. I’d like to know at what impedance the CAP-2100 starts to deviate from behaving as a perfect current source. I bet it’s a low number.

The bass was the most obvious area of improvement, but not the only area. Another striking change was the magical appearance of soundstage depth in my system. I always thought it was a shortcoming of the Platinum Audio Solos that they just didn’t have much soundstage depth. Wrong again. I started with a relatively flat soundstage with hints of depth, and plenty of width and height. This was pretty good. The CAP-2100 preserved the width and height, but added at least two meters of depth with well done recordings. I finally was able to get a soundstage that stretched from just in front of the speaker plane, back though the wall of my house practically into my neighbor’s yard. I just sat there listening with my eyes closed and a silly grin on my face.

A third area of my system I had blamed on my Solos was resolution of detail. I believed I just needed better speakers to squeeze that last little bit of detail out. I was always aware that there was just a little veil of obscuration between my ears and the sound, like having pretty clean glasses, but not brand new glasses right out of an ultrasonic cleaner. Maybe I still need better speakers and source electronics, but the CAP-2100 brought out more detail and precision than I thought was possible, given my system. With the Plinius, I had plenty of detail recovery above about 1 kHz, but in the midrange and bass, the sound could get a bit muddled during complex passages. The Classé cured this issue, leaving nothing but sparkling clear, detail-rich sound at all frequencies.

The combination of the detail resolution and the bass performance led to an amp that sounded incredibly alive and exciting. And what was so impressive was that the Classé had replaced a vary fine amp. In fact, having gone back to the Plinius toward the end of the review period, I was still impressed with the performance of the 8150i. The Classé is just better, in every way.

The only possible problem is that the CAP-2100 did not sound as warm and rich as the Plinius. This is likely a reduction in low order harmonic distortion, a price that is required to improve extraction of detail. I think this is a small price to pay. The CAP-2100 is the best component I have ever had in my system.


I would have no reservation recommending the CAP-2100 to anyone who wants a no-compromise integrated amplifier. Affordability is the only issue, but if you want the best, it is an issue you just have to work out. Since I want to say, "I bought the review sample," it is an issue I am working on as you read this review.


- Chris Groppi -

© Copyright 2005 Secrets of Home Theater & High Fidelity

Go to Table of Contents for this Issue

Go to Home Page


About Secrets


Terms and Conditions of Use


Our Vault pages may have some display quirks. Let us know if we need to take a look at this page or fix a bug.
Connect with us
  • Instagram
  • Google+
  • YouTube
  • LinkedIn
  • Pinterest
Secrets "Cave"