Channel Islands Audio C-100S Power Amplifier

Little Powerhouse

Equipment report
Solid-state power amplifiers
Channel Islands Audio C-100S Power Amplifier

One of the more egalitarian aspects of high-performance audio is that not all manufacturers are multi-national corporations. Some are smaller, more focused operations such as Channel Islands Audio, which opened its doors in 1997, 22 years ago. Founded by designer Dusty Vawter—who began his audio career as the head of the technical service department at Audio Alchemy—Channel Islands Audio (CIA) specializes in well-built, high-performance audio components manufactured to last for more than one product cycle. What’s more, the components are not outrageously priced; those in CIA’s “Classic” line all retail for under $600. CIA also makes six different accessory power supplies, five preamplifiers, and four power amplifiers.

Here, we will be looking at the C-100S stereo power amplifier ($1500), which is CIA’s lowest-power amplifier, though it still produces 180 watts into 4 ohms and 100 watts into 8 ohms. Its footprint is only 8.5" wide by 2.75" high by 10" deep and it weighs a scant six pounds. One of the reasons the C-100S weighs so little and takes up so little space is because its entire aluminum chassis gets used as its heatsink so it doesn’t require big cooling fins.

Tech Tour
The C-100S stereo power amplifier utilizes a Hypex Class D power module. And while many amps use those amplifier modules, most are “complete” amp circuits that require little more than a power supply and input and output connections to be fully functional. The C-100S is different because it uses an abbreviated Hypex amplifier section without input or power-supply sections. The C-100S amplifier uses a proprietary and completely separate power supply that is incased in its own separate and shielded partition at the front of the amp. The amplifier employs its own front-end circuit that is also separate from the Hypex board. If you look at the photo of the C-100S amplifier’s inner workings, you can see that the two Hypex boards are connected directly to the output connectors and can be easily replaced after four connectors and two screws are removed. This not only gives CIA an option for Hypex circuit board updates in the future, but also makes repairs to the C-100S stereo power amplifier simple and easy for customers anywhere in the world.

The Hypex module was chosen primarily because it employs a patented control loop and output filter that provides flat frequency response regardless of the load impedance. Most other Class D output stages are optimized for a 6-ohm load, and exhibit a rising response into 8 ohms and a roll-off into 4 ohms. 

Few power amplifiers have a variable gain option, although this is not a unique feature. But the C-100S can be set for either 26dB, which is the usual standard, or a higher sensitivity of 32dB. This 6dB increase makes it easier to use the C-100S power amp with a passive, no-gain preamplifier. However, changing the setting switches on the amplifier’s backside does require a toothpick and a steady hand.

Ergonomics and Setup
Installing the C-100S stereo power amplifier within a system is simple—just connect the speaker cables to the amp’s five-way binding posts, and join an input to the amp’s single-ended RCA input jacks, plug it in to a power source, turn it on, and you’re ready to go. This is a good place to mention that the C-100S amp only has single-ended RCA jacks for inputs. If you have a long cable run and prefer balanced XLR connections this could require adapters (which will negate the advantages of the balanced line).

During a majority of the review period I used the C-100S stereo power amplifier in my nearfield desktop system where it was attached to the CIA PC-4 Mk II passive preamplifier/attenuator either being fed by the Chord Qutest DAC or connected directly to the single-ended outputs of the PS Audio DSD Jr. I used a variety of loudspeakers including the Audience 1+1 Mk III, Role Audio Kayak, ATC SCM7 Mk II, Silverline Minuet Plus, and Mark Volti Crespi. When I installed the C-100S in my primary room-based system, where it was connected to the single-ended outputs of the Mytek Manhattan II DAC while driving a pair of Spatial Audio X2 loudspeakers, I did notice a bit of hiss coming from the tweeter/midrange ribbon drivers when I was closer than four feet away. This hiss was not present when the Spatial X2s were connected to the Pass Labs X150.8 power amplifier, which was attached via a balanced cable connection.

In some systems the ability to use the 32dB gain instead of 26dB can deliver better signal-to-noise, but in both of my systems I discovered that 26dB was a better match since it allowed me to use a more compatible setting on my preamplifiers and gain controls. Since CIA has a 30-day trial period for all its products you will have ample time to try both settings to determine which works best in your system.

I like small-footprint, lightweight power amplifiers that generate little heat. You can put them anywhere, leave them on all the time, and move them without risking a hernia. The only disadvantage of an amplifier as small and lightweight as the C-100S stereo amp is that some of the larger, heavier, and stiffer interconnects and speaker and power cables may be harder to use with the C-100S unless you add some weight to the top of its small chassis to keep it in place. I used a VPI brick combined with a weighted doorstop.