Although we come across a number of amplifiers each year, we still get excited everytime “the guy in the big brown truck” drops off a new product at our test lab. Recently, the good folks at Cadence sent us an example of one of their latest creations, an addition to the popular ZRS series of amplifiers, specifically the new ZRS C9. The popularity of these amplifiers has a lot to do with the amount of performance and features available for the price. We were very eager to see if the new Cadence C9, priced at only $299.00 USD (slightly higher in Canada) would continue the tradition.
The Cadence ZRS C9 is a full range Class AB four channel amplifier. Rated at 100 watts x 4 into 4 ohms, and 150 watts x 4 into 2 ohms, the amp I unpacked was relatively large and looked like it meant business. The C9 features a black anodized brushed aluminum heatsink that measures a bit over 15 inches long, 9.6 inches wide, and about 2.3 inches tall. The amp looks good, with beefy heat sink fins, with a laser etched Cadence logo and silk screened model number on the top in red and white. The connections and controls are situated on each end of the amplifier, and the mounting feet are slotted tabs that are part of each sheetmetal end panel. Wiring connections are the ubiquitous hex screw type, albeit these are cast from solid brass and then nickel plated for maximum current transfer. The power connections will accept 4 gauge cables, and the speaker connections will easily handle 10 gauge cable. Also on this end of the amp are a pair of 30A, ATC style fuses.
On the opposing end of the amplifier, there are a lot of adjustments! These included gain, filter type, filter slope, crossover frequency, 2ch/4ch input switch, frequency multiplier switches, bass boost and a clever “Bass Focus” control, a subsonic filter that can be used as the highpass section of a bandpass filter, as well as an interesting switch that was labeled “Clone Function”. Thankfully, the amp comes with a good installation guide that explains the proper use and setting of each control. After a bit of reading I understood the purpose of this switch is to allow the settings for channels 3 and 4 to be automatically applied to channels 1 and 2, thereby eliminating the need to set everything manually, and theoretically providing more precise adjustments when all 4 channels are used at the same settings. Also on this end of the amplifier are the input RCA jacks, as well as a pair of full range output jacks that can be used to drive the inputs of another amp, like a dedicated subwoofer amplifier for example. The ZRS C9 also includes a wired remote control that changes the level on channels 3 and 4.
Setup and Listening:
As usual, the first place the amp got connected was in the quiet and carefully controlled environment of my listening room. To test this amp I decided to use channels 1 and 2 to drive my component speakers, and channels 3 and 4 would be connected to a pair of 12-inch woofers in a small sealed enclosure. I specifically chose the sealed box so I could experiment with the subsonic filter and the Bass Focus control.
During my adjustments, I found I had a tough time reading the red silk screening used for the controls, and while it looks artsy and cool in bright light, it’s going to be hard to read in a dimly lit trunk. I suggest a re-think here. After setting the “front” channels to 45Hz high pass, and the rear channels to about 80Hz low pass, I got the gains adjusted, and began my listening. Keeping in mind that this amplifier costs less than what a lot of folks spend on a cell phone, I was really pleased with the overall performance of the amplifier and I thought it sounded clean and natural, with plenty of power for all but the most extreme volume levels. The top end was very noise free, and hada sense of airiness and space that I don’t hear in many of the new full range class D designs. My only minor gripe was a slight lack of focus in the stereo image. The bass was tight and articulate, and I was very impressed with the functionality of the Bass Focus control. You see instead of just a simple “Bass Boost” feature, (which is also provided) the Bass Focus control allows you to dial in boost at lower frequencies that can help compensate for a lack of enclosure volume or cone area. The effect is excellent, but like any good thing, too much can be bad. Thankfully the Cadence engineers understand this too, and limited the amount of available boost to about 7dB. This feature is also useful when combined with the subsonic filter to give your mids a bit of additional punch as well, but again, always use care and caution when applying boost to any speaker system.
Read on for Results
After I was done with my listening, I brought the amp into the electronics lab and removed the bottom cover. Inside I found a fairly basic layout using a single sided PCB and thru-hole parts. The build quality was good, especially for an amp of this price range.
For those of you that keep score, the power supply uses three high temp 2200µF 25V caps, and the audio section has a total of 13,200µF of capacitance. The power supply switching is handled by six 50N06 MOSFETS, and each channel is driven by a dedicated pair of complimentary bipolar transistors.
On The Bench:
Okay, time then to get the performance numbers out of the ZRS C9, and see how she performed on the unerring Cogent test bench. As I suspected from my listening session, the amp is a very good performer for the dollars invested. Power figures were just a hair shy of the published numbers, but in fairness the difference would be completely inaudible to even the most skilled listeners. The ZRS C9 excelled in the signal to noise department, measuring a seldom reached -94dBA at 1 watt. Stereo separation was also very good at better than-65dB.
Other high points included measurements showing the C9 has very low output impedance, and the frequency response extended well past human audibility, way out to 80kHz in fact! The overall frequency response was extremely flat, with less than 0.3dB of difference from below 10Hz to 20kHz. This kind of performance is seldom found in a 300 dollar amplifier!
It wasn’t all roses and sunshine, however. I found that at certain points in the rotation of the gain controls there was about 1.5dB of difference between left and right channels, which could easily explain the lack of focus I’d previously noted in the stereo image. Yes, it was possible to get them to track almost identically, but that only happened at either end of the pots rotation, places where the gains are not likely to be optimized for most systems. One other niggle, the “Clone Function” seemed to be more of a “distant cousin” function, as it did not achieve the perfect matching of the gain settings I expected. This problem could be related to the tracking problems of the gain pot, and I could get better results matching the gains individually with my multi-metre. Still, the crossovers were very accurately duplicated, which I suppose is what most people will be more worried about. And to be fair, I have to admit I still prefer amps with individual gain pots for each channel because I’m one of the very few people who uses a meter to adjust gains to within 0.1dB. Keep in mind the differences I measured in the ZRS C9 would be only barely audible, but they were there so I had to mention it.
After all my usual tests were performed I tested the protection functions by dead shorting the outputs during operation. The circuits worked as intended, I removed the short, cycled the power and all was well again. While I was at it, I also checked for any audible turn-on or off noise, but the ZRS C9 was dead quiet in that regard.
The Cadence ZRS C9 is a very good amplifier for the money. In many respects it has better performance and more useful features than many of its competitors. I especially liked the Bass Focus feature- a useful control in almost any system. The build quality is good, and my abusive tests seem to indicate that the amp should be very reliable. The flexibility of the crossovers and the inclusion of bandpass capability make this amplifier a joy to do system tuning with. If you’re a fussy listener on a tight budget, you’d do well to check out a ZRS C9 at your local Cadence dealer. It’s a lot of amp for the money.