Kicker's impressive ZX350.4 amplifier.
Stillwater Designs, now better known as Kicker, is an "All American" company that's been
around a long time. Back in the day, they originated the "kicker" box before anyone else even thought about it - that's probably why people still refer to them as "kicker" boxes. In the early 1990s the company started building amplifiers and has since quietly grown into a large force in the market. This time we take a look at the latest stage in the evolution of the Kicker amplifier, the ZX350.4.
Description
Kicker rates the 4-channel ZX350.4 amplifier at 60 watts per channel into 4 ohms, 90 watts into 2 ohms and 2 x 175 watts bridged into 4 ohms. The amplifier is an unregulated Class A/B design with both RCA and speaker-level inputs, and crossover and bass boost for each pair of channels. Visually, the amplifier retains its family resemblance to Kicker amps from the past several years. It has predominantly a textured black finish with a trio of rubber-capped knobs for each channel on the top plate. Swooping "V" contours in the top sheet metal frame the Kicker badge, and a red strip of silicon rubber lines the top plate on both sides.
The ZX series is an "upside-down" style amplifier. The main chassis is an aluminum extrusion that forms the bottom and sides of the amp. A cover plate made of stamped steel with the design and vents embossed in it covers the top of the amplifier. Adorning this piece are two badges (one for the logo and the other for the model number) and the control knobs for the gain, crossover and bass boost. The cover plate fits into two red silicone-rubber extrusions along each side of the heatsink. The molded plastic endcaps hold it in place.
The power/ground/remote terminal, two 20-amp fuses and the power/protect indicator light are all found on the left endcap, while the speaker connectors, RCA and hi-level inputs, fader and crossover switches are on the right endcap. Crossover frequency, gain controls and bass boost level controls are located toward the right-hand side of the cover plate.
The circuit layout inside is pretty much what you'd expect from looking at the outside. The
power supply and the amplification/output section each occupy half of the main board, with an empty 1" strip running right down the middle as a buffer between them. There are other ways of controlling noise from the power supply, but it looks like isolation is important to the engineers at Kicker. The preamp section is nicely contained on a daughter board suspended above the output end of the main board. Both circuit boards are double-sided, but the preamp board uses mostly surface-mount parts while the main board uses all through-hole parts.
Starting with the power supply, power and ground is accepted through two large brass blocks. These two blocks will accept up to 4-gauge cable, although the manual recommends 8-gauge for this one as it is the smallest 4-channel in the series. B+ runs through a pair of 20-amp fuses and a small inductor. It then goes past three 2,200F capacitors for primary filtering and on to two pairs of high-speed, 49-amp switching Mosfets. A TL494 pwm controller drives the switching through the toroidal transformer at about 36kHz, achieving rails of + and - 30VDC. Secondary filtering consists of four 3,300F capacitors to stabilize the rails.
Jumping over to the input section, the first thing I noticed is that the signal grounds are extremely well isolated from the chassis ground. With 40k ohms of isolation, this amplifier will never participate in any ground loops in your system - that's for sure. The signal and shield conductors from the RCA are all fed into low-noise op-amps, thus making this a differential input. This style of input will better reject noise radiated into your RCA cables. The owner's manual reinforces this format by recommending twisted-pair cables rather than big fat coaxial RCAs. Differential inputs are typically found on more expensive amplifiers and have the potential for much better sound quality than less expensive designs. The gain control is accomplished through additional op-amps, rather than the cheaper (and noisier) style of attenuating the signal to ground.
Lastly, the output section consists of four complementary pairs of TIP35C/TIP36C output transistors, each capable of dissipating 125 watts, or 250 watts per output channel, which is more than adequate for this unit.
Performance
The amp performed well on the bench, meeting or exceeding every specification as listed in the owner's manual. The S/N ratio was a very respectable >94dB and the frequency response
measured 13Hz to an astonishing 66kHz. The crossovers drifted ever so slightly from the published spec, but the difference was small and the curves were textbook. While filters are spec'd at 50Hz to 200Hz, the lowpass range was measured 54Hz to 203Hz, and the highpass was 45Hz to 180Hz. The bass boost was right on with the published 18dB boost, but centered at 41Hz rather than 40Hz. Trust me, you're not going to hear the difference on any of this.
The protection circuits worked well, both short-circuit and thermal. I like that they're self-resetting so you don't have to turn the system off and back on. On the bench the amp fired up smoothly and there was no turn-on or turn-off noise in the car at all.
Manual
The owner's manual really cuts to the chase. On page 2 there's a place to write down the purchase details; then it tells you how to mount the amp. Wiring is next, still on page 2, and then it slows down a little to cover different system configurations and the setting of controls. Page 5 covers troubleshooting and specifications, while pages 6 and 7 are the warranty covered in four different languages. Speaking of warranty, Kicker provides a 2-year deal when purchased from an authorized dealer. As always, keep your receipt.
Stillwater Designs, now better known as Kicker, is an "All American" company that's been
around a long time. Back in the day, they originated the "kicker" box before anyone else even thought about it - that's probably why people still refer to them as "kicker" boxes. In the early 1990s the company started building amplifiers and has since quietly grown into a large force in the market. This time we take a look at the latest stage in the evolution of the Kicker amplifier, the ZX350.4.Description
Kicker rates the 4-channel ZX350.4 amplifier at 60 watts per channel into 4 ohms, 90 watts into 2 ohms and 2 x 175 watts bridged into 4 ohms. The amplifier is an unregulated Class A/B design with both RCA and speaker-level inputs, and crossover and bass boost for each pair of channels. Visually, the amplifier retains its family resemblance to Kicker amps from the past several years. It has predominantly a textured black finish with a trio of rubber-capped knobs for each channel on the top plate. Swooping "V" contours in the top sheet metal frame the Kicker badge, and a red strip of silicon rubber lines the top plate on both sides.
The ZX series is an "upside-down" style amplifier. The main chassis is an aluminum extrusion that forms the bottom and sides of the amp. A cover plate made of stamped steel with the design and vents embossed in it covers the top of the amplifier. Adorning this piece are two badges (one for the logo and the other for the model number) and the control knobs for the gain, crossover and bass boost. The cover plate fits into two red silicone-rubber extrusions along each side of the heatsink. The molded plastic endcaps hold it in place.
The power/ground/remote terminal, two 20-amp fuses and the power/protect indicator light are all found on the left endcap, while the speaker connectors, RCA and hi-level inputs, fader and crossover switches are on the right endcap. Crossover frequency, gain controls and bass boost level controls are located toward the right-hand side of the cover plate.
The circuit layout inside is pretty much what you'd expect from looking at the outside. The
power supply and the amplification/output section each occupy half of the main board, with an empty 1" strip running right down the middle as a buffer between them. There are other ways of controlling noise from the power supply, but it looks like isolation is important to the engineers at Kicker. The preamp section is nicely contained on a daughter board suspended above the output end of the main board. Both circuit boards are double-sided, but the preamp board uses mostly surface-mount parts while the main board uses all through-hole parts.Starting with the power supply, power and ground is accepted through two large brass blocks. These two blocks will accept up to 4-gauge cable, although the manual recommends 8-gauge for this one as it is the smallest 4-channel in the series. B+ runs through a pair of 20-amp fuses and a small inductor. It then goes past three 2,200F capacitors for primary filtering and on to two pairs of high-speed, 49-amp switching Mosfets. A TL494 pwm controller drives the switching through the toroidal transformer at about 36kHz, achieving rails of + and - 30VDC. Secondary filtering consists of four 3,300F capacitors to stabilize the rails.
Jumping over to the input section, the first thing I noticed is that the signal grounds are extremely well isolated from the chassis ground. With 40k ohms of isolation, this amplifier will never participate in any ground loops in your system - that's for sure. The signal and shield conductors from the RCA are all fed into low-noise op-amps, thus making this a differential input. This style of input will better reject noise radiated into your RCA cables. The owner's manual reinforces this format by recommending twisted-pair cables rather than big fat coaxial RCAs. Differential inputs are typically found on more expensive amplifiers and have the potential for much better sound quality than less expensive designs. The gain control is accomplished through additional op-amps, rather than the cheaper (and noisier) style of attenuating the signal to ground.
Lastly, the output section consists of four complementary pairs of TIP35C/TIP36C output transistors, each capable of dissipating 125 watts, or 250 watts per output channel, which is more than adequate for this unit.
Performance
The amp performed well on the bench, meeting or exceeding every specification as listed in the owner's manual. The S/N ratio was a very respectable >94dB and the frequency response
measured 13Hz to an astonishing 66kHz. The crossovers drifted ever so slightly from the published spec, but the difference was small and the curves were textbook. While filters are spec'd at 50Hz to 200Hz, the lowpass range was measured 54Hz to 203Hz, and the highpass was 45Hz to 180Hz. The bass boost was right on with the published 18dB boost, but centered at 41Hz rather than 40Hz. Trust me, you're not going to hear the difference on any of this.The protection circuits worked well, both short-circuit and thermal. I like that they're self-resetting so you don't have to turn the system off and back on. On the bench the amp fired up smoothly and there was no turn-on or turn-off noise in the car at all.
Manual
The owner's manual really cuts to the chase. On page 2 there's a place to write down the purchase details; then it tells you how to mount the amp. Wiring is next, still on page 2, and then it slows down a little to cover different system configurations and the setting of controls. Page 5 covers troubleshooting and specifications, while pages 6 and 7 are the warranty covered in four different languages. Speaking of warranty, Kicker provides a 2-year deal when purchased from an authorized dealer. As always, keep your receipt.
Listening
The ZX350.4 was installed in the trunk of my Buick and initially connected to the front separates and the rear 6 x 9s. The crossovers were set for fullrange and the subwoofer was not hooked up.
I started out as always with Donald Fagen's Kamakiriad, which is a very well-mastered recording. There is a lot going on in all of these tracks, so it can really reveal any shortcomings with the amps and speakers. Track 1, "Trans-Island Skyway" starts out with a guitar riff, adding bass, keys and percussion as the intro builds. The bass line is pretty busy and can sound muddy, but the Kicker came through. Not only was the bass clean and clear, but everything else sounded distinct and well-balanced. The center image was a little fuzzy and quite low. I checked out "Tomorrow's Girls" for the highs. The cymbals in the intro were clear and smooth. "Snowbound" revealed good low-end clarity on the Fender Rhodes keyboard and bass guitar.
Tracks from Dada's Puzzle and Mary Chapin Carpenter's Come On, Come On reinforced my initial impressions that the response and clarity were excellent, but the image remained low and somewhat indistinct.
I returned to the trunk and changed the configuration. I kept the front separates connected but set the highpass to 100Hz. The other 2-channels were bridged and connected to the subwoofer with the lowpass set to the 100Hz. I repeated some earlier tracks with good results, and then went to "Posters" on the Dada CD. This one starts out with a great drum solo, adding electric guitar along the way. It sounded great, but didn't get as loud as I really like it. No foul here, it's just a smaller amplifier than I have permanently installed. In this configuration it should put out 60 watts each to the front speakers, and 175 watts to the subwoofer, where I normally have 100 watts to each corner and over 300 on the subwoofer.
Conclusion
I like this amplifier a lot because it did what it said it would do. The Kicker ZX350.4 is a very straightforward unit that is usable in several configurations. When auditioning the amp in my car I didn't feel the imaging and staging were as good as my reference amps, but I realize that it's not an issue for most people. However, clarity and frequency response were very impressive and that's something every consumer should be concerned with.
The ZX350.4 was installed in the trunk of my Buick and initially connected to the front separates and the rear 6 x 9s. The crossovers were set for fullrange and the subwoofer was not hooked up.
I started out as always with Donald Fagen's Kamakiriad, which is a very well-mastered recording. There is a lot going on in all of these tracks, so it can really reveal any shortcomings with the amps and speakers. Track 1, "Trans-Island Skyway" starts out with a guitar riff, adding bass, keys and percussion as the intro builds. The bass line is pretty busy and can sound muddy, but the Kicker came through. Not only was the bass clean and clear, but everything else sounded distinct and well-balanced. The center image was a little fuzzy and quite low. I checked out "Tomorrow's Girls" for the highs. The cymbals in the intro were clear and smooth. "Snowbound" revealed good low-end clarity on the Fender Rhodes keyboard and bass guitar.
Tracks from Dada's Puzzle and Mary Chapin Carpenter's Come On, Come On reinforced my initial impressions that the response and clarity were excellent, but the image remained low and somewhat indistinct.
I returned to the trunk and changed the configuration. I kept the front separates connected but set the highpass to 100Hz. The other 2-channels were bridged and connected to the subwoofer with the lowpass set to the 100Hz. I repeated some earlier tracks with good results, and then went to "Posters" on the Dada CD. This one starts out with a great drum solo, adding electric guitar along the way. It sounded great, but didn't get as loud as I really like it. No foul here, it's just a smaller amplifier than I have permanently installed. In this configuration it should put out 60 watts each to the front speakers, and 175 watts to the subwoofer, where I normally have 100 watts to each corner and over 300 on the subwoofer.
Conclusion
I like this amplifier a lot because it did what it said it would do. The Kicker ZX350.4 is a very straightforward unit that is usable in several configurations. When auditioning the amp in my car I didn't feel the imaging and staging were as good as my reference amps, but I realize that it's not an issue for most people. However, clarity and frequency response were very impressive and that's something every consumer should be concerned with.
The ZX350.4 is stylish, somewhat aggressively so. At a retail price of $349, and a max power of 387 watts, it comes in at 90 cents per watt. As a general rule, anything with a retail price under a dollar per watt is not bad (for an amp below 500 watts). Overall it's a good amp at a reasonable price.
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