With so much work put into the amplifier's cosmetics, this is not an amplifier destined to be installed underneath your seat. As well, with a suggested retail of about $800, you're going to want to show everyone. The titanium finish looks really good and appears to be fairly tough and scratch resistant.
The top of the amp has large vents cut into it for airflow. Dead-center on the amp is its cooling fan. Approximately four inches in diameter, Phoenix Gold claims it's a variable speed design. The top also features "viewing windows" that show off the electronics of the amplifier. This is a trend in amplifier design that's still popular.
Connections are all made on one side of the amplifier, simplifying wiring and allowing for a neat install - important if you're a competitor. Power and speaker connections are all made via gold-plated screw terminals. The two are as far apart from each other as possible. A single set of RCA inputs are the only inputs to the amplifier, with no hi-level inputs. Hi-level inputs are probably not something you're looking for in this price range though. Another set of RCAs is for the output of the built-in variable 24 dB highpass/lowpass crossover.
Other goodies on the amplifier include their TAIM (Timed Acoustically Integrated Muting) circuit to kill turn on/off thumps, a bass boost circuit for up to 18 dB of boost at 45 Hz, and a three color LED that displays power-on, thermal or overload protection. There are also ports for Phoenix Gold's optional LPL44 low pass level controller and RDDP, Remote Diagnostic Display Panel.
The internals of the amp have a very clean layout. The large heatsink takes up a good amount of real estate. The design is regulated Triple Darlington, the norm for most Phoenix Gold amps. The circuit board is covered with good thick traces and has adequate capacitance.
Testing
On the bench, the ZX600ti lived up to all the specifications listed on Phoenix Gold's Web site. Nearly all their specs are given at 14.4 volts. That's the typical voltage a vehicle alternator charges at, but not necessarily the voltage one might see at the end of 20 feet of power cable. Power at 12.6 volts is what you may see with the engine turned off.
Phoenix Gold says the ZX600ti is designed to be stable into low impedances such as 2 ohms bridged. That's the same as 1 ohm stereo. Testing at those low impedances, the ZX600ti did indeed run, not engaging its protection circuit. Since it's not recommended, the amp was not tested into lower impedances.
According to Phoenix Gold, the amplifier employs output current sensing that allows the ZX600ti to automatically optimize the power supply to low impedances. Looking at the output numbers, it appears to work fairly well. Two ohm output is not double that of 4 ohm output; could be there's a good deal more.
It appears the circuit is only engaged at lower impedances judging by the very similar 2-ohm power output at 14.4 and 12.6 volts. However, at 4 ohms, the difference between 14.4 and 12.6 volts is much like an unregulated design. If you're a power monger, take note that while the ZX600ti will certainly work in 1-ohm stereo or 2-ohms bridged, it's not at its most efficient.
Checking heat sink efficiency by driving the amplifier at full rated power with a 20 Hz sine wave input -- performance at 4-ohms stereo was good, going for hours without a problem. But at 2 ohms stereo, the amplifier would cycle on and off, despite the fact that the fan was running and moving a good deal of air. Using music, which is a dynamic load versus static, this probably wouldn't happen.
Features
The ZX600ti has a bunch of extras that one would expect at this price point. Checking the crossover section, it is a 24 dB slope and is variable over the rated frequency range. Using the optional LPL44 low pass level controller was a breeze. It attenuates the amp's output up to 22 dB. I did not test the RDDP which duplicates the tri-color LED as well as displaying voltage at the amplifier.
A note about the LPL44 low pass level controller and the crossover. It only works when the crossover is set to lowpass. That makes sense because it's called a low pass level controller. The crossover is high pass or low pass, but not both, meaning you couldn't use the lowpass on the ZX600ti's speaker outputs and the highpass RCA outputs to drive another amplifier.
Testing the TAIM (Timed Acoustically Integrated Muting) circuit, I found that it works as advertised. There were no turn-on or turn-off noises and thumps. The bass boost circuit added quite a bit of thump as well. Be careful with this one. Centered at 45 Hz, you can dial in as much as 18 dB of boost, enough to potentially overload some woofers. Connecting the speaker outputs together to simulate a short engaged the amp's protection circuit saving the amp from frying.
Overall
Phoenix Gold's Titanium Series is pretty bold looking. Not meant for simple installations or hiding under a seat, you'll want to put this amp on display. It meets all the manufacturer's specs from their Web site, and has the expected premium features. Power output into low impedances is solid, but it does get very hot into 2 ohms stereo.
The crossover, bass boost and remote level control make it super flexible. Efficiency is normal for a regulated amp and its fully protected against abusive owners. If you're a competitor, you'll like the amp because according to Phoenix Gold, its IASCA and USAC power rating is only 75 watts per channel. All told, a good pick for a flashy or competition system.