Lightning Audio Strike S4.600
www.lightningaudio.com
Lightning Audio strikes the market with the high-power, stylish S4.600 amp.
Lightning Audio
S4.600 Specs

Price & Contact: Call for pricing; 480-967-3565; www.lightningaudio.com
All measurements @ 14V unless otherwise specified
Frequency Response (4-ohm IHF Load, 20 Hz to 20 kHz, 1 kHz Ref.:
channel 1 & 2, +0.02 dB, –0.4 dB; channel 3 & 4, +0.3 dB, –0.7 dB
L/R channel error (max deviation 20 Hz to 20 kHz: channel 1 & 2, 0.7 dB; channel 3 & 4, 0.2 dB
Phase Response (4-ohm IHF Load, 20 Hz to 20 kHz, 1 kHz Ref.): channel 1 & 2, +14 degrees, –20 degrees; channel 3 & 4 +10 degrees, –23.4 degrees
Signal-to-Noise Ratio (Below Rated Output, “A” weighted):
channel 1 & 2 -94.8 dB; channel 3 & 4, –94.7 dB
Distortion at Rated Output @ 1 kHz: channel 1 & 2, 0.12% @ 180 watts; channel 3 & 4, 0.11% @ 450 watts
Output Power (resistive) minimum output (20 Hz to 20 kHz @ 1% THD+N, all channels driven into 4 ohms: 75 watts x 2 + 173 watts x2 @ 14 volts; 62 watts x 2 + 143 watts x 2 @ 12.8 volts; 39 watts x 2 + 92 watts x 2 @ 10.5 volts
Output Power (resistive) minimum output (20 Hz to 20 kHz @ 1% THD+N, all channels driven into 2 ohms): 103 watts x 2 + 248 watts x 2 @ 14 volts; 85 watts x 2 + 204 watts x 2 @ 12.8 volts; 54 watts x 2 + 130 watts x 2 @ 10.5 volts
Output Power (4-ohm IHF Reactive Load @ 60 Hz to 1% THD+N): 252 watts + 562 watts
Crosstalk (Referenced to Rated Output, 20 Hz to 20 kHz): channel 1 & 2, –58.5dB; channel 3 & 4 –45.8 dB
Damping Factor @ 100 Hz, 2 ohms: channel 1 & 2, 63; channel 3 & 4, 81
Voltage for Rated Output: channel 1 & 2, 144 mV to 4.5 volts; channel 3 & 4, 147 mV to 4 volts
Idle Current Draw: 0.7 amps
Current Draw @ 1/3 Maximum Power: 57.6 amps @ 253.6 watts
Efficiency @ 1/3 Maximum Power: 31%
Power-Up Noise: 31.2 dB SPL
Power-Down Noise: 44.2 dB SPL

by Brian Smith
The Strike S4.600 is a 4-channel amp featuring high level inputs, selectable high or low pass filters with variable cutoff frequency, bass boost, remote bass control, and line outputs. Power ratings for this unit are listed as 60 watts x 2 + 150 watts x 2 into 4 ohms and 90 watts x 2 + 225 watts x 2 into 2 ohms. In a bridged configuration, the S4.600 is rated for 180 watts + 450 watts into 4 ohms. Three accessory items were included with our test unit, the Powercell and two Fanmodules. The Powercell is a 0.5 Farad cap that can be connected via a large modular plug. The Fanmodules are replacement top panels for the amp that are fitted with 2.25-inch muffin-type fans.

Performance
The S4.600 utilizes a separate power supply for each pair of channels, which are dissimilar in maximum output power. Channels 1 and 2 produce about 75 watts each into 4 ohms while channels 3 and 4 produce about 173 watts each into the same impedance. This essentially defines the S4.600 as two separate amps that share a chassis and power connection. In the lab, this made the testing a bit more involved, producing nearly twice as many specifications. In the accompanying table, I’ve included separate specs for each section of the amp in most cases. Current draw and efficiency tests were performed as a single amp, with each section adjusted to one third of its respective maximum output. Turn on/off noises were a bit high by competition standards, but the differences between the noises of each section of the amp were negligible.

One interesting effect of the dual power supplies is that no matter how hard you drive channels 3 and 4, 1 and 2 remain unaffected and vice versa. However, this is a test bench phenomenon; we have a voltage regulated power supply. In a car, when 3 and 4 hit hard enough to cause a voltage drop, 1 and 2 might see it as well unless you have plenty of caps and reserve alternator power.

From a performance standpoint, the S4.600 is quite impressive. Channels 1 and 2 provide a clean, quiet power source for your front stage while channels 3 and 4 can be used to drive rear speakers at 173 watts x 2 or as a substantial subwoofer amp in a bridged configuration.

Installation
As you can see from the previous sections, the S4.600 has installation flexibility to spare, although it will probably be a bit large for passenger compartment locations. The amp’s end caps provide a unique finished appearance but their fit and method of attachment leave a bit to be desired. Each side of an end cap is attached with a fastener that screws into the amp’s heat sinks. The horizontal orientation of these screws allows the end cap to pivot around them just enough to cause wear on the aluminum brackets that hold the end caps on, so we don’t suggest you make a habit of removing them except when it is really necessary.

The S4.600 could also use a little attention in the heat sink department. All of the amp’s power supply and output devices are clamped to the interior of the black panel that runs the length of each side of the amp. We’d like to see an amp with this kind of output potential with a little more surface area in its heat sink design. With an excess of 800 watts on tap, I’d consider those Fanmodules as a necessity rather than an optional accessory. (Lightning Audio notes that the S4.600 uses mass (weight and size) to dissipate heat. While the amplifer’s heatsink may have little surface area as reported, the unit does, in fact, have a lot of thermal mass.)

On the other hand, the Powercell can safely stay in the optional category. I connected the Powercell during our testing session but noticed no improvement in performance on steady-state measurements. This isn’t surprising; a cap should only make a difference on a dynamic measurement. Even on such a measurement, we would be unlikely to notice a difference because our voltage regulated power supply is absolutely full of caps. In an automotive system, a good cap can produce a subtle improvement in the dynamic performance of an amp. However, most people don’t listen to music with a dynamic range that’s wide enough to reveal the difference. So, rather than giving you a list of cap specs, I’ll just stick with a good idea that we often recommend: demo it. Due to its plug-in design, this should be the easiest A/B comparison in the business. 1. Install the amp 2. Listen to a piece of your favorite music 3. Plug in the Powercell and listen again. Better yet, get a friend to deal with the plug and remain completely blind to the switching process. If you hear a difference, get out your wallet. If not, consider the possibility that your musical tastes preclude the necessity of installing a cap.

Connections & Adjustments
Connections to the S4.600 include speaker-level inputs (with modular plug), line level RCA inputs and outputs, telephone-style remote connector, and 5/16-inch spade receptacles for all speaker connections. Power, ground, and Powercell connections are made at one end of the amp with large modular plug receptacles. The Powercell’s plug is connected directly to the capacitor’s terminals while the power/ground plug accepts up to 8-guage wires. (Lightning Audio reports that the Powercell’s direct connection to the amplifier is the most effective means of connecting a capacitor to an amplifier.) Fanmodule power connections are located on the amp’s circuit board and are made with small dual pin connectors. All adjustments on the S4.600 control one pair of channels and include input sensitivity, remote bass control (channel 3 and 4 only), bass boost (0 to +13 dB @ 50 Hz (channel 3 and 4 only)), crossover mode select (channel 1 and 2 flat or high pass, channel 3 and 4 flat or low pass), and crossover cutoff frequency (variable from 40 Hz to 400 Hz with 12 db-per-octave slopes).

Manual
The manual for this unit covers both the S835 and the S735 (the 2-channel version). Both subjects are covered reasonably well with system diagrams for several configurations. The biggest surprise came in the system design section. It actually says that speaker placement is the most important consideration for a great sounding system. This is absolutely correct, but you won’t find many amp manufacturers that are willing to print that little pearl of wisdom in their manuals. The truth shall set you free.