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(More customer reviews)This amp does exactly as advertised. I put amp in my 1993 4x4 Ford Explorer. Since I don't have a super cap, I connected a high density AGM battery directly to it with 8 AWG cables less than 2 feet long and connected an oscilloscope to the amp's power terminals to monitor the battery voltage. I connected four Kappa 682.9CF 4-Ohm speakers that can handle 100 watts, and proceeded to jam. The voltage level wiggled about 0.3 Volts at most. Moving the scope to the speaker terminals confirmed that the RMS voltage of the audio signal was exceeding 100 Watts and I could see clipping going beyond that level but the Kappa speakers popped before the clipping started. I tried both the stock wiring which is either 16 or 18 AWG wire and 12 AWG fine wire to the speakers. None of which made any difference. I could be wrong but I don't think 125 Watts is that much over 100 Watt speakers that they should so easily pop so it doesn't look good for those 5x7 speakers but I've yet to look into it and that will be another review. I guess I'm asking too much from a small speaker. So, I have two issues with this amp. First, the amp has a low frequency boost for two of the channels, and none for the other two...shucks! I discovered that this boost really accentuates the low low frequencies and makes these Kappa speakers sound quite impressive although not much beyond a high listening level because these lows cause them to pop excessively as per noted above. So I wish I could do the same for the other two channels. Bummer. The head unit has low frequency boost also but not as low as this amp's low frequency gain has control over. The second issue is that this amp has a prominent hiss. The noise comes from the input gain stage because turning the input gain down to half way minimizes this hiss to be on the edge of acceptable. At this level, the hiss is noticeable only when the engine is off and there is nothing playing. Comparing this amp to my over 20-year old Alpine 3553 as far as audio quality is concerned is on par with the Kappa amp with accurate frequency response but that old Alpine has absolutely no hiss even at maximum input gain, but to be fair, it's only 35 Watts/channel at 4 Ohms. On the other hand, it's half the size of the Alpine and I guess it's kind of hard to make class-D amps noise free at the cost of size. That's OK, I fortunately managed the noise level. By the way, disconnecting my head unit from the Kappa amp did not affect this hiss. My head unit is the Kenwood KDC994 which has 4-Volt outputs. For those of you who mentioned that your speakers pop or click when your new head unit switched from song to song, it's likely because you're using the stock amp or bought an amp that has its inputs not floating or not at 0 Volts. My stock amp has a 4-Volt offset on its inputs and my speakers popped when each song ended and again when each song started and my Kenwood forced the offset to 0 Volts. That popping went away with this new amp and my Alpine amp. Finally, the amp seems well built and the adjustment controls and switches have a high quality, smooth feel to them while adjusting them. I'm happy with the head unit and the amp, but obviously, not so much with the Kappa speakers since they popped at a level I didn't expect. The battery is a high capacity AGM marine type 23 AH battery. I could run the amp for about 4 hours before the battery Voltage dropped to about 10.6 Volts which is essentially the depletion point. Oh yeah, one final note. I couldn't really address thermal issues because it's cold this time of year but the amp never got warm enough to notice. I don't think I can push it good and hard with these speakers because they pop to easily. I admit, I am a bit bass happy when it comes to a good song that benefits from it but I tone it down on easy songs, I promise. My test music consisted of highly dynamic music from rock, classical, Celtic, country, and Christian, much of which had extensible deep bass instruments, the kind that shake your pant leg because the speaker is next to your leg. I did some rap which the speakers just could not handle. I dropped a star due to the noise issue. Otherwise, it's a great amp, at least in the winter time.
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