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Tuesday, September 22, 2020

Doug's Domain

Doug Vetter, ATP/CFI

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Saturday, July 20, 2013

Arc Amps Arrive

During a visit to the Arc Audio website this week I noticed they were running a "free shipping" special for the month of July so I decided to pull the trigger on a pair of KS 125.4's. My guess is the deal was only worth about $50 but that's better in my pocket than theirs.

Until I clicked "buy" the deal was by no means done, however. Even after I thought I had completed my amplifier research I briefly considered JL's XD400/4 Class D product. It was well reviewed in its own right, met my space constraints, supported differential inputs, promised very low power consumption and was $20 less per unit than the 125.4. Forum research revealed, however, that when compared to the Arc 125.4, there was no comparison. The 125.4 was the clear winner in the sound quality department.

Truth be told, I expected as much, as a Class H amp (which is to say, a Class AB amp mated with a power supply whose rail voltage tracks the music signal input to reduce power dissipation) has one hell of an advantage over a Class D design: the fact that at very low power the output devices are in Class A and thus providing the absolute best, most linear audio reproduction possible.

I knew the physical specifications of the amps before I bought them, obviously, but I was pleasantly surprised when I took them out of the box. I was expecting something closer to 2" thick, but if you ignore the slightly offset mounting flanges and the Arc Audio emblem, both of which contribute to overall height, the actual height of the amplifier case is closer to 1.5" or about the height of a 2x4. I have already verified they will fit nicely on the rear deck without significantly encroaching on trunk space. And with all the amp's controls easily accessible in that position it should make initial setup and ongoing tweaking very easy.

Unfortunately the 125.4 isn't cheap but given the level of engineering talent that went into building it -- something I can now personally relate to given I've started building amplifiers as a hobby -- I think it's a steal.

Activated Carbon Microfilter

One of the things I really like about my E46's OE microfilter is that it's manufactured with activated carbon so it tends to reduce organic vapors like diesel exhaust. The E36's microfilter, while effective at simple particle filtration, does nothing for exhaust vapors.

Given that I paid almost $40 for the last OE microfilter I decided to look for aftermarket or OEM alternatives that incorporate activated carbon. This led me to find an ATP brand unit which I purchased on Amazon. I installed the filter a couple months ago but decided to wait to report the results, which are favorable. While it doesn't eliminate exhaust vapors, it does tend to reduce them. As it's possible to buy two of the ATP units for the same price of a single OE filter and achieve noticeable results, I'd call this a win.

Note: If you click on the link to Amazon and buy the product a small amount of your purchase will help support the site.

Mileage: 237000