Audio Research M300 monoblock power amplifier J. Gordon Holt Follow-up

J. Gordon Holt wrote a Follow-up on the Audio Research M-300 in January 1988 (Vol.11 No.1):

Some additional listening to a pair of these big amplifiers, which I reviewed in Vol.10 No.9, revealed that they do have one relatively minor weakness: their low end is not quite as detailed or tightly controlled as that of some big solid-state amps (like the Krells and Thresholds). Otherwise, their sound continued to enchant me until...I had turned the volume down while changing a record, and when I next touched the knob, a static discharge produced a very small click through the speakers, followed by a little plume of smoke from one amplifier. (Why is it always the right channel that goes out?) Its AC fuse was blown, and a replacement fuse went the same route.Audio Research said they had a "small modification" which prevents this from happening, but admitted they had already shipped "some" of the vulnerable amps before the weakness was discovered. The mod will be in all M-300s made after mid-October 1987, but since ARC doesn't serial-number their products sequentially (why not?), you can't tell whether or not a new M-300 is the latest version. You can tell, though, by peering through the top cage and looking for a small (6"-wide) circuit board near the rear, piggy-backed on the main board. Both are vertical, so what you'll see of the new board is its upper edge, just below the top of the cage.Unmodified amps can be updated by any Audio Research dealer or by the factory, and naturally, any which break down in use are covered by their warranty. The only catch is, if your dealer isn't local, you have to pay to ship the amp back to ARC, which can be costly, even at surface rates. They'll pay the return shipping, but under the circumstances, we think it would be fairer if they paid for the round trip. After all, it's not the customer's fault that this apparent design weakness in the M-300 wasn't discovered before it went on sale.ARC also has a performance upgrade for the M-300—a new storage capacitor bank which is claimed to provide better sound than the caps originally supplied. This kind of upgrade is not, of course, covered by the warranty, so there's a $95/amplifier charge for it.—J. Gordon Holt

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