Acoustic Research AU
The other big item from the Sybe Bakker collection, and not necessarily ranked lower than the AR3a's, is the AR Amplifier. Notorious for smoking its resistors, it spend a lot of after-sales hours in the factory with power problems, and to the extent that Acoustic Research made comprehensive guarantee extensions to keep the fans happy. Visible factory modifications eventually followed and I'm not sure if this problem persisted to the end, or whether this problem was at all present in the export units of 220 volts. Be it as it may, these were the early years of solid state, and this was the world's first high current amplifier, the first capable of successfully driving the new generation of small-box-big-voice speakers, so to be fair the people at AR applied the new technology extremely well and successfully overcame the amplifier's teething problems. Collectors and fans recognise this, and with the amps coming onto the used market scene in really isolated cases, they are snatched up quickly when they do. An expert restorer like Vintage AR drive the point home by elevating these units to a standard exceeding original factory specifications, demanding a premium which the AR community pays without blinking an eyelid.
Dr Sybe Bakker's unit came without the optional wooden exterior, so without question I would add that somewhere in the future, either as a newly built part or sourced from the used market. The faceplate was remarkably unscratched and merely required a very light cleansing and quick polishing, followed by a similar treatment for the control knobs. One of the two rear face plates were loose and bent, but that was successfully flattened out straight and then glued back down onto the chassis.The amp however showed its age when the top cover came off. Dust and foreign objects thirty years in the making was covering most of what was inside, and aware of the not-excellent but scarily possible conductive characteristics of dust, all that had to brushed-blown-sucked out before any power switches were thrown. A thorough visual check for any other possible signs of trouble was done before the cover went back on. Both speaker fuses were kaput, but I couldn't detect any burnt residual fuse wire or black/grey soot inside the glass tubes, so I hopefully assumed that the cause of malfunction was due to due something like mechanical shock! Lining the amp up with confirmed working source and output components, I could finally after more than a morning's cleaning fire up the old warhorse. A quick crackle, a short buzz, and the decibels were pumping against the walls! Everything sounded good, and my amateur ears could not detect any false notes except for a firm encounter with stray voltages when I touched the chassis (the set was not grounded as clearly prescribed by the AR manual). Considering the initial disappointment with the AR3a speakers, this was tremendously good news.
During December 2009 I finished the restoration of the AR48 speakers, and it was time to separate the music from the movie setup. Hooking the 48's up with the AU was approached gingerly at first, intently watching and listening for any age-related signs of failure, but soon enough I had the door and window panes moaning under the onslaught. Of course it's a documented fact that instead of the published specification of a very conservative 60 watts at 4ohms, these amps consistently tested at 100 watts plus during reviews. I can only assume that the international 220-volt machine was a more robust built not sharing the initial teething problems of the US model; this example was performing as well as when it came out of the shop decades ago. I was sure that performing the recommended internal restoration would indeed improve the audio qualities of this amp, but at this stage I simply adored the sound and it was going to be a painful wait until the AR3a's were ready!
(to continue)