Audio Research VS55 Stereo Tube Amp with 6550C tubes

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This VS55 stereo amp was used to power the rear speakers of a 5.1 channel system for 4.5 years up until early January this year, when I had to purchase a solid state amp that my family needed for convenience. I used this VS55 with the original 6550C tubes while the other VS55 I'm selling (see separate entry in Audiogon) was used for my main speakers. In June 2011 one tube blew and I replaced all 4 power tubes with new 6550C tubes that I had purchased earlier from Audio Research as a spare set (purchased 5 so there will be a single spare delivered to the purchaser). The number of hours on the replacement tubes is estimated at 350 hours. Since the tubes are expected to last at least 2000 hours they still have more than 80% of life expectancy remaining.

In addition to the 4 power output tubes, the amp contains three 6N1P input/driver tubes that are still the original ones because they normally last for at least 5000 hours, and I would estimate them at approximately 2300 hours currently. On average the amp was used 10 hours per week.

This amp produces noticeably sweeter high-end than most along with very detailed sound, as well as wide and deep soundstage with warmth that brings to life musical instruments with astonishing realism. You'll also be amazed at how much bass this 50 watts per channel amp can produce if your speakers can deliver. A famous reviewer wrote that this amp is the most vivid way of demonstrating tubes versus transistors, and he was so right.

The amp is in excellent visual and operation condition but just to be safe I'll say 8 out of 10 in case you'll find any minor flaw that I couldn't find. The amp will be delivered in its original box and packaging materials. The original power cord, manual, fuses, and plastic screwdriver used for biasing will be included. Each tube will be marked so that you'll know in which socket it has been biased, because the biasing is done individually for each tube. (Try not to leave fingerprints on the tubes as this will shorten their life). Always give the amp a minimum warm-up time of 20 minutes to sound best and/or check bias. You should have a good DVM (digital voltmeter) to verify the bias of 55mv (representing 55ma) on each tube (give or take 5mv, but not more than 5mv apart from the other tube within the same channel). Ignore the manual recommendation of 65ma bias as Audio Research changed this recommendation early on to 55ma when they switched to Svetlana tubes in place of the initially supplied Electro Harmonix tubes that were troublesome. The amp is very stable so you will not need to verify bias often. Once every 3 to 4 months is what I used to do and usually found that the bias stayed within the desired range.