Test system: Vandersteen Model 2C speakers; Sherbourn 5/1500A 200 wpc SS amp; Audio Refinement Pre-5; Carver SD/A-360 CDC; Newcastle SD-860 universal player. Music: Elton John
MATW &
GBYBR (SACD); Fleetwood Mac
Rumors (DVD-A); Alan Parsons Project
I, Robot (HDAD); Sam McClain
Soul Survivor (XRCD); Supertramp
BIA &
COTC (CD); Fuel
Something Like Human (CD); Foo Fighters
One By One (CD).
OK, let me start with the good: the fit and finish of the Shuguang Audio 502B Integrated Amplifier is good and it is very heavy. It has 4 sets of good quality gold plated RCA stereo inputs and 5-way binding post speaker connections with taps for both 4 and 8 ohms. The connections are placed far enough apart that I didn't have any trouble inserting my Outlaw Audio PCA ICs with locking barrels. The power and input selector buttons had a good solid feel and the unit uses mechanical relays, rather than IC switches. There's a built-in delay (2 min, IIRC) for the tube heaters to warm up. It would be nice if there were pre-in and pre-out connections, but no doubt that would add considerably to the price. It's a good looking amp and there aren't many things prettier than the glow of tubes in a darkened room.
Because of some issues, I think I had it the longest, over a month and I put over 100 hours on it. I know that sounds like a lot to some people, but I left if running all day a number of times to burn in the power tubes. When I received the amp it had a bad 12AT7 preamp tube and the bias levels were seriously out of whack, almost 100 mV (the recommended setting is 30 mV). The manual was useless, it has serious translation problems, which I communicated to Ralph. In fact I was communicating with Ralph a lot, trying to sort things out and get the amp running properly.
As soon as Ralph heard about the problems he supplied me with an almost complete set of replacement tubes, which I installed at various points during the evaluation. Unfortunately, the test points for the bias adjustment were poorly designed and badly placed, making the adjustment process much more difficult than necessary. A serious issue is that the adjustment pots and test points are located immediately adjacent to the power tubes, which are very hot. Getting burned is a distinct possibility, if you're not careful.
Sadly, I could not get the amp to sound good, which was a huge disappointment. The frequency response seemed restrained, almost truncated. I didn't have a spectrum analyzer, but I wouldn't be surprised if the high end rolled off at 10KHz and the low end at around 100Hz. The mid-range was there, but sounded exceptionally forward, probably because of the poor low and high frequency response. What 'low' frequencies there were sounded sloppy and distorted. At the 'high end' of the frequency response the amp sounded thin and shrill. Because of the frequency response issues, I could not make an evaluation of the dynamic range.. But without low bass the amp lacked anything like 'punch'.
To try to improve the sound quality I swapped in a number of the replacement tubes Ralph had provided, tweaked the bias levels, tried both the 8 ohm and 4 ohm speaker taps and swapped the polarity. The best I could get it to sound like was an FM car radio and that was connected tot he 4 ohm taps, with the polarity swapped. (Vandersteen 2Cs are 7 ohms.) The poor performance of the 502B became even more incredibly obvious as soon as I put my Sherbourn amp and AR preamp back into the system. The improvement in sound quality was immediate and unmistakable, even my tone deaf wife noticed the change as soon as she walked through the door, and without knowing I had switched back. Overall, I was seriously disappointed with the 502B.
FTR, Ralph was responsive to the problems I had with the amp and got the replacement tubes to me quickly. Also, he was aware of my dissatisfaction with the amplifier, but did not ask not to post it or soften my comments.
