As I mentioned in a previous thread, a while back I picked up an Adcom GFA-555II for use in my home office system. While not quite the equal of my GFA-5802, the 555II has been a solid performer. Move ahead to about 10 days ago... I threw in a token bid for a GFA-555 (the first generation, not the II) and when I checked on it later in the day I was surprised to find that I won the auction for $234.00. I wasn't in immediate need of the amplifier but was none the less happy for three reasons. First, I had gotten what I consider to be a good deal; second, I now have the opportunity to tryout a few additional bi-amping options on the Infinity RS 9 Kappas; finally, I have the opportunity to compare both generations of 555 amplifier head-to-head.

Given the Stereophile reviews of both the 555 and 555II I was curious what I would (or wouldn't) hear. I hadn't read the Stereophile reviews in sometime and I decided that I wouldn't revisit them until I had finished listening. Basically I didn't want my opinions to be influenced by what I was "supposed" to be hearing.

The only thing I remembered from the Stereophile reviews was that the 555 was supposed to have a "grainy" top-end, which was improved in the 555II. So far all of my listening has been through my home office system, which includes B&W DM 602 S3 speakers. I consider these speakers to be quite a bit darker than my 9 Kappas, which may explain my first observation, namely that the supposed "grainy" top-end of the 555 was nowhere to be heard. At least it was not significantly different than the 555II. A-B -*test*-('")ing is tough because so many of the details are quickly forgotten as cables are swapped. The one thing I did believe I could hear was a little bit more weight in the bass. After swapping back to the 555II to confirm, I was left with the impression that there is a slight difference, but it is in fact very small. I finally revisited the Stereophile reviews and read that they had also heard this slight difference in the bass.

I still need to listen to both amplifiers with them connected to the big 9 Kappas, but so far I would declare the con-*test*-('") a draw. The 555II does seem to be a bit better constructed, as some of the details were better tended to during the update. However, the original 555 is still a well built piece. The 555II also has a triple darlington output stage, which was intended to improve the amps ability to drive difficult low impedance loads. If you need that capability then the 555II is probably the better choice. However, for any other situation I really feel that these two amplifiers are sonically equal.

Rob

Very nice write up. Thanks, Rob.

Thanks for the write-up Rob. I gave my new GFA-555 Pro a long listen this morning while doing chores around the house. My impression is the 555 Pro is musical in the midrange and treble. The bass wasn't as punchy or well defined as I like but I suspect my choice of preamp has something to do with this. I'm thinking about getting one of Adcom's Straight Line preamps which should be as tranparent as possible.

Have you tried different source components? For years I had been using a Carver TL-3220 CD Player and felt the same as you about my system, and needed to use "loudness" on my Carver CT-7 preamp to boost the bass to where I thought it should be. Once I updated that to an Adcom GDA-600 DAC (and later to a PS Audio Ultralink Two DAC, both using a DVD player as a transport) the low end was all there, and I no longer had a need for the "loudness" control. The preamp could still be your problem, I just recommend you take a controlled approach to figuring out what you really need to upgrade.

Rob