AB 600LX Power Amp

This is just a simple power amp made to accept input from a preamp, DI box, etc. The volume controls are detented rather than continuous, making them less prone to wear and easier to set precisely. Balanced inputs are available, ground lift can be switched on or off, and the amp can be switched between dual or mono mode, and can be bridged in mono. The only outputs are banana plug binding posts, which can be a nuisence if all you have is 1/4" cables. This amp is convection cooled via a large heatsink on the back. There is also a fan on the side of the unit that is activated in case of high internal temperatures, however the amp is so efficient that I've only had the fan activate when the amp was being used outside in 95 degree weather at full input exposed to the sun. Because no fan is used in the amp's main cooling, it is extremely quiet. Excellent features for a power amp, as good as any other for a preamp-poweramp instrument rig. The output ratings are 450w/4ohm stereo, 300w/8ohm stereo, 900w/8ohm bridge. The only weakness of this amp is that it isn't rated into a 2ohm load, although it probably would be able to handle it.

The reason I am reviewing this amp is because I find it to be particularly well suited for a bass rig preamp-poweramp setup. The most notable characteristic of this amp's sound is BASS. When used in a PA rig, this amp produced several times as much low end as a Peavey DECA switchmode amplifier, and had much better low end extension than even a conventional class AB amp. I have never heard better articulation and extension in the low end than from this amp. It will actually make speakers with poor low end sound beefier, stronger, puchier, and will make a decent set of subs POUND. When I used it in my bass rig, it had far stronger output than my Acoustic 150 - even with a low-quality dual 12" enclosure! I should also note that the amp is incredibly quiet, no noticable hiss, even if you put your ear right up to the speaker. The sound is very clear overall, in fact many professionals use these amps to power studio monitors because of their clarity and low noise characteristics. In a bass rig, I would definitely an AB over a Stuart, nothing can deliver low end like a class AB amp with a linear power supply. Switchmode amps like Stuart or Hartke just can't deliver the juice. And this amp sounds at least as clear.

I have not had this amp long enough to rate it's reliability, but I can definitely make a judgement based on its design, and how many older models of these amps I have seen still in use. The construction is rock solid, it is obviously built to last, and the use of an external heatsink instead of a fan-cooled tunnel means that there is little chance of the components getting dirty and corroded. At gigs I have never had any problems at all, even when pushing the amp into clipping.

I have dealt a little bit with AB, they are sometimes hard to reach, but are easy to deal with.

If you are looking for a power amp for a bass rig, I would recommend that you take a look at the AB 600LX or other models in the Precedent line before buying a Stuart or Crown. The performance is comparable if not better, and because few people know about AB the amps can usually be purchased quite cheap used.