The Swart Atomic Space Tone Pro

The Swart AST Pro (an updated Gibson Scout from the 50s) ships from the manufacturer as a 6V6-powered one-channel combo amp with one tone control: check out all the specs at Swart’s website.  I’ve been using this amp for months in my studio and have formed definite opinions on the strengths and weaknesses of the AST Pro.

If you’re a Strat or Tele player this amp represents absolute tonal paradise. Basically, the AST Pro loves vintage-style (weak) pickups like the AlNiCo single coils in your garden variety Stratocaster, etc. With my EJ Strat, partstele, G&L Legacy, SC-2, ASAT, and Comanche (all single coil guitars ranging from low to med-low output) the AST Pro is just breathtaking. The more you turn the volume up from 1 to about 7 or 8 it just sounds better and better. The harmonic complexity is stunning as the amp begins to breakup. And cranking the amp with a Strat yields a pretty cool early 50s tweed fuzz flavor. It’s prefect for blues and roots type music and all my pedals sound good in front of it.  If you’ve been looking for a small combo that can handle a lot of low frequencies this amp has it in spades: it can produce a tremendous, solid low end.

Several cool features of the AST Pro include the external speaker switch on the back so that with a mere flip of the switch you can route the signal to, in my case, a 2x12 open-back Bogner cabinet. The AST is extremely light, small, and portable. Also, the amp is self-biasing so dropping in a pair of 6L6 power tubes is quick and easy and you have your choice of rectifier tubes (it ships with a GZ34 but can be swapped out for a 5Y3).

The reverb is luscious but anything above the 2 or 3 mark and it gets into special effects territory. The trem sounds pretty good, though, I tend not to use it very often. But I've never been too enamored with tremolo of those effects I might use once in a blue moon.

So, anyway, if you’re a single coil fan this is a tough amp to beat and you can do a lot with it: gigging, recording, practicing, whatever. However, once you start plugging hotter guitars into the AST Pro the rewards are fewer.

Once you hit the front end with bridge humbuckers, for me, the AST Pro becomes agitated -- hit a big open chord with the volume at around 2 or 3 and you've got a good crunch already -- turn up much beyond that and you should be prepare to be assaulted with a a lot of fuzz that reminds me of a tweed 50s Fender Twin; it's a jagged 'brassy' kind of overdrive, for lack of a better description. You might like it and, then again, you might not. Even plugging into the ‘Lo’ input only resolves the fuzziness of this amp to a point.  Replacing the pair of 6V6 with 6L6 does not actually improve headroom as much as you might expect, contrary to some reports. It does, however, change the breakup character of the amp; not better, just different. Likewise, the GZ34 rectifier tube will not dramatically alter the headroom nor will running the amp into a more “efficient” cabinet.  I think some people have been guilty of wishful thinking rather than actual experience in this respect. With my PRS SC58 I can coax a nice crunchy rhythm grind with this amp on “2” while running the guitar into the Lo input with 6L6 tubes and the GZ34 rectifier tube into any of my speakers. The AST is not a clean amp by any stretch of the imagination. If you need more headroom look at the Super Space Tone (SST). However, using the Lo input and playing through a neck hum bucker with the volume pot down a bit with the amp's volume up around 3 or 4, combined with a light touch, you can get some killer, semi-smooth jazz tones with just enough grit and bite to move you out of lounge lizard territory. 

If you’re a Les Paul player and looking for headroom and sufficient volume to play out and compete with the rest of the band you will need to mic the amp up or, really, you'll probably need to look for something else.

However, this limitation is also a virtue for the person looking for a good recording or low-volume amp. Plug in your LP and get superb classic rock rhythm distortion without bothering anybody next door. Drop in the 6V6 tubes, 5Y3 rectifier tube, use the Hi input and you can get some crunch with the volume at very reasonable levels. Of course, if you ease up on your picking you can coax a bit more of the cleans out of the amp (turn it up to 3 or 4 and you're okay as long as you're playing with some sensitivity and not just rocking out. Moreover, if you're into solo improvised looping and do not need clean volume to keep up with a band and are not trying to fill up a large space with loud, hum-bucking guitar then this might just be the most awesome amp on the market. Indeed, with my SC58 and some delay pedals I can coax some of the best tones I've heard in 30 years. It really is luscious and awe-inspiring. 

In short, if you’re looking for a cool amp with character to plug your Fender-inspired instrument into then you’re in heaven. If you’re wanting a versatile amp that plays well with all kinds of guitars, can cover a wide range of sounds and musical genres, and can work well in a variety of situations then I think you have to look at something else.  A couple of other facts may drive some users nuts: all the controls are on the back of the amp -- luckily there are only a few so you can memorize their location with ease. But reaching for controls after a few beers and you might be sticking your hand right into the tubes. 

The AST and the AST Pro are pretty much one-trick ponies but they are unbeatable amps so long as you only ask them to do what they are capable of doing. When you push the AST in a direction it does not want to go or if you do not like its one basic tonal flavor then you might be disappointed.