Using it with humbuckers, it gets a little muddy since the 10" speakers don't have the low end punch the later 15" models had. Simply a speaker issue since I believe the head is the same.
Using it with single coils, and single/buckers combo, it puts out a wonderful bluesy sound that does exactly what it says it should. It breaks up nicely when pushed, and the tremelo unit is probably it's strongest feature. Almost Leslie-like. And with the pedal tremelo off-on option, you can, with a little practice, recreate some great Bo Diddley stuff.
Knobs go to 12, that is a cute function that makes you think you got more than you do, but it will get plenty loud, and mine breaks up about 8 or 9 with my guitars set at 4 to 6.
I just like the sound of this amp - sad they got rid of the twin 10", but apparently people wanted more bottom end, so now it's just a 15" new, and I think 2009 was the last year. Only a few new ones out there. The twin 10" setup gives you much better clarity, I believe, with string bending and other single string techniques, and the little added crispness that you need for those slow, single string blues riffs. More of the old sound, rather than the rock-blues distorted sound you hear today.
You can achieve a fairly decent rock sound with the boost function, but it's a little digital for my taste in boost. Better to run up the normal until the speakers just start breaking up if you want to go there. I also think two ten" speakers would be louder than one 15", just more paper to push air.
Over all, this is a great little amp that obviously sold a lot of copies, made in Mississippi, all tube, how cool is that?
One option that was suggested by a blog was to put a 3/4 plywood cover on the back, leaving an opening at top and bottom. Supposed to simulate the lower end some people desire. Also provides some protection for the tubes, but they do have to be vented. I don't know. I really like mine the way it is.
Mine has had the tubes replaced. The tolex is gone and a rough surfaced but nice black paint job has been applied. Original grillcloth is there. My Peavey and Delta Blues plates on the front are gone, a thunderbird is the only thing on the front, but looks cool. Front baffle screws have chrome plastic covers, looks great. So my amp obviously has had some wear and tear, but it sounds like brand new. The pedal is not the original, but the original design is just two foot buttons with open/close toggle with a common ground. Three wire stereo 1/4" jack. It works fine. With what mine might have gone through, I cannot complain. It seems like a tank. Quiet as a church mouse until you play.
I have heard a lot about the lack of a standby switch. Shortening the life of tubes, etc. We'll see. My current tubes are Russian, I've been told the older Delta Blues came with Sylvania tubes. It sounds great with the Sovteks. And it doesn't get very hot with the tubes right there. Very easy access.
I think, for a tube amp, this is a tank.
Bought it used for $350 based on the sound. Cannot complain. Have a number of amps, all different types, but this one is definitely my blues amp. I'm really glad I picked it up.
I'd look for another if I lost it, but I'd want the twin 10". I have larger speakers in my other tube amp, (Crate Palamino), and it is harder to get crisp definition.
(You can, by the way, plug in external speakers but I believe they have to add up to 16 Ohms.)
What I love about it is the definite blues sound, with clarity for the old time blues, and the incredible ease of getting to the tubes. Also, the chicken head knobs are nice, as is the nice, bright red On light.
I don't hate anything about it, but do dislike the rear mounted contols, and the lack of a standby switch, plus the white paint they used for control numbers on the chrome control panel. Should have been black. But that's all kind of nit-picky.
Overall, if you find one, try it out. It gives a few Fenders a run for the money, and is a LOT cheaper.