The Ampeg J-20 is my favorite amp ever made. I own a Reverbrocket, used to have a SJ12, I've played on a 1960's Gemini and one that I believe was a V33 (all I remember was that it was a billion watts). It is a great amp, very warm, very responsive. If you add a reverb pedal to it you have yourself a very complete amp. Without a reverb pedal it also sounds great and quite unique(remember that it was designed without reverb). This is my review that I posted on musicians friend:
Incredible tones.... msrp is too steep!
Posted by Mr.Wednesday from Montreal, Que on Apr 13, 2009
Experience w/product: I own it
Reviewer's Background: Active Musician
Reviewer's Play Style: Funk, Blues, Alternative
Well I've had 5 days to do naughty things with this amplifier. Here are my findings:
The layout is very simple. The tone knob is quite expansive and reacts quite nicely with the volume. Vibrato is very simple to figure out even for someone who's never used vibrato before. The controls have an obvious impact on the effect. Between the regular and bright inputs you will definitely be able to find your sound. Interestingly the bright input is kind of fender-y as it is surely brighter than the typical Ampeg tone.
The sound is incredible. I A/B'd this amp with a Vox AC15CC1 (in the store), my Ampeg Reverbrocket, and a Fender Pro Junior (Woody). This amp has a unique tone; really something special. Firstly at 20 watts it is insanely loud and the clean headroom is huge so if you play a style where you need a beefy clean sound this is your amp. It has a really nice clear break up at around 7 that works really well with distorted chords. The amp also loves pedals and I was able to get some really thick tones from my Little Muff as well as my Rat. In sound charcter it is not as big as a fender but a lot punchier. For styles like funk and blues this thing is a beast. It was warmer than the Pro Junior but had a little less cut. Same with the Reverbrocket; although I personally prefered the distortion from the distortion chanel on the Reverbrocket. The AC15 was nice to but really there was just something about this amp. Maybe it's because I'm an Ampeg lover, either way this amp is great. The lack of Reverb is fine by me. I hooked up my Holy Grail plus and it took to it quite well. Personally I found it really sounded really good with my Dan Electro Spring King.
The Vibrato alone makes this amp a worthwhile purchase. Upon hearing it I immediately had the sensation of having bitten into a rich chocolate cake. It is nice warm and smooth. This amp is all tube (event the vibrato is tube powered and the rectifier is tube powered as well), point to point wired with an Alnico speaker (I can't wait till I've broken it in). This is a great amp.