Hi,
I have both of these amps. Here is some observations that i have had using them with a Sunn 215B cab:
A. Silver stripe along the entire width of the face.
1. The older model of the two. Not sure of the years.
2. Has distortion.
3. On back, there are 2 RCA female plugs that are ungrounded. Ground the one on the left and the distotion goes on. Ground the one on the right and I think it activates the treble boost.. I made a self grounding RCA male plug that i always have in the left side--even with the distortion at 0, I think amp sounds fuller.
4. 1/4 amp output is inverted on mine. eg. If I use a normal, non crossed cable from the amp power output, the speakers move in instead of out on most cabinets. I figure this is because the JBLs + and - markings are the opposite colors of all other manufactures... could be wrong..
5. Has 1/4 in preamp in, and 1/4 in preamp out (phase is same as amp output--need phase inverter on DI or board to use.)
6. Switch on back to invert polarity of mains power.
B. Black face, red logo, with white box around knobs.
1. Sounds very similar to Silver stripe model - bassier/stronger at low levels than silver - can't go as loud though, not sure why. break up and bass at high volumes not as good as silver face.
2. No distortion.
3. Not sure how the power output behaves--have not taken into shop to test for phase. Sounds better, eg more bass, when cross cable is used though.
5. Has 1/4 in preamp in, and 1/4 in preamp out.
6. No switch on back to invert polarity of mains power.
7. Construction and durability seems better to me. Wood case completely surrounds metal chassis.
hope this helps..
