As I understand it, this a clone of the MF XA-50 made by LJM. The version of the board I have is green, and was indicated somewhere as the second and improved clone by LJM.
I hope somebody can give some guidance on how I can improve the overshoot/stability on these amps. I had them for some time, and did not like the sound much (bass was good, but the rest sounded harsh..) so they were left in the scrap box. I'm hoping the issue is the overshoot/ringing, because they measure ok on distortion measurements.
I played around with one of the boards on the scope with square input, and the things I found are:
-Massive oscillation with 0.5uF parallell to 7,2ohm load. Added a LR on the output, and there is ringing, but it is damped.
-Overshoot on the flanks with 4k square wave. Hardly visible with no load, but gets worse with lower loads and higher output voltages.
I attached some pictures with schematic and some scope shots with 1,8ohm load and no LR(worst case), 7,2ohm & LR(better), and one without load(pretty good).
So, the question is what should I try to tweak? When it comes to compensation and ringing, I'm pretty much clueless.. but maybe I can learn a little with some help here, and at the same time get a usable amp?
I hope somebody can give some guidance on how I can improve the overshoot/stability on these amps. I had them for some time, and did not like the sound much (bass was good, but the rest sounded harsh..) so they were left in the scrap box. I'm hoping the issue is the overshoot/ringing, because they measure ok on distortion measurements.
I played around with one of the boards on the scope with square input, and the things I found are:
-Massive oscillation with 0.5uF parallell to 7,2ohm load. Added a LR on the output, and there is ringing, but it is damped.
-Overshoot on the flanks with 4k square wave. Hardly visible with no load, but gets worse with lower loads and higher output voltages.
I attached some pictures with schematic and some scope shots with 1,8ohm load and no LR(worst case), 7,2ohm & LR(better), and one without load(pretty good).
So, the question is what should I try to tweak? When it comes to compensation and ringing, I'm pretty much clueless.. but maybe I can learn a little with some help here, and at the same time get a usable amp?