Markbass CMD 121P

[kedo]

I have played my acoustic and Yamaha double basses through the Markbass with New York extension for a couple of years. I love the portability, sound and everything about the system. Trouble is the combo is off again for repair. The power amp has already been replaced twice! I don't play particularly loud but the fault always becomes apparent when I play a low note and get a loud harsh raspberry instead of a note. The amp still works after I reduce the volume but you know that all is not well. Markbass really stand by their warranty and are very helpful. My concern is that it is something I am doing wrong in my use of the amp. The first time it happened was as a result of a short burst of feedback howl from my acoustic bass. I love the equipment and will persevere, but wondered if It would be sensible to buy a Little Mark III and bypass the built-in amp in the combo which I think is an earlier model, and have some back up.
Any suggestions or thoughts on what I might be doing wrong would be welcome.

[Beer of the Bass]

It's odd that this is happening repeatedly. Are you using any sort of preamp with the double bass? I don't know whether this could be the cause of your problem, but some piezo pickups have a lot of sub-sonic output which can be hard on amps and speakers and using a preamp with a highpass filter built in can clean this up.

[kedo]

Thanks for your thoughts. I use a Fishman Platinum pro on my acoustic but this latest episode occurred whilst using the Yamaha Silent Bass without preamp. There is probably a big signal from that instrument.