GK 200mb Distortion

[Badaboom]

Hi, have a GK200Mb 1x12 amp for more than a decade, and it was about 15 yrs old when I bought it. Lovely sounding, excellent portability. Speaker was replaced last year and box fully sealed up - but it has developed some muddy distortion at low/mid volume specifically on lower frets of E string but also on A if bass is cranked up. Latest tech to take a look at it suggested it might be the limiter as the speaker/sealing is ok... however it sounds fine through a MBX112 cab which is essentially the same speaker config. Anyone had similar experience with this amp or MB150 versions?

[BassBod]

Could be the foam edge on the speaker, they rot after 15 years or so - mine went suddenly, and I just noticed one day that the low end seemed to have gone...then saw the speaker had lost most of its edge. I probably did two or three gigs with it like that before I looked! Good news is it can be-edged or replaced (got one from Thomann) but getting into the cab is a job in itself..then sealing it up again.

[Badaboom]

Thanks - I did have the speaker replaced about six months ago for exactly the reason you describe, it virtually fell apart: and the unit was resealed - but I still get the distortion. It's a mystery that two guitar/amp techs have not figured out.... So far.

[BassBod]

Question is, is it electric or physical? Another good trick is to put a short jack to jack cable between the effects send and return jacks. The socket on the return is switched, and that can cause similar symptoms if it gets corroded. Its a link to the power amp section so any problems there are usually audible.

The metal cab and front grill are prone to rattles - look for stripped screws (you will find some!) or missing rubber gasket around the grill?

Best of luck - nice amps!