Hi, after turn on my CODE 25 at very high volume with a mic turned on I almost got deaf. I turned off the Amp in 1 second... BUT, after that all the low tones/frequencies are distorted/buzzing/ugly dont know how to explain (E string with or without Cab, Amp, Mod, Rev, Del), they are buzzing coming from any Guitar or even music coming from the Bluetooth ... High tones sound fine. I tried to reset the amp and did a firmware update but I still have the issue. Also i tried several guitars, usb cables, guitar cables and even my PC but I still have this distorted low tones. Could anyone give me any advice besides going to the maintenance?
Sorry, no idea. You should email Marshall support directly.
Can you record it and put it on youtube or soundcloud so we can hear it?
If it sounds the same through the headphones its obviously not the speaker.
It sounds like you have tried everything. It could be a power amp or power supply problem, but unless you have some knowledge of electronics then you probably have no option other than to contact Marshall Service.
I found a post about MG50 and this small peace of MG's analysis sounds like my issue. Maybe that's why guitar input sounds strange even through headphone and music coming from AUX is ok.
"The input stage may be affected by transient-voltage/current spikes caused by faulty equipment or DC fluctuation. D1 and D2 (1N4148) back-to-back diodes connected between the supply rails and input are limiter clamping diodes, used to protect the circuit from input signals above 15V+VF (15.65V) or below -15V-VF (-15.65V) which can damage the circuitry."
Any comment on that?
Do you know if I can get the Schematics from Code25 through the support team considering we don't have an Marshall Service Centers in São Paulo/SP, Brazil?
I received a idea from another Marshall Forum: "If it has a line out you could feed that into the line input (3.5mm jack, above the headphone socket). This will effectively remove all the cab simulation and onboard FX in the CODE".
So I craft a cable to plug my external multi effects modeler and another pedals direct to the AUX port... And it's working.
I've bypassed the DSP and Guitar Input and the sound coming from loudspeakers is nice again.
But I'll keep looking for the schematics and maybe I'll repair the input one day.
Maybe I could replace the Input PCB but I don't know if it's possible or if the cost will be fair.