A client told me about a problem with his Marshall MG100HCFX amps, where vibration from the speaker can nudge the knobs enough to move the sound away from a saved preset, and about the way he gets round it.
We were talking about the case study notes I keep, and he said he had something for me, so I turned on voice typing on my phone and recorded the conversation. I’m writing it up in case it helps someone else.
On these amps, when you change a parameter the preset number flashes to show the sound is different from the saved version, and once you save it the display goes steady again. His problem was that he’d be playing and the light would start flashing and the number would disappear, when he hadn’t touched anything. Something was changing his settings and it wasn’t him.
Why the preset light flashes
He asked me if I could think why. My guess was that the flashing meant the current settings no longer matched the stored preset, so even if the amp had vibrated slightly and a knob had moved from 76 to 77, the light would show it.
He said that was it, because he’s playing through a speaker, and as he explained it, even a bit of sound vibration is enough to move any knob that isn’t turned all the way down to zero, and that changes the parameter.
His answer is to turn every knob on the amp to zero once the sound is stored, including the volume and the master.
Looking back over the notes, I wanted to add one more step. Once the knobs are at zero, you need to reselect the preset from the amp’s menu controls, so the preset is loaded while the knobs are all at zero and they won’t move about.
- Set up the sound and save it to a preset.
- Turn every knob to zero, including the volume and the master.
- Reselect the preset using the amp’s menu controls.
Marshall and the MG amps
He told me he’d reported it to Marshall and that he reads about other people having the same problem all the time, but as far as he knows Marshall never did anything about it.
He still buys these amps, because for him they’re the most hardworking stage amps you can get without valves, and he finds a lot of far more expensive amps sound fizzy and lack warmth. It slightly bugs me that the amp isn’t behaving as it should, but his workaround makes sense.
If you gig with one of these amps, save your sound first, then turn the knobs down to zero and reselect the preset before you play.
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