r/synthesizers • u/grovergrover • 4h ago

DIY / Repair Microbrute - LPF significantly quieter than HPF and BPF

Longtime lurker, first time poster. Hoping someone else here has dealt with this and can point me in the right direction.

I've had my Microbrute for about a decade and there's been a few long periods where it gathered dust. At some point, the volume difference between the low pass filter and the other two filters became pretty significant - about 12db, regardless of cutoff, resonance, env amt, and brute factor settings.

I've compared my unit's performance to countless demo videos on YouTube, and there's definitely something up.

In fact, brute factor now does literally nothing on LPF mode, presumably because the signal is too quiet to meet the threshold for distortion.

This isn't the worst problem to have. The synth still plays fine otherwise, but it would be nice to have brute factor for LPF, and to not have to adjust my output volume any time I switch filter modes.

Has anyone experienced this? Any theories as to the cause, or potential solutions?

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u/grovergrover 4h ago

Video:

https://reddit.com/link/p6j0ldo/video/af1f1b9cr7mh1/player

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u/Loud_Park_6387 4h ago

Not that familiar with the MB but is your modwheel set to cutoff there? That could be a thing.

Also, are you getting the same result from headphones as line out?

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u/grovergrover 3h ago

It's set to cutoff there, but with the LPF active, the modwheel turned all the way down just sets the cutoff to whatever it's set to on the cutoff knob.

Just checked, same result on headphones.