MF-104M Feedback

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Re: MF-104M Feedback

Post by Control_Voltage » Wed Oct 22, 2014 11:42 am

Hello Everyone!!!

104M Feedback Control and Mods
1) On the back of the MF-104M there is a trim pot labeled VR1 FB Amount. This sets the maximum amount of feedback. Moog factory sets it so that at 3:00 with ~400mS delay in long mod echos neither reduce or increase. You may adjust this trim pot for more or less maximum feedback.

2) R62, which is located to the left of the two diodes near U11 and above the text D23 on the lower right corner of the PCB sets the amount of limiting of the input signal and the feedback trails.  Removing or increasing this resistor could provide more wild feedback but may requires and input signal with less transients (pre limited) or the BBDs may distort.  It may also set the maximum feedback level to sit differently in the mix with input signals than before.  Stock we set it to 3.4K. Try replacing it with a 100k-500k potentiometer in series with a 1k resistor and dial it to taste. This is akin to setting the amount knob on a soft knee limiter.  Caution this requires delicate surface mount soldering.

Remember meddling with the innards of a pedal during the warranty will void the warranty, and may permanently damage your device if done improperly.

That being said, information is power. Enjoy!

Andy Hughes
Service Department Manager
Moog Music, Inc.

Posts: 18
Joined: Sun Oct 12, 2014 12:14 pm
Location: Madison, WI

Re: MF-104M Feedback

Post by Rooftree » Thu Oct 23, 2014 4:12 pm

Andy: Great info. Thanks! I really appreciate you (and Moog) sharing details like that.

It will be a week or two before I have time to open up my 104 and adjust the trim pot. I'm looking forward to hearing the difference.

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