ADA Preamps > Original MP-1

It’s An Addiction, I’m Sure!

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Moff40:
Just scored my 3rd MP-1 from a local person, with another MC-1.  V1/Switch top, 1.38 EPROM, so I’ll be hitting MJMP up.  Everything functions as it should, and the MP’s in pretty clean condition.  Looks stock except for perhaps some parts changed during routine service, the battery mod, and it looks like one of the power caps was changed.  MC-1 has been used a lot.

No real issue, except it has much lower output overall than my other two (and yes, I did make sure it was switched to “line level” output :D).  Any other ideas as to why that might be?

I have to stop buying these things…  :)

MarshallJMP:
Try switching the topswitch up and down a few times, sometimes these have bad contacts.

BTW is the output low on all 3 voicings?

Moff40:
Yeah, all three voices.  And they all sound fine, just quieter.  Where I could get by on 10:00 on my other MP-1s, I have to set the overall volume in this one to 2:00 or 3:00 to get the same percieved output.  But the headphone output is as stong as the other two, so whatever is “attenuating” the signal appears to be after the headphone out.  I did toggle the top switch quite a bit.  Toward the back is line level, right?  That’s the “louder” of the positions.

rnolan:
Yes toward the rear panel is Line lv position.  Maybe give the switch a spray with contact cleaner and toggle a few more times (they do gum up).  So the headphone out has it's own pot, I wonder if the main (front) output pot also needs a clean? And is the knob aligned correctly (i.e full off 7 o'clock (ish), same as the other units)?

MarshallJMP:
The only 2 things behind the headphone out are the topswitch and the front vol pot pot and one opamp used as a buffer. Since you have sound the opamp should be fine.

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