New Member, with question re Bass Boost Mod on Fender Rhodes Mark I

[nvilletele]

Hello all, I've just joined up. 

I've got a Fender Rhodes Mark 1 stage 73, which when I got it had a modification to the bass boost circuit, removing it completely and instead there's a 1/4" jack where the bass boost knob used to be.

I had an explanation from the seller when I bought this some years ago, though don't recall much beyond him saying the boost wasn't needed and how this mod did something or other.

I've done research and understand the bass boost is really only a bass cut, restoring full bass when set at its max level, and that somehow or other the bass boost circuit muddied the sound or otherwise messed it up in some way.

When using the original jack, the volume knob does nothing.  When using the jack where the bass boost used to be, the volume knob works.

I've searched around for information on this modification, and found a lot of other types of mods to bass boost, but haven't found any mention of this specific mod. 

I'd appreciate any general info concerning this mod, which I was told was fairly common. 

[sean]

Well, it sounds like someone made the main jack be straight from the harp, and the jack where the bass boost knob should be has the volume control inserted.

You could take a few minutes to trace the wires and make a drawing for us, and snap a few photos.


Mark I namerail circuitry should look like this:
https://ep-forum.com/smf/index.php?topic=4650.msg22605#msg22605


Sean

[pnoboy]

The bass cut control does not muddy the sound.  However, Fender chose to use a 10k pot for the volume control, which does remove some of the sparkle from the sound.  A nice change can be made by changing the volume pot to a 50k audio taper, the bass pot to a 250k reverse-audio taper, and the capacitor to 10 nF.  These parts are usually in stock at Antique Electronics https://www.tubesandmore.com/.

[shmuelyosef]

Until very recently I was running my Rhodes (1974 Mk 1 Stage 73 Fender) directly into an off-board preamp and effects board, but decided to make another try at it. I wired up a version of the original, but with 250K and 1M potentiometers (special audio taper) from Emerson and appropriately chosen poly-caps. It sounds great, very low noise and perfect response.