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RD112's picture

By-Pass Tone Controls on RD100 with 100mV Insert Jack

Hi all,

It appears that the 100mV insert jack could be replaced with a Mono Plug jack, and then add a 68K resistor from the tip input to the 0.1mF capacitor to completely bypass the Treble-Mid-Bass adjustment.

Is this possible, and has anyone tried it? And with what result?

the idea comes from my Vox Lil' Night Train which has a Thick and Bright switch that by-passes the Tone controls.

PDF icon LilNighTtrain_OM_EFGS1.pdf1.61 MB

Line Out?

Have you tried a mono cable from the Lil Train Line Out to the MM 100mv Line In? Might be fun. Go easy with both of the volume controls. -mgriffin

RD112's picture

100mV or 3V?

No, Haven’t tried the Lil’ Night Train into the MM.
Just a Chorus pedal into the 100mV, which works perfectly.

I will try it and let you know.


No modification needed

No modification is needed. Plugging a mono plug into either of the insert jacks makes the jack work like an input (the ring is shorted to ground). Adding a 68k resistor will not make a difference in sound. Actually, the 68k resistor is paralleled by a 4.7k resistor if you use the Hi input.

You will lose some gain from the preamp stage but you can probably make up for it by adjusting the gain controls or you can add your own clean boost or maybe an OD pedal with some eq in it to tailor the sound. Certainly a neat opportunity to experiment.

Lars Verholt

RD112's picture

Lil' Night Train into 100mv Input

Yes!... the Lil' Night Train line-out to the 100mV insert jack works.
I'll be playing around with this a bit more, then provide an update.
Thanks for the comments.

RD112's picture

Lil' Night Train into 100mv Input

To wrap this up, I made a 3.5mm mono-plug to 1/4-inch (6.3mm) mono-plug mono-cable from an RCA cable using push-in plugs (RadioShack brand LOL).

Into the 100mV jack, the gain and volume controls on both amps are active...and seem best controlled through the RD. Super Loud!. This gives access to the Reverb and Distortion switches on the RD100 as well.

Into the 3-V jack, only the gain and volume control on the Vox are active...as expected.

Plugging the guitar straight into the 100mV works well...a little bit of gain/volume is missing, but not much.

The Treble/Mid/Bass on the RD are by-passed in all cases, and improves the "clean" sound all around.



Years ago I bought a VOX AP2 headphone amp. I'd forgotten about it and recently discovered it hiding in my desk drawer. Since you had luck with the Lil' Night Train, I decided to give Baby VOX a try with my RD65-112. All I can say is WOW!! Why did it take me so long to figure this out. Thanks for being the trail blazer and/or guinea pig. -mgriffin

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