CE-1 - Adding a threshold trimmer to the Noisegate

[nickbungus]

Hi Guys.  Long time since I started a topic!

PDF Schematic Link

Is it possible to add a trimmer to control the threshold of the noise gate in the Boss CE-1?  I've read on here increasing C42 will keep the gates tail longer.  I believe I was advised changing R66 and R67 for a trimmer could work.

I've noticed gating when doing the classic impedance mod (330k for r11 and 500kA level pot) to make the pedal 'guitar friendlier'.

[Mark Hammer]

One can also leave the threshold where it is, and simply adjust the gain of the op-amp feeding the envelope follower/rectifier.  That's what the average auto-wah does.  Presently, IC3 is set to a gain of 143x.  If you replaced R72 (3k3) with 1k in series with a 5k trimmer, that would provide a range of gains for the envelope follower of 79x to 471x.  So from around half of what it does now to around 3 times the sensitivity.  At maximum sensitivity, using the same 1uf value for C39, it would introduce a bit of audible bass rolloff at around 160hz, but most sensitivity settings would still incorporate the entire guitar signal for driving the gate.

And just so we're clear, the wet signal is gated out (bled off to ground by Q12) whenever one stops playing.  So, making the sensing circuit more sensitive means it won't take as much to turn Q12 off and allow the output of the BBD to proceed, while reducing the sensitivity means the wet path will be silent until you play.  Note that, like any envelope follower circuit, C41 and C42 determine how quickly the gate turns on and off.

[nickbungus]

Thanks Mark.  You're a legend

[Mark Hammer]

Just a retired guy with a hard drive full of schematics, a lot of time on my hands, and a big mouth.

Are you building one, and if so, what BBD are you using?

[caspercody]

I also would like to know what BBD you are using?

[nickbungus]

I'm using the original,  mn3002.  I wouldn't know where to begin to use something else.

[caspercody]

Where did you get a mn3002?

[nickbungus]

I've got 3 from ages ago.  It's a project I toy with on and off.   I think they are quite expensive these days