MXR/CAE MC-404 wah internal gain trimpot feature

[Hank-]

I've had this wah for a long time now & so far thought that the internal 'gain adjust' trimpot was to get the volume of the wah at unity when active. I had it turned to 12o'clock, thinking that it did just that, well it whats I perceived the change in sound as.

Today I wanted to reset the wah to its factory state by having all trimmers inside back to default position. I did that, as well as, tried the trimmers at their extremes. Now here's when I noticed something I hadn't before with the 'gain adjust' trimpot.

It seems to adjust the midrange frequency of the wah and not so much as the volume of the wah effect. Clockwise turn raises it & anticlockwise lowers it, this freq change is applied to both the yellow & red inductors, so some settings seem to work best for one particular fasel. Also it does read 'range gain adjust' on the pcb. The manual thats comes with it is hardly containing info regarding the internal trimpots. So for those that have been wondering about the gain adjust trimpot then that's what I found, thought I'd share it.

I wish these controls were on the outside of the wah, i can see why they aren't for accidentally changing them all the time. Still, its quite a versatile wah feature wise.

[Kurohog]

Re: MXR/CAE MC-404 wah internal gain trimpot feature

Dear Hank-,

Thank you very much for sharing this info.Could you also share pictures about the default positions? I have quite a lot of trouble to getting the trimpots to original positions after my brother messed with them one afternoon.

[blueman335]

Re: MXR/CAE MC-404 wah internal gain trimpot feature

Thanks. I've got one, need to play around with the trim pots more.

[Hank-]

Re: MXR/CAE MC-404 wah internal gain trimpot feature

Dear Hank-,

Thank you very much for sharing this info.Could you also share pictures about the default positions? I have quite a lot of trouble to getting the trimpots to original positions after my brother messed with them one afternoon.

I have mixed feelings about the gain adjust trimmer on the pcb after posting this thread. It sounds better in the factory stock position rather than when adjusted at unity gain, also if set a bit higher than stock then the wah starts to feedback/squeal . I pretty sure I'm hearing a frequency change with it. But anyways, here is a pic I had taken years back before adjusting the internal pots, I find the wah sweep sounds better with a CTS pot & not that much with the Dunlop Hot Potz II. Also I like the Q trimmers set a little higher than the factory stock setting, I have the red one pointing 'H & E' position & the yellow one pointing between 'I & H' letterings of the trimmers.

A tip, Its a lot more effective to mark the trimmers using a marker pen before ever adjusting them from factory settings if you ever want to restore it back to stock, something i learned quite late in my tweaking life lol

[Kurohog]

Re: MXR/CAE MC-404 wah internal gain trimpot feature

That's incredibly helpful, thank you so much. I will keep the marker tip in mind as well for similar future situations.

[PFDarkside]

Re: MXR/CAE MC-404 wah internal gain trimpot feature

I agree with marking factory trim pot settings. Thankfully, my adjustable wah of choice (Teese RMC3) is provided with a list of settings to assist in dialing it in and provide some starting points.

Also, an interesting note, they are all labeled things like "Q", "Gain", "level", "mids", "bass", etc. but with the exception of "Q", all they've really done is replace a resistor with a variable pot at different stages of the circuit. Most of the adjustments are interactive with each other, and they've been named with the best description of what it changes. Only the true EQ based adjustable pedals (Teese EqWahlyzer, Dunlop Petrucci) control the bands stated.