Help me add a "Bass cut" toggle to my AMZ mosfet boost

[rosssurf]

I have built the following AMZ  Mosfet Booster in the link below. I am using it to increase the gain into my Peavy Classic 30. I use average gain for the dirty channel on that amp and step on the AMZ for a higher gain sound. I was wondering where i could put a toggle that cuts a little bit of the bass freqencies. I am learning a little about high pass RC combos' and I do not see on the schematic where that might be. Should i add the mod to the beging of the circuit? or toggle the output cap? any help is appreciated.

http://www.aronnelson.com/gallery/main.php/v/French+connection/Vero+Layout/AMZMosfetBoost.jpg.html

[bipedal]

Try it on the end of the circuit.

It should be really easy to incorporate a bass cut switch simply by toggling between the 0.1 uF output capacitor (the"stock" setting) and a smaller value cap.

You'll have to try out different cap sizes there, use your ears to guide this.  Maybe start with something like 0.047 uF and adjust to a smaller value if still too bassy.

[fuzzo]

I did that on my AMZ mosfet booster , works really well. Just put a switch to select between 1uF and 10uf for the cap linked to the pot. (You can put a lower values ).

[rosssurf]

fuzzo Do you mean a switchable cap AFTER the 100uf cap that goes to lug 2 on the pot? leaving all other stock parts in place? or do you mean to replace the stock 100uf cap for C5 and make it switchabe to be either 10u or 1u?   This sounds very different from what bipedal  is saying about making C4 (.1uf stock) swithable. ?.    would both of these accomplish the same thing.
Sorry for my confusion here, and thanks for your help folks.

[fuzzo]

I meant make C5 switchable. 10uf (stock) /  1uf (less or more, your tastes). wil cut the bass.

(actually to make a bass cut at input you've to reduce the input cap, something like 1n or even less. I tried that too and I wasn't really happy with it, I searched some information to tweak it , found that trick described here, tried it and liked it. I'm almost sure Catalinbread did the same thing in his famous booster, it's the same circuit)

[Ben N]

Rather than switch between caps, you might just leave the smaller one in the circuit and switch the larger one in and out, should make the operation of the switch a bit smoother.

Another place to look at is the bypass cap on the source. My understanding is that this produces more of a shelving effect, as opposed to the slope of the hipass filter. If you make the cap smaller you will roll off more lows--like the difference between the input stages of a typical Fender, with its 25uf bypass cap and big bottom, and a Marshall, with 0.68 uf and tighter bottom (less low end).

[rosssurf]

fuzzo you stated " I meant make C5 switchable. 10uf (stock) /  1uf (less or more, your tastes). wil cut the bass."



On my layout in the link above, C5 is 100uf stock?.., not 10uf.  Could you clarify? sorry for my confusion, my brain is full at  the moment
..Thanks for having patience with me.

[ubersam]

You can add a resistor to ground on the output side of C4 to form a high-pass filter with a low cutoff freq. A 2.2K will cut from 723Hz (72.3Hz will be -6db), a 4.7K will cut from 338Hz (33.8Hz will be -6db).

[fuzzo]

I don't know what exact values is used in the Jark Orman's scheamtic. I opened mine today and the values for the tiny cap is 2u2 with the switch the big one (the regular one, 10uf or 100uf I can't see the value) is placed in // to the 2u2 to increase the bass response.