[37] AMZ Mosfet Booster

Date: August 9th, 2007 | Comments : [5] | Categories: DIY.

AMZ Mosfet Booster

AMZ Mosfet Booster

While looking through some old materials last night, I found this old sketch, which is one of the original drawings of the AMZ mosfet boost. I drew this quickly in my notebook while working with a breadboard determining the values of the input voltage divider.

As you can see, not much has changed since the original drawing except for the grounding of the 9v zener.

Also, I’ll save you the trouble of flipping the image to see what is on the back side of the page… it is some early drawings of warp controls, which have since been published in my Lab Notebook.


5 Responses to “AMZ Mosfet Booster”

[457] Jolio Cornolio Says: 6:33 am, July 1st, 2008


as I’m sure you’re aware, there’s a few commercially available knock offs of this circuit. I’m looking for a way to warm up the tone of the pedal a la Catalinlbread, but would changing the value of the input cap have much effect? I’ve read you page which states that the bass response of the mosfet is pretty much optimised, but that’s not really my aim. Just a nice fattening, warm swiatchable alternative would be goo, and very easy for a numbnuts like me to do….

[458] admin Says: 8:16 am, July 1st, 2008

Changing the input cap value does not have any real impact on the circuit for guitar or bass use… as shown, the -3db low freq rolloff is 16Hz, while the lowest note of the bass is 41Hz and 82Hz for a guitar.

Change the cap if you like, but you won’t hear a change or any fattening.

The best way to fatten the circuit would be to lower the power supply voltage… 6v would be a good starting point.


[607] Amit Says: 1:32 am, February 3rd, 2009

Hi Jack,
Thanks for the design.
I started getting some Hi-fi noise (HISS all across the spectrum).
I do use a highly filtered power supply and running it on 18v.

Anyways, i tried a lot of things and something worked out great worth mentioning for all other users of the booster or any other hi gain design with electric power supplies.

Adding a 1000Uf or Higher value (preferably 3300uf) 25v or more electrolytic capacitor across ve and gnd closest/on to the pcb would get rid of that.

For reasoning: being a high gain circuit, somehow the DC power wires pick up noise even if filtered at source, and adding the capacitor at target shunts all that ac junk to ground.

[608] admin Says: 3:01 am, February 4th, 2009

The Mosfet Booster pc boards that I sell have power supply filtering onboard, which is not shown in the online schematic.

Typically, hiss does not come from the power supply. It is coming in from the signal input and is only being made more prominent because the booster is amplifying both the signal and any noise that is riding along on the input.

Try making the 47pF capacitor larger… I suggest 470pF in this case.


[738053] Brian Says: 2:31 pm, September 17th, 2015

Hi there, I built this on a breadboard to see how it works. It gives plenty of boost, I did as recommended in the other article and played with the 62k resistor to get the correct voltage. I set it up so it would work as a buffer or boost. However one issue I have is noise. So much noise that if I run it into a drive channel as a buffer or a boost it creates a lot of noise. Now I don’t have a 9.1V zener. Could this be why I’m getting noise. I tried replacing the 47pf cap with a 470pf cap and that didn’t help. It actually removed some of the high end of the signal.


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