AMZ Mosfet Booster substitution questions

[rosssurf]

I am currently building the AMZ Mosfet Booster seen in the following link. I do not have all of the exact values for a few of the parts and I was wondering if the following substitutions work or make any audible difference in this circuit?
http://www.aronnelson.com/gallery/main.php/v/French+connection/Vero+Layout/AMZMosfetBoost.jpg.html?g2_imageViewsIndex=1


1) 120pF, or 10pF / instead of 47pF for C2

2)  56k, or 68k / instead of 62k for R2

3)  0.15uF, or .068uF / instead of 0.1uF

4)  1N34A, 1N4148, 1N4001, 1N4002, clear glass ones that say DJ025 with what looks like a "T" below it / instead of the 1N4739

Thanks in advance

[rosssurf]

..bump  Help!

[CynicalMan]

Substitution 3 will work (I'd suggest the .15u cap), but 4 wont. The diodes you have are normal silicon or germanium diodes whereas you need a special 9.1V zener diode.

[rosssurf]

Thanks Cynicalman. Good reading!

[Crazyyellowfox]

When I built the AMZ mosfet booster a good seven years ago at least now, I left out the diode
completely and it still worked out just fine, the diode is only there to protect the mosfet from
voltage transients. Be warned though that you could kill a mosfet (or two) without it.

For R2, try your 56k in series with a 4.7k which you probably have as 4.7k is awful common,
that'll get you pretty close to 62k.

C2 might work as a 10pf, more than likely... if it's too bright you could always add a second 10pf.
The .15 will work fine in placeof the .1, all a larger value in that location is going to do is extend
your bass response down below the audible range of the guitar.

[rosssurf]

Thanks Crazy Yellow fox. I appreciate your help and the explanations

[Mugshot]

i read somewhere that you could use an LED instead of the 9.1V Z diode required.

[Mugshot]

follow-up Q:

i recently built J. Orman's Mosfet boost and had to substitute an LED (see above) for the 9.1V Z dioded, and a 3.3M in place of the 10Meg required. how much would the 3.3Meg resistor affect the input impedance? is the 3.3Meg too low?

[PRR]

> 1) 120pF, or 10pF / instead of 47pF for C2
> 2)  56k, or 68k / instead of 62k for R2
> 3)  0.15uF, or .068uF / instead of 0.1uF
> 4)  1N34A, 1N4148, 1N4001, 1N4002, ... 1N4739

The 47pFd is arbitrary, not essential, good practice. You have 300pFd in your guitar cord already, so another 0 or 120pFd makes little diff. Omit it. You may pick up radio stations, especially with the input open.

The 62K musta been handy, or maybe "optimized" for a specific MOSFET. Different MOSFETs may favor different values, and it may not be at all critical. Try 47K. Try 100K.

0.15u will give you a half-octave more bass. Or would, if this were the only bass-cut. It's not, and it is not critical. Heck, a low-leakage 5uFd electrolytic would work. Or, depending what comes after, a 0.01uFd.

The Zener is optional. Some abnormal (but not impossible) inputs (speaker lines, cat in a wool sweater on a dry day) can blow the MOSFET. However most MOSFETs are internally protected?

> use an LED instead of the 9.1V Z diode required.

Hmmmm.... back in 1978, LED leakage was so bad it would farkle the bias, but I guess semiconductor fabs are generally better now. The thing is that the protection must allow the 1V to 3V swing needed to wobble the MOSFET, yet clamp before 20V, the specified blow-up point of the internal insulation. That's why a plain diode aint right, and an LED may-or-may-not allow happy operation. If it clamps too soon, the circuit distorts, and I think it is supposed to be "clean".

The exact clamp voltage is not critical, any Zener 4V to 18V is fine. Last I checked (a while back), Radio Shed still stocked 12V Zeners.