Author Topic: amz mosfet boost input cap question  (Read 1744 times)

skrunk

amz mosfet boost input cap question
« on: May 29, 2010, 08:06:50 AM »
I've been mucking about with jack orman's mosfet boost on my breadboard after my mate asked me about a bass booster and I suggested the amz.
Now from what I've read, no mods are needed to tweak it for bass as it's set up for full range response as it is.
Some discussion here:

http://www.diystompboxes.com/smfforum/index.php?topic=76597.0

However, changing the value of the input cap (even to 0.027uf) clearly gives a different sound, beefier and gainier.
It may be the fact that a higher value cap seems louder that I prefer how it sounds, the 0.001uf jut seems weak by comparison.

Is it perhaps just colouring the tone by altering its harmonic make-up or something, while the 0.001uf gives a more transparent tone?
Would love to hear some folks thoughts on this as to what is happening by changing that cap.

FWIW I've dropped the 10M resistor to 4.7M, biased to 5v and used a 10pf cap instead of 47pf.

I also came across the HBE Bajo Mos which appears to be the 'bass version' of their Uno Mos which is practically a part for part clone of the AMZ.
So I'm wondering what they might have done to make it different from the stock circuit if modding it for bass is redundant.
According to this article:

http://www.bassguitarmagazine.com/index.php?option=com_content&view=article&catid=39:pedals&id=224:hbe-bajo-mos-pedal-issue-36

They say:

"We also extended the frequency response so there would be no low-end loss".

Maybe the Uno Mos is set up more as a treble booster?
Maybe they just used the same circuit and called it something else (again)?  :icon_lol: