McGillwell - Fet Booster

All about modern commercial stompbox circuits from Electro Harmonix over MXR, Boss and Ibanez into the nineties.
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Bernardduur
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Post by Bernardduur »

Anyone ever heard of these pedals? I got one in from a friend and it isn't working.

The DC jack was placed afterwards and short circuited one of the lugs of the pometer (not the grounded one) as it wasn't secured well enough. The print is epoxied in all the way.... All I can spot are two ceramic caps.

The website of him is weird........ I spot the fet boosters besides the anti snore units here...........

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2014-06-11 22.34.46.jpg
2014-06-11 22.36.06.jpg
2014-06-11 22.37.00.jpg
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Bernardduur
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Post by Bernardduur »

The potmeter is grounded on the middle lug and ' blends' two signals. To one side it lowers the volume, to the other it cuts treble. Like putting a volume and a tone knob together in a single potmeter.
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Bernardduur
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Post by Bernardduur »

So I found out that the epoxy could be removed with a hot soldering iron. It turns to dust :)

So here's the schematic:
McGillwell - FET booster.JPG
McGillwell - FET booster.JPG (15.66 KiB) Viewed 1614 times
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blackbunny
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Post by blackbunny »

Have you played it yet? Does the unusual combined vol / tone pot give a range of useful tones? :hmmm:

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Bernardduur
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Post by Bernardduur »

I was pretty wrong with that assumption; the knob is a split gain knob.

When it is set in the middle of the turn, the unit has a tad more volume when compared to bypass mode.

When turned to either side, the gain increases but also the tonal response. To one side you get a nice full boost that is a bit heavy on the lower mids (22u section)
When turned to the other side you get a nice shrill boost with more treble.

The potmeter is not that fully funcional as it quickly jumps in gain and volume on the far sides of the turn. Yet, the sound is pretty decent. On higher gain settings even a small amount of clipping is introduced
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Post by mirosol »

I was heading for the post office, but couldn't help myself.
Attachments
McGillWell-FETBooster.png
http://tagboardeffects.blogspot.com/
http://mirosol.kapsi.fi/
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Post by rugeb »

MIROSOL:
Two caps 22nf in vero?
Schematic: 22nF and 22uF
What is the correct value?

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Post by rugeb »

Sorry !! today I'm asleep..... :mrgreen:

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Post by karul »

rugeb wrote:MIROSOL:
Two caps 22nf in vero?
Schematic: 22nF and 22uF
What is the correct value?
Take a another look. There are two 22n and one 22u, on the schematic and vero.

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Post by karul »

rugeb wrote:Sorry !! today I'm asleep..... :mrgreen:
it happens ...

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