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Author Topic: Simple Preamp please check my work  (Read 7740 times)

galaxiex

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Re: Simple Preamp please check my work
« Reply #15 on: May 24, 2015, 09:56:03 PM »
Here is the revised Pre-amp that I last used with the Cana Kit amp.

Very modest gain of 2.5 to keep the Cana Kit amp out of clipping.

Everyone will notice that I copied Fender's input scheme and the rest is "stolen" circuit fragments from the web.  ;)

This seemed to work pretty good.
« Last Edit: May 24, 2015, 10:02:31 PM by galaxiex »
Fear leads to Anger, Anger leads to Hate, Hate leads to Suffering.

J M Fahey

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Re: Simple Preamp please check my work
« Reply #16 on: May 25, 2015, 05:19:13 AM »
Looks good, very good.
Loved its simplicity  :dbtu:

galaxiex

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Re: Simple Preamp please check my work
« Reply #17 on: May 25, 2015, 10:12:55 PM »
Thanks JM! :)

Simple is what I was going for.
Can get complicated later (but doesn't have to) after the basic amp is working.

Now I am waiting for the 1875 chip to get here....

Oh, btw, anyone see any problem with using the above pre-amp with a split supply?
All the 1875 circuits I see use a split supply.

Can I simply eliminate the bias arrangement (virtual ground?) of R6, 7, 8, 12 and C7 of the above schematic,
and connect the gnd of the op-amp (pin 4) and the FET source resistor R13 to -V of a split supply of say +-15V or +-18V?
All other gnd's go to gnd of course...

Oh wait... pin 3 of the op-amp would also go to gnd, and would the FET gate need a gnd ref?

Argggh, I'll re-draw the schem to see what it looks like...

BRB

Somehow this doesn't look right to me...
« Last Edit: May 25, 2015, 10:44:02 PM by galaxiex »
Fear leads to Anger, Anger leads to Hate, Hate leads to Suffering.

Loudthud

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Re: Simple Preamp please check my work
« Reply #18 on: May 26, 2015, 12:00:25 PM »
Q1 needs a ground reference for it's Gate. A 1Meg to ground or just short out C4.

galaxiex

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Re: Simple Preamp please check my work
« Reply #19 on: May 26, 2015, 07:43:56 PM »
Thank You Loudthud!

Here we go.
Fear leads to Anger, Anger leads to Hate, Hate leads to Suffering.