Preamp Fun

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Preamp Fun

Postby TDR1138 » Thu Jul 14, 2011 11:00 am

Ken - Is it possible to get the preamp schematics from G&L? I don't recall seeing them on the site (maybe I missed 'em). Still in the mood to butcher... er, tinker more, and t'would be nice to have an official road map...
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Re: Preamp Fun

Postby Ken Baker » Fri Jul 15, 2011 7:57 pm

I don't know. I don't think they're all that closely held.

There are a couple of them on G&L's site, here and here, but I don't think they're current.

I'll ask.

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Re: Preamp Fun

Postby Ken Baker » Sat Jul 16, 2011 8:01 am

It'll be a few days. Paul is traveling.

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Re: Preamp Fun

Postby TDR1138 » Mon Jul 18, 2011 10:43 am

gracias!
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Re: Preamp Fun

Postby Ken Baker » Tue Jul 26, 2011 8:54 pm

Here you go.

Image

PDF is here.

Note that R7 differentiates the circuit.

The drawing specifies L-2000, L-1500, and Climax. However, the circuit is actually the same for all the L series and ASAT basses.

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Re: Preamp Fun

Postby deltafred » Tue Dec 06, 2011 6:23 am

I finally got some time on my circuit sim program 'QUCS' and in response to a question from TDR1138 about increasing the bass hump (somewhere between 40Hz and 100Hz) I did a bit of playing and came up with the following plots for different component values to try and achieve this.

Component values and numbers are based on Ken's schematic above for the L-2000.

The black dotted line is the stock values, R5 was varied from the stock value of 21.5k through to 220k in 5 equal steps. I will leave it to those who are interested to do the maths to determine exact values.

The first plot is for the stock value of C5 (47nF)

L-2000_47nF.jpg
L-2000_47nF.jpg (82.74 KiB) Viewed 10712 times


Next with C5-22nF

L-2000_22nF.jpg
L-2000_22nF.jpg (82.05 KiB) Viewed 10712 times


Lastly with C5=47nf and R6=10k

L-2000_47nF_10k.jpg
L-2000_47nF_10k.jpg (83.14 KiB) Viewed 10712 times


Disclaimers.

1. If you plan on modifying your preamp then you do so at your own risk. Make sure you are confident and competent with a soldering iron an understand the risks of damaging your board, bass, and self etc with a hot iron.

2. Ken, myself (deltafred), and bassesbyleo.com accept no responsibility whatsoever for any damage you may incur or expenses rectifying these.

3. Modifying your preamp will no doubt invalidate any G&L warranty/guarantee. (I have not checked this but would assume so.)

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Re: Preamp Fun

Postby TDR1138 » Tue Dec 06, 2011 6:52 am

Thanks Fred!!!!
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Re: Preamp Fun

Postby Ken Baker » Tue Dec 06, 2011 2:34 pm

Thank you!

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Re: Preamp Fun

Postby TDR1138 » Mon Dec 12, 2011 9:08 am

Ok, experimented a bit over the weekend... The differences weren't as obvious as I hoped. Volume difference, yes, tonal differences, not really. I tried various combinations of R5 @ 100k, C5 @ 22nf and R6 @ 10k. I'll keep playing with it. I might put these components on a switch for a short while, just to make it easier to A/B things.

One thing I did do, though, was to enlarge the wire connection holes and put slightly thicker wires in/out of the preamp. The stock wires were always just too thin of a gauge and broke easily when moving things around. Ok, sure it was never a problem when the preamp was mounted and not being moved around, but still...
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Re: Preamp Fun

Postby wneff » Mon Mar 07, 2016 7:57 pm

Thank you fellow Ubuntu user for the plots. I will try some myself.
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