Revised Treble Bleed Circuit

[frets]

Hi Guys😸,

I wanted to share my revised variable treble bleed circuit.  In testing, it works quite well.  However, I am seeking input as to any improvements you all may have.

This second iteration retains the dip switch cap selection.  The values for selection are now 680pF, 1nF or 1.68nF.  The series resistor drops in value from 22k to 10k.  Finally, the parallel resistor drops from 150k to 100k.  In breadboarding this circuit, it has more control than the previous.  One basically sets the cap value and then adjusts the trim.  The capacitors have more of an influence.


I have played with the cap values, moving the 680pF down to 560pF.  I can’t discern any audible difference. So I bumped it back to 680pF as that is a prevalent value on treble bleeds.

On single coils, the  adjustments are more nuanced than on Humbuckers.  For my testing, 1nF with the adjusting of the trim worked the best.  But of course, treble bleeds are typically a very subjective subject.

I have not subjected this version to any modeling.  I don’t have the software to do so. 

But any suggested modifications would be appreciated.  If any😸

[stevewf]

I like the variability.
For an S-style, have you considered putting, somehow, the trim pot in the trem cavity? For ease of adjustment w/o removing/loosening the pickguard. Drawbacks to doing so?

[gckelloch]

The results will depend on the pickup parameters, how many are active, and in what configuration. The cable capacitance b4 the first preamp also has a big effect. Bill Lawrence has a 330pF/82k parallel value in a few of his Strat diagrams. A low C cable was standard for him. The low R-value keeps the volume from dropping as quickly, but the peak drops a bit more than with higher R. 150k is more level with a low (-200pF) C cable. Higher Cap values lower the peak freq as the volume is dropped. All this is from the GuitarFreak chart:

guitarnuts2.proboards.com/thread/3627/guitarfreak-guitar-frequency-response-calculator

It works pretty well in the free LibreOffice app, but I have to restart it frequently when the GUI screws up. Using it has helped me a lot.

[mikecg]

Hello again frets,

Now I'm confused!

You mention a  series resistor value of 10 k, and a parallel resistor value of 100 k, but if I am reading them right, your pic shows a trimpot value of 100k (marked 104), and an SMD resistor of 100k (marked 1003)?

Also - is your circuit just a 'two component', capacitor in parallel with resistor type, but with variable resistor and switched caps, or something a little different?

[frets]

Mike,
Oh boy, that was a mistake. I should have a 10k resistor on there. Thanks for catching my droit. You will find the longer you’re on the forum that my mistakes happen frequently😸

And my circuit is just a two component layout with a series like on a Fender and a parallel.

[mikecg]

 frets,

Ok - thanks for that.