Workbench HD cap values Conversion Chart

Started by Elantric, August 22, 2013, 12:13:46 PM

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Elantric

Im in the USA and the typical convention is to use microfarads - while nanofarads is used more in the UK / EU

http://www.translatorscafe.com/cafe/units-converter/electrostatic-capacitance/calculator/nanofarad-%5BnF%5D-to-microfarad-%5B&%23181%3BF%5D/

http://www.diystompboxes.com/wiki/index.php?title=DIY_FAQ

For those who want to know here is a conversion chart to make sense of the Workbench HD cap values

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1.1nF = .0011 uF (microfarads)

2.2nF = .0022 uF (microfarads)

4.7nF = .0047 uF (microfarads)

11nF = .011 uF (microfarads)

22nF = .022 uF (microfarads)  =  Typical Gibson Tone Cap with 500K Tone pot)

47nF = .047 uF (microfarads)=  Typical Fender Tone Cap with 250K Tone pot)

100nF = .1 uF (microfarads) = Some Fender Tele's use this as a Tone cap with 1 Meg ohm Pot

Elantric

http://www.tdpri.com/forum/tele-technical/108759-please-explain-how-value-tone-pot-capacitor-interact.html



TDOWNS Wrote
QuoteOk. You just had to ask. So, I spent a little time with PSPICE today so you can see the electrical response of the tone pot. The pickup is a Tele bridge. The conditions are as follows:

    Pickup inductance = 3.2H
    Pickup resistance = 7.4K
    Pickup interwinding capacitance = 160pF
    Volume pot = 500K (set at max CW)
    Tone Pot = 500K but 442K actual
    Tone cap = 0.05µF
    Cable = 20ft
    Amp input impedance = 1MEG
    Amp input capacitance = 100pF


The labels on the graph are TONE KNOB SETTING (0 thru 10)/RESISTANCE. Remember it is a audio (non-linear) pot. The resistance values for the 0 through 10 positions are based on experimental data I collected on audio pots a few years ago.



Notice the resonance peak with no tone pot connected aka the no-load pot. You can now see how the TBX would give you everything between the max CCW and almost open.

I doubt some of you would experience the same no-load response as plotted because every amp input impedance is not as high as 1 meg. If the amp input impedance is more like 500K, that no-load response will be less pronounced. But, a Fender Twin is 1MEG input impedance.

Look at the curve for the 500K pot set on "8". Having a 250K pot (277K on the plot) is like a 500K pot turned down to "8".

Regarding the tone cap value, it matters most at a setting of "0". With the 0.05µF cap, the resonance is moved down to 300Hz. At other points on the dial, it is simply destroying the resonance at ~3.5kHz. If you used a smaller cap value, that resonance would be higher than 300Hz.
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