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DIY Stompboxes => Building your own stompbox => Topic started by: mdame on January 24, 2011, 11:40:35 AM

Title: Capacitor Bass Rolloff Question
Post by: mdame on January 24, 2011, 11:40:35 AM
I am wanting to put a beavis style voltage sag mod on a positive ground fuzz face.  Should i wire the pot to resist the negative instead of the positive?

I am also wondering about a bass cutoff switch.  How can i figure out the bass rolloff points of the output cap values?
Title: Re: Capacitor Bass Rolloff Question
Post by: mdame on January 24, 2011, 07:51:41 PM
bump
Title: Re: Capacitor Bass Rolloff Question
Post by: kurtlives on January 24, 2011, 08:07:53 PM
If your FF is postive ground wire the pot in series with the V- of the power supply.

To find the roll-off (corner frequency/-3dB roll-off).

f = 1/2*Pi*R*C
Title: Re: Capacitor Bass Rolloff Question
Post by: mdame on January 25, 2011, 09:53:08 PM
Thank you!
Title: Re: Capacitor Bass Rolloff Question
Post by: brett on January 26, 2011, 08:04:10 PM
Hi
to clarify, that's f=1/(2*pi*R*C), where
f is frequency (Hertz), R is resistance (Ohms) and C is capacitance (Farads).

Rule of thumb says that when R1*C1=10, f = 30 Hz (ie no loss, R1 in kOhms, C1 in microFarads, e.g. 10k and 1uF). 
R1*C1 = 1 gives noticeable/useable bass roll-off (f=300 Hz, e.g. 10k and 0.1uF or 100k and 0.01uF).
cheers