Can you tell the the frequency of a tone control is by it's resistors and caps ?

[pbman1953]

The book that came with this amp doesn't list the frequencies for it's main tone knob set. The bass control  has a main roll in this amp. If it's all the way down there isn't any sound. My question is if you can tell what the frequencies are based on what Fender used for the resistors and caps?


I'd like to lower the frequency of the Bass control, if possible.


Thanks

[Rontone]

Would Tone Stack Calculator help?

https://www.duncanamps.com/tsc/

Edit: There is also TSC online through browser here - https://www.guitarscience.net/tsc/info.htm?

There is a Fender tonestack in there that can be altered to these values, and you can study the frequencies on the graph

The schematic shows a 10nF cap for the bass cap in the tonestack? That has quite a large drop from the original 100nF

[pbman1953]

The caps in the bass circuit are .1 & .047


While in the Fender tab, and based on the default caps in the calculator, where do you read the centered frequency?

[tubeswell]

Basic formula for simple low-pass or high-pass tone filter:

 f = 1/(2Pi x R x C)

Where:
f is the frequency cutoff point in Hertz (at -6dB per octave)
R is resistance (in Ohms)
C is capacitance (in Farads*)
Pi is 22/7 (so 2Pi is 44/7)

*i.e., 100nF (aka 0.1uF) = 0.0000001F, 10nF (aka 0.01uF) = 0.00000001F and so on


For more elaborate circuits, use a combination of the above with voltage division and summed bode plots. (Merlin’s books are excellent for instruction on this.)

[pbman1953]

Thanks for the info!


I need to understand this graph first. I sent a screen shot.


Based on the picture what is the center bass frequency. I don't know what line to see that. Once I know I can play with the values


Thanks

[tubeswell]

If you twiddle around with the tone controls in the spice model, you'll see the TMB tone stack boils down to 2 basic filters that are also present in the classic fender Treble/bass tone stack - but with the addition of a mid pot that controls the amount of 'scoop'.


The two main filters are:


1) a low-pass R/C filter where the amount of bass can be 'bled out' by the Bass knob at full CCW cut, or dialled back in with full CW rotation; and
2) a high-pass C/R filter controlled by the treble knob. At full CW rotation the treble pot is a straight high-pass filter, a


With each of the pots a full cut, the highs and/or lows are attenuated.


The mid pot is a another R/C filter that depending on the rotation, either dumps the mid frequencies to ground or puts the mid cap 'in parallel' with the bass cap (depending on the rotation of the Bass pot) so as to put more 'mids' back into the signal path.


Merlin's books cover the math.

[pbman1953]

I really appreciate everyone's help but let's take it from a different angle.


My amp uses a .1 and .047 cap for the bass circuit. An old Bassman uses a .1 and a .1. Does anyone know what the Bassman Bass knob frequency is? 


If I know that I can easily read the graph once I start entering different values