I have constructed this negative feedback eq: https://instruct1.cit.cornell.edu/courses/bionb440/FinalProjects/f2005/asa27/ASAfinaldemo.htm

I am using it for my head amp now. Is this circuit pratical? It works, but I think it's for larger power. Right now I have it as a single chanel and the output of the single op amp I used feeds to another op-amp. Should I change anything? what sort od slope would it have? I am going to be looking at different frequencies with my oscope to get an idea but i'm curious if it is practical for a small head amp.

Also, the pots I am getting in will be 50k because I cannot find the same ones I want in 100k, what effect will this have?

 

Hello,

The used circuit makes use of the Baxendall tone control ciruit.

In the circuit there is a 1nF capacitor and a 270 Ohms resistor at the output of the opamp.
This will cut the high frequencies a bit.

The use of 50K pots in stead of 100 K pots will probably shift the frequencies and control range a bit.

Bertus

 

Hello,

The used circuit makes use of the Baxendall tone control ciruit.

In the circuit there is a 1nF capacitor and a 270 Ohms resistor at the output of the opamp.
This will cut the high frequencies a bit.

The use of 50K pots in stead of 100 K pots will probably shift the frequencies and control range a bit.

Bertus

I didn't think about the 1nF cap...

 

I didn't think about the 1nF cap...

The 1nF/270Ω hanging on the output will not make an audible difference in the output. I can't imagine why they are there.

 

The 1nF/270Ω hanging on the output will not make an audible difference in the output. I can't imagine why they are there.

I don't believe they as far as high frequency response goes becuase I do not notice any difference between having the pot positions "flat" and connecting my headphones directly into the music source which goes to show that the circuit does not alter the input's response unless the dials are moved from "rest" positions. Which is proper as far as that goes.

To calculate db boost/attenuation do I measure the voltage, and count how many times it doubles and add 3db per doubling? Oh and do I look at db from voltage or calculated power?