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Parallel shunt RC network of op amp feedback loop

Started by Miyagi_83, November 25, 2024, 05:04:47 AM

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Miyagi_83

Hi, everyone.
Probably a basic question here. I've seen a couple of op-amp-based preamp and pedal schematics where the feedback loop leg going to ground is arranged as in the image attached, namely as a parallel combination of two RC networks.
What, if any, advantage does this setup have over the more simple approach, with just one resistor and one capacitor?
Thanks in advance for any input.
M.
"The ill and unfit choice of words wonderfully obstructs the understanding."
Sir Francis Bacon

Loudthud

The one with the smaller cap is providing a treble boost. The one with the larger cap sets the low frequency response.

Miyagi_83

"The ill and unfit choice of words wonderfully obstructs the understanding."
Sir Francis Bacon

Tassieviking

The 100pF cap with the Gain pot form a Low Pass filter.
The 15nF with the 27k resistor form  a High Pass filter at 393 Hz
The 470nF with the 120k resistor for a High Pass filter at 2.8Hz
When 2 filters overlap the fall or rise of the filters change.
( as far as I remember)

This is a good link to read up for you:
https://www.electrosmash.com/proco-rat
I like the calculators on this site because I'm lazy:
http://www.learningaboutelectronics.com/Articles/High-pass-filter-calculator.php
There are no stupid questions.
There are only stupid mistakes.

Miyagi_83

"The ill and unfit choice of words wonderfully obstructs the understanding."
Sir Francis Bacon

Miyagi_83

That's some great stuff, guys. I mean, I did know it was a high-pass filter (I'd learnt that from Teemuk's book), but I wasn't aware that putting two in parallel enables you to amplify different frequencies. It opens up a whole lot of design possibilities.
"The ill and unfit choice of words wonderfully obstructs the understanding."
Sir Francis Bacon

Tassieviking

There are no stupid questions.
There are only stupid mistakes.

Miyagi_83

Quote from: Tassieviking on November 25, 2024, 09:56:02 AMHere is another calculator design tool place thingy, it can be a little bit harder to use:
http://sim.okawa-denshi.jp/en/
I didn't know about this one. Thanks! I'll check it out when I get home.
"The ill and unfit choice of words wonderfully obstructs the understanding."
Sir Francis Bacon

Miyagi_83

Quote from: Tassieviking on November 25, 2024, 09:56:02 AMHere is another calculator design tool place thingy, it can be a little bit harder to use:
http://sim.okawa-denshi.jp/en/
Oh, brother, this is awesome! <3) It's got a bunch of useful features. I'm bookmarking it for sure. Thanks again for showing me this :dbtu:
"The ill and unfit choice of words wonderfully obstructs the understanding."
Sir Francis Bacon