# Passive RC low pass filter tutorial!

Video duration: 8:33
A tutorial on passive low pass RC filter circuits, and how they affect the frequency content of signals. An example of an RC filter that could go before a subwoofer’s amplifier is given. The sound clips are from Pendulum’s Slam in Hold Your Colour. More videos at

## 32 thoughts on “Passive RC low pass filter tutorial!”

#### Afrotechmods

(November 9, 2019 - 7:58 am)

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(November 9, 2019 - 7:58 am)

thanx

#### Jan Marc Baniqued

(November 9, 2019 - 7:58 am)

Simply amazing.

#### Eugene Pohjola

(November 9, 2019 - 7:58 am)

Howdy.
One may cascade RC filters to get steeper attenuation. The trick is simply that each next branch should have an impedance of 10 times the previous. For most practical uses each branch may be calculated using the basic formula. The inter-loading will be small.
So if we want a 40 dB attenuation per decade we use a 1 k resistor in the first branch and calculate the corresponding capacitor. In the next branch we use 10 k and a capacitor of 1/10 of the previous.
However. The following amplfier input impedance needs to be 100 k or higher.
If some inter-loading can be accepted a smaller factor may be used, say 5 times.

#### Sami Rahim

(November 9, 2019 - 7:58 am)

You are really great

#### Dip Ahmed

(November 9, 2019 - 7:58 am)

Good sir

#### Standard E

(November 9, 2019 - 7:58 am)

How is input voltage taken into the equation? It seems that more or less peak voltage would effect this circuit changing the cutoff frequency.
Also, how would I go about filtering a frequency based signal (50% duty) into a variable DC output?

#### Rodrigo Belinchon

(November 9, 2019 - 7:58 am)

yeahhh

#### Toneconsultant gmail

(November 9, 2019 - 7:58 am)

Cool. I do have to really think to get all this, but it’s cool

#### Reyes馬克喬爾

(November 9, 2019 - 7:58 am)

The old school winamp equalizer…👍

#### mughato amugha

(November 9, 2019 - 7:58 am)

thank you so much.. Deep down from my Heart… AWESOME

(November 9, 2019 - 7:58 am)

I really appreciate your effort for making such useful videos.

#### George Aruldoss

(November 9, 2019 - 7:58 am)

Thank you! Excellent!

#### HongYi Fan

(November 9, 2019 - 7:58 am)

I hope u were my circuit professor

#### Siavosh Kasravi

(November 9, 2019 - 7:58 am)

Again a resistor. I can't understand why there should be a resistor. Is it to tune the output voltage peak or ampere peak or both?

#### Cagney Moreau

(November 9, 2019 - 7:58 am)

thanks for making this video!

#### kalib_PR

(November 9, 2019 - 7:58 am)

Someone likes motor storm haha

#### Zarina Abdibaitova

(November 9, 2019 - 7:58 am)

can you tell me what kind of app do you use?

#### xierxu

(November 9, 2019 - 7:58 am)

Electrical engineering is sexy asf.

#### Markus

(November 9, 2019 - 7:58 am)

Спасибо! :)) Блестящее эксплэнэйшн (объяснение) 😍

#### OffdaRoots

(November 9, 2019 - 7:58 am)

“Winamp winamp winamppppp
It really whips the lamas ass”

#### MrMkhu9099 mk

(November 9, 2019 - 7:58 am)

How do we find the transfer function?

#### ytrew

(November 9, 2019 - 7:58 am)

what the triangle symbol (with a square on it) is used for?

#### Satvik Sharma

(November 9, 2019 - 7:58 am)

Awesome video sir

#### z lariviere20

(November 9, 2019 - 7:58 am)

if my sub ends up rattling my door off the car i'm going to consider that a win. realistically though personally my goal is to get the loudest cleanest bass with little to no rattling.

#### TiTO

(November 9, 2019 - 7:58 am)

Video: You can not make a perfect filter that works like this.
Arduino: Hold my beer.

#### vignesh raj

(November 9, 2019 - 7:58 am)

What if I use 100-ohm resistor with 10micro farad capacitor instead of 1K resistor and 1 micro Farad capacitor
both give 150Hz frequency in low pass filter.
which one to choose ?

#### Garbage man

(November 9, 2019 - 7:58 am)

I can't get it to work at 100 hz with 10 milli farad capacitor either did the math wrong (because I am in grade 7 I know nothing about math) or it doesnt work with that high farad capacitor

#### l l

(November 9, 2019 - 7:58 am)

Hey dude,
Great job in doing that video… Ive got one question:
I wanna filter out the bass frequency of a audio signal and then higher its min. Voltage with a dc offset, to make its voltage completely positive to read it out with a arduino…
But the problem is:
How to do that? As soon as i connect the dc offset voltage source in series, it makes the low pass filter not work anymore….

#### Derock Tyler

(November 9, 2019 - 7:58 am)

Your videos are the best! Thank you

#### phpimusique

(November 9, 2019 - 7:58 am)

Amazing, great video! Thanks so much for that =)

#### Atomic t c g

(November 9, 2019 - 7:58 am)

Can we use as in subwoofer