Bypassing hpf for audio

Thread Starter

popeman

Joined Dec 15, 2017
9
Hello,

This is probably a rather simple question but could someone suggest a good way to bypass the 2nd order hpf shown below?
SW1 and SW2 is a dual gang switch and I'd like to use the first position for bypassing the filter.

Many thanks!
 

Attachments

LowQCab

Joined Nov 6, 2012
1,110
You NEED a HPF, to keep your "Tone" "Clean", instead of "Muddy" / "Muffled" sounding.
But you want it to be "inaudible" as far as your "Tone" goes.
So simply add 2 more, much larger, Capacitors,
to the presently empty Switch positions.
Which should have a much lower frequency roll-off, lets say, around ~50hz for a Guitar.

I would have done this with Op-Amps, and Dual-Ganged-Pot for adjustability,
rather than using discrete Transistors and switching Capacitors.

Probably, what you are trying to achieve is actually a rather sharp
Frequency-Response-Boost at around ~1khz.
You should try this with an Equalizer-Stomp-Box.
.
.
.
 

Thread Starter

popeman

Joined Dec 15, 2017
9
You NEED a HPF, to keep your "Tone" "Clean", instead of "Muddy" / "Muffled" sounding.
But you want it to be "inaudible" as far as your "Tone" goes.
So simply add 2 more, much larger, Capacitors,
to the presently empty Switch positions.
Which should have a much lower frequency roll-off, lets say, around ~50hz for a Guitar.

I would have done this with Op-Amps, and Dual-Ganged-Pot for adjustability,
rather than using discrete Transistors and switching Capacitors.

Probably, what you are trying to achieve is actually a rather sharp
Frequency-Response-Boost at around ~1khz.
You should try this with an Equalizer-Stomp-Box.
.
.
.
Thank you LowQCab
After some investigation I agree that an op-amp with a dual gang potentiometer for variable frequency is more appropriate.
 

AnalogKid

Joined Aug 1, 2013
9,362
WAY too much missing information ...

What is the intent of this circuit? What is it supposed to do?

What are the three switch positions now?

Without more component values, the circuit operation is unclear. What are the four filter corner frequencies?

ak
 

AnalogKid

Joined Aug 1, 2013
9,362
You NEED a HPF ...
Based on nothing but post #1, exactly none of this response makes sense to me. Are there 20 posts somewhere that I can't see?
Which should have a much lower frequency roll-off, lets say, around ~50hz for a Guitar.
Really? The E string on a guitar is 82 Hz, so that's over 2 dB of gain error, plus phase errors out to its third harmonic.

ak
 

Thread Starter

popeman

Joined Dec 15, 2017
9
Based on nothing but post #1, exactly none of this response makes sense to me. Are there 20 posts somewhere that I can't see?

Really? The E string on a guitar is 82 Hz, so that's over 2 dB of gain error, plus phase errors out to its third harmonic.

ak
AnalogKid, this circuit/ idea is for low level line signal. The C3=C5=150nF constructs a 2-pole HPF with Fc at around 100Hz (the impedance of the following stage is roughly 3kOhms)

The two switches switch between two different Fc and I was gonna use the first position for bypassing the filter. In fact, for setting the Fc well below 20Hz so a higher value capacitor would be on the first position.

As I said, I decided to go with a standard sallen-key topology that will give me variable Fc.

Thanks for trying to help anyway :)
 

LowQCab

Joined Nov 6, 2012
1,110
Based on nothing but post #1, exactly none of this response makes sense to me. Are there 20 posts somewhere that I can't see?

Really? The E string on a guitar is 82 Hz, so that's over 2 dB of gain error, plus phase errors out to its third harmonic.

ak
Yes, most definitely YES,
The world of Amplified-Musical-Instruments makes ABSOLUTELY NO SENSE.
It does not follow ANY Rules.
It's all about "the Character of the Distortion", known by Musicians as just "My Tone".
There are all sorts of squishy adjectives to go along with this,
that are completely impossible to define by anyone,
that are used to describe "the Feel that it gives me".
There are plenty of "Mind-Games" that enter into the equation as well ........
Such as Equipment with God-Like qualities which can never be duplicated
by any other piece of Equipment, but which, cannot be measured, only "felt".

Many Musicians, quite-literally, can't play their Instrument if the "Tone" is not "right".

You have to be a Musician,
as well as a Sound-System-Engineer,
and an Audio-Electronics-Engineer,
to even begin to wrap your head around it,
and even then, it's a totally subjective "interpretation".

It takes decades of real-world experience to gain
merely an "acceptable" level of competency in this field.
You can't learn it from a book, you have to "experience it".
.
.
.
 
Top