Hi all,
As usual, in the morning, instead of scrolling through Facebook or something like a normal person, I'll look up various simple audio circuits and try to follow each component in order, and pick out what it's doing and why the designer might have chosen that specific component.
Call it self educating...
or insomnia or whatever
In regards to non inverting op amps, it's usually pretty easy to do.
An example is the Tube Screamer's clipping circuit I attached below.
One question spread over 3 points:
- I often see small capacitors (C4 in the Tube Screamer) in the feedback of op amps, I understand this is to negate the buildup of parasitic capacitance, and that the value is generally small because it will create a low pass filter - only on the signal that is passed through it. (right?)
- Looking on mouser, the only logical type of capacitor to purchase for this is either a ceramic or MLCC because they seem to balance cost, size and longevity. However, putting a ceramic or mlcc in the audio path makes me uneasy, since I've seen all the heated online debates about capacitors... which I hope to never get into.
- Is this totally unfounded? Or is there an alternative solution that doesn't cost a fortune both in money and PCB realestate? How integral is this component to the audio signal really? Cuz it sure is tempting to just use an MLCC like I have been for the last while... But I have noticed some undesirable 'crackling' lately too. Hmm
I also stumbled upon the famous Klon Centaur circuit the other day and was quite intrigued by the design.
Something confuses me here, and it shouldn't...which means it really bothers me.
In the feedback of that Op amp you will notice R11||C7, and R12||C8 all making (?high pass?) filters, which is fine and dandy...
It was always my understanding that this network eventually needs to lead to ground, however you can see that it goes through the Gain pot, and back into it's non inv input, picking up Vcc/2 along it's way...which queues a few questions:
- How does this not change the DC biasing for the op amp? When the gain is down, the biasing is where?
- How can this actually create gain without just hitting the rails?
- There are two 'boxes' of filters; one is tied directly from the output to inverting input, and one is in between that and the non inv. input...How do these react differently with the gain? I'm assuming that the R11||C7 combo is always acting on the signal, while the R12||C8 combo is only acting on the 'boosted' portion of the signal...is that correct?
Please excuse my poor nomenclature on the topic, if I've made some mistakes in that regard.
It would be incredible if somebody could start at C5, or at the non inv input and just walk me through the klon circuit a little bit.
As always, I appreciate you and your time!!
I hope you're well
Alex
As usual, in the morning, instead of scrolling through Facebook or something like a normal person, I'll look up various simple audio circuits and try to follow each component in order, and pick out what it's doing and why the designer might have chosen that specific component.
Call it self educating...
or insomnia or whatever
In regards to non inverting op amps, it's usually pretty easy to do.
An example is the Tube Screamer's clipping circuit I attached below.
One question spread over 3 points:
- I often see small capacitors (C4 in the Tube Screamer) in the feedback of op amps, I understand this is to negate the buildup of parasitic capacitance, and that the value is generally small because it will create a low pass filter - only on the signal that is passed through it. (right?)
- Looking on mouser, the only logical type of capacitor to purchase for this is either a ceramic or MLCC because they seem to balance cost, size and longevity. However, putting a ceramic or mlcc in the audio path makes me uneasy, since I've seen all the heated online debates about capacitors... which I hope to never get into.
- Is this totally unfounded? Or is there an alternative solution that doesn't cost a fortune both in money and PCB realestate? How integral is this component to the audio signal really? Cuz it sure is tempting to just use an MLCC like I have been for the last while... But I have noticed some undesirable 'crackling' lately too. Hmm
I also stumbled upon the famous Klon Centaur circuit the other day and was quite intrigued by the design.
Something confuses me here, and it shouldn't...which means it really bothers me.
In the feedback of that Op amp you will notice R11||C7, and R12||C8 all making (?high pass?) filters, which is fine and dandy...
It was always my understanding that this network eventually needs to lead to ground, however you can see that it goes through the Gain pot, and back into it's non inv input, picking up Vcc/2 along it's way...which queues a few questions:
- How does this not change the DC biasing for the op amp? When the gain is down, the biasing is where?
- How can this actually create gain without just hitting the rails?
- There are two 'boxes' of filters; one is tied directly from the output to inverting input, and one is in between that and the non inv. input...How do these react differently with the gain? I'm assuming that the R11||C7 combo is always acting on the signal, while the R12||C8 combo is only acting on the 'boosted' portion of the signal...is that correct?
Please excuse my poor nomenclature on the topic, if I've made some mistakes in that regard.
It would be incredible if somebody could start at C5, or at the non inv input and just walk me through the klon circuit a little bit.
As always, I appreciate you and your time!!
I hope you're well
Alex