Pax Writer
New Member
Hello experts
I promised a friend to try to help him build a low-pass op-amp circuit, although I have next to no experience with that kind of circuits.
Being lazy, I "constructed" my circuit from an application note called "Filter Design in 30 Seconds" (I know it looks nothing like Audio Guru's illustration, but I thought if a bunch of engineers would publish that app note, it couldn't be all wrong).
Based on the schematics and calculations (and what I happened to have in my component bin) in that app note, I made the circuit, which I attached to this thread.
It uses a TL072, and the first opamp is supposed to be a low-pass filter with a transition frequency of 300Hz. The second was just used as a sort of general amplification circuit.
The whole circuit is powered with 9V from a lab supply.
The first circuit seems to work to some extent while the second is just dead.
I'm aware that my circuit probably has many problems, but what are the main mistakes I've made? Is there any way to make this circuit work, or do I need to start over?
I have tested the circuit both by humming into the mics, but also using an old B&O tone generator, moving from 50Hz to around 10kHz.
Note: Its getting late around here, so I'll hop to bed and won't be able to answer for the next seven hours or so, just so nobody thinks I'm ignoring their answer![Smile :) :)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
I promised a friend to try to help him build a low-pass op-amp circuit, although I have next to no experience with that kind of circuits.
Being lazy, I "constructed" my circuit from an application note called "Filter Design in 30 Seconds" (I know it looks nothing like Audio Guru's illustration, but I thought if a bunch of engineers would publish that app note, it couldn't be all wrong).
Based on the schematics and calculations (and what I happened to have in my component bin) in that app note, I made the circuit, which I attached to this thread.
It uses a TL072, and the first opamp is supposed to be a low-pass filter with a transition frequency of 300Hz. The second was just used as a sort of general amplification circuit.
The whole circuit is powered with 9V from a lab supply.
The first circuit seems to work to some extent while the second is just dead.
I'm aware that my circuit probably has many problems, but what are the main mistakes I've made? Is there any way to make this circuit work, or do I need to start over?
I have tested the circuit both by humming into the mics, but also using an old B&O tone generator, moving from 50Hz to around 10kHz.
Note: Its getting late around here, so I'll hop to bed and won't be able to answer for the next seven hours or so, just so nobody thinks I'm ignoring their answer