I am building a crossover based on the following design from Rod Elliot:
The trick here is: I am using a single rail supply AND... the audio signal ground is shared by the amplified that this circuit drives.
Thus... I am experimenting with a circuit as follows:
1) The op amps are powered directly from the +/- 12VDC
2) I am using the common "voltage splitter" at the signal input and using a 1uF capacitor just before the signal is fed to the center tap of the op amp non inverting input.
3) Not shown in the photo above, I have another similar output buffer op amp and the output of that op amp is fed through a capacitor and 10k resistor (shunt to ground) to remove any DC from the output.
Now for the part that I struggled with all night....
The ground connection shown in the photo above for the filter network (R and C connections to ground).... What I have done - and it appears to work perfectly (as far as I can tell)... I created ANOTHER voltage divider network with two 10k resistors between +/-12vdc and "grounded" those connections to that middle point.
When 12v is applied, all op amps are sitting at 6vdc. Since the filter network is expecting a reference to "ground" (which should be 0dB - or 6v), I assumed this would work. And.. it seems to work as far as I can tell.
I fed a dozen signals though it and watched the scope for any distortion - could see none that I am aware of.
My question is: is this the correct way to do this? I see some other diagrams and tutorials mention passing this through a capacitor to the negative power side - but that did not work for me in this case - and all those guides are based on basic gain situations - not for a filter network as I am dealing with. When I place a capacitor between the R or C and negative, I get sound - but badly distorted. This is with anything from 22 - 100uF.
-Dean
The trick here is: I am using a single rail supply AND... the audio signal ground is shared by the amplified that this circuit drives.
Thus... I am experimenting with a circuit as follows:
1) The op amps are powered directly from the +/- 12VDC
2) I am using the common "voltage splitter" at the signal input and using a 1uF capacitor just before the signal is fed to the center tap of the op amp non inverting input.
3) Not shown in the photo above, I have another similar output buffer op amp and the output of that op amp is fed through a capacitor and 10k resistor (shunt to ground) to remove any DC from the output.
Now for the part that I struggled with all night....
The ground connection shown in the photo above for the filter network (R and C connections to ground).... What I have done - and it appears to work perfectly (as far as I can tell)... I created ANOTHER voltage divider network with two 10k resistors between +/-12vdc and "grounded" those connections to that middle point.
When 12v is applied, all op amps are sitting at 6vdc. Since the filter network is expecting a reference to "ground" (which should be 0dB - or 6v), I assumed this would work. And.. it seems to work as far as I can tell.
I fed a dozen signals though it and watched the scope for any distortion - could see none that I am aware of.
My question is: is this the correct way to do this? I see some other diagrams and tutorials mention passing this through a capacitor to the negative power side - but that did not work for me in this case - and all those guides are based on basic gain situations - not for a filter network as I am dealing with. When I place a capacitor between the R or C and negative, I get sound - but badly distorted. This is with anything from 22 - 100uF.
-Dean