DIY high pass shelving filter circuit not working as expected.

[nguitar12]

I just built this high pass shelving filter circuit. However it is not working as expected. This circuit is claim to have no volume drop when the boost/cut pot is centered. However after connecting this circuit the guitar volume drop significantly. Also the signal will suddenly disappear when the boost/cut pot reach the last 10% of the rotation.

Beside these I can hear that the circuit is actually working the frequency control pot seem working completely normal to me. I a using 5532 and power the chip using two 10k resistor voltage divider.

Any thought on the reason?

Thanks

[nguitar12]

ok so I added a 1uf cap on the input and output now the signal will not suddenly disappear when RV1 is reach last 10%. But still this circuit has quite a lot volume drop and guitar tone is darken. Can someone please help? Thanks

[samhay]

Do you have a buffer in front of it?
It wants to be driven by a low-impedance source (buffer), not a high-impedance guitar pickup.

[nguitar12]

Do you have a buffer in front of it?
It wants to be driven by a low-impedance source (buffer), not a high-impedance guitar pickup.

No I connect the circuit to my guitar exactly like the schematic. It is the main reason why the volume drop and darken the tone? I thought that A2 is the input buffer isn't it? (Sorry for being noob if it is not)



Will this buffer work on this circuit? If so what should be the resistor value? Thanks

[samhay]

A2 is a buffer, but not the input buffer.
Yes, the AMZ JFET buffer will work fine. Use the resistor values in the schematic.

[Kipper4]

You might like this Nguitar.
From Sam Hay a pick your flavour preAmp

http://www.diystompboxes.com/smfforum/index.php?topic=112900.0

[nguitar12]

Thank all. Will try adding buffer in the next couple days.

[Ruptor]

I a using 5532 and power the chip using two 10k resistor voltage divider.

I assume you have a large capacitor on this divider. I would have thought 10K is a bit high for the source impedance of the supply to the chip.
You can check if the circuit is loading the guitar signal by looking at the level on the input and comparing it when it is plugged in to something that works correctly. To increase the input impedance of the circuit couldn't you raise the values of R1,2,3,4 and RV1 perhaps by three or four times I think would be enough?

[PRR]

It needs a buffer to take guitar. Raising resistor values 4X even 10X won't make it guitar friendly, and gets into increased hiss. The excellent AMZ buffer is marginal for this studio-world tone network; I'd throw an op-amp at it.

It is drawn for DUAL (+/-) supply, but I guess you sorted this out.