Why My FV-1 build is so noisy?

[nguitar12]

Recently I finished my fv-1 build. Everything work fine except the circuit is so noisy. It is something like the (sssss.......) white noise. I am building the circuit according to the following schematic:



I try to input a line level signal and lower the output and the problem is gone. So should I build an amp to boost the guitar level to level instead of just using a simple fet buffer? Is the noisy problem normal to fv-1 circuit if the input is guitar signal?

[PRR]

> should I build an amp to boost the guitar

Yes.

Aim for gain of 4, but be prepared to go 2 or 8 after testing.

[nguitar12]

> should I build an amp to boost the guitar

Yes.

Aim for gain of 4, but be prepared to go 2 or 8 after testing.

Thanks and will try soon.

[Digital Larry]

In addition to getting the input closer to the headroom limit without clipping, here are a few random comments, not sure how much all of these affect the noise though.

Cap connected to pin 3 is 10 uF on the reference schematic from Spin I am looking at.

10k "load" resistors on output seems a bit drastic - why so low?  In my mind the function of those resistors is simply to make the DC level 0 to avoid popping.

Put power supply decoupling caps as close to the chip as possible.

There's no loading cap on the crystal - 10 pF to 22 pF typically recommended at pin 9 to ground.

Frank over at the Spin forum goes on and on about having at least a solid ground plane beneath the chip on a 2-layer PCB and recommends 4-layer PCB with power and ground planes for best performance.  I'd say he's the most qualified to offer suggestions on your design.