Line level FX and impedance

[skrunk]

Hi folks, first post and all that so be gentle...

I'm building a few fx that I'd like to use at line level. I understand that guitar fx expect a high impedance signal from the guitar and was wondering what I can do to modify them to work better at line level.
I was looking at Craig Anderton's book where some of his fx can be built for line or guitar level and was trying to figure out how this worked.
It seems the input resistor and sometimes the capacitor values can be adjusted for line level applications, but I couldn't see any kind of golden rule at work here, though my limited electronics knowledge doesn't help.
I find fuzzes in particular don't like a line level signal, but lowering the volume going in can help.
So is it just a case of sending the pedal a lower volume or does impedance matching have more going on than that.

Sorry if this has come up before, I've searched and read through a few topics, but still find it a bit confusing.
Any tips or pointer for line level fx would be very much appreciated.
Thanks.

[John Lyons]

Welcome!
There are a couple things going on here.
Line/instrument level going in and Line/instrument going out.
Line in is somewhat easy but depends on the circuit.
You can add a 50k pot to the input of the circuit and use this to
drop the input level. Line level is 10X higher than instrument roughly.
Just wire it up like a typical volume control. It will depend on the circuit
if the line in will be "too much" signal coming in, if it distorts etc.
For a fuzz or distortion it may not matter.

Input impedance is another issue.

For the output it gets trickier. You need to boost the output roughly
10x to get it back up to line level. You can build a booster to do this.

Search these terms on the forum here.
Adjusticator (RG keen's circuit you can fins in the GEO link at the top
of the forum page.

Line level

There is a lot of archive here so search away!

John

[skrunk]

great, thanks john!
funnily enough I was checking out your webpage last nite, lovely work.
I've been at the hammertone myself the past few days.

I can adjust volume going in to the pedal using a gain knob in the software I use (audiomulch) easily enough and also where it comes back in, so that's not much of a problem.
If it's just a question of volume going in and out I'm ok. Just thought impedance might be another matter.
I'll do some more searching and try a few things out and I've got a pcb for a booster circuit here too, so I'll try that.
cheers.