Re: Hagerman Metal

Posted by induction on Sep 01, 2021; 1:18am
URL: http://guitar-fx-layouts.238.s1.nabble.com/Hagerman-Metal-tp50209p50222.html

It's not ideal, but in most cases it will be sonically undetectable. Remember that a traditional volume control is just a big resistor to ground that gets tapped somewhere in the middle, and we have those built into the guitar. Also no material used in pedals is anywhere near perfectly resistive. So signal leaking to ground is unavoidable even without pulldowns. The trick is to make sure the leaks are small enough to be unnoticeable.

The sonic result of signal leaking to ground depends on how much current is available in the signal (aka source impedance). Passive pickups do not generate much current, so we go big with input pulldowns or passive input volume pots at 1M or higher. (Sometimes we actually want to bleed off treble or volume, in which case we use smaller values.) Directly after a buffer, the source impedance will be tiny, so we can often get away with much smaller pulldowns and output volume pots. 10k is a common value for output volume pots, but we usually stick with big output pulldowns for convenience, I guess.

So if we have 10 pedals in our chain, and they are all wired with 1M pulldowns that are only visible to the signal when the circuit is engaged, then we should be fine. When the pedals are engaged, the pulldowns are all separated by active components that amplify the current, and the pulldowns don't add up cumulatively. But if the pulldowns are wired on the input jacks, then the signal sees all of them all the time. When the pedals are disengaged, we have an unbuffered 100k path to ground, which isn't horrible, but might be noticeable in some situations.

If you look at a lot of pedal schematics, you'll see AC and DC leaks to ground all over the place. Sometimes it's intentional for signal shaping, and sometimes it's just required by the topology of the circuit. Circuit designers account for them in the tone shaping, and do a lot of ear testing to make sure the result is what they want.

Think of it like this: if you have a pinhole leak in your water line, your shower will still work fine. If the hole is a couple of inches wide, you might not be able to rinse the shampoo out of your hair.