Cable Capacitance, Buffers and Cable Length ?

ICBM

TheMarlin said:

It's a pre amp.  An old pre amp, reworked for modern applications.  It not a buffer, but does have an effect on impedance loading.

If it takes a high-impedance input signal and produces a low-impedance output signal it is a buffer, as well as being a preamp. That's why you don't have any cable loading issues.

Why would you want to have "no buffers", anyway?

ecc83

"Just out of interest, what qualifies as a low output impedance? I'm guessing in the low kOhm range?"

How long is a piece of string? (or more to the point the guitar cable!) If we take the chap with 50feet as reasonable maximum and call that 15mtrs? At 100puff per mtr that gives turnover frequency at 10kHz for a Z out of 10k...ish!

Note tho' that a 10k pot will not have a Zout of 10K, worse case is at 6dB attenuation and is 2.5K. This assumes that the pot is driven from a near zero Zout amplifier which is fair for OP amps.

Note too that a cable LOOKS like part of an RC filter to a pot but it is a much more complex, "resonant" situation when connected directly to a guitar.

Dave.

Dave_Mc

^ I think that's getting beyond my pay grade )

I generally use a 6M cable from guitar to first pedal (normally use my klotz la grange which is fairly low capacitance I think- 67pF per metre is what I got when I looked it up on the klotz site), and then probably a 3M van damme cable to the amp (I can't remember for sure but I think around 90pF per metre rings a bell... or maybe it was 30pF per foot) and then whatever patch cables I have in between.