by bordonbert Sat Sep 19, 2015 12:09 pm
The rumour is that the H is 250k and the L is 25k. With an Effects Loop Send output impedance of 220 Ohms and a Return input impedance of 25k, the L will have its contour influenced by the match but the idea of tone suck is really a non-worry Conrad! I'd bet that what you are hearing is your ears' perception of tonal balance as volume changes. It's worth looking at the ear's sensitivity curves.
Hearing Sensitivity Curves If your non tech then don't worry about not understanding everything you see there. Just look at how each curve's bass mid and treble balance changes as the loudness decreases. Lower volumes mean more perceived bass. That's your ear not your equipment. And what is your volume pedal designed to change?
The loop out at 220ohms is low enough to take care of that end and is unaffected in any way by having 25k of pedal resistance stuck on the end of it, (the same as its own following input). The 25k input will see no difference at high pedal settings being fed from 220 ohms into about 12.5k, then a difference between the original 220 ohms and the pedal resistance selected as the volume is dropped. The designers will have done their sums and made sure that the frequency breaks of the input cap etc will be well outside the audible frequency band.
Since the last century the whole idea has been virtually non-existent in every way if linked equipment is used correctly. 50 years ago when no one really cared about matching this was a common issue, pretty quickly designers realised they needed to design their equipment properly and worked out the consequences and it ruled out the whole idea in anything but a "can measure it on the bench" way. And what you can measure at 250kHz and above can't be detected by anything other than maybe a mutant bat with golden ears in a sound booth! The only way it crops up now in an easily distinguished way is in equipment designed by amateurs on pedal sites!
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