what really matters with unpowered pedals regardless of brand is the impedance; if you have an active bass or run other buffered pedals between it and the volume pedal, then a low impedance volume pedal (25k) will give you the smoothest sweep.
if you want to run a passive bass straight into the pedal, then you need at least a 250k pedal or you'll get tone suck, and even then you might still lose a little clarity.
active volume pedals (where they themselves are powered by 9V) have the buffer built-in, so there's no loss or weirdness with the sweep no matter where you run it.
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