Hi
I'm trying to also replace the pot on the VCAN with an ALPS.
The one shown on RockGrottos accessories page is a 50k pot, and the one linked on this thread is a 10k.
I have less experience with this, what is the difference (beside the resistance rating :/) and which should I get?
Thanks !
10K is the usual pot impedance for portables, I guess because it takes less voltage to provide a high input signal. This increases the Signal-to-Noise ratio and yields better performance overall. One might conclude that lower impedance pots always result in a higher S/N ratio, but ...
10K can result in a loss of bass frequency if your source is AC-coupled (has output capacitors). If those capacitors are not sized large enough, the resulting RC circuit with the volume pot as the "R" and the output capacitor (per channel) of the source as the "C," will produce a bass cutoff filter. For most portables, however, this is an acceptable compromise in using a 10K pot.
On the other hand, a common impedance historically for volume pots is 100K (tube amps, receivers, etc.). However, the S/N ratio is worse, because it attenuates the source signal more than a lower impedance pot. Plus, the cable capacitance in longer connecting cables can result in some high-frequency loss.
This is why we typically have settled on 50K for headphone amplifier use. It preserves bass frequencies for all but the worst-implemented sources, has very little cable interaction that might reduce high-frequencies, and is a good compromise on S/N ratio. Unfortunately, 50K is not an impedance that Alps likes to manufacture as standard. Those of us that do have them (AMB, Beezar, or other DIY suppliers) and sell them have to purchase them through high-volume, custom-manufacturing runs from Alps - at considerable expense.
Yes, there are other manufacturers of stereo volume pots that can be had at 50K, but none with the excellent channel-matching that exists with the Alps RK27 (Blue Velvet). The Alps RK097 is not quite as good, but still better than most any other volume pot out there - and of course, it's small enough to be used in portables.
I hope that explains it a bit.
