While mounting my Ambika, I think I have exchanged the 100k pot for a 10k pot (I did not notice that there were different pots…) So one of the 8 pots is a 100k, but I do not know which pot it is (I tried to use the multimeter but could not track it). I was expecting some painful desoldering but it does not seem to have an influence on the UI (values can go from 0 to 127 with all pots, and I can reach all 128 values with any pot) so I left it as is. And the remaining 10k pot seems to control the volume well…
Is there any problem? It should be I guess, otherwise there would be not different kind of pots(?) If this is a problem, is there a way to track which pot is 10k or 100k?
Pots and resistors need to be measured with one leg lifted off the board, otherwise the rest of the circuit alters the resistanse measurements results… Lift one leg, set your multimeter on Resistance (Ohms) on a scale of 100k, then measure the middle pin with either of the outer ones (the one you lifted). While turning the pot on the one end the resistance should be 0R, while turning the pot on the other end it will be 10k or 100k, and that settles the pot value.
As for the influence on the UI, I don’t know much about the architecture of the Ambika (in fact I know next to nothing because I haven’t built anything yet), all I know generally about the pots is that other values, except other resistance mean other impedance too…
the parameter you’re going to control with the 100k pot won’t be very practical to use - nearly all the values will be concentrated near one end of the taper.
To know which pot is the 100k, just move the 8 control pots to 12 o’clock : the 10k pots will have a value near 63, and the 100k log will have something very different (i think that it should be something like 15 or 20).
the 10k linear pot used as a volume will display very little difference in the volume through the right half of its course.
the pots are only scanning CVs for parameters. whether you have 10k or 100k doesn’t matter much. the only difference is that higher resistances are more likely to pick up noise (jumping values / parameters) but there shouldn’t be a noticable difference.
@danik and rosch : the main difference here is that the 100k pot is an audio taper, as opposed to the linear taper of the 10k pots. In terms of impedance that won’t make much difference as used in the ambika, but the way the values are scaled are very different.
I suspect that Olivier could have used a 10k audio pot for the volume control, but that he chose a 100k to make the difference between audio and linear tapers more obvious.
ok I’ll remind this procedure if ever I decide to change the pot
as I said, there was no such thing happening actually, that could be explained by rosch’s explanation
ok, so I leave everything as is instead of risking damaging the mobo by unsoldering the pots.
Thanks to all!
Ah, I see, I didn’t know the 100k was logarithmic. Again, I haven’t built an Ambika yet, hence the generic answer about pot measurements.
Trivia: I learned about pots and impedance the hard way, when I put a dual gang 500k log pot as analog stereo volume control on my MBSID, making consoles everywhere squeal for my first 4-5 gigs (with an exception of a Hi-Z DI Box that was used in one) until I changed it to 10k.
You should be able to unsolder the pot easily without any damage done to the mobo by using solder wick or a desoldering pump. I always prefer not to settle or cut any corner on a project, even if I have to tire myself with some really boring procedure, because a workaround is sure find its way to get to kick you in the butt at the worst possible moment (also learned that the hard way)
Well, the issue with a 100k audio pot is not that the value won’t go from 0 to 128, it will. As I explained, there is an imbalance between the values. On an audio pot, the 50% point should be near 3 o’clock, the middle point should be near 15% of the total value. And a linear pot is well… linear. The 50% point is at noon, the 80% point is near 3 o’clock, and so on.
If all of your control pots display a value close to 63 when set to noon, that means that either your 100k pot was not logarithmic, either you had some luck and you inserted the 100k audio pot in the right spot.
I tested the pots at noon, and one of them (P8) seems to be at a value of 20 instead of 64. I guess this is the 100k. I may try to unsolder it with a pump…
did it! it was the right pot to unsolder. The unsoldering went not too bad with a pump for a first attempt.
Everything is working nicely now…
Many thanks to all!
yep logarithmic response is not so good
I’m glad your Ambika is OK