looking for sealed 10k log pots

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Fenris

Well-known member
Joined
Dec 11, 2012
Messages
54
I need about 16 sealed 10k log pots, 1/4" shaft, for my console. Something under $5 each. The stock pre's used lin pots and a resistor to change them to log, but it results in the minimum gain being too high. I searched Mouser et al but I can't find what I need. Help would be appreciated.

My previous console had unsealed mic gain pots and the crackle drove me bonkers. What the heck do other mic preamps use? It's a standard design, 20 dB pad and input transformer into a 5534.
 
Just because they are sealed doesn't mean they won't crackle at some point.  I prefer cleaning a pot when needed and therefore have an opening.  The sealed pots become throwaway pots if they don't open up somehow.  Also are you sure you don't have some DC leakage on the pot from Caps?
 
Agree. Sealed or not has little to do with pot noise, unless you are in a very dirty environment.

Problem is most likely DC offset and/or leak

Schematic for reference?

Jakob E.
 
Why not to use the thing as it is but with higher value linear pot? What values are the pot and the loading resistor in the original unit? Maybe scaling them up a bit is enough and you don't need to get log pots which are less predictable (bad tracking between channels. Also I suspect an antilog is used, which is more common in preamps and even harder to get the exact part and that's why usually a linear pot loaded is used.

JS
 
Try Omeg PC16ECO series.

MCM handles these guy in the states But only carry Logs and Lins
if you need Rlog order them direct from Omeg

MCM  http://www.mcmelectronics.com/product/OMEG-PC16ECO10KB-/287-2056
Omeg  http://www.omeg.co.uk/e16typ1.htm

Best..

GARY
 
Here's the schematic.
http://fenrisaudio.com/MI64micpre.JPG
It was much too sensitive and I replaced R50 with a jumper to lower the minimum gain to unity. This looks like a  two-terminal application which means I can't use a tapering resistor.

Those plastic shaft pots look really cheap. I can use unsealed pots, but I was hoping to find some nice sealed pots with large square enclosures similar to the original lin pots.

What consoles use sealed log pots? I could contact the manufacturer. Seems to be a custom made item, not available off the shelf.
 
Use a 10k "audio" taper Bourns conductive plastic pot.
http://www.mouser.com/ds/2/54/96-12659.pdf

Excellent quality and reliability.

That would make Lo Gain settings nicer & more predictable.

But your Minimum Gain will not change. (Shorting out R50 as you've done is the best you can do)  It's still more than 46dB gain range on a single pot which is stretching things.
 
> I replaced R50 with a jumper to lower the minimum gain to unity.

Or "less".

Without R50, at minimum gain, the poor '5534 has to drive R49 47 ohms directly. THD will rise and maximum output level will fall.

Put R50 back. ('5534 can drive the 377 Ohms OK.)

If you want a lower minimum gain, raise R49 to 470 Ohms. If you still need maximum gain, use a switch to select 47/470 Ohms.
 

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