Using blue Alps as vol control

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I purchased some Blue Alps (50k and 10k) to be used for various pre-amp builds. They seems to be "good enough" for "high-end" use so I don't have to spend 400 USD for e.g. a Khozmo every time (used that for BA-3 pre). But I was a bit surprised how bad the channel match are in these Alps. Only one of the 10k is spot-on. So what do you do? …..just use them without checking the channel match and close the eyes? :)
For the 50k stereo pots a typical variation between channels if I set at 1 o'clock is something like 12.7k and 12.3k …. 0.4 k difference out of 12k ….so that is 3-4 %. I think that is a lot? ….I have not calculated what that relates to in dB between channels…...so maybe I should do that before complaining to much…...I would like < 1 dB channel error.
Are "stock" Blue Alps "Pass Lab certified"?
 
You need to measure the attenuation instead of the absolute resistance value at the wiper, because the resistive elements may vary by up to 10% or more, and the attenuation may still be better than that.

In practice, the ratio Rwiper/Rtotal will give you the attenuation.
 
Official Court Jester
Joined 2003
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It seems Alps only guarantee <2-3dB tracking error.


Good idea with 100k Lin and shunted wiper. Then I have to find a good quality 100k lin. It seems Alps don't specify lin/log so I assume they are all log.

I'm pretty much same clueless in Law and Medicine .... but that doesn't mean that there are no laws and cures

:clown:
first rule of Engineering - you need to learn where and how to find and extract needed information
 
In practice, the ratio Rwiper/Rtotal will give you the attenuation.


The above mentioned 50k. One channel measure 47.1 k and the other 47.5k (why do they call them 50k pots?). But the error from wiper to one end is not consistent. It depends on the wiper setting. So I can not just add a 0.4 k resistor to the resistive element but I may be able to correct the error a bit.


A typical setting measuring the side that goes from 0 - 47k:
34.5/47 = 0.734
35.2/47 = 0.749
So with 1V in I get 0.734V out in one channel and 0.749 out in other channel. Relative to 1V it is -2.69 dB vs -2.51 dB ….so that it not much of a difference.....?
 
Wait until you're confronted with contact rectification, resistive element composition (carbon/cermet/conductive plastic), wiper geometry, and so on, and you still have to wire it up with OFC/silver/litz/solid core..., and solder with Sn/Pb/Ag.

Dealing with the unknown is a lot more fun! :)
 
Official Court Jester
Joined 2003
Paid Member
My opinion.
I tried the DACT attenuator, it felt nice with soft clicks.
However I found the larger ones with Dale resistors sounded cleaner. (To my old ears)
I use twin mono ladder type as passive attenuator between music server and F6 amp
https://www.ebay.co.uk/str/ATOPELEC/DALE-23-Step-Mono-Ladder-Type-/_i.html?_storecat=3427425219 (Other suppliers are available)

from experience - I don't trust these switches , unless I didn't opened it and put some quality grease in ( Vaseline at least)

some of them even need patient de-burring of all edges inside , or you'll get no contact situation in less than a year

I'm using 2 section/24 position ones for my Iron :Pumpkin: as relay command - greased with Mo-Si , both sections in parallel .... that way I can trust them ..... while I had 4 problematic pre-finished attenuators , of 5 I bought several years ago , and all of them gone Dodo in less than a year

however - they're cheap , just buy more :)
 
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