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Using blue Alps as vol control
Using blue Alps as vol control
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Old 15th April 2019, 08:24 AM   #1
MEPER is offline MEPER  Denmark
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Default Using blue Alps as vol control

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"?
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Old 15th April 2019, 08:41 AM   #2
ClaudeG is offline ClaudeG
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I could be mistaken, but very quickly, aren't 4% mismatch at the end only... 0.34dB?
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Old 15th April 2019, 08:44 AM   #3
Zen Mod is offline Zen Mod  Serbia
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Using blue Alps as vol control
next time buy 100Klin , shunt viper to gnd with 22K and you'll have much better tracking and better LOG transfer function

Potentiometers (Beginners' Guide to Pots)
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Old 15th April 2019, 09:23 AM   #4
MEPER is offline MEPER  Denmark
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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.
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Old 15th April 2019, 09:29 AM   #5
MEPER is offline MEPER  Denmark
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The tracking on these seems quite good (if we can trust his measurements):
DACT Type 21 Stepped Attenuator Potentiometer 50K for Amp/Preamp, 2A3, 300B... | eBay
I have never seen such a small stepped attenuator.
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Old 15th April 2019, 09:32 AM   #6
El Reino is offline El Reino  Finland
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DACT is good potentiometer.
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Old 15th April 2019, 09:45 AM   #7
MEPER is offline MEPER  Denmark
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I could not resist…..so I ordered 2 pcs of the 10k version. If source can drive it the lower value should be the better choice.
But I think they have "stolen" the name from the "real DACT"?
DACT - Danish Audio ConnecT
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Old 15th April 2019, 09:57 AM   #8
Zung is offline Zung  Switzerland
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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.
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Old 15th April 2019, 10:13 AM   #9
Zen Mod is offline Zen Mod  Serbia
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Using blue Alps as vol control
Quote:
Originally Posted by MEPER View Post
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


first rule of Engineering - you need to learn where and how to find and extract needed information
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Old 15th April 2019, 10:43 AM   #10
Zung is offline Zung  Switzerland
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Quote:
Originally Posted by Zen Mod View Post
next time buy 100Klin , shunt viper to gnd with 22K and you'll have much better tracking and better LOG transfer function

Potentiometers (Beginners' Guide to Pots)
Yes, but higher risk of contact rectification induced distortion.
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