How to bypass a stereo potentiometer

Discussion in 'DIY Discussion' started by logon, Jul 5, 2019.

  1. logon

    logon

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    My 1st post here: hi all of you!

    Just as in subject: how to bypass ALPS potentiometer 10KΩ?

    I want just remove the potentiometer, but not sure how to do that in a correct way.
    I read many suggestions, but none really explicative and all of them without a simple schematic.

    Any addressing will be more than welcomed!
    Many thanks in advance
     

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    logon, Jul 5, 2019
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  2. logon

    field effect

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    It will need you to determine if you need to attenuate , or not to attenuate. To bypass the dreadful design of a potentiometer then just use 4 resistors , 2 for each channel. one is the series element, which is in series with your source component, the second resistor is arranged from the series resistor you just placed which is the output, then have the second resistor arranged to ground.

    A level that will be comfortable will be to use 22k in series and 1k to ground.

    Much better is to escape all of the issues of potentiometers and use Light Dependent Resistors which provide if done correctly both contact-less attenuation and contact-less switching of inputs, requiring a shunt pair and a pair for each input you require.
     
    field effect, Apr 25, 2022
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  3. logon

    Sergeauckland

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    The problem with Light Dependent Resistors is that they are also voltage dependent, so cause considerable distortion. As far as I'm aware is is NO correct way of using them as audio attenuators without adding distortion.

    Ordinary common or garden variety resistors have minimal voltage dependency, so cause no added distortion.

    S
     
    Sergeauckland, Apr 26, 2022
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  4. logon

    field effect

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    No they are are for all intents distortion- less , certainly the circuits I have tried.
     
    field effect, Apr 26, 2022
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  5. logon

    field effect

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    Have you any actual experience to comment ?
     
    field effect, Apr 26, 2022
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  6. logon

    Sergeauckland

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    Yes, when I was a young engineer, I measured LDRs to use as audio attenuators and ruled them out due to distortion caused by a small but easily measurable resistance dependence on voltage. Compared to a resistive pot which has unmeasurable distortion and no voltage dependency, there was no contest.
    S
     
    Sergeauckland, Apr 27, 2022
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  7. logon

    field effect

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    What is the part number of the part you measured ? I am thinking you perhaps satisfied your interest by measuring the wrong type, as there is massive difference between open faced LDR's and encapsulated audio types. It would be a real pity to be labelling audio type LDR's with anything other than being outstanding devices.
     
    field effect, Apr 27, 2022
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  8. logon

    Sergeauckland

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    It was a long time (like 50 years ago) so don't remember, other than it was a CdS cell, probably an ORP12.
    However, recent measurements of both the Stereo Coffee and The Truth preamps using photocells don't inspire confidence that they are as good as a passive pot.

    It just seems to me a very complicated way to achieve something simple, and with worse performance, so why?
    S
     
    Sergeauckland, Apr 27, 2022
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  9. logon

    field effect

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    50 years is a long time... So no relationship to audio purpose LDR's, as I thought, and comments therefore unrelated to them. Stereo coffee uses NSL32SR3 which are dedicated audio purpose devices , from the images I have seen , whereas Truth does use the type you refer to, which are the inferior open face types.
     
    field effect, Apr 27, 2022
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  10. logon

    field effect

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    Because the resulting audio reproduction is outstanding.
     
    field effect, Apr 27, 2022
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  11. logon

    Sergeauckland

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    How can it be better than a simple pot, which has zero distortion?
    You might prefer the sound, but your preference doesn't make it better, just your preference. The numbers are with the simple pot. Anyway, if it has a sound, it's not transparent, and if it's not transparent, it isn't hifi.

    S
     
    Sergeauckland, Apr 27, 2022
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  12. logon

    field effect

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    Think again, Not according to measurements where the pot is anything but at full volume as seen here:
    https://pinkfishmedia.net/forum/threads/alps-potentiometers-gain-and-distortion.68076/

    and the same false method, measuring at full volume is used by audio Science review
    "Preamplifier Audio Measurements
    Let's start with our usual dashboard, feeding the unit 4 volts and measuring 4 volts out in passive mode (volume set to max): " https://www.audiosciencereview.com/forum/index.php?threads/schiit-freya-s-preamplifier-review.10960/
     
    field effect, Apr 27, 2022
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  13. logon

    Sergeauckland

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    Utter bollocks. That measurement is just wrong. It can't be right, as there's no mechanism on earth that could cause that.
    A pot is just two resistors, it can't cause distortion, as there are no non-linear elements.

    S
     
    Sergeauckland, Apr 28, 2022
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  14. logon

    field effect

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    No quite different to two resistors in construction, as you have not accounted at all for the moving mechanical parts they use. I suspect the Pink Fish measurements showed a slightly worn- not brand new pot, which sadly happens to all mechanical wearing surface on surface devices Load resistance is certainly a cause of non linearity in pots as shown here: https://users.wpi.edu/~orourke/ece2010jor/PotLoadingExamples.pdf

    Distortion with LDR's is mainly as I see 2nd and 3rd harmonic. however reduces dramatically when the LDR is not hard ON or OFF, and I think good designs, have researched this, and are doing absolute wonders for our appreciation of music.
     
    field effect, Apr 28, 2022
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  15. logon

    Sergeauckland

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    You're confusing linearity of output with rotation, and linearity of transfer function between input and output. There is NO non-linearity of transfer function with rotation, so no distortion. There is of course significant non linearity of output with rotation, in that, say, 50% rotation does not necessarily result in 50% output, as it depends on the load. However, the output at whatever level is still 100% linear to the input, just smaller.

    As to the appreciation of music, that's entirely a subjective matter, in which I have no interest, only what the equipment does in terms of its technical performance.

    S
     
    Sergeauckland, Apr 28, 2022
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