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Thread: Passive pre-amp

  1. #21
    Join Date: Jan 2013

    Location: London

    Posts: 21
    I'm Richard.

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    Apology required from me given subsequent explanation.
    Saw initial post and was irked by it.
    My mistake.
    Sorry.

  2. #22
    Join Date: Jan 2009

    Location: Essex

    Posts: 20,457
    I'm openingabottleofwine.

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    Quote Originally Posted by Bigman80 View Post
    That's the one. Conductive plastic fared better here. Yes it may be 3 times the price but it has to be a better investment.

    I do have a 3 conductive plastic pot somewhere and I felt that was better than an alps blue too.
    Go for the best: https://www.cw-industrialgroup.com/P...entiometer-RCP. They are fitted in the preamps I use.
    Barry

  3. #23
    Join Date: Nov 2015

    Location: Wolverhampton

    Posts: 8,975
    I'm Oliver.

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    Quote Originally Posted by Barry View Post
    Go for the best: https://www.cw-industrialgroup.com/P...entiometer-RCP. They are fitted in the preamps I use.
    Have you compared them to Khozmo or similar Barry?
    Analogue: Technics SP10 MK2 > Phonomac AT-1010 MK6 tonearm > Ortofon Kontrapunkt b > Bigbottle Jfet MC Valve Phonostage (Telefunken Valves)
    Digital: Raspberry Pi 3+/Allo Boss 1.2/Isolator 1.3 & 2x LPSU's with Volumio & JRiver
    Amplification: Nelson Pass DCB1 with Khozmo 48 Step Series Attenuator & Krell KSA100 MK2 Amplifier
    Cables: SPOTFIRE Speaker Cable & SPOTFIRE IC Cables & SPOTFIRE Tonearm cable
    Speakers: Pioneer CS-77A

    Price List For SPOTFIRE Cables here:https://bit.ly/2Uxiv3j

    Alternative reading: http://www.audioaddictsforum.com

  4. #24
    Join Date: Sep 2013

    Location: North Island New Zealand

    Posts: 1,333
    I'm Chris.

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    Quote Originally Posted by thingfish View Post
    Kiss.......is a great concept and that should be a passive pre requisite.

    But.............

    It's more complex than that.....or is it really?
    If you think of a attenuator in terms of being simple and that simplicity to be exactly where the audio path goes - what is the simplest ?
    The answer is in the image. A variable resistor with no contacts coupled by light.
    Attached Images Attached Images

  5. #25
    Join Date: Feb 2013

    Location: scotland

    Posts: 303
    I'm alan.

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    Now that as Spock would say...is Ilogical captain !!!

  6. #26
    Join Date: Sep 2013

    Location: North Island New Zealand

    Posts: 1,333
    I'm Chris.

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    Yet it is the simplest in terms of audio path being preserved, and at the same time being a variable attenuator and a switch for inputs in its Off state

  7. #27
    Join Date: Nov 2015

    Location: Wolverhampton

    Posts: 8,975
    I'm Oliver.

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    LDR are proven to add distortion

    Simplest isn't the key.

    Lowest distortion is where the OP should be aiming.
    Analogue: Technics SP10 MK2 > Phonomac AT-1010 MK6 tonearm > Ortofon Kontrapunkt b > Bigbottle Jfet MC Valve Phonostage (Telefunken Valves)
    Digital: Raspberry Pi 3+/Allo Boss 1.2/Isolator 1.3 & 2x LPSU's with Volumio & JRiver
    Amplification: Nelson Pass DCB1 with Khozmo 48 Step Series Attenuator & Krell KSA100 MK2 Amplifier
    Cables: SPOTFIRE Speaker Cable & SPOTFIRE IC Cables & SPOTFIRE Tonearm cable
    Speakers: Pioneer CS-77A

    Price List For SPOTFIRE Cables here:https://bit.ly/2Uxiv3j

    Alternative reading: http://www.audioaddictsforum.com

  8. #28
    Join Date: Sep 2013

    Location: North Island New Zealand

    Posts: 1,333
    I'm Chris.

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    And lowest distortion is with a good LDR circuit.

    LDR's simply reflect back how good or poorly the anode and cathode are driven, do that well and distortion
    disappears, however do that poorly and figures and graphs you are poised to paste, are what results.

    What does it take to drive the anode and cathode correctly, is what you need to ask. You also need to ask
    yourself why graphs of distortion are not provided with potentiometers passing audio signals ?
    https://pinkfishmedia.net/forum/thre...tortion.68076/
    Last edited by Light Dependant Resistor; 12-06-2019 at 22:16.

  9. #29
    Join Date: Nov 2015

    Location: Wolverhampton

    Posts: 8,975
    I'm Oliver.

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    Quote Originally Posted by Light Dependant Resistor View Post
    And lowest distortion is with a good LDR circuit.

    LDR's simply reflect back how good or poorly the anode and cathode are driven, do that well and distortion
    disappears, however do that poorly and figures and graphs you are poised to paste, are what results.

    What does it take to drive the anode and cathode correctly, is what you need to ask. You also need to ask
    yourself why graphs of distortion are not provided with potentiometers passing audio signals ?
    https://pinkfishmedia.net/forum/thre...tortion.68076/
    Alps and the like do add a modicum of distortion, which is why I moved to Stepped Attenuators.

    There is a forum that offers free measurements of HiFi equipment. Why not send them one of your preamps for testing? I'll try and find a link.

    Have your Stereo Coffee preamps been tested already?

    I am afraid independent testing with published measurements consistently support the claim that LDR's drift over time and add distortion.
    Analogue: Technics SP10 MK2 > Phonomac AT-1010 MK6 tonearm > Ortofon Kontrapunkt b > Bigbottle Jfet MC Valve Phonostage (Telefunken Valves)
    Digital: Raspberry Pi 3+/Allo Boss 1.2/Isolator 1.3 & 2x LPSU's with Volumio & JRiver
    Amplification: Nelson Pass DCB1 with Khozmo 48 Step Series Attenuator & Krell KSA100 MK2 Amplifier
    Cables: SPOTFIRE Speaker Cable & SPOTFIRE IC Cables & SPOTFIRE Tonearm cable
    Speakers: Pioneer CS-77A

    Price List For SPOTFIRE Cables here:https://bit.ly/2Uxiv3j

    Alternative reading: http://www.audioaddictsforum.com

  10. #30
    Join Date: Sep 2013

    Location: North Island New Zealand

    Posts: 1,333
    I'm Chris.

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    Quote Originally Posted by Bigman80 View Post
    Alps and the like do add a modicum of distortion, which is why I moved to Stepped Attenuators.

    There is a forum that offers free measurements of HiFi equipment. Why not send them one of your preamps for testing? I'll try and find a link.

    Have your Stereo Coffee preamps been tested already?

    I am afraid independent testing with published measurements consistently support the claim that LDR's drift over time and add distortion.
    I think you are referring to Audio Science Review - I am nearly ready to send Amir a cased unit to review.
    I too thought stepped attenuators were good, which was in 1992 hearing them with Vishay bulk foil resistors
    Just as Rob expresses here in the last paragraph https://robmid42.wixsite.com/diyaudi...ich-ldr-preamp
    stepped attenuators are not very high on the list, when compared to LDR's

    Both of your presumptions, expressed as fear, are wrong.... which time will prove. There should be a review
    at Pink Fish forum in about 3 weeks, sorting through what sounds best.

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