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Thread: Reducing the output of a passive pre-amp

  1. #1
    Join Date: Apr 2016

    Location: Bishops Stortford

    Posts: 944
    I'm Chris.

    Default Reducing the output of a passive pre-amp

    Hi

    I have a simple Axiom Signature passive and the output is far too high for my needs. So I would like to reduce it by say 15db. You will see from my questions that, although I can wield a soldering iron, I am no electronics expert

    Can I achieve this by:

    1. Replacing the existing 1.2K resistors with higher values - if so what?

    2. Putting additional resistors elsewhere in the unit. If so where and what values?

    Thanks in advance
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  2. #2
    Join Date: Feb 2010

    Location: Maidenhead, Berks

    Posts: 266
    I'm Lee.

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    What's the value of the pot?
    Cheers Lee

  3. #3
    Join Date: Apr 2016

    Location: Bishops Stortford

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    I'm Chris.

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    Quote Originally Posted by lilolee View Post
    What's the value of the pot?
    Its a Noble 10Kohm pot. At the moment I can get reasonable volume with the pot fully turned off and a movement of maybe 1mm is good listening level and 2mm just too loud. I am running an experiment of a 1000wpc amp into 100db sensitive speakers (dont ask!). Sounding pretty good but need more volume adjustment to be sure.
    SW1X Universal Music Server UMS I Signature with Power Supply Unit PSU I Signature
    SW1X USB II
    SW1X DAC III Special
    SW1X Open Baffle Speakers containing both vintage and modern alnico drivers and paper cones. All silver wired and crossover-less where possible - 4" vintage Siemens Klangfilm tweeters, 8" SEAS X2-08 EXOTIC W8 midrange drivers and vintage 15" Altec VOTT 416 bass drivers
    Hi fi Collective twin mono ladder stepped attenuator, with Charcroft Z-foil and silver wired.
    DRD 45 single ended, 45 triode, monoblocks,
    Silver mains cables, interconnects and speaker cables by SW1X

  4. #4
    Join Date: Feb 2010

    Location: Maidenhead, Berks

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    I'm Lee.

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    Either 27k or 33k will give you about 15dB.
    Cheers Lee

  5. #5
    Join Date: Apr 2016

    Location: Bishops Stortford

    Posts: 944
    I'm Chris.

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    Quote Originally Posted by lilolee View Post
    Either 27k or 33k will give you about 15dB.
    Excellent. If its not giving you a leading question, where do I stick them. I'm guessing in the left and right wires that join the input phonos with the volume control. Or is it in place of the Caddock resistors?
    Last edited by bumpy; 19-05-2020 at 12:02.
    SW1X Universal Music Server UMS I Signature with Power Supply Unit PSU I Signature
    SW1X USB II
    SW1X DAC III Special
    SW1X Open Baffle Speakers containing both vintage and modern alnico drivers and paper cones. All silver wired and crossover-less where possible - 4" vintage Siemens Klangfilm tweeters, 8" SEAS X2-08 EXOTIC W8 midrange drivers and vintage 15" Altec VOTT 416 bass drivers
    Hi fi Collective twin mono ladder stepped attenuator, with Charcroft Z-foil and silver wired.
    DRD 45 single ended, 45 triode, monoblocks,
    Silver mains cables, interconnects and speaker cables by SW1X

  6. #6
    Join Date: Apr 2016

    Location: Bishops Stortford

    Posts: 944
    I'm Chris.

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    Quote Originally Posted by bumpy View Post
    So where do I stick them. I'm guessing in the left and right wires that join the input phonos with the volume control. Or is it in place of the Caddock resistors?
    Itching to order a couple of suitable resistors, so can anybody answer this question?
    SW1X Universal Music Server UMS I Signature with Power Supply Unit PSU I Signature
    SW1X USB II
    SW1X DAC III Special
    SW1X Open Baffle Speakers containing both vintage and modern alnico drivers and paper cones. All silver wired and crossover-less where possible - 4" vintage Siemens Klangfilm tweeters, 8" SEAS X2-08 EXOTIC W8 midrange drivers and vintage 15" Altec VOTT 416 bass drivers
    Hi fi Collective twin mono ladder stepped attenuator, with Charcroft Z-foil and silver wired.
    DRD 45 single ended, 45 triode, monoblocks,
    Silver mains cables, interconnects and speaker cables by SW1X

  7. #7
    Join Date: Mar 2017

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    I'm Dennis.

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    Painting the hall through the letterbox anyone?

  8. #8
    Join Date: Oct 2012

    Location: The Black Country

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    I'm Alan.

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    Quote Originally Posted by bumpy View Post
    Itching to order a couple of suitable resistors, so can anybody answer this question?
    Yes between input and volume pot.

  9. #9
    Join Date: Apr 2016

    Location: Bishops Stortford

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    I'm Chris.

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    Thanks Alan
    Can I just ask is a 33K resistor what they call 3.3R?
    SW1X Universal Music Server UMS I Signature with Power Supply Unit PSU I Signature
    SW1X USB II
    SW1X DAC III Special
    SW1X Open Baffle Speakers containing both vintage and modern alnico drivers and paper cones. All silver wired and crossover-less where possible - 4" vintage Siemens Klangfilm tweeters, 8" SEAS X2-08 EXOTIC W8 midrange drivers and vintage 15" Altec VOTT 416 bass drivers
    Hi fi Collective twin mono ladder stepped attenuator, with Charcroft Z-foil and silver wired.
    DRD 45 single ended, 45 triode, monoblocks,
    Silver mains cables, interconnects and speaker cables by SW1X

  10. #10
    Join Date: Feb 2013

    Location: W Lothian

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    I'm Grant.

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    3.3r is 3.3 ohms.. you need 33kohm...or am i getting old

    you want 3 orange bands..
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