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Thread: khozmo passive pre amp question

  1. #1
    Join Date: Oct 2009

    Location: Birmingham, UK

    Posts: 351
    I'm Phil.

    Default khozmo passive pre amp question

    Hi folks , im interested in a khozmo passive pre , but im concerned about the pots resistance which is 200k , im not sure he is measuring the resistance from the right place , does the pots resistance have any effect on volume level , im using a tisbury passive pre which is 10k , im told 50k is
    ideal with my ming da 805 monblocks , also use a long dog moving coil valve phono stage , I think its the series resisters that you have to measure
    and there Vishay z foil , basically I need to make sure its the right resistance 200k and if it is will that be ok with my kit can anyone help with this cheers phil.
    Phil.

  2. #2
    Join Date: Oct 2012

    Location: The Black Country

    Posts: 5,096
    I'm Alan.

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    I think 50K would be ideal but I see no problem going up to 200K, particularly driving the monoblocks.

  3. #3
    Join Date: Oct 2009

    Location: Birmingham, UK

    Posts: 351
    I'm Phil.

    Default

    Thanks alan , do you think the volume level would be any different cheers phil.
    Phil.

  4. #4
    Join Date: Oct 2012

    Location: The Black Country

    Posts: 5,096
    I'm Alan.

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    The only likely difference is the vol pot may be a few degrees further round depending on the actual input impedance of the monos.

  5. #5
    Join Date: Oct 2009

    Location: Birmingham, UK

    Posts: 351
    I'm Phil.

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    Thanks very much , phil.
    Phil.

  6. #6
    Join Date: Apr 2012

    Location: London

    Posts: 577
    I'm James.

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    Pretty sure they used to make them to your desired impedances if you emailed them? Might be worth a try if you're thinking of buying new anyway?

    Sent from my BLA-L09 using Tapatalk

  7. #7
    Join Date: Nov 2013

    Location: Powys

    Posts: 989
    I'm David.

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    Quote Originally Posted by Jazid View Post
    Pretty sure they used to make them to your desired impedances if you emailed them? Might be worth a try if you're thinking of buying new anyway?
    I emailed them recently for advice on the correct impedance for my Quad 306, very helpful and the preamp arrived pretty quickly from Poland. I'm very pleased with it, definitely a set up from the Tisbury.

  8. #8
    Join Date: Sep 2013

    Location: North Island New Zealand

    Posts: 1,403
    I'm Chris.

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    Hi
    200k suggests as being excessive resistance, as to use such values you really need to have a emphasis capacitor to correct
    for frequency loss in the upper resistance ranges above about 100k . Inferring quite a difficulty with a potentiometer vs a stepped resistor type.
    (which could have such a progressive range of emphasis capacitors placed to correct for frequency loss across the highest resistance values)

    High value potentiometers also suffer from what is called Johnson noise. The history of the rheostat is in its centenary year, although
    pencilled in differing designs earlier it has a patent registered to https://en.wikipedia.org/wiki/Mary_Hallock-Greenewalt

    If choosing to pass audio signals via a potentiometer 50k being 25k from mid volume in each direction would be the upper maximum. Lower values
    with 15k being ideal is preferable, as lower values enable your source and load impedances to easily drive such a passive L pad


    Even with LDR's I avoid using any resistance above 63k, usually using 50k - but of course this resistance is NOT in the audio signal path
    rather arranged as a current sink on the LDR cathodes. .

  9. #9
    Join Date: Oct 2009

    Location: Birmingham, UK

    Posts: 351
    I'm Phil.

    Default

    Thanks again for all your help I have decided against that khozmo , also looking at dave slagle
    Phil.

  10. #10
    Join Date: Nov 2015

    Location: Wolverhampton

    Posts: 9,762
    I'm Oliver.

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    Quote Originally Posted by oceanobsession View Post
    Thanks again for all your help I have decided against that khozmo , also looking at dave slagle
    I went from slagle to a preamp with a Khozmo Stepped Attenuator.

    No looking back from me.
    Analogue: Technics SP10 MK2 > Phonomac AT-1010 MK6 tonearm > Ortofon Kontrapunkt b > Bigbottle Jfet MC Valve Phonostage
    Digital: Orchard Audio PecanPi with JRiver
    Preamplifier: DCB1 with Khozmo 48 Step Series Attenuator or Neurochrome Differential Preamp
    Amplification: Neurochrome Modulus 686
    Cables: SPOTFIRE Speaker Cable & SPOTFIRE IC Cables & SPOTFIRE Tonearm cable
    Speakers: Mordaunt Short Performance 880

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

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

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