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  1. #1
    Senior Member
    Join Date
    Jan 2017
    Location
    Leyden
    Posts
    569

    pre amp hiss from 1 channel

    Recently I noticed that I have a hiss on one of my channels. After testing it became clear it comes from my tube pre amp, an Octave Phono Module.

    The pre amp has the following tubes.

    1) ECC88/6922 tube in the XLR direct drive output module
    2) ECC83/12AX7 Input tube
    3) ECC81/12AT7 main amplification
    4) ECC88/6922 output buffer

    Since all of these tubes are used as stereo tubes, one tube for both channels I'm not sure which tube I should replace or check first.

    Edit1:

    The is hiss is not affected by volume. When the volume is set to zero it's there and the same when at 10. It doesn't get louder of softer.


    (wish I could post pics on this forum directly without the need to look for a place that lets me share them, I used to use Facebook for this but I don't think it allows sharing any more).
    Pre amp: Ocatve Phono Module Power amps: Octave MRE130 Turntable: SAC Girati Grande. Tonearm: Dynavector 507mkII Cartridge: Dynavector Ikeda 9TT Streamer: Aurender A10 Power Distributor: Anzus Mains D8 Speakers: Raidho X-3 Speaker Cables: AudioQuest Rocket 88 XLR Interlink: Ansuz A2, XLR Interlink: Purist Audio Design - Venustas Phono interlink: Cammino Serie 1.0 - PH 1.0s Power cables: Anzus Mains Ceramic, two Pom, Aluminium, X series Audio Rack: Rack of Silence 4 and 2.

  2. #2
    Senior Member
    Join Date
    Feb 2016
    Location
    west Michigan
    Posts
    627

    Re: pre amp hiss from 1 channel

    Not having the schematic to know exactly how the tubes are used in the circuit, the least expensive way would be to obtain one of each type of tube (I.E. one 12ax7, one 12at7 & one 6922) and simply use the new tube to replace an existing tube one at a time until you discover the culprit.. Kind of labor intensive but will get the job done.
    My System:
    Lumin A-1
    Joule Electra LA150 Signature Plus
    Pass XA30.5
    Line Magnetic 845ia
    JMR (Reynaud) Offrande Supreme V2
    18" Open Baffle Subs
    Cables: Teo Audio, Cerious Tech, Fusion Audio.
    Two dedicated 20 Amp circuits. Shunyata Hydra. EP2050
    DIY bass traps and custom curved diffusors.

  3. #3
    Senior Member
    Join Date
    Jan 2017
    Location
    Leyden
    Posts
    569

    Re: pre amp hiss from 1 channel

    So I found the faulty tube, it was the Gold Lion Genelex ECC88/6922 tube in the XLR direct drive output module. I replaced it with the stock tube which came with the amp.

    Anyone some ideas what would be a good tube for this location in my amp?
    Pre amp: Ocatve Phono Module Power amps: Octave MRE130 Turntable: SAC Girati Grande. Tonearm: Dynavector 507mkII Cartridge: Dynavector Ikeda 9TT Streamer: Aurender A10 Power Distributor: Anzus Mains D8 Speakers: Raidho X-3 Speaker Cables: AudioQuest Rocket 88 XLR Interlink: Ansuz A2, XLR Interlink: Purist Audio Design - Venustas Phono interlink: Cammino Serie 1.0 - PH 1.0s Power cables: Anzus Mains Ceramic, two Pom, Aluminium, X series Audio Rack: Rack of Silence 4 and 2.

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pre amp hiss from 1 channel

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