In love with capacitor coupled output sound

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Comments

  • corticocortico Posts: 348
    That Krell layout look pretty clean, though!
    "If it measures good and sounds bad, -- it is bad. If it sounds good and measures bad, -- you've measured the wrong thing." Daniel Von Recklinghausen
  • agfrostagfrost Posts: 2,060
    mhardy6647 wrote: »
    agfrost wrote: »
    SCompRacer wrote: »
    I have some resistor pictures but they are not G rated. >:)

    This old Krell KSL pre with phono board had a few caps.

    r9ygtioj4e0i.jpg

    That should be the centerpiece of someone's rig...

    Well, yeah, maybe -- but I am not sure I'd want my signal goin' through all of that stuff on any given day.

    :blush:

    I bought that Krell from Rich, it's my daily driver! :blush: My ears tell me it's the best of the small preamp stable I own (see signature).

    I can roll my PS Audio in passive mode when I want less stuff in the signal path though! It's very nice, as well--needs some TLC with cleaning the volume and source pots to avoid noise/scratchiness when fiddling with them. That project's having a hard time moving up on my to-do list, though...
    Jay
    SDA 2BTL * Musical Fidelity A5cr amp * Marantz DV-9500 * Modded Adcom GDA-600 DAC
    Micro Seiki DQ-50 * A hodgepodge of cabling * Belkin PF60
    Preamp rotation: Krell KSL (SCompRacer recapped) * Manley Shrimp * PS Audio 5.0
  • SCompRacerSCompRacer Posts: 6,686
    agfrost wrote: »

    r9ygtioj4e0i.jpg

    That should be the centerpiece of someone's rig...[/quote]

    I agree! B) The phono stage isn't bad at all either.
    Make yourself necessary to someone. Ralph Waldo Emerson

    Salk SoundScape 8's * Audio Research Reference 3 * Bottlehead Eros Phono * Park's Audio Budgie SUT * Krell KSA-250 * Harmonic Technology Pro 9+ & Pro 11+ * Signature Series Sonore Music Server w/Deux PS* Twisted Pear Buffalo III Dual Mono ESS Sabre32 DAC * Heavy Plinth Lenco L75 Idler Drive * AA MG-1 Linear Air Bearing Arm * AT33PTG/II & Denon 103R * Richard Gray 600S * NHT B-12d subs * GIK Acoustic Treatments * Sennheiser HD650 *

  • corticocortico Posts: 348
    Got the second unit in! It has an earlier serial number and looks pretty clean inside.
    Bummer, the right channel is weak and distorts :( I measured the following voltages:

    Right Channel:
    0mvdc between J713 and J715 (adjusting R729 as no effect) should really be 7.5mvdc
    ~47vdc between J715 and ground (adjusting R723 as no effect) should be ~29-30vdc

    Left channel:
    7.5mvdc between J714 and J716
    29vdc between J716 and ground (all seems good and adjusts well)

    I have opened up the same thread on AK and the peeps there will guide on this one. My knowledge is limited when it goes beyond checking values and replace parts.

    My cap order is on the way, first I'll replace power supply first electrolytic , main amp electrolytic coupling caps and main filter.

    If problem persists I will move on transistors and diodes.

    Any tips here would be appreciated as well.
    gsce2vfs2ijo.jpg
    ds8nutfs14sw.jpg
    "If it measures good and sounds bad, -- it is bad. If it sounds good and measures bad, -- you've measured the wrong thing." Daniel Von Recklinghausen
  • corticocortico Posts: 348
    ... cap choice for this recap:

    Jensen 4 poles for main filter (big fat one)
    Jensen 2 poles for speaker coupling caps (left of main filter)
    Black gates for main filter on power supply board
    Elena Silmic II for all other electrolytic caps
    3rr3wa6b9qg0.jpg


    "If it measures good and sounds bad, -- it is bad. If it sounds good and measures bad, -- you've measured the wrong thing." Daniel Von Recklinghausen
  • corticocortico Posts: 348
    edited February 10
    just thought I should share this list of common transistors found in vintage audio and their modern day substitution, always pay attention the pins layout as this may very.

    http://hudsonvalleyhifi.com/technical-data/transistor-substitutions

    Came across this useful list when was looking for replacements for a few transistor on the power board that may be responsible for the right channel issue.

    c20bs9i6xikp.png

    I will take a look at the transistor:
    H709 (2SC959-2N3440)
    H711 (2SA606-2N5416)
    H705 (2SC371Y)
    H707 (2SA562Y)
    also resistor R747 and R749 (0.24ohm 2W wire wound) will replace with mills.
    "If it measures good and sounds bad, -- it is bad. If it sounds good and measures bad, -- you've measured the wrong thing." Daniel Von Recklinghausen
  • corticocortico Posts: 348
    edited February 10
    In the meantime, I got wood cases made for both... I think I hear sound improvements :blush:
    rclqio59aaru.jpeg
    "If it measures good and sounds bad, -- it is bad. If it sounds good and measures bad, -- you've measured the wrong thing." Daniel Von Recklinghausen
  • corticocortico Posts: 348
    edited February 19
    Power amp board came out today, easy to disconnect. The whole module With heatsink came off.

    I only had to unscrew it from chassis, disconnect the shielded audio cable that brings the L-R signal from preamp, power supply line from main filter, separate coupling caps and ground connection.

    These orinsl wire will be redone with new and heavier gauge wire. The caps will get replaced as well. I will use 6800uf Jensen 4 pole instead of the 4700uf big filter and 2 Mundorf mlytics will take the place of the original 3000uf output coupling cap.

    It’s important to document everything with pictures and notes, and this thread will help to review work as well.

    I have flipped the board and attached it back to the heatsink, this avoids bending the transistors leads to many time, and gives easy access to both sides of the board..,

    setm9bv56u73.jpeg
    m3eyl8uup6dm.jpeg





    "If it measures good and sounds bad, -- it is bad. If it sounds good and measures bad, -- you've measured the wrong thing." Daniel Von Recklinghausen
  • corticocortico Posts: 348
    edited February 21
    I have made a few more measurements today and probably found the cause of the channel imbalance, resistor R743 measures more than twice its value!!

    There are also other small discrepancies between L and R channel actual resistors readings. This reiterates how important his to overhaul a vintage unit if it’s intended to use it everyday and there’s no “collectors” value or interest.

    I will replace them all with audio grade Takman Rex carbon film resistors. They are specifically designed to have very low inductance and microphony. Supposedly, It will produce most of the warmth of a carbon comp without all the drift and noise...
    8zacmhs0c7m8.jpeg

    R743 looks cracked:
    mzxvdjztj79o.jpeg


    The Takman look cute too...
    t785h5me912a.jpeg
    "If it measures good and sounds bad, -- it is bad. If it sounds good and measures bad, -- you've measured the wrong thing." Daniel Von Recklinghausen
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