Lehmann audio black cube se2 custom loading questions

Discussion in 'Audio Hardware' started by merlperl, Jun 30, 2020.

  1. merlperl

    merlperl Forum Resident Thread Starter

    Location:
    Sherman Oaks, CA
    I need assistance from someone that has in depth understanding of the Lehmann audio black cube se 2. Specifically with regard to loading.


    I am waiting for delivery of a Hana ML. The specs are: impedance-8 ohms @1khz. Suggested load impedance->100 ohms


    I have read online that this cartridge really sings at between 121 and 243 ohm loading. I would like to get to this number with the Lehmann.


    I have several questions:


    1. Can I just buy two 121 ohm metal film resistors, put them in the custom loading spots at R104/R204 and just activate that switch (switch 3)? The manual says if a resistor is placed there it is always connected in parallel to the 47k input resistor and the 100pF input capacitor. Does this mean the 47k input resistor is always active and I need to account for that in the resistor values? If so then how would I calculate the correct resistor value to put into the custom loading slot to achieve my desired loading of 121 ohms?
    2. What does the 100pf input capacitor do? Should I leave it off?
    3. Can I use Vishay MELF resistors? These seem to be recommended for audio applications
    4. Do you recommend any resistors?
     
  2. merlperl

    merlperl Forum Resident Thread Starter

    Location:
    Sherman Oaks, CA
    Follow up question: when adding a resistor to the custom loading slot on the BCSE2, does the resistor need to be soldered in there?

    it seems like that would not encourage experimenting with different resistors.

    I’ve not opened it up yet so I don’t know what to expect
     
  3. merlperl

    merlperl Forum Resident Thread Starter

    Location:
    Sherman Oaks, CA
    Ok so I researched and it does NOT require soldering...
     
    Strat-Mangler likes this.
  4. merlperl

    merlperl Forum Resident Thread Starter

    Location:
    Sherman Oaks, CA
    Starting to answer my own questions via extensive research. Still would love a convo with someone that has done custom loading on the Black Cube SE Ii
     
  5. edwyun

    edwyun Active Member

    Location:
    USA
    I had a Lehmann Black Cube SE and Decade, which essentially work the same. You do not need to take into account the 47K resistors if your custom resistors are in the correct slots (I believe the 3rd slots are correct for that). You need to set the correct DIP switches for MC and the 3rd slots, though. I would get a range of resistors to play with, e.g., 100, 150, 200, etc. When I custom loaded resistors, I used high spec Vishay or MKP resistors and had the resistor pairs matched. You do not need to worry about the 100pF for MC.
     
  6. Davey

    Davey I carry the moon inside a silver bag

    Location:
    SF Bay Area, USA
    I don't see R104/R204, there are two custom slots shown in manual, R103/203 is used with the dip switch, and R102/202 is in the circuit regardless of switch positions. They are both in parallel with the 47K input resistance. The 47K won't matter much at these low resistor values, but formula is (47000 * 121) /( 47000 + 121), so if you use the 121 ohm resistor, it will actually be 120.7, no biggie ... the rest of the resistors in the circuit are just cheap metal film, so not sure it makes a big diff to just change one of them, but won't hurt ...


    [​IMG]
     
  7. edwyun

    edwyun Active Member

    Location:
    USA
    The slots affected by the DIP switches are what you want to use.
     
  8. Davey

    Davey I carry the moon inside a silver bag

    Location:
    SF Bay Area, USA
    Personally speaking, I'd use the unswitched slot if going custom, why add the extra switch contacts?
     
  9. merlperl

    merlperl Forum Resident Thread Starter

    Location:
    Sherman Oaks, CA
    Thanks!

    I think I have it now...
     
  10. merlperl

    merlperl Forum Resident Thread Starter

    Location:
    Sherman Oaks, CA
    Wait so if it’s in parallel with the 100 ohm (which I believe is switchable), will it be best to use a 21 ohm resistor and activate the 100 ohm? Or does that mean it will always be on anyways (the 100ohm)?
     
  11. Davey

    Davey I carry the moon inside a silver bag

    Location:
    SF Bay Area, USA
    If going custom, you would normally open all the load switches so you just have the 47K in parallel with your custom load. Loads in parallel do not add, I mentioned the formula above, but you can get as inventive as you like with the switched and unswitched loads to create intermediate values. For instance, if you have 121 ohms in the custom slot and close the 1000 ohm load switch, that will net around 108 ohms.
     

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