1650t OT confusion

Discussion in 'Amp Tech Center' started by DucDone, Jun 14, 2021.

  1. DucDone

    DucDone Tele-Meister

    Posts:
    141
    Joined:
    Apr 9, 2011
    Location:
    Bergen
    Hi. I have this Hammond 1650T that I have installed in a Hiwatt type of amp. I am though a bit confused over the primaries, usually there ar only three eires her, but in the 1650t there are more. Any advice on how to connect these?
     

    Attached Files:

  2. danlad

    danlad Tele-Meister

    Posts:
    357
    Joined:
    Mar 24, 2015
    Location:
    Here and there
    It's something to do with having interleaved windings being a more hifi transformer than the usual simpler taps we know and love.

    What speaker impedance are you wanting?

    Other options are here, showing how to wire for 8 & 16 ohm speaker loads:

    https://www.hammfg.com/files/products/1608-1650/all-except-1645.jpg

    EDIT Sorry you said primary! Screens for ultra linear operation it will be.
     
  3. 2L man

    2L man Tele-Holic

    Age:
    61
    Posts:
    562
    Joined:
    Nov 23, 2020
    Location:
    Finland
    That kind of secondary saves copper on the wire which needs to be used when for 4 ohms two coils are connected parallel because 4 ohm load current is higher so wire does not melt. For 8 ohms there is extra wounds but still both 4 ohms are parallel. For 16 ohms two 4 ohm coils are used series and then current is half what 4 ohm take.

    When typical secondary is wound using same thickness wire it is too thick between 8-16 and if that section is wound using thinner wite the wire is too thick between 0-4 and 0-8.

    However it is not the copper wire cost why that OT is wound like yours but transformer other variables effect there which are more important for HiFi.

    On primary there are connections for Ultra Linear operation where Screen voltage is taken. UL operation is something between pentode and triode and it is used on HiFi amps. I did test it for guitar but it made sound not interesting.
     
    Last edited: Jun 14, 2021
  4. 2L man

    2L man Tele-Holic

    Age:
    61
    Posts:
    562
    Joined:
    Nov 23, 2020
    Location:
    Finland
    That kind transformer is interesting because it allows 8 and 16 ohm loudspeakers used same time and input impedance stay same when 8 speaker is connected to single 4 ohm coil and 16 speaker to 8 ohm coil.

    1900 ohm impedance is quite small for typical quitar amps so doubling it obviously should be done?

    This allows interesting options using two "smaller" 16 ohm loudspeakers series on 8 output and one "bigger" 16 on 4 output and input impedance changes to 3800 ohms which is fine for example EL34 push pull. Now when both outputs deliver same power those two 16 ohms peakers series connected can be half the power what that third is.

    If those two smaller also have 3db lower sensitivity than bigger one this setup produce about equal workload for all speakers and speakers produce about equal texture to the sound they are capable to produce. Tweed Bandmaster is one interesting combo which uses three speakers...
     
    Last edited: Jun 14, 2021
  5. DucDone

    DucDone Tele-Meister

    Posts:
    141
    Joined:
    Apr 9, 2011
    Location:
    Bergen
    But what about the primaries?
     
  6. danlad

    danlad Tele-Meister

    Posts:
    357
    Joined:
    Mar 24, 2015
    Location:
    Here and there
    Connect to screens for ultra linear operation
     
    Wally likes this.
  7. DucDone

    DucDone Tele-Meister

    Posts:
    141
    Joined:
    Apr 9, 2011
    Location:
    Bergen
    Ok, thanks.
     
  8. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

    Posts:
    3,932
    Joined:
    Dec 30, 2019
    Location:
    california
    As @danlad has pointed out the inside primary taps are for an ultra linear setup. You can connect them directly to the screens or you can tuck them away and use the OT in a *normal* circuit. I suppose I should have written *a more conventional guitar circuit*. hah. There is a difference when using ultra linear. Fender tried it for a while after the Silverface era, iirc. You can try it both ways and report your findings...

    what is normal.jpg
     
    DucDone and Wally like this.
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.