SH Spotlight Steve's secret weapon in mastering many of your favorites, the Tube-Tastic Teletronix LA-2A.

Discussion in 'Music Corner' started by Steve Hoffman, Jul 18, 2018.

  1. Claus

    Claus Restaurant Critic

    Location:
    Germany
    It is nice vintage stuff still holds very well over decades.
     
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  2. Steve Hoffman

    Steve Hoffman Your Host Your Host Thread Starter

    Many people still have no idea what this machine does. For me, it fleshes out thin, mean mixes, makes them more 3D lifelike sounding. Occasionally I’ll use it for its true purpose, but not often.
     
  3. gonz

    gonz Forum Resident

    Location:
    Phoenix, AZ
     
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  4. Steve Hoffman

    Steve Hoffman Your Host Your Host Thread Starter

    I never use it like that, don’t worry.
     
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  5. Bern

    Bern JC4Me

    Location:
    Michigan
  6. Strat-Mangler

    Strat-Mangler Forum Resident

    Location:
    Toronto
    I vaguely remember reading a post of yours where you stated the audio needed to be run through multiple times through such a unit to add life and that tube magic. Is that right or is my memory wrong?
     
  7. Steve Hoffman

    Steve Hoffman Your Host Your Host Thread Starter

    Once is enough.
     
  8. Pants Party

    Pants Party Lunch

    Location:
    Washington, DC
    Cool, love seeing stuff like this! Thanks for sharing.
     
  9. Steve Hoffman

    Steve Hoffman Your Host Your Host Thread Starter

    You're welcome.
     
  10. ajawamnet

    ajawamnet Forum Resident

    Location:
    manassas va 20109
    Here's a link to an early Teletronix manual from the Library of Congress:
    http://lcweb2.loc.gov/master/mbrs/recording_preservation/manuals/Teletronix Model LA-2A Leveling Amplifier.pdf
    There's a schematic in the back...

    Note that schematic in the LOC PDF:
    [​IMG]
    differs a bit from the UREI schematics:
    [​IMG]

    Note the redlined switch in the LOC schematic for setting between compression and limiting functions - just shunts out the 2.7K resistor in the photocell circuit... The UREI schematic incorporates that redline.

    Supposedly the T4A's can no longer be manufactured:
    Teletronix T4A T4B T4C Electro-Opto-Attenuator Info

    Not sure which T4 is in Steve's unit.

    There's a $25.00 documentation package available at Gearsluts:
    Teletronix LA-2A Secrets - The most complete information [LA-2A-SECRETS] - $23.99 : Welcome to the GearSlut Store, Lots of cool toys for recording engineers, producers and musicians


    For those that are not familiar with an opto compressor, photocells (one in the audio path at the gain pot) and one on the meter circuit) are driven by an EL light source. The light source was coupled to photocells.
    [​IMG]


    Not unusual to use optical things like light bulbs - directly or indirectly - for current limit. The UREI studio monitor crossovers used them:
    [​IMG]

    The UREI 813's used them - when you'd crank the control room vol, you'd see them glow. A while ago, repaired a bass guitar speaker cab for a local club (the Birchmere) that used old style dome lights for protection. I typically use polyfuses in designs I do.
     
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  11. ajawamnet

    ajawamnet Forum Resident

    Location:
    manassas va 20109
    As to more modern version of opto driven compressor/limiters, we still design audio stuff using these:
    NSL-32SR2 Advanced Photonix | Isolators | DigiKey
    Just did a design last month using these...

    But believe me, they don't sound like an LA-2A. I don't think anything does. They've tried with various DAW plugins. Not so much...

    EL nightlight - https://www.amazon.com/GE-55507-Electroluminescent-Night-Light/dp/B0017C7YRM
    Similar, larger version of the EL is in the T4's

    If you're an IEEE member:
    An Improved Method of Audio Level Control for Broadcasting and Recording - SMPTE Journals & Magazine
     
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  12. ajawamnet

    ajawamnet Forum Resident

    Location:
    manassas va 20109
    On that webpage they mention the LA-4. We used those to drive broadcast loops to transmitter sites over equalized phone lines. The thing was that the output transistors for the 600 ohm output were similar if not the same as those used in the Advent 300 receiver's power amp used to drive speakers.
    [​IMG]
    Lots of headroom and drive. UREI always made silly amazing overbuilt gear.

    Another interesting use for LDR's is for bringing bias up on a pro audio multitrack - it keeps ir from causing a pop when punching in. Scully's used them...
     
    Last edited: Sep 6, 2018
  13. ajawamnet

    ajawamnet Forum Resident

    Location:
    manassas va 20109
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  14. Philo

    Philo Onlooker

    Location:
    Springfield, VA
    I buil a drip audio LA2A clone. Sounds amazing, especially on guitar and vocals.
     
  15. ElevatorSkyMovie

    ElevatorSkyMovie Forum Resident

    Location:
    Oklahoma
    So you know lil' Rocket Man? I hear he's a hoot....
     
  16. ajawamnet

    ajawamnet Forum Resident

    Location:
    manassas va 20109
    I heard he's into flatt and scruggs type stuff.
    There was a remake on utube:
     
  17. vonwegen

    vonwegen Forum Resident

    Man! I would love to hear what you could do to my Hansaring tracks with this sonic gem!

     
  18. Ryan Lux

    Ryan Lux Forum Resident

    Location:
    Toronto, ON, CA
    How does the current Universal Audio LA-2A compare to the originals? Anyone know?
     
  19. Steve Hoffman

    Steve Hoffman Your Host Your Host Thread Starter

    I'm not anyone, but I know. It sounds pretty good. Get the right tubes in there and you're good to go.
     
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