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Difference between "Early" and "Later" versions of Leslie 31H, to pair with A102

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  • Difference between "Early" and "Later" versions of Leslie 31H, to pair with A102

    Greetings all,

    Wondering if someone could clarify the differences between the "Early" version and "Later" version of the Leslie 31H, specifically with regards to sound and value? (I don't even know exactly what is different, a better amp in the later ones I think?)

    Basically, is there so much difference between them that I should jump on one and be wary of the other?

    I found someone selling a Tall Boy for $300. I can't test it, but all indications are its in excellent shape. The family of the late owner is selling it and doesn't know much about them, they are just trying to clear storage space. But I don't know if its an early or later model and won't be able to check until I am on site.

    I have never played on one, but LOVE the sound of the Tall Boy and would LOVE to pair with my A102 (I will be picking up the same day).

    For $300, I am willing to take the risk on buying it without testing it if it is "the" Tall Boy, but I need to know if I should be more cautious if it turns out this is one of the early 31H's with the earlier model amplifier?

    Is there really that big a difference in the sound? Is the value of the earlier model significantly less, or is it still worth $300 it if its in good shape?

    Thanks!

  • #2
    I've become something of a specialist in these, so here goes:

    You will find one of three different amps in the 31H. The first is the wide-body Type 1 amp (only retrospectively called the Type 1) that used a motor switching system unlike any later Leslie cabinet. (In fact, I've recently seen an early 1949 Type 1 Leslie 31H.) These 31Hs were only made in 1948 and 1949. (There is an older 31A.)

    In mid-1949, with SN 5200, Leslie introduced the 6H/Type 2 motor switching system that's still in use to the present as the standard 122 Leslie interface. This required adding some components to the front end and, I think, changing the relay, but the rest of the amp was the same. An extra 6J5 tube was added for the motor-switching circuit. The chassis is still the wide-body design.

    In early 1952, with SN 8000 Leslie introduced the 32H "Series III" amp that has the narrow chassis used by most subsequent Leslie amps to the present. There were some circuit improvements like dropping the screen voltages below the plate voltages on the output tubes. It uses the Type 2/6H switching. These amps were made through 1957. The crossover wiring changed though the component values remained the same.

    All the amps use basically the same fairly simple audio circuit. Earlier amps use 6L6G output tubes; later ones use the Tung-Sol 5881, Tung-Sol's upgrade of the 6L6G. We can now use 6L6GCs, which didn't exist when these amps were made. The Type 1 amps use 5Z3 rectifiers, which were the same tube as the 5U4G with a different base.

    If your organ is set up for a Leslie 122, then you can use the Type 2 wide-body amp or the 32H without modification. You can't use the Type 1 amp; however, the Type 1 amp can have the front end modified for 6H motor switching. I've done this to three 31H Type 1 amps. It's considered a standard practice because it makes them compatible with any 122 hookup. If you want, you can even update an earlier amp to the 32H circuit.

    Any 31H or 32H amp needs to be VERY thoroughly gone through at this point in history, which would include replacing all paper dielectric capacitors and aged electrolytics if this has not already been done, and the 31H should ideally have its original field-coil woofer in the cabinet since that is a big part of the sound. If the field-coil woofer is missing, it's worth a lot less. Earlier 31Hs use a Magnavox FC woofer. Around 1951 or so, they switched to the Jensen F15LL.

    In general, there's not a huge sound difference among the various 31H cabinets. The differences are more technical.

    The amps are nominally 30 Watts, but I have bench-tested ones I've rebuilt at closer to 40 Watts. I think Leslie was rating them conservatively.

    Hope that helps!
    I'm David. 'Dave' is someone else's name.

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    • #3
      That help tremendously, thanks so much!

      I just wanted to make sure I was not going to get burned spending 300 on what could be an early 31H, and have it sound nothing like the classic Tall Boy.

      I am definitely not planning to "plug and play", I will be having a technician come and inspect it for me.

      Since I am not at all electrical-savvy, is there something visual I can look for to ensure this has the original field-coil woofer, or any other red flags I should look for (visual, since I won't be able to connect to anything before I buy)?

      Comment


      • David Anderson
        David Anderson commented
        Editing a comment
        There are photos of 31H cabinets on the web. You can google them and get an idea of what things are supposed to look like. Check the amp for blown fuses or something like a 20A fuse.

    • #4
      The field coil 15" has, well, the field coil magnet on it (photo attached). To look at it you'd need to open up the back panel. It would require some tinkering to adapt a field-coil Leslie amp to run a permanent magnet 15" - not unheard of; I bought a 21H that had that done to it. The field coil speaker will have four wires, two for the signal and two for the magnet. There's also the large black upper loop/bridge/whatever you want to call it that isn't on a permanent magnet speaker. You will probably hear a tonal difference between a permanent magnet and field coil speaker - the field coil is a much stronger magnet, giving the speaker more to push against and more bass response. Because of the hi-fi and jukebox collector's market, they're priced on the high end if you're trying to find another - maybe $300-$500? I don't have my finger on that market. The tall-boys I own both have the series 2 amplifier, and as others have said, there is very minor (if any) difference in tone between this and the series 3. I've never actually seen a 1st gen amplifier - I have a 31A, but someone had replaced its amplifier with a series 3. One other thing I noticed is that as-designed, the tremolo switch at the organ will only control the upper rotor. There is a small switch on the side of the cabinet to manually switch the lower rotor on and off (pictured). To get around that you simply get a power splitter or something that will let you plug both motors into the socket controlled by the console's tremolo switch (pictured). The amp in this Leslie is currently in my garage on the workbench awaiting a rebuild... the project list continues to grow and get away from me.
      You may only view thumbnails in this gallery. This gallery has 3 photos.

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