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Reverb Tank Questions

Discussion in 'Amp Tech Center' started by Archie343, Jan 23, 2021.

  1. Archie343

    Archie343 TDPRI Member

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    Novice amp enthusiast here

    In planning my first amp build, I've come across an issue with parts I need. The reverb tank I need for the schematic I've put together requires a tank with high input impedance, in the K-ohm range to be close to the output impedance of a 12AU7 at 4k. These high impedance tanks are hard to come by, and I don't want to have to order from America (especially since no shipments can take place right now)

    If I had a tank with input impedance of 600ohm, would it still function ok? is there any way to improve the efficiency with that set up? Here's the general schematic I'm following (based off of a swart reverb, taken from https://guitar.com/guides/diy-workshop/build-tube-spring-reverb-unit-amplifier/ )
    [​IMG]

    Thanks in advance!
     
  2. goldguitarguy

    goldguitarguy Tele-Meister

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    If you can’t find a tank with the proper input impedance I recommend using a reverb driver between the drive tube and the reverb tank to covert the high impedance.

    An impedance mismatch greater than a factor of two will will give you issues.
     
  3. goldguitarguy

    goldguitarguy Tele-Meister

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    Also if you’re in Canada you can still get packages from the states. Just got an order from Amplified parts and EBay this week...
     
  4. Jon Snell

    Jon Snell Tele-Holic

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    Look for a 4FB2C1B
    That has a 1.6k input impedance (the highest that is made for physical reasons) and use either a buffer cathode follower or transformer with a standard tank.
     
  5. Archie343

    Archie343 TDPRI Member

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    The schematic I'm following leads to a mismatch of around 3 times, and I agree, it would be foolish to push it any further out of balance.

    I was looking for a tank starting with 8F because of space requirements. I think using a transformer and an 8A tank would be easier, hopefully I can find an appropriate sized one as there aren't many vendors in the UK right now. Online I have seen discussions about 100v line transformers that have 6kohm:8ohm impedance ratio, and that seemingly would work.

    Thanks !
     
  6. Archie343

    Archie343 TDPRI Member

    Age:
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    Funny you should send both these.. they're already in my ebay basket haha. I was just unsure that they would do the trick but thanks for clarifying for me. Makes life a whole lot easier.

    Cheers!
     
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