Deluxe Reverb speaker mismatch?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by 55hz, Jan 30, 2012.

  1. 55hz

    55hz Member

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    I've heard/read from some folks that in a Deluxe Reverb, the transformer really wants to see a load around 16ohms instead of the factory rated 8ohm speaker load. Can anyone speak to this? I know plenty of people have run 16ohm loads from their DR's forever. Is the above true or false?

    www.thegearpage.net/board/showthread.php?t=133804

    I found this link...Please see the post by John Phillips
     
    Last edited: Jan 30, 2012
  2. Tele Wacker

    Tele Wacker Member

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    I'm 62 and I've never heard of this. I don't know anyone who runs a 16 ohm speaker but I'm sure there may be some folks who do. I'm staying with my 8 ohm with my Deluxe Reverb.
     
  3. 55hz

    55hz Member

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  4. wyatt

    wyatt Member

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    From that same thread...
    The above info is correct, and it's pretty much repeated in the tube manuals and tube data sheets across decades of print without argument. The optimal primary (tube-facing) resistance for a pair of push-pull 6V6s is 5K-8K ohms.

    The stock DR OT ratio is 6.6K:8.

    A speaker impedance is relatively static...it doesn't change, it forces change elsewhere... the speaker isn't "mismatched" to the OT, instead it forces the OT to mismatch to the tubes...which are far more reactive to the way the circuit is working.

    So, when you swap the speaker to 16-ohms, you change the primary impedance the tubes see to 13.2K. It will alter the tone of the power amp and decrease it's efficiency/output/headroom in a noticeable way because the whole power amp won't work as effectively as it was designed.

    While some designers favor a 8K (like the Tweed Deluxe used) over a 6.6K primary with 6V6's, I've never seen anything to substantiate Phillip's claim, nor does he offer any reference. 13.2K is way out in left field, my guess is he just prefers the sound of a weakened DR.

    While a 16-ohm speaker shouldn't hurt a DR, it is far from the optimal match...and certainly NOT what the amp "wants to see."
     
    Last edited: Jan 30, 2012
  5. 55hz

    55hz Member

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    Thank you, sir! <tips hat>
     
  6. Stu Blue

    Stu Blue Member

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    John Phillips is much missed on this forum for his honesty, knowledge and general sanity. I would see no reason to doubt his evidence... also it makes me feel better about having stuck a 16ohm G12H in deluxe reverb back in 1972 ( it recorded beautifully... A&R men asked how I got that sound, etc).

    John said (my bold)
    You might be amazed by this, but actually 16 ohms is a better match for a Deluxe Reverb than 8 ohms is. Really! Fender made them like that for some reason... the actual 'correct' match going by the OT turns ratio is somewhere around 13 or 14 ohms if I remember rightly, but 16 is close enough.

    No, I didn't believe this at first when I read about it either - but I checked it using different loads and metering the output power at each. Sure enough, more power was produced at 16 ohms than 8, which indicates a better match. In fact, the stock 8-ohm load is a better match if you put 6L6s in the amp...

    Assuming the OT
    is an exact reproduction of the old spec, what you should get is slightly more power, and a tighter, more controlled and even tone with less flub at the bottom end when it's pushed hard. And definitely no risk whatever.
     
  7. LarryN

    LarryN Member

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    I used an old 15 ohm greenback in my DR and it sounded stupendous. I never noticed if it was lower in power. It sure didn't act like it. I remember that post and it may have influenced my decision. It was long ago.
     

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