series/parallel wiring and output transformer

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by ccoker, Oct 22, 2005.

  1. ccoker

    ccoker Supporting Member

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    I have a Rivera R30 right now, it has an 8 ohm output, not adjustable..

    I want to hook up two speakers and both are 8, so, I can do series at 16 or parallel at 4
    I called Rivera and he said run them at 4 (even though the amp says 8 min) but that the tubes will run hotter, I was tight on time and didn't get a chance to dig deeper

    I have had plenty of other amps and have always thought series wiring sounding fatter.

    My thinking (and I may be wrong here) is that if I run them at 16 the amp is less efficient, fine with me, I get to turn up the master a bit more and get more power tube action


    I guess my real question is with an 8 ohm tap, what really happens when you run at 4 vs 8 vs 16?

    I know that if you have a multitap you should always run at 16 as it uses all of the windings...

    I may replace the speakers I have now and so I have the chance to another set of 8s or go with two 16s in parallel to get 8

    bottom line is tone, I want the fattest and warmest tone

    thanks
    Charles
     
  2. VaughnC

    VaughnC Supporting Member

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    Generally speaking, with a tube amp it is safer to run into a lower than normal impedence than higher....but most tube amps can handle one impedence step up or down with no problems.

    Series or parallel wired speakers will sound different so that's a matter of personal tonal preference. However, wiring speakers in series is more risky than parallel wiring because if one of the speaker coils opens in a series connection, there will be no load on the amp....which can be bad news for your amp's output transformer.
     
  3. bob-i

    bob-i Member

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    Typically when you run at a lower impedance you'll heat up the output stages, higher impedance will lower the power somewhat.

    When the manufacture makes a recomendation I'd follow it. I'd wire those speakers in parallel.
     
  4. TheAmpNerd

    TheAmpNerd Member

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    NO NO NO...
    Danger Will Robinson

    The purpose of multitap is NOT TO ALWAYS RUN IT AT 16 OHM!s
    If so, then every tranny would just be 16 ohms and
    no one would ever worry again about it.

    HOWEVER

    The multitaps purpose is to enable you to select impedence
    that best matches the wiring and speakers in your cab.

    So if you have a Super Reverb use 2 ohm (not 16)
    So if you have a vibrolux Reverb use 4 ohm (not 16)
    Or if you have a Marshall running a Mesa Recto
    4 x 12 you can run it either 4 or 8 ohm (not 16).

    What fool hearty person told you to "always run
    it at 16 ohms?"

     
  5. ccoker

    ccoker Supporting Member

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    I was saying that I have always heard (correct or myth) that if you can use the 16ohm tap (say you have a cab with 2 8s and you can go 16 or 4) that the 16ohm tap uses all the windings and sounds better (assuming you have a 4/8/16 adjustable OT)

    I have also read recently that that is BS that it doesn't matter (toneally)
     
  6. Wakarusa

    Wakarusa Member

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    There are so many threads on this that it starts to make my head hurt. The summary is:

    - "better" is in the ears of the beholder

    - the difference in tone and dynamics can be subtle, but is certainly measureable. A mismatch can impact frequency response and power (see "better" above). Matched, but using a different tap tends to impact damping factor (again see "better").
     
  7. ccoker

    ccoker Supporting Member

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    yep
    I posted this before I did some searches and read up..

    thanks
     
  8. Fuchsaudio

    Fuchsaudio Member

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    I've heard the "16 ohms sounds best" adage before. I think it's rooted in the theory that at 16 ohms less windings are used to convert the output stage impedance down to a speaker impedance, so 16 ohms is "better sounding". Again, totally subjective, but it has been tossed around for a long time. Just my two cents.
     

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