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70v speaker and amp questions

Discussion in 'Speakers' started by jaxontrumpet, Mar 20, 2017.

  1. jaxontrumpet

    jaxontrumpet New Member

    Hey guys,

    I think I messed up, help! I have a guitar cabinet that had a dead amplifier in it. It's conveniently rack size long. I just purchased a 70w/70V mono amplifier on ebay not knowing was a 70v system was. Well... I just found out what one was.

    The original purpose was to have a very transparent sound that I could combine with lots of different pre-amp systems.

    Could I just add a 70v transformer to the current vintage low wattage speaker and make it work or should I return it before it has a chance to arrive?

  2. onplane

    onplane What! No Wake???

    Rochester, NY
    Yes, you can make it work with a 70v transformer, but remember 70v is not high quality. It's designed for distance NOT sound quality.

  3. whoaru99

    whoaru99 Epic Member

    Well, it is a guitar application so the ranges of fidelity that get rounded off by a mediocre transformer probably isn't that big of a deal. Heck, maybe it'd even have a good tone.

    That said, I'd return it/cancel the order if possible and get something that's intended for typical speaker impedance without matching transformer.
  4. Xtinc

    Xtinc Well-Known Member

    N. CAL
    Has it already shipped? If so, how do you plan to return it before it arrives? Most ebay sellers offer returns, but some charge a return fee and buyer is responsible for return shipping cost which can be quite high.
  5. jaxontrumpet

    jaxontrumpet New Member

    I think I'll give it a shot and if it works I will tell the internet and if it doesn't I will try to resell it down the line. We play pretty experimental music, not exactly hi-fi, and it might sound good for something. Heck, I think the speaker in the amp is out of an old organ. Thanks for reassuring me that I won't blow anything up.
  6. valvenator

    valvenator curious bystander, serious procrastinator Subscriber

    You might get lucky as some 70V amps also have taps for 4 and/or 8 ohm speakers.
    BTW, is this a tube or solid state amp. Most old tube amps are marked with how much wattage they use, not how much they put out.
    Tell us what you bought and maybe someone here who is familiar with it can offer more help.
    BTW #2: Old organ speakers make for excellent guitar speakers. Just make sure it can handle the wattage if you plan to crank it up.
    Last edited: Mar 21, 2017

    I LIKE MUSIC Super Member

    If you are unable or do not want to return the amplifier and it does not have standard output taps, a transformer like this would likely work okay.

    The power level taps would allow you use it even if the amplifier turns out to be rated at less than 70 watts.

  8. whoaru99

    whoaru99 Epic Member

    When I suggested about the transformer I meant the transformer you'd add to a normal speaker to match it to a 70V output.

    The 70V output is expecting quite a bit higher impedance than a typical 4, 8, or 16 ohm speaker. For example, a fully loaded 70W, 70V system expects a load of 70 ohms. Not quite sure how it would react to 8 or 16 ohms straight up.
  9. Ken Boyd

    Ken Boyd AK Subscriber Subscriber

    No reason why a 70 volt amp wouldn't sound good. Most the systems I have installed in places use a 70 volt system and many of them sound really good, you just wouldn't know because most of the times we install limiters on the volume controls so someone doesn't accidentally blast out the place when its full of customers. Crown, Crest, QSC, all make some really good 70 volt amps, many of them with multiple channels, and options for switching to 4 or 8 ohms. Most of them will be safe with even lower impedences that that, as Crown claims any load is safe, but it might go into protection. But you do need to use that transformer if your going to run it in the 70 volt taps, just tap your speaker at the highest wattage tap as that will allow your speaker to play the loudest. They offer those different tap settings so that you can reduce the volumes depending on your needs if say a speaker is hooked in a line of speakers and one falls right above a booth or table you might want to lower that tap setting on that speaker so as not to be to loud.
  10. loudnoises

    loudnoises Escalates Quickly Subscriber

    Pondside, NH
    MIght be worth looking into the amp itself, some 70v and 25v amps have an 8ohm amp feeding a transformer. This old dukane i've been poking at is 8ohm native and has an xformer for the 4ohm, 25v, 70v and 100v taps. At least it seems that way, the only connection from amp board to transformer is the 8ohm tap.

    What amp are you working with?
  11. bowtie427ss

    bowtie427ss arigato gozaimashita Subscriber

    Land of Milk & Honey Boo Boo
    What practical or advantageous purpose could inserting a pair of transformers in the speaker circuit of a guitar amp serve?

    This seems like an exercise in adding useless complexity to the simple.

    Return the amp. Put the time and effort into something that offers more return.

    Just my .02 y'all understand.............................

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