Realistic HP-100 Eletrostat

Discussion in 'Headphones' started by Big Bill, Nov 27, 2009.

  1. Big Bill

    Big Bill Summertime Rolls.....

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    I was going thru an old box of [reel to reel] tapes of my late fathers while at my mother’s house yesterday and found this Electrostatic headphone apparatus. Does anyone know anything about these?

    Bill.
     

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    Last edited: Nov 28, 2009
  2. Sir.Byrd

    Sir.Byrd Lunatic Member

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    I've never seen those but they look COOL! I wonder how they'll compete with your Grados...
     
  3. Big Bill

    Big Bill Summertime Rolls.....

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    I dont know, but I think the enigizer is screwy. I can "vaguely" remember [could be my imagination] when I was youg, my father saying it only worked for a few days before it quit. He was going to return them but waited to long. As for my Grados, I love them, just disappointed in the poor build quality of them.

    Bill.
     
    Last edited: Dec 11, 2009
  4. 2DualsNotEnough

    2DualsNotEnough Super Member

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    i had a set of these I found at a thrift a few years back.Ive heard that they were made by Stax for Radio Shack.They need to be hooked up to the speaker terminals on your amp or receiver.Also,leave them on for at least a day or so to energize them before using them.I thought they were broken,until someone told me that.I had them setup with a Sonic Impact T-amp,and sounded pretty darned good.UofMTiger has the setup now.I really enjoyed them,but the cord was so short they werent feasible for me.
    Let us know what you think of them.
    Jimmy
     
  5. Big Bill

    Big Bill Summertime Rolls.....

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    Could it be that simple? OK, I'll try it!
     
  6. 2DualsNotEnough

    2DualsNotEnough Super Member

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    If you listen to them after several hours of energizing,you might notice the sound coming back.After a full day or more,the sound came back totally.I hope thats what it takes for yours,too.
    Jimmy
     
  7. Big Bill

    Big Bill Summertime Rolls.....

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    Ive plugged it in to the wall socket, I'll try them in the afternoon.
     
  8. Big Bill

    Big Bill Summertime Rolls.....

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    Is it for the bennifit of the enigizer or the headphones?
     
  9. wualta

    wualta < Spike Milligan, 1961

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    The headphones.

    Back in the early '70s, Stax was still trying to set up their own dealer network in the US, so in the meantime they did OEM jobs using the components of their 1969 SR-3 headphone for Radio Shack, Magnavox, Marantz, Lafayette, KMart and Superex, and those are only the ones we know about. The HP-100 only shows up in the 1974 Radio Shack catalog, p. 31.

    So you have, basically, an SR-3 that hasn't been used in years. The diaphragm is metallized but the bias voltage that makes the headphones work has to seep onto the diaphragm through a big (tens of megohms) resistor, a process that takes up to three days. You can use the 'phones in the meantime, but the channel balance is likely to be off.

    Think of one of those old glass fever thermometers with the restriction in the column to help hold the reading after you take it out of your mouth, and you'll have the idea. Once the diaphragms have a full charge, they'll hold a good bit of it for months and come up to full bias within seconds of being turned on. Many people just leave them on-- they don't draw that much power, and they're protected from dust.

    [​IMG]
    REALISTIC HP-100

    You'll notice the HP-100 isn't brilliant or too bright like many of its contemporaries. The bass isn't supertight but it's present and the 'phone is nicely linear through the midrange. Not a bad way to get your feet wet.

    .
     
    Last edited: Nov 30, 2009
  10. Sir.Byrd

    Sir.Byrd Lunatic Member

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    So what is the verdict, Big Bill?
     
  11. Big Bill

    Big Bill Summertime Rolls.....

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    Wow! Thanks!
     
  12. Big Bill

    Big Bill Summertime Rolls.....

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    Waiting...

    I'm still waiting for them to energize. I tried again today, but only got a small amount of sound from them. :tears: Hopefully tomorrow!
     
  13. wualta

    wualta < Spike Milligan, 1961

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    Something's not right, then.

    If you've got the thing arranged as it is in your photo, and the energizer's plugged into the wall, and it's been 2 days, there's a problem. Could be as simple as a dirty PHONES-SPEAKERS switch. Your dad's diagnosis could be correct.

    Any chance of finding or borrowing a different energizer from a fellow AKer in your area?

    Here's a schematic, just in case:

    [​IMG]
     
  14. Big Bill

    Big Bill Summertime Rolls.....

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    I'm out of deoxit, but have some Rat Shack cleaner/lube spray. I'll clean the switch in a moment, plug'er back in over night and try'em once more in the morning.
     
  15. Big Bill

    Big Bill Summertime Rolls.....

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    Would leaving a signal running from the amp to the energizer help or not?
     
  16. wualta

    wualta < Spike Milligan, 1961

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    No. The bias signal is constant DC and is supplied from the power transformer in the energizer rather than derived from the input signal. Which means that the 'phones are getting all the bias they're ever going to get with no music being played.

    .
     
    Last edited: Dec 1, 2009
  17. uofmtiger

    uofmtiger Super Member

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    I still have this setup and I am happy with it. As was mentioned, the midrange is where they really hit the sweet spot. If you are a basshead, you probably won't be real happy with them because they do not put out deep bass. Also, if you are used to Grados, these are not as bright.

    The short cord is the main limitation. Over at head-fi, someone posted a diagram of how to make an extension, but that is not really my area of expertise, so I just moved the setup next to my bed.

    [​IMG]

    I have it setup with a Roku Soundbrige, Entech 203.2 DAC, Super T-amp, and mainly listen to vocal and jazz stuff which is where the setup really shines.
     
  18. Big Bill

    Big Bill Summertime Rolls.....

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    progress...

    Hey guys, I cleaned the phones/speakers switch and have let them charge ever since Wualta recommended it. I tried them today and the sound is starting to come in! I’ll post back in a day or so with their progress.

    Bill.
     
  19. Big Bill

    Big Bill Summertime Rolls.....

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    Wow uofmtiger, thats a nice setup you have there! Thanks for your post, I'm waiting for mine to charge now.
     
  20. wualta

    wualta < Spike Milligan, 1961

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    Hey, good news! Keeping fingers crossed and hoping..
     

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