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Inspire IHA-1 tube headphone amp

Discussion in 'Headphone Amps (full-size)' started by burn1, Oct 18, 2014.
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  1. BlakeT
    Man, I'm sitting here listening to my IHA-1 and it is such a wonderful amp....  Thanks Dennis Had!
    I finally settled on my tubes- a 1952 Brimar U52 and a pair of 1945 TungSol 6SN7GT VT231 Black Glass Round Plates.  Absolutely, positively no more tube rolling for me.  Tube rolling can be a counter-productive disease.  In my view, I think you find a tube combo that works for YOU and then just stick with it.  
    With the tube combo settled I can now free my mind of all of my equipment OCD tendencies and redirect my focus to enjoying my music collection.  
  2. Schopenhauer
    That's an elite complement of tubes! I'm still working with stock. Haven't really tried the 6BX7s I got. Keep looking at some Psvane tubes, but since I've never really heard anything about them I'm reluctant.
  3. smitty1110

    Nice, I'll have to keep this combo in mind. I actually have an IHA-1 and a pair of RCA 40's 6BX7's to go in it. I was thinking about some Sylvania 6SN7GT VT231's, but the glowing recomendation for TungSol will certainly be taken into consideration [​IMG]

  4. Xcalibur255
    I tried to ask Moon Audio a few technical questions about this amp but the email just bounced back undeliverable.  If anybody else has reached out to them with questions about the Dragon Inspire, can you tell what was the best way to get in touch with them?
    I'd love to be able to ask Dennis directly since they are pretty technical questions but I don't see any way to do so.
  5. smitty1110

    You can contact Dennis through Ebay, his username is radioman731.
  6. Xcalibur255
    I had that thought too, but the message size limit is really small and they won't allow you to leave your email address for outside contact.
  7. Xcalibur255
    Okay, I was able to get in touch with Dennis.  I will share Dennis's reply here because I think the information is potentially helpful to owners of this amp.
    The three questions I asked are: 
    1) <How is the driver gain stage configured (two gain stages by treating each triode section inside of the 6SN7 as its own stage to increase gain, or a single stage with both triode sections paralleled)?>
    The reason knowing this might be helpful is to determine how sensitive the amp might be to tubes with noise or microphonics issues.
    2) <What is the rating on the power transformer secondary winding that provides heater current to the rectifier?>
    I was curious if rectifiers with heater current draws over 3 amps were safe to use in the amp.  There are some nice rectifiers out there such as the 5AW4 and 5AU4 which draw 3.8 amps but many amplifiers cannot handle tubes over 3 amps.
    3) <Which of the three compatible driver tubes is the bias circuit most optimized for?>
    It's not really possible to perfectly hit the operating "sweet spot" of both the 6SN7 and the 6BX7/6BL7 so I was curious which tube Dennis had favored.
    Here is what Dennis told me:
    First up,  both sections of the 6SN7 are run in parallel as one triode gain stage.  I have used NOS TingSol 6SN7's for years without any problems with either section.  I have some brown base NOS TungSol tubes in one of the IHA-1 amplifiers in the shop listening room.  The secondary of the power transformer offers a 3 amp, CCS rectifier winding.  I would think that 800 ma. additional would not be an issue on this low voltage high current winding.  The bias is idealized for the 6BX7.  The only difference is a bit higher 2nd order with the 6SN7 but it is down better than 40 dB.
    My thanks to Dennis Had for taking the time to answer these questions.  I think the most useful takeaway is the info about the rectifier current limits.  Since technically the winding is rated for 3 amps it's probably best to consider that the limit.  I think its probably best to consider 3 amps the limit in the interests of the longevity of the transformer, but it's good to know that it can handle a little more if a person wanted to try other tube options.  This technically means that nearly every 5 volt rectifier you can think of is usable in this amp.  A personal thought I would add to this:  it would probably be best to only try a 3.8 amp rectifier while using 6SN7s in the amp.  The 6BL7/6BX7 pulls more heater current so this would end up being a worst case load on the power transformer and would probably make it run awfully hot.  With 6SN7s there is probably still an overall margin of safety even with the secondary technically being over limit.
    Hopefully others find this info a little bit helpful.
    ZERUNG likes this.
  8. smitty1110
    Thanks @Xcalibur255, that's a lot of good information there.
  9. smitty1110

    Just noticed this older post. Dang, you have as many inspire products as I do. Glad that I'm not the only guy with Inspire speaker amps around here!
  10. Xcalibur255
    I have to say I'm surprised this amp is not taking off better on Head-fi.  Maybe it just hasn't gotten the right exposure yet.
    I'll be ordering mine soon at any rate.  Will be fun to compare it to my other tube amps.  :)
  11. smitty1110
    I really need to get mine back to get it a proper weekend listening session. I just got my replacement tubes (All NOS Sylvannia) that should take it to the next level.
  12. BlakeT
    Yeah, I don't get it at all.  Perhaps Moon Audio needs to refocus the marketing on the IHA-1.  I just don't think people are aware of this wonderful amp.
  13. Bellasperson
    It is an exceptional value. Using a single vendor would seem to be a limitation but Dennis does not seem to be motivated by volume sales.
  14. Xcalibur255
    Has anybody tried running ECC32s in their IHA-1?  Seems like it would be a really good application for the tube.
  15. smitty1110

    I haven't, but I'll get some after my next pay day to test it out. Do you have a spec sheet for them?
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