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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. Xcalibur255
    My 45 is a custom build designed and built by 2359glenn.  As far as I know it's one of a kind and a lot of the design choices, both visually and electrically, were my own personal ones.  The tubes in it are KenRad UX-245s, I'd date them between 1928-1930, and they are by a long shot the best 45s I have run in the amp.  My 45 is my pride and joy, but like the Inspire it doesn't drive every type of headphone well so it's good to have other amps around for variety.  The amp in the middle is an OTL made by the same person.
    The 6BX7s I bought from a trusted seller, and I believe the were new old stock.  The sound is excellent, it's just not very loud.  :)
  2. BlakeT
    I am running the Tung Sol 6SN7's listed in my signature.  I also have 6BX7GT's that I rolled when using my T1's.  That is why I am perplexed by the lack of volume.
  3. Xcalibur255
    Yeah, I can't really think of what could be wrong with the amp that wouldn't also manifest as distortion or malfunction.  Except maybe the secondary winding on the transformers being wrong, but the odds of that are awfully low.
    The T1 is higher sensitivity than the DT880, and the 6SN7GT is double the gain, I think those things combined might explain the difference in our experience.  The Inspire just doesn't seem to have lots of gain to spare the way many amps do.
  4. BlakeT
    Note that LCD's were being used in this mini review from Innerfidelity at RMAF.
  5. Xcalibur255
    A little mini review based on my listening so far:
    I've had the Inspire on all evening.  The low level detail retrieval this amp has is impressive.  It's also the most unforced musical presentation I've ever heard.  Even bad recordings that are mixed hot sounds great on the Inspire.  I dare say it almost lives a wee bit too much in that beautiful midrange, but this is certainly a showcase of everything that's great about tubes.  The whole frequency range is very natural and coherent, but on the LCD-2s sometimes the upper ranges feel a little too polite.
    I compared a bit to my 45 and came away surprised.  The 45 is a very upfront sounding amp, at times I have wondered if maybe the driver stage isn't overloading the 45 tubes a bit, but it brings a sense of true to life scale to music that is well recorded.  When comparing against the Inspire this quality of the 45 seem a little less appealing with some material, and reveals some soundstage/imaging congestion I hadn't really heard before too.  I think the Inspire might resolve a bit more fine detail too, it has an advantage here what with the 45 amp having two gain stages and coupling caps.  The additional components in the signal path filter a bit of plankton.  Both are very detailed overall but the two amps have a somewhat different sense of character in how they present it.  My 45 has more true to life vocal tones and feels like it has more dynamic scale on some recordings.  It also has faster and harder hitting bass.  The Inspire's bass is coming along and sounds better than it did on my first listen, but the 45 just out slams it and still has great control.
    I'm really impressed with the Inspire.  I didn't buy it thinking it would give my 45 an honest run for its money.  I have more money sunk in that 45 in pure parts costs alone than what the Inspire costs to buy.  Weighed with costs in mind I think the Inspire might be the better amp.  Dennis's many years of experience really shows.  This minimalist design really pays off in producing music that sounds completely natural and believable.  The Inspire doesn't necessarily hit you with that big "wow" factor the way some amps do on the very first listen, but once you settle in with the amp it wins you over completely.
  6. BlakeT
    Great write up XCalibur!  I sincerely enjoyed reading your thoughts and impressions.
  7. Amish
    This is one amp I really would love to add to my stack. I've been drooling over this since he started selling his amps on Ebay. I'll own one in another year or two for sure. Well whatever he is producing at that time anyway.
  8. smitty1110
    One of my personal goals is to get Dennis to mKe a DHTbeadphone amp, 2A3s or 45s as the output tube. Of course the wallet is a bit too thin to ask for a commission from him, but maybe some day...
  9. Xcalibur255
    Truth be told it might be more of a side-grade than an upgrade.  Different presentation but not clearly better.  Dennis would have no choice but to make a DHT design a 2 gain stage amp, there just isn't enough gain in a 45 or 2A3 on its own.  Then you have to either do interstage transformers or coupling caps, and you've got some resistors in the signal to derive the proper grid voltages for both stages.  Strictly speaking the DHT tubes are better sounding tubes with lower distortion, but once you have stacked all these extra components against them the advantage has been eroded.  45s do have the most beautiful tone of any tube though, and are worth running for that reason alone.
    A very interesting idea would be a 10Y as a driver stage.  Still just barely enough gain, but enough, and then the whole amp is DHT.  10s are getting very very rare though, you run the risk of not being able to re-tube the amp if one dies.  This is why we switched to the C3g for my 45 amp, but I bet a 6BX7 would have done well too.
  10. Xcalibur255
    Thank you!  I wondered if the write up would even be useful to anybody, since the comparison was to an amp only I have heard.  I could have drawn comparisons with the Icon HP8 Mk2 (the only other commercially available amp I own), but the Inspire is in a different league from that amp, it didn't seem like a worthwhile comparison to make.
  11. atubbs
    I don't have the LCD-2, but I'm able to drive the LCD-3 and HD800 to pleasantly loud levels with still about half the volume dial remaining. With 6BX7GTB. That's with a Yggy but I had the same experience with the NAD M51. It did not have enough power to drive the HE-6. Seems a little suspect that you've gotta use that much of the dial.
  12. Xcalibur255
    Were you at 12 noon, or 12 clicks on the attenuator?  The way the volume indicator is mounted 12 noon is click 18 or 19.
    I once had my OTL amp configured in a way that resulted in gain almost this low, 8x on the first stage and 2x on the second for a total of 16.  I could get up to 2 or 3 o'clock on the dial in that situation too.  With a gain of only 10 and some of that being lost to the ratio of the transformer the math adds up and I don't have any reason to suspect there is a defect in my Inspire. 
    Maybe I just listen louder than I think I do?  LCD-2 is one of those "gotta turn it up" headphones after all because of how it's voiced.
    On a side note, using a 5Y3G rectifier changes the voicing of the Inspire somewhat compared to the rectifier I started with.  It sounds more unfront and intimate with vocals, and soundstage layering is more dense...... less airy.  Still sounds good, just a bit more close and personal than the big breathy sound of the 5R4GY.  I have a 5Z4G Brimar to try next then whichever I like best will stay in the amp while I roll drive tubes.
  13. bazelio
    Reviving a somewhat oldish thread here....  Is everyone experiencing a hum with this amp still?  It sounded like it attenuates a few seconds after power-own, but just curious how prevalent it is out there.
  14. Xcalibur255
    Sometimes I can hear the faintest suggestion of it, totally non-objectionable.  IMO it's just a totally normal part having an amp with this kind of design.  Because the right output transformer is so close to the power transformer it's going to pick up a bit of stray magnetic field.  Making the chassis much larger would have been the only solution, or going with a very exotic winding design in the mains transformer and pushing the price up.
    I'm surprised and a little sad that this thread is so dead, and that this amp gets so little attention on Head-fi.  I am utterly in love with my IHA-1, it's hard to imagine the music sounding much better than this.  With good tubes in it this thing is a giant slayer in the tube amp world.
    Alexander N likes this.
  15. BlakeT
    Agreed.  Based upon my experience with my IHA-1 and given the design chops of Dennis Had and marketing of Moon Audio, I sincerely thought this amp would be a hit.
    For whatever reason, that hasn't happened.
    We audiophiles/audio enthusiasts are an interesting bunch.  I've never cared about buying stuff that is popular but I suspect many people are afraid to be early adopters or jump on board with gear that isn't mentioned frequently in online forums.  I think the majority want to purchase from popular manufacturers for some feeling of safety in numbers.
    I do think it is a shame that people are not getting to experience this terrific product.  I love mine.
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