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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. exdmd
    Has anyone been able to do a direct comparison of the IHA-1 with a fully optioned Amps & Sound Kenzie Encore (upgraded coupling caps and input transformers)?
  2. Aornic
  3. Xcalibur255
    This amp has always been under the radar with the community and I never understood why.

    I do think you are understating the volume issue a bit for those people who do not have the input transformer option. I believe those are 4:1 ratio transformers, which takes the Mu of the amp from 20 to 80 (or from 10 to 40 if you prefer the 6BX7). This is just my personal opinion but I feel the sweet spot for Mu factor on a headphone amp is in the 50-100 range. Any less leaves the amp without enough headroom for quiet recordings, any more is just extra that will never be used and serves only to raise the noise floor (and usually results in design compromises to combat that effect). The new input tranny option gets the IHA-1 into the right range IMO.

    I'd be curious to hear what effect they have on the sound character of the amp. No transformer is completely transparent. I'm also curious about the mention of 6BX7 tubes not being compatible anymore. I could understand adjusting the operating points or re-specing the output transformer primary to optimize the design for the 6SN7 (I know the original design is actually optimized for the 6BX7) since it's a more popular tube. However, that shouldn't result in the 6BX7 becoming electrically incompatible. It would just mean a little more distortion when using that tube (and a little less when using a 6SN7, which was likely the point). The only thing I could think of for an explanation would be downsizing the power transformer, since the 6BX7 heater current is considerably higher than that of a 6SN7.
  4. Aornic
    Have you tried 6F8Gs? I greatly prefer them overall for pre-amp tubes.
  5. DaveUpton
  6. Xcalibur255
    I haven't because they are electrically identical to 6SN7s, so I felt no need since I already have the 6SN7 tubes I truly want for the amp. Buying the 6F8G equivalent of a 6SN7 tube used to be a good way to save money on desirable tubes like the black glass round plate Tung Sols, but the prices have come up a lot in recent years.

    I always though the 6BX7 option was a great choice for the amp. They are inexpensive tubes and compete well with the most expensive 6SN7s.

    You might enjoy trying out an older NOS 5Y3G on the rectifier side of things. Or even an old 80 using a socket adapter. The new production tube that comes with the amp isn't a very good representation of the 5Y3 sound IMO.

    You can kind of tell this is the tube Dennis designed the circuit for. It can't quite compete with tubes like the 5R4GY (which I'm also a big fan of for this amp) in terms of resolution, but there is a certain "rightness" and charm to the tone and overall presentation that makes the slightly softer sound easy to forgive.
  7. tjkurita Contributor
    I just purchased one of these and I am really enjoying it. I think it is being offered at the right price for the performance and it has a "small shop" feel to it, which is nice. I get the sense that if anything went wrong I'd be in good hands as a customer. Sound-wise it is quite nice. Very easy on the ears, polite sounding, but with nice resolution. It has very good clarity but is not sparkly or bright. I could listen to this amp all day without any fatigue. It falls short of my main amp in dynamics, soundstage, and energy but I attribute a lot of that to the power supply. This isn't to say the IHA1 is sluggish or laid back, it is just very even sounding. And providing a sufficiently beefy power supply would require a separate chassis and commensurate increase in price. I think a higher end version of this amp with a better power supply would still represent good value even at a higher price. But headphone dynamics are less of a priority for me than speaker dynamics and I really think it is worth every penny of the cost just as it is.

    I like this amp very much as a preamp as well. It can be used very effectively to add life to a sterile sounding solid state amp. My main amp is all tube, pure Class A, draws a steady 2 AMPS of power and generates A LOT of heat. During summer months I like to use a good SS amp instead and I look forward to seeing how this sounds as a pre in my main system. For now I am using it as a desktop pre with bookshelf speakers and a T amp. There is a good bit of hum in the right channel and I can only go up 1 click on the attenuator for most of my desktop listening (!!). A previous post mentions a fix for the hum by sending it back to Moon Audio. But I don't feel like boomeranging it right back to them when I've only had it a few days. Putting a 100K resistor between the preamp out and the speaker amp eliminates the hum and resolves the lack of range on the attenuator. Anyway, the fact that it works so well as a preamp just adds to the value to me.

    I've been in this hobby for so long that most products I purchase are underwhelming or "yeah, okay that's fine." But this little amp is really surprising for the price. It sounds great and I plan on keeping it permanently because of its size, neutrality, politeness, and versatility. I love it!
  8. Compassionator
    Yup, and Dennis is easy to deal with and very responsive (humble too), which is somewhat unusual for a designer of his stature. This is very interesting as an "upgrade" in the same vein: https://www.caryaudio.com/products/slp-05/ Don't know how much he had in the design if at all. Very tempted to try it.....
  9. tjkurita Contributor
    That SLP 05 looks like a very serious piece of kit! If you do try it I would be very interested in impressions, in spite of the fact that I am not in the market for one. It seems like the price is pretty high for this, in the $8-$9K range?

    I continue to be very satisfied with the IHA-1. As part of a desktop system it gets A LOT of use. Minimum of 4 hrs. per day every day since the day I got it. Not a blip or a blurb, no noise, no static, no problems at all. Really a very good, reliable amp. And the stock tubes have been strong, quiet, and well matched. I use it to watch movies at my desk, to play games, to listen to music, to watch baseball. I am not using it as an "audiophile device" with a mental log of how many hours are on the tubes, critical listening sessions and the like. This thing is a workhorse and it is excellent. Placing that resistor between the IHA-1 and the amp resolved the only issue I had with it, which was a bit of hum and too much volume.

    I would very strongly recommend this amp to anyone looking for a versatile, reliable, great sounding amp whether tube or SS.

    Edit: I couldn't agree more with Aornic's review of this amp. His thoughts on the amp match quite well with my own so I think there is a distinct sound to the amp that can be reliably heard and then articulated in words. He focusses a lot on tube pairings as well which demonstrates the transparency of the amp and the benefits of a direct-coupled design. If you are considering this amp, his review will definitely provide you with great insight into its sound.

    Here is mine with old RCAs across the board:

    Last edited: Dec 30, 2018
    Admiral Kolchak and phthora like this.
  10. DelsFan
    I once asked Drew about the feasibility of offering a "separate power supply" option - just remove the appropriate parts and put them in a different box! You can tell I studied Civil and not Electrical Engineering. He said it wasn't practical, and the expense (and perhaps nuisance) of having to design a custom "several strand" power cable to go between the two "boxes" was an additional drawback.

    If I ever get ready to make a purchase (so: get my Study organized), I still think the IHA-1 with Lundhals, to go with my HE-1000 headphones, is where my heart (and pocketbook) lies.
  11. tjkurita Contributor
    Yes. I have a feeling that if any benefits are to be expected from a separate power supply it would involve making it a different amp altogether. The price would be three times higher and it would only make it incrementally better in terms of sound. Dollar of Dollar, this is one of the best amps I've heard, as much for what it doesn't do (coloration, frequency boosts/scoops, tube drift) as for what it does.

    The only area where this amp *might* lack, and this is why I am replying to your comments, is that it does not have as much power as a lot of other amps. I am often between 11 o'clock and 12 o'clock on the volume. The HE-1000 are planar, right? Will the IHA-1 have enough power? Have you tried the IHA-1 with your HE 1000?
  12. comzee
    Which is true, but probably not a bad thing.
    The problem with the iha1 is that the PSU transformer is too close to the right channel output transformer. If it's dead silent in your listening room, you can hear super low dB hum in the right channel because of this.

    The designer of the amp, Dennis, also makes custom amps and sell them at his eBay page. I have one of them named the "Fire-Bottle". It's a pentode amp (kt88) preamped with a single 6sn7. Similar design and case as the iha1, same problem.
    Thing is, it's not an issue because it's a speaker amp, so the hum that comes out of the right channel (because of transformer interference) is inaudible on the speaker unless you put your ear right up to it.

    Awhile back I bought an adapter (speaker taps to 4 pin balanced) to try it with headphones, hd800sdr and HE6. The fire-bottle is just a beast of an amp, the clarity, dynamics, punch, resolution, is astounding.
    I tried getting Dennis to build a custom headamp Fire-Bottle for me, for 6+ months, and finally gave up. The thing is, he doesn't sell his stuff for profit, it's more of a fun hobby for him. He just didn't care to design an off-board PSU for me, could never get him to do it.

    It's unfortunate, because the Fire-Bottle with off-board PSU for headphone use would be just glorious. I currently own an Eddie Current Aficionado, high end 2a3 amp. Although it's amazing, I'd still rather have a Fire-Bottle for headphone use.
    Even tho the fire-bottle works with headphones with my adapter, it's that right channel hum that ruins it (5x worse on Fire-Bottle than iha1 with headphones, because it is a speaker amp and all).

    Pipe dream would be he releases his topologies open source for DIY, and I'd just make one myself with off-board PSU. Dennis has some of the best tube amp design out there.

    All in all, the iha1 is still an amazing amp for the price. I greatly prefer it to any SS amp I've heard. I still own it, but lent it out to a friend when I bought the Aficionado.
    Admiral Kolchak likes this.
  13. tjkurita Contributor
    Great stuff, Comzee!! Really interesting. I think my ears are not sensitive enough or I have not concentrated enough to hear the right channel hum you refer to. I wonder if shielding of some kind might resolve that. 95% of the time I'm using the IHA1 as a preamp and there is big hum in both channels when connected directly to my amp. But placing an attenuator (resistor) resolves it for me.

    I bet you could have a good builder reverse engineer your fire bottle, or build an outboard PSU for you. I would be interested in hearing one of those. I have't owned a kt-88 amp in about 20 years. It was actually a Dennis Had designed Audio Electronic Supply AE-25. It used the KT88 in triode or ultra linear switchable. I didn't own it long enough to get to know it. I soon bought a 300B amp and never looked back. I would like to revisit higher power tubes at some point. I wish Almarro was still in business.

    comzee likes this.
  14. biglazymoose
    Hey all! Just picked this up and looking for some tube recommendations. I have the stock Sovteks and JJ SY3S rectifier.
  15. comzee
    Hmm, I'd stay cheap until you've had it for awhile.
    This 274B + some cheap RCA NOS would be a good upgrade.
    If you're half way decent with soldering this is also an easy upgrade, pair of these.
    Last edited: Oct 13, 2019
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