845 DHT SET electrostatic headphone amp

Discussion in 'Headphone Amplifiers and Combo (DAC/Amp) Units' started by fls.audio, Dec 21, 2019.

  1. fls.audio

    fls.audio Almost "Made"

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    I've just came into this very nice board. Seems to be a place with lots of knowledge to learn and share.

    I've been a veteran from Head-fi since 2007 but haven't posted much, just fooling around in the dark.

    My biggest hobby is building amps. During the last few years, I've got some amps built and as at this very first post, I'd like to share my most favorite amp so far.

    It's a DHT SET amp for electrostatic headphones, well, you can say it's just for Stax. I opted for the almighty 845 tubes, DC coupled by a D3a. The amp is transformers coupled using Hitachi amorphous AMCC cores. Power and output transformers were winded by myself. It has been quite an adventure to build this monster. Probably I'm the second person on Earth who built a 845 amp for Stax. Frank Cooter was the first and I was deeply impacted by his designs.

    The amp has been powering my 007MKI for a while and I was satisfied with the sound. I have some Kevin Gilmore amps (Megatron, Carbon and T2) that were set aside after this was finished. At first I experimented with B+ 1100v but decided to settle on just 800v. The input is also coupled by permalloy core transformers.

    After this amp, I've so many design ideas for Stax using these big boys transmitting tubes. Next one probably is a Sakuma-inspired amp, 211 driving 845 with separate power supply.

    That's it for now, I hope to enjoy the time being here. :)

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  2. purr1n

    purr1n Finding his inner redneck

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    Very nice! Did you ever get a chance to hear Frank Cooter's amp. I've lost touch with him a so I have no idea if he's still active on any of the boards.
     
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  3. fls.audio

    fls.audio Almost "Made"

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    Unfortunately no, I’m not located in the US. Yeah, I also tried to contact him many times asking about his designs but got no response. I hope he’s just taking a short rest for the time being.
     
  4. dBel84

    dBel84 Friend

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    Very nicely done. Do you have a link to some of your other DIY projects. Thank you for sharing..dB
     
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  5. Thenewerguy009

    Thenewerguy009 Friend

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    How many hours did it take you to build that amp?
     
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  6. elmoe

    elmoe Friend

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    Very cool looking amp!!
     
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  7. fls.audio

    fls.audio Almost "Made"

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    It was like 3 months from scratch. Making the output transformers took most of the time, lots of trials. I experimented with 3 different cores and ratios to finalize the one I liked most.
     
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  8. elmoe

    elmoe Friend

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    What does building an amp like this cost, parts wise?
     
  9. fls.audio

    fls.audio Almost "Made"

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    I don't have a link for them, they are all over the place in my phone and iPad. Here are some I still got handy on my phone:

    My in process KGSSHV Carbon with extra thick aluminum plates:

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    Standard KGSSHV:

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    Dynahi with different configs:

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    Megatron with different configs:

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    My junk shelf with hundreds of different cores for transformers, 90% of them are C-core.

    [​IMG]
     
  10. fls.audio

    fls.audio Almost "Made"

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    Quite a bit, I'd say. Lots of discarded parts and metals during the trials.
     
  11. dBel84

    dBel84 Friend

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    You clearly put a lot of thought and effort into making your amps. Beautiful work.
     
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  12. Armaegis

    Armaegis Friend

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    Do you have a winding machine? I mean, the fact that you make your own transformers is remarkable enough; I just want to know to what level of insanity to be impressed.
     
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  13. fls.audio

    fls.audio Almost "Made"

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    Well, yes :) Not as modern as those of Lundahl but it works perfectly for personal use. Here is a choke I’m winding for a 211 amp. Lots of factors to decide the quality of transformers. I read that Tango artisans even spent time making insulation paper on their own, which is a tremendous effort.

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  14. fls.audio

    fls.audio Almost "Made"

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    Recently I also experimented with toroidal transformers. Got some made for a Goldmund Telos 2500 clone, very special amp, probably the best SS power amp I’ve ever heard.

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  15. Sonorus

    Sonorus Almost "Made"

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    You are an artisan.
    Respect!
     
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  16. fls.audio

    fls.audio Almost "Made"

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    Thanks, I’m hardly an artisan, just someone trying to improve the builds one after one. My own dream is to spend some days at those Japanese audio companies and learn how they work, get the hang of their philosophies. It’s always fancy to read how Audio Note (the real one) builds their amps, making their own capacitors is a step above others.
     
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  17. Armaegis

    Armaegis Friend

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    So people can make their own transformers, capacitors, we even see a couple folks making their own graphite resistors... but does anyone out there make bespoke vacuum tubes?
     
  18. NationOfLaws

    NationOfLaws Friend

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    I’d read it’s pretty dangerous to handle the metals you need for vacuum tubes but I don’t remember where I read that so I wouldn’t fight you over it if you told me that’s incorrect
     
  19. Donald North

    Donald North Friend

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    Kondo-san was a pioneer in the 80s but in my opinion AN UK leads the two in materials research and innovation for transformer cores, resistors, electrolytic caps with Rubycon, winding their own film caps in house, and working first with Vaic, then Elrog, recently with Psvane on tube innovations

    I would say Thomas Mayer who bought Elrog and Audio Note UK who are partnering with Psvane.
     
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  20. fls.audio

    fls.audio Almost "Made"

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    Yes, seems to me ANUK is in a better financial situation to expand their business. I had a chance to work on one of their output transformers which were shorted. The cores were pretty good. The way they run business depends heavily on boutique and fancy parts.
     
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