Elekit TU-8900 2A3\300B Single Ended DHT Tube Amp - Build, Impressions, and Review

Discussion in 'Headphone Amplifiers and Combo (DAC/Amp) Units' started by Maven86, Oct 19, 2021.

  1. Maven86

    Maven86 Facebook Friend

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    I actually downloaded your PDF over on HF earlier. Really awesome write up, the mod with the transformer wiring sounds very tempting to do...

    I think there's a lot of truth to this. From my experience, I look at it this way. If you give 3 winders 3 of the same iron cores, you'll likely have 3 different sounding transformers. Winding methods play an even bigger part than core material in the final sound, it's almost like a secret family recipe of sort.

    That being said, it's also been my experience that if you gave that same winder another type of core to work on, say permalloy (Ni), the resulting transformer will also sound different than the iron but still have traces of their "house sound". It's like the audio equivalent of an artists signature on two different kinds of paintings.

    +1 on the Monolith Summits. Ward, and Yves have also been excellent to deal with.
     
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    Last edited: Oct 22, 2021
  2. Whitigir

    Whitigir Rando

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    Having balanced input with transformers is fun and actually quiet enjoyable, or should I say worth an upgrades. Even though I had some strange issues here and there, I have solved it, and now I am enjoying it tremendously. Most of my stuff are all true balanced, so in comparison between RCA vs modified balanced inputs, there are clear upgrades in perceived performances.

    I will try to use a few more brands of transformers to tweak the input a bit and see if the experiences would go anywhere more positive ? Between tubes rolling and modifications experiments, my wallet cries :(
     
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  3. Ryu

    Ryu Friend

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    Absolutely gorgeous build! Eagerly waiting for those sound impressions! I've been looking at upgrading from my Modded Crack for a while, and have heard great things about these kits.
     
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  4. Maven86

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    Thanks. Things have been busy but I'll do some final comparisons this weekend and have the impressions up by Monday night.

    I've liked the Crack+Senn combo but I'd say the Elekits are voiced very differently. If possible, I'd recommend having a listen before splurging on a kit.
     
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  5. EagleWings

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    Elekit TU8900

    I’ve been wishing to join the DHT game for a very long time and was finally able to do so with the Elekit TU8900. I got mine with the Lundahl Amorphous transformers. With literally zero soldering experience, building the amp was NOT exactly a walk in the park. Thanks to @famish99 , @Jh4db536 and @baseonmars , who provided helpful tips along the project. Just to be safe, I would not recommend this kit as your first project. Some things I would like to share with folks, who are interested in building this amp, but are new to soldering and DIY.

    Soldering and Building:
    Meticulous planning and taking it slow will ensure avoiding any errors. A good work bench, a PCB holder and appropriate lighting will go a long way. I used the WBT leaded solder, which has a bit of silver content. I learnt recently that, it may be best to avoid solders with silver content for PCB sodlering. Had I known, I’d have gone with the Kester 63-37 leaded solder.

    Headphone Out:
    As this is primarily a speaker amp, it has a resistor divider network for its headphone out, to bring the gain down to more useable level with headphones and also to present a load that is safe for the OPT. In case you want to bypass this resistor network, you can plug the headphones straight to the speaker terminals. If you don’t plan on driving speakers, then connecting the headphones directly to the speaker taps would be the easy route. I intend on using speakers with the amp and I want to retain the feature that mutes the speaker-outs when you plug in a headphone into the headphone jack. So I modded the resistor network of the headphone board to not have any resistors. All I had to do was skip all the resistors and use a wire to jump at the R125/R225 positions. You can see the Red and Blue wire on the headphone board in one of the pics.

    Please Note: This amp has a ton of gain that, if you bypass the resistor network, you might not have enough headroom to adjust volume. Even with a 300 Ohm Sennheiser and a DAC with 2 VRMS line out, you can hardly get past 8 o’ clock position. A DAC with a volume attenuation or putting an attenuator between the DAC and the amp would help. For the purest and shortest route for headphones, you can wire straight to the secondaries from the OPTs. You would need a couple of 4 pin VH connectors and a separate 6.3mm female socket.

    TU8900 - 2.jpeg

    Coupling Caps:
    Victor offers the V-Cap CuTF or the ODAMs as the standard upgrade options. From what I gathered, V-Caps can be a bit hi-fi sounding. As the Wavelight is already a bit hi-fi sounding, I wanted to push the tone towards the organic/natural side. After vetting my options, I ended up going with with the Audyn Copper Max. Even the Audyns Cu Max are slightly longer than the provided hole for the cap. I had to file away a bit on the short edges to make the hole longer to fit the Audyns. Victor advises not to use caps with wax, so I couldn’t use Jupiters. Duelunds are too wide for the hole and you might have to do something like what @Maven86 is doing. Audionote, Mundorf and Jensens were some options which seemed like the appropriate size for the cap hole in the PCB.

    Tubes:
    For the input/driver tubes, Victor offers the Sylvania 12BH7A and the Brimar CV4003 (12AU7). I’d recommend doing research on the input/driver tubes to find out if Victor’s offerings will fit your bill. Else, I’d recommend picking up the tubes of your choice from elsewhere. Based on the 12BH7 an 12AU7 I have on hand, I feel a 12BH7 is required to take full advantage of this amps dynamics and tactility. But it could be that the Brimar 12AU7 I have on hand are dynamically gimped.

    Victor offers good prices on the Linlai (Cossor) tubes. I picked up a pair of Cossor WE2A3 and a pair of Cossor Black Plate 300B (I wish I had gone for the Cossor WE300B instead). @yotacowboy has written some nice comparisons between the Linlai Elite 300B and Linlai WE300B clones. I would think the same would apply to the 2A3 counterparts. The long and short of it is, the WE clones have a bit of a tubey character, while the Elites are tilted towards clarity and neutrality.

    TU8900 - 3.jpeg

    Sound:
    I hear the tubes, caps and transformers require 50-100hrs of run-in. So I will hold-off from sharing any sound impressions for now.

    TU8900 - 1.jpeg
     
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    Last edited: Nov 5, 2021
  6. Maven86

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    Thanks for the impressions. I've had a similar issue with gain in non-NFB mode and almost feel like a step down transformer might be useful depending your source's output voltage. Do you still have this problem when turning NFB on?


    Also, sound impressions are now up.

    Elekit TU-8900 2A3\300B Single Ended DHT Tube Amp - Build, Impressions, and Review
     
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  7. Tachikoma

    Tachikoma Almost "Made"

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    Somewhat OT, but did you commission the Otomon 801A specifically for headphones? How much did that cost?
     
  8. EagleWings

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    Thanks man. That was a great write up with comparisons. I am yet to test the NFB mode. @Jh4db536 reported back pretty much what you wrote about the NFB mode. So I have not been keen to try it. I’ve been busy and sick this week, so haven’t had a chance to listen to the amp this week at all. But hoping to give it a shot sooner or later.
     
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    Last edited: Nov 12, 2021

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