Elekit TU8600

Discussion in 'Headphone Amplifiers and Combo (DAC/Amp) Units' started by Griffon, Sep 24, 2017.

  1. bhk1004

    bhk1004 Acquaintance

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    went through the schematics after a member on diyaudio let me know that elekit just needs resistor swaps to change the output impedance to whatever I wanted, and it seems like I could "theoretically" be able to swap out the resistors to lower the output impedance. I say theoretically, because I have no idea if this will affect anything else. Currently its sitting at 2x 120ohm resistors and 1x430ohm resistor.

    I would probably make the base resistor around 4-10w, and cap out the maximum position at somewhere between 240-300 ohms. I was thinking maybe a 5/35/200 resistor setup to make a 240/235/40/5 output ohm setup. Also considering just maintaining the HE Adaptor as my 10ohm tap, and doing a more stepped approach on the headphone positions. possibly a 40/40/160 which would translate to 240/200/80/40 output ohms on the headphone jack. Weighing my options at the moment.

    I am a little bit concerned with what rating I should go with on the 5ohm resistor if I decide to use this? The takman resistors that the amp uses seem to be rated between .25-1W, but the V rating is oddly rated (500V max). Should I be concerned with a 5 ohm resistor pulling more than a few W of power on a high demand low ohm planar and burning up? Never really messed with resistors before so any advice is appreciated.

    Below is the headphone jack and the jumper schematics in case anyone wanted to see.

    [​IMG]
     
  2. bhk1004

    bhk1004 Acquaintance

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    Below is a link to what I ended up doing.

    Summary: Swapping resistors works as expected. The size of resistors that I ended up using required me to use a Pin Vice to slightly increase the holes in the PCB as the new resistor wires were larger. Life is good and I am happy.

    https://www.diyaudio.com/forums/elekit/351252-elekit-tu-8600s-available-july-2020-a-post6455801.html

    Copy pasting below for anyone that doesnt want to click into the link.

    Soooooo after a long day out with the family, my resistors had arrived early in from Parts Connexion. Was planning on ordering from the USA (located in NJ) but I had asked them a few questions, and they were amazing with some help pointing towards what I needed and some options, that I had to give them my business even with the shipping from Canada. Not like my order was huge, only 20 bucks, but also on their side they know I only needed a few resistors and had no issues answering all my questions.

    So below are some considerations that I selected my resistors. Just an FYI I think all the takman upgraded resistors in the kit are 0.5W resistors, which makes sense for the stock zphone (120-670ohms).

    Why does this make sense? Lets take a look at my guesstimate at what the power rating is for each of the positions below. My assumption is that the amp is advertised at 9w of power but doesnt tell you at what ohms, so I am guessing it makes it at 8ohms like every other 300b amp. We can guess using an online calculator to get a generic number that the amp potentially is making at the ohm below.

    Position 1 : 670Ω Watt = 0.107
    Position 2 : 550Ω Watt = 0.131
    Position 3 : 240Ω Watt = 0.3
    Position 4 : 120Ω Watt = 0.599

    The new positions that I have below and a guess at the power rating.

    Position 1 : 240Ω Watt = 0.3
    Position 2 : 210Ω Watt = 0.342
    Position 3 : 40Ω Watt = 1.8
    Position 4 : 10Ω Watt = 7.2

    I ordered a 5w for the 10Ω, and a 1w for the 3 remaining. Realistically, I probably could have ordered a 2W 10Ω resistor, and probably 0.5W for the rest. As position 4 uses only 1 resistor, it will take the full voltage brunt, and the other 3 positions will be sharing the load across at least 2 resistors so I dont believe it would have been an issue. This is my understanding of how voltage is shared across multiple resistors but someone can correct me if I am wrong.

    Your selection probably depends on your use case? I selected a 5W as I dont have any headphones that go below 30W that are power hogs, and at 30W this amp should make around 2.4W of power. Of course like mentioned earlier, this is all just estimates as Elekit does not provide in-depth power measurements. I also wanted resistors that were all similar sizes and slightly over spec because I am crazy.

    Below is what I ordered.

    Mills Resistor 10R Ohm 5W MRA-5 Series (Qty 2)
    $5.92
    Takman Resistor 200R Ohm 1W REX Series (Qty 2)
    $2.10
    Takman Resistor 30R Ohm 1W REX Series (Qty 2)
    $2.10

    So the reason I mentioned earlier the that the stock resistors are probably 0.5W (might be 0.25, not sure) is because the wires on the new resistors I ordered are larger than the resistors that come with the kit and do not fit the PCB.

    Well, I have been in a bad mood for awhile due to the headphone jack on this amp for too long and nothing was going to stop me tonight now that I had my resistors in hand.

    I had the below Pin Vice on hand as I needed it to drill out my Hakko Desolder gun a few months ago.

    https://www.amazon.com/gp/product/B07FJ6VD2P/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

    So after using the Hakko 301 desolder gun to remove the stock resistors, I went slowly and used the pin vice to drill out the PCB holes SLIGHTLY larger. IF you decide to do this, please go slowly without pushing hard(very slightly). You want the drill bit to do all the work. If you push too hard, there is a chance you can lift the pad and that will require you to repair the PCB. I also used my finger right against the hole I was hand drilling slowly to be able to feel when it was coming through. It also stops me from going too fast or pushing too hard as I will stab straight into my finger haha.

    Also make sure that you maintain at least a 1cm clearance from the edge of the PCB and the edge of the resistor. As my resistors were larger, if you do not maintain the 1cm clearance, you will tap the case when you are reinstalling the pcb. I just pushed back the resistors as I installed them lifted off the pcb to get my clearance I needed.

    So the conclusion, this works as intended. I have much more volume in Positions 1 (240 ohms) with my 300 ohm headphones (zmf/sennheiser) and I am able to finally drive my planar headphones off of position 4 (10 ohm). I am getting the same power that I was getting off of using the speaker tap adaptors. Everything sounds great, and finally the amp is where I am happy with it.

    Below is a picture of the resistor locations.

    [​IMG]

    Picture of the Pin Vice I used which I linked earlier.

    [​IMG]

    Picture once everything was installed.

    [​IMG]

    Last bonus picture. Not sure if this is common knowledge, but I got jealous of Victor's install of his transformers as they were much cleaner than mine. He told me that I could get hex standoffs so you can tuck your wires under the transformers, instead of on the side. This sounded great to me as I could create a bit more separation between the difference wires, and also looks great. Not that anyone will ever see it, but made me feel better.

    [​IMG]

    Victor, if you are reading this, Elekit really need to fix this on this amp. The headphone tap is really broken and cant drive anything below 120 ohms properly. Position 1 and 2 is honestly completely useless, and lower ohm taps need to be setup for further flexibility. The output ohms for the headphone taps across different models of Elekit amps seem to point towards they are realizing this is a problem and are experimenting. Hopefully they figure something out for the 8600S as well. To be honest, if they shared the Zphone in their specs, I probably would have bought either the 8800 or 8200 amp instead. Another bad habit, manufacturer really should share more specs than is currently shared as specs on their amps across their vendors.

    This amp sounds too good to have something this simple causing issues for the headphone jack. Its literally switching 6 resistors to different specs and probably wouldnt cost anymore than the resistors they are using currently. If there is an increase in cost, maybe it will go up 5$. Maybe they are purely focused on the speaker amp portion of the amp and don't care about the headphone side? I am not sure.

    Anyways. I am happy and off to listen to some music before sleeping.
     
  3. yotacowboy

    yotacowboy McRibs Kind of Guy

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    So what are folks impressions on different coupling caps? I'm going to burn a pair of AN UK copper foils, but I've got some Miflex and VH Odams that'll go in eventually. So far though with barely 15 hours on it, this amp is killer.
     
  4. Phantaminum

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    Me and @famish99 have the V-Caps installed and they are fantastic! Really great caps. Sound bright and rough at first, but when they are burned in they smooth out, have great resolution and good bass.

    I’m really enjoying this amp with the Verite but the Z-Out could be better implemented for headphones.
     
  5. Tachikoma

    Tachikoma Almost "Made"

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    Have you considered just putting a 10 ohm resistor across the speaker terminals and running headphones directly off the taps? The residual noise is supposedly only 36 microvolts, which is comparable to solid state.
     
  6. bhk1004

    bhk1004 Acquaintance

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    I have the vcap cutf as well, they sound amazeballs. Really needed some epic amounts of burn in though. As mentioned very metallic, bright, harsh as they burn in. Amazing once they finally found their footing which I think was over 200 hours. Continued to just smooth over after 50 hours and has been fantastic.
     
  7. yotacowboy

    yotacowboy McRibs Kind of Guy

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    I'm going to just add continual updates in minor doses, if that's okay with anybody paying attention to this thread. If anyone objects, I'll be happy to hold off and put things together in a more formal review.

    Anyhow, the first thing that is kind of interesting is how this amp seems to present differently between HE speakers in my setup and known variables like HD600. Thru speakers it's glorious, open, and spacious, and does both highs and lows in such an effortless way. Bass with no bloat, highs are more spacious and defined than mono Aegir. Thru Hd600, it's a different beast, using the 240R loading. It's much more specific - almost as if the space between instruments is more well defined, but almost to an eery almost artificial way. The blackgound is almost too well defined, compared to the speaker setup. I'm happy to write more to try and describe more betterer. Anyhow, lemme know if this is confusing or tends towards noise and I'll quit. Bottom line, this amp is f'ing legit "5-digit $ Hi Fi" compared to stuff I've heard in shows and in showrooms.
     
  8. Phantaminum

    Phantaminum Friend

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    Just to update this thread and apologies on how long it took -- Yes, the lower the output Z the more gain you're getting. On the highest setting or setting 1 for the jumper I can get to around to around 9'oclock to a nice listening level. Jumper 2 = 8:30, Jumper 3 = 7:00, Jumper 4 = 6:30 - 6:45. If you decide to go with the lowest Z-out, then you may run into a pot imbalance even with the TKD potentiometer.

    @bhk1004 Did you run into any issues with the much lower output-Z with the changes you made?
     
  9. bhk1004

    bhk1004 Acquaintance

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    Not an expert at this so not 100% sure how Zout converts to gain, but i do know that with the original Zout i wasnt able to properly drive any planars.

    I have mainly been using the 240ohm and 10ohm, and havent had channel imbalance issues with my headphones. Mainly have been running HE6/hd800/verite C. The HE6 sound the same as they did off the speaker taps to me. I have always had a little bit of channel imbalance between 6-6:30 on my volume pot, but then again i think i had some imbalance of that nature on all amps ive ever had.
     
  10. yotacowboy

    yotacowboy McRibs Kind of Guy

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    Okay - been playing with different output impedances and as far as gain structure the best match for stock gain loading with HD600 seems to be "4" using FreyaS output. But i'm still getting some hiss. Not sure if its my tubes (Psvane in the gain stages, Gold Lion in the 300Bs, but going to try some NOS Tele's and some NS Linlai). But boy howdy aside from some constant hiss, this setup bests my old EC Af + HD600. Better tone, better body, better grip, better bass, and better decay.
     
  11. Phantaminum

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    From what I can tell it’s when other parts are added to the chain that causes some type of noise. It’s a bit sensitive in that regard. If I connect it to my Sys +, with either the Matrix Sabre Pro or Bifrost 2 that connect via a USB cable to my PC; it picks up a hell of a lot of noise when the video card ramps up. If I connect to either using the Pi2AES as a source I don’t hear any background noise. I wonder if @tommytakis experiences this with the TU-8800?
     
    Last edited: Mar 7, 2021
  12. tommytakis

    tommytakis MOT: E.T.A Headphones

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    Hmm my 8800 was pretty silent regardless of source. After I powder-coated the chassis, it did get slightly noisier, but still very quiet once I properly grounded everything.
     
  13. bhk1004

    bhk1004 Acquaintance

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    Another member had noise floor issues which were resolved with tube covers over the 12xx7 tubes. Just slip over the aluminum cylinders, don't need to fully install them. Might help.

    As also posted earlier. The stock OI for the different positions are below. Makes sense you see the best results at position 4 for probably most headphones out there. 1-2 is kind of unusable. 3 might not be bad for almost 1 to 1 match with some of the 300 ohm dynamic phones. Also what drove me to change the resistors and drop the OI.

    Position 1 : 670Ω
    Position 2 : 550Ω
    Position 3 : 240Ω
    Position 4 : 120Ω
     
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  14. yotacowboy

    yotacowboy McRibs Kind of Guy

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    Just wanted to check in with some speaker impressions on the TU-8600 now that I think I'm thru the break in period and have rolled in some different tubes.

    When I first fired up this amp I was sitting on the floor next to it to make sure if it caught fire I could quickly turn it off. My first three thoughts after the tubes heated and started playing music: thank god no fire, and, good lord it sounds glorious, then, it's missing a channel!

    Long story short, reflowed the left channel, and now we're good. Still no fires!

    The original tube compliment I used were Genelex PX300bs plus the fancy Psvane 12AX7/12AU7s. Compared directly with Aegir monos, there was so much more tactility and nuance. Tonally, and without DSP'ed subs, the Elekit's extended lower and had greater grip than Aegir minus subs. There was still a little haze around the upper midrange, especially in the lower right handed piano work. Anyhow, blackground and delineation of microdynamics was curb-stomping the Aegirs.

    When I first auditioned the speakers I own (cheapo Audio Note) they were relegated to the "home theater" demo room since they weren't really the kind of thing this local dealer does in volume - much easier to sell the AN-E SPes and silver wound transformers in his neighborhood. So when I auditioned the AZ's it was through whatever "crap" the dealer could piece together. Perhaps (?) luckily, the amp was a fairly-high-in-the-range 300B Audio Note amp being fed by a 2.1 CDP.

    I was astonished by the nuance and inner detail these speakers were resolving, and so when a used pair popped up locally, I snapped them up. And for quite some time, I was always searching for something that would make them sound like what I heard during the demo. PP El34, Class-D, weirdo (but highly regarded) Class AB, Schiit's version of Class A, etc.

    But nothing fully meshed with the speakers the same way as a 300B SET seemed to. So, along comes the affordable, if DIY, TU-8600. I kinda had to give it a shot as I was cross shopping the Kaijus.

    So, kind of the cliffhanger ending of audio reviews, I know, but the TU-8600 put the "majiks" back into my speaker rig.

    I'll write moar tomorrow with some tube impressions, but the most glowing way I can end this is to say that the Aegir's are going up for sale. And that should say something given their darling status around here. Anyhow, if folks don't like the review style, just let me know, and I can shift back to more substantive rather than historical input.
     
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  15. gixxerwimp

    gixxerwimp Professional tricycle rider

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    This might be a first for impressions on this forum. Keep up the good work! :punk:
     
  16. gepardcv

    gepardcv Almost "Made"

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    What’s the sensitivity on the speakers you use with the TU-8600? I’m tempted to pick up the kit, but I don’t have horns or anything super-sensitive like that. (No other experience with tube power amps, either, FWIW.)
     
  17. yotacowboy

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    Manufacturer claims 94dB/w. I'd have to "get good" with measuring stuff to confirm. Right now I'm a hack in terms of repeatable/verifiable measurements. i.e. sorely lacking both accuracy and precision.

    To pick up where I left off, I can say my cheapo AN's are finally sounding the way I'd always wanted them to. Plus, some increased detail and image specificity thanks (i think) to YggyA2 being a bit better DAC overall than anything NOS AN.

    There's a neat sense of depth that's associated with the dynamics. N.B. I listen t a lot of electronic music, and I get this sense that when dynamics go up, things move forward in the soundstage and become bigger in space. It's physically involving and really adds to the macrodynamic experience.

    The other thing the TU8600 does that draws me into the experience is that seemingly intentionally down-mixed sound seems to stay properly positioned, no matter what else is going on in the mix. Kind of deblurring a front-to-back placement regardless of the overall dynamic content.

    Lastly, for now, is that low level listening has become so much more engaging, even though cranking up the volume doesn't get slightly hashy and spitty like it did with Aegir's.

    I'm constantly left a bit gobsmacked that 9 watts can sound this authoritative and delineated in the bass.

    I hope these additional impressions help!

    Edit: so I neglected to mention any tube rolling stuff, so here it goes. I didn't want to spend too much on an initial tube compliment in case I sucked at soldering things and ate tubes. But, I also didn't want to put junk tubes in, in case a junk tube would fry anything. I know, that's doubtful given the relative sophistication of the biasing and tube protection in this particular circuit, but go ahead and call me a belt and suspenders kind of guy.

    Anyhow, the Genelex Gold Lion 300Bs are actually quite good. Now that I've held some tigers by the tail and limited variables (only swapping 300Bs) they're missing some air and spaciousness, but I could probably be happy with these as daily drivers. In fact, I think that's what I'm going to settle with since I tend to listen to the radio quite a bit.

    The Linlai E-300Bs are quite simply the best new stock Chinese tubes I've ever heard. I had had my eyes on what was coming out of the Psvane factory after they decided to remake the WE300B, and then try to improve on the Permalloy plate design. I don't have any inside information, but from my research the Psvane ACME series (and Audio Note derivative based on tighter tolerances) they were going to be my near-term "end tube" if everything sounded fine. Then the whole Linlai/Psvane split took place. So I decided to take a chance on the Linlais. And I'm glad I did. With the TU8600, these tubes bring me as close as I can recall to hearing my "absolute sound" of a full Audio Note obscene price system that Vu Hoang let me spend hours with on multiple occasions at De Ja Vu Audio years ago. Now, let me be clear, these aren't good value - the Genelex are comparatively better value - but the thing that has bugged me most about the decision to run a 300B SET amp is that IF I found that I liked the sound of the topology, I'm the kind of person/idiot that would eventually spend the bucks on the new stock Western Electrics. To find something that pleases me (immensely) for roughly 1/2 the price of the WE300Bs is a good thing, imho. Not entirely practical, but at least prudent. I'd still love to hear some (borrowed! LOL!) WE NS 300Bs.

    Anyhow, this is more for the tube rolling thread, but I think some more impressions on these Linlais would be nice. For folks willing to drop ELROG/WE money, I'd be interested to hear direct comparisons.

    Also, NB, swapping between some 12ax7s and 12au7s I had from prior amps (RCA clear tops and smooth plate Teles netted less difference with the Linlais, but more difference with the Gold Lions in position).
     
    Last edited: Mar 19, 2021
  18. gepardcv

    gepardcv Almost "Made"

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    With 94dB/W speakers (presumably rated at 1m distance and 1kHz), 9W is plenty of power to fill a not-too-large room, even if real-world sensitivity declines by a few dB/W for the low frequencies. Whatever that amp does with the first couple of watts that it actually needs for normal listening must be pretty good, though.
     
  19. yotacowboy

    yotacowboy McRibs Kind of Guy

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    Yeah, I would not be shocked if actual measured sensitivity in situ with boundary reinforcement with these was closer to 89-91. When I had EC Af, I tried using it as a speaker amp and it ran out of gas, but sounded glorious as a balanced preamp. Could also be a gain structure thing.
     
  20. yotacowboy

    yotacowboy McRibs Kind of Guy

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    Some updates: I recently installed the different HP-stage resistors, and it makes a significant difference with HD600. No more hiss, and much better volume control. Oddly, I'm liking the 10R setting the best. That being said, tonality is a bit wonky and soundstage is pretty closed in with headphones. BUT, that likely has more to do with the fact that I swapped in some VHAudio CUTFs for the coupling caps and they've got maybe 100 hours on them. I've yet to try with Elex or some incoming LCD2Cs. Big watts and planars (I'm hoping!) do some majiks.

    All I can say regarding the CUTFs is that they're a bit of a rollercoaster, and I can't wait for them to be fully burned in. The glimpses I've got so far of what they *could* eventually settle into are another step above the An UK copper foils I initially built the amp with. Transparency in spades and there's this eery sense that when I walk around the room there are actually instruments/sound sources in the room with me. It's stopped being sound from speakers, and is now sound within a space in my condo. I kinda side-stepped the ODAMs and the MiFlex caps, but at a later point I might roll those in as well.
     

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