Time to DIY like it's 2009! (hobby has changed, man)

Discussion in 'DIY' started by Beefy, May 29, 2021.

  1. Jh4db536

    Jh4db536 Friend

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    We have our preconceptions of the original retail product. i don't have such experiences.

    The DIY Sangaku is outta the bag, this time at a price that's apparently more reasonable. I've actually never heard an original retail product, so its all new to me. If i had been on the OG loaner, i probably wouldn't have touched this. Fun Fact Korg Nutube is Technically a Directly Heated Triode. This to me is an experiment more than anything, and i didn't intend to build it according to the schematic although i did at first as pictured below.

    TLDR: the nutube by itself IME is capable of End Game because it does everything subjectively that i would expect in a totl tube amp. getting it to drive a power tube, headphone, or speaker is a challenge to overcome.

    Looks to be a 4 stage amp: Opamp input > NuTUbe > Jfet > Opamp output

    i want to make it very clear that i am not impressed at all with the way this sounded when i finished building. I Do believe there is Potential for something good after this experience. The NuTube itself actually does sound Very good. The correlation is high with respect to the Nutube and overall amp sound; and therefore, it must respond very well to modifications. Aside from the specified range of B+ and filaments, it is highly sensitive to the same modifications you would do to a regular tube amp. In other words, this amp is extremely malleable for tuning and voicing without touching the solid state section.

    I would say microdynamics and bass quality is its weakness and i feel it's related to the solid state output stage not being able to keep up with sustained deep bass notes. Macro dynamics and mids are its strengths. I find this to sound more traditional triode-like than my pure tube amp; if you're expecting something close to neutral this is not it. Has a very midforward presentation (i like but might not be everyone's jam)

    With tweaks and tuning this can sound Muscular aF, tone saturated, lively, Phat, less dry, more euphonic, and really really Fun AggroFi without being so revealing and harsh with terrible recordings. That is not an excuse for poor performance. I think the bass is a little more flabby than a comparable AMB M3 with the default large value cathode cap installed in the Sangaku. Everything else, the AMB M3/Rebel is blown away.

    [​IMG]
    [​IMG]

    What surprised me most is how tubey this amp sounds for a hybrid with so much silicon in it ... that is the reverb (decay and sustain not as good as real 2a3), separation, layering, triode n shaped sound (mid forward AND rolled off fr at extremes; idc what squiggles it measures at 150ohms). Also, with all the opamps and Sand in the signal path, there doesn't appear to be obvious sins of Omission or bleached sound. It also might work well on non 300ohm headphones (i use senns), but that's usually where amps that sound like this fail.

    The Korg stage appears to be built almost exactly to the datasheet suggestion. This stuff is still infant vanilla and there is still little creativity going on with it ;).

    The application use case for a Korg is a bit difficult. It is very low power and i dont believe it can be used in anything less than 3 stage amp. It's really only good for gain. It's too weak to drive a power tube.

    Apparently, the original designer of the Sangaku removed the MCU control and converted everything to through hole. Looks to be major emphasis on compactness and fitting everything in a single hammond case. The liberal use of ceramic caps everywhere in the Korg section, i personally believe this makes the amp sound inorganic timbre, desert dry, but does sharpen up the picture a bit. In a pure tube amp build, these would be electrolytics and/or crossover grade film caps.

    I hypothesize that given the Nutube is extremely low power (17mA filament and microamp anode), that having a basic LM317 and ~70v multiplier B+ PSU, it somehow performs very very well. My guess is it's behaving like a flea watt tube and soo efficient that the PSU doesnt matter. I am actually amazed that this is capable of such potential while having so many Features that a purist would consider blasphemy.

    [​IMG]
     
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    Last edited: Sep 20, 2021
  2. Beefy

    Beefy Friend

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    HA! It's awfully tempting to just keep building stuff. But I'm at the point where my 'toy' fund is depleted for this year, and I'm really asking myself... How much more desk space am I willing to give up? What more I could possibly want, and does X equipment provide that? Here's my whole office stack as of right now...

    [​IMG]
    (Yes, I had to put a sticky note over the volume knob so that people couldn't see my crotch in reflection. And holy crap is my pin board mounted crooked)

    What I really love about this setup is the incredible simplicity of the signal chain:

    Vref -> R-2R ladder -> connectors/cables -> volume pot -> OPAMP -> MOSFET -> headphones

    It is fully DC-coupled from start to finish, with a single active component (albeit monolithic) providing gain. On a technical level, many will prefer the fact that the Pass is discrete with less feedback vs OPAMP with lots of feedback. But based on your schematic from the diyaudio thread the Pass also adds input coupling caps, brings a higher output impedance, and seems to need a Zobel network on the output for stability. I'm not convinced the power supply could best the S11, even when you take into account the limitations of the single rail. All things considered, the Pass might sound incredible, and your board is definitely amazing, but I'm really only seeing a sideways move.

    I think that if I am going to build anything new at this point, I need to go completely different. And maybe not headphones. A zany 300B amp is probably much more likely.

    The WHAMMY has some great aspects, but I think it could be way better on a technical level. I worry about proximity of an unshielded transformer to the active components, use of a single dual OPAMP cuts out some really great options (including the ADA4627-1 I used here), and it is needlessly capacitor-coupled. But what really concerns me is that I'm not sure the design is particularly well-optimised. For example, check the M3 parts list, about half way down there is a table with OPAMP choices, gain settings, and corresponding compensation capacitor sizes. A LOT of effort was put in to create this to make sure every permutation worked perfectly. This attention is surely what made the M3 so great. For the WHAMMY it sort of devolved to, "Eh, throw whatever cheap OPAMP you like in there, and install a 100nf compensation cap if it oscillates". I've seen a lot of people with high DC offset as a result (even despite the coupling caps!) whereas my amp is sitting pretty under 0.2 mV.

    I am jealous of the bias circuit though, the negative tempco of the M3 bias makes it difficult to dial in. And I should add, the WHAMMY presses the 'value' button in a way the M3 can't, simply because of size and casework.

    To TLDR again, I can see lots of sideways moves. What's the next step up? I still don't know. I'm starting to think I might not care. I look at this stack and I am completely content, and that is something I did NOT expect when I started this thread.
     
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    Last edited: Sep 20, 2021
  3. JeffYoung

    JeffYoung Friend

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    I hear great things about DHT amps, but I've never built one....
     
  4. Jh4db536

    Jh4db536 Friend

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    Been trying to clear my Massive Backlog of builds (sorry guys who gave me stuff i have a mountain of gear to fix / build) that i might have to stop taking commissions for a little while. Elekit's are like Lego's for audio fanatics as in they come complete with all parts, finished and cut chassis, and boards ready to stuff. This is not a difficult build, but it has a very high parts count and it is a pretty complex amp. It actually sounds good too, in fact this is one of the best cap coupled 2a3 amps i've ever heard for the <2000 price that will do headphones And speakers in a single box. I believe speaker performance is much better than headphone performance granted i haven't tried running headgear off speaker taps yet. With nonAM opt, i believe this amp configuration favors macro performance. You might be able to get a different balance of macro/micro with AM lundahls that are shipping this month (that is it focuses more on slam, slap, toe tapping mid and fundamental notes engagement over micro details and 3d layering/separation). This is the first time i've heard an elekit DHT. The elekit house sound seems to be drier than DNA, big and deep sound, middle of the road in terms of presentation forward/back. I do not like the sound of NFB mode personally. I believe it is closer to modern EC than DNA. I believe the Elekit house sound or at least this amp is Cold Metallic sounding(either new CUTF caps and/or Lundahl OPT) and on the Lean side even with NFB disabled and it gets even moreso when NFB enabled.

    Latest one is the newly released Elekit 8900 (autodetect 2a3 and 300b)
    Has Lundahl (NonAM), TKD, CuTF couplers (i have em in backwards but they are socketed)
    Amp is 3 stage BH7A driver (dual triode) and 2a3/300b powertube, SS rectified
    automatically detects tube in socket during startup, steps down filament for 2a3, soft start (proprietary logic boards)
    This one has defeatable NFB set by jumpers, no tertiary windings, 3.2K single primary OPT, 8 and 6ohm? dual secondaries.
    Lots of Organic Polymer cathode caps in series (they really went hard on low ESR philosophy). 330uF in the gain stage, 1000uF in the buffer and power stages. It sounds pretty straight even in no NFB mode from what im used to, while having a lot of the 3d effects of tubes. Well implemented SS gives it pretty tight bass. Bass texture despite having these huge cathode values is on the lower end. Don't think they can be rolled given 330uf values, what i believe could be 24v cathode (needing 35v caps), and 14 cathode caps makes blackgate unfeasible unless you do the gain stage only.

    [​IMG]
    [​IMG]

    [​IMG]
    [​IMG]
    This tube amp features Logic, smart management of operating points[​IMG]
    NFB selection jumpers, turret mounts for coupler cap rolling (i mounted on dsub pins) and yes i removed the stock couplers.
    [​IMG]

    Edit:
    I was using alligator clips because i was troubleshooting connection issues with the RCA input board. I like how they are very solidly mounted, yet not chassis mounted for easy servicing.

    Mainly resistors in the signal path to step up or down attenuation and match impendences. I believe the signal path comes pure off the mainboard, through the jumpers to the headphone jack board (the resistor network is here), splits off to the speaker output board.

    [​IMG]
     
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    Last edited: Sep 30, 2021
  5. Beefy

    Beefy Friend

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    Awesome!

    I've been quite curious about the Elekit, because they do seem like great kits, but I am a bit wary of their use for headphones versus speakers. Finding detailed specifications or schematics is nigh on impossible.

    Basically, I'm wondering how the headphone out is hooked up through the sets of jumpers. Is it just resistors on the output of the speaker taps? Or something a bit more sophisticated?

    Thanks for the edit, that is what I expected. A bit disappointing that headphones are always an afterthought in projects like this.
     
    Last edited: Sep 29, 2021
  6. Jh4db536

    Jh4db536 Friend

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    Here are the differences in the speaker out vs Headphone board
    [​IMG]
     
  7. Beefy

    Beefy Friend

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    One thing I am noticing with my R-2R -> M3 -> Focal Clear stack is some oddities in the sound staging.

    My test track for sound stage is The River by The Tea Party. From the start of the song there is a guitar riff that pans from left to right and back again. I'm very used to this sounding like it moves far in front and behind me in a flat circle. But with the upgraded/current rig, it sounds much more like it goes above and below my head, with very little forward to back. Not unpleasant, but very audibly different.

    I'm racking my brain to think when this showed up; could be the AD8610 to ADA4627 OPAMP switch, could be the new phones, could be the DAC switch. Hell, it could be hearing loss from my shrieking children. In any case, I think some tweaking is still needed...
     
  8. Armaegis

    Armaegis Friend

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    I'm curious if you replace just one of the 4627 back to the 8610 if the changed soundstage will only affect one side...
     
  9. Beefy

    Beefy Friend

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    Yeah, that's my first test as soon as I can dig the AD8610 out of my parts bin.

    I'm also warming up my other rigs right now to rule out brain and ear injury :D
     
  10. Armaegis

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    So you're saying the kids have caused brain damage now too? :confused:
     
  11. Beefy

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    Something that all parents should never rule out. Stroke, insanity, hearing loss, all distinct possibilities that come with the territory.

    Anyway, just had a quick listen from three phones from three different sources in my home setup. Really distinct differences on this particular track. AD900 from my laptop's headphone jack has the flatter forward-back panning I remember. SR-Lambda from Exstata is a little 'higher'. HD650 from Crack is higher again. Listening yesterday would have the Focal Clear at the 'highest'.

    I'll take the AD900 and HD650 to listen from the R-2R -> M3 at work, as well as the different OPAMPs. But I think maybe now that is everything is complete and I am really listening, I am finally hearing the soundstage limitations that people describe in the Clear. I never trust my hearing memory for this sort of thing; maybe I should.

    EDIT, and also, every time I listen to my SR-Lambda and HD650 back to back...... Holy shit the Stax are good. They aren't my tonal preference for everything, but on pure technicalities, they kick so much arse.
     
  12. Cspirou

    Cspirou They call me Sparky

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    Speaking of kids I regularly think about how my kids are going to be exposed to music. This is one of the big reasons why I still like physical media and why I want to setup an RPi media player that anyone can access.

    My son sees my vintage CD player and stack of CDs and always ask me to play a random CD from the set. He even knows how to find the exact track for the song he likes. Looking back my exposure to music at home was largely through my dad's HiFi and playing whatever CDs he had.

    Right now though most of the music I listen to is on my computer or my phone. Which is convenient for me, but no one else. First they need to boot up the computer, login (with my password) and open whatever the music app is to finally start playing music. And that's only if I'm not already on the computer as well. With physical media you see exactly what you want to play.

    It's why I really like projects like this

    https://mobile.twitter.com/ChrisJPatty/status/1078065910487760896
     
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  13. Beefy

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    I've moved overseas and interprovince enough times that physical media isn't an option, everything is digital. I was using Plex on the TV/Xbox to access my own FLAC collection for a while, but even that has fallen by the wayside to Spotify.

    In relation to the kids specifically, I thought having Spotify and Amazon Echos around the house would be great for this. And it was great for a while! Until I was listening to what I thought would be a metal auto-playlist and The Wiggles started. Might need to spring for the family package......
     
  14. Cspirou

    Cspirou They call me Sparky

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    Netflix adding individual profiles was a total game changer. I was no longer getting recs for people that like Grey's Anatomy and Gilmore Girls
     
  15. Cspirou

    Cspirou They call me Sparky

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    I've moved across the Atlantic a couple times and I totally get this. But I think there's something to be said about the physical media 'experience' which is why I cited a project that tries to stay close to it.

    This sort of interaction is why I think there has been a resurgence with vinyl among non-audiophiles. It's a way of engaging with the music in a more meaningful way than having it show up on a playlist.
     
    Last edited: Oct 1, 2021
  16. m17xr2b

    m17xr2b Friend

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    I'm starting to feel old, new tech with overflowing zero's of THD for peanuts does nothing for me, old fashioned hot glass...sign me up.

    There's one amp which I keep coming back to, the bottlehead crack. The last crack is in pieces, a nice amp which fell out of favour once the DIY bug kicked in hard and I saw the imitations it has. With fresh experience under the belt and a need for an amp in my temporary place I hauled the boxes of components and started tinkering.

    The goal is a mini Teton and a prototype for that final OTL headphone amp. I already have plenty of parts and selection was easy:
    - Sowter custom power transformer from the previous crack. Sowter doesn't make mains transformer anymore so it's a bit special for me.
    - Full film power supply caps, clarity caps for the 1st and 2nd stage, Jensen Oils for the last stage, 100uF each.
    - GOSS selected chokes 4 x 10H
    - 70uF ClarityCap CMR, by far the highest end output cap fitter in a crack or any OTL high impedance headphone amp. I won't do bypasses.
    - 15uF Mundorf Supreme decouple for input stage.
    - no volume control, Slagle AVC will perform volume duty.
    - tube rectification, hybrid bridge with the bendix 6754
    - anything else is salvaged or improvised, if I don't have to buy it I won't.

    With the PSU fully calculated, assembly started. I never work from of a schematic, freestyle is my thing on a I'll know it when I see it approach.

    Two days of fiddling just with the layout, settled on this for the shortest path.
    [​IMG]

    About 15 hours of 3D printing. Tea and hawk watching while waiting. This little 110£ printer has paid for itself many times over and it's still kicking.
    [​IMG]

    Iron and sockets fitted, I hate adaptors and went with both 6SN7 and 12AU7 inputs.
    [​IMG]

    Caps and resistors installed, heaters soldered and tested. The outputs are easily removable without soldering. Fitting removable feat on both sides of the frame made the install easier than usual.
    [​IMG]

    Rat's nest added, AC voltage below, DC above.
    [​IMG]

    Turn on was un-eventful, magic smoke stayed inside and no fireworks, voltage checks OK, some component tweaking will be needed to fine tune.

    And in an actual case, maybe even a top plate someday if Santa will be gracious.
    [​IMG]

    Inputs are unusual at the front but I wanted a short signal and as far as possible from the iron.

    And brought over the Wavedream for some banging tunes.
    [​IMG]

    That's DIY for you, don't have an amp? Build one.
     
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  17. Beefy

    Beefy Friend

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    HA! That is insane, in the best possible way. Superb work!
     
  18. Armaegis

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    @m17xr2b Do you have to flip switches or anything if switching the input tubes? or is it just make sure only one kind is plugged in at a time?
     
  19. m17xr2b

    m17xr2b Friend

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    One tube at a time, no switches. If I plug both, the plates will be in parallel operation, probably will sound fine.
     
    Last edited: Oct 3, 2021
  20. peef

    peef Friend

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    On the complete opposite end of the scale, has anyone tried out the LT3042? While diyAudio folks seem to like them for digital stuff (they have a 1MHz+ bandwidth), I've had really good success using the PNP circuit in this app note to regulate the supply on my class A power amps. Just finished prototyping a standalone regulator board, leveraging some tricks from the evaluation board's layout that I missed the first time around, but with provisions for film caps.

    [​IMG]

    [​IMG]
     

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