Nobsound EL34 Single-ended Class A tube amplifier

Discussion in 'New Gear - Values' started by Frank Sol, Jul 13, 2015.

  1. freQ(*)Oddio

    freQ(*)Oddio Super Member

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    2,797
    Location:
    Adirondacks
    true that!
     
  2. premington

    premington New Member

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    11
    Hi Folks!

    Been since last December since I posted to this thread. The Nobsound amp is still used almost daily, and has proven to be a reliable performer that sounds pretty good.

    I have a question about hum. My only complaint about this amp is it produces a pronounced HUMMMMMMMMMMM regardless of what source is inputted (computer or turntable). The hum is reduced or increased with the volume control, so the higher the volume, the louder the hum. I've rolled the tubes with three different sets, so I know it has nothing to do with the tubes. Does anyone know what's producing this hum and how I can get rid of it?

    I do notice that if I shake/adjust the power plug going into the back of the unit, the buzzing intensity changes. Sometimes it drops down 50%, but then it climbs back up. That leads me to believe it's a poor grounding issue maybe?

    Has anyone dealt with this with their Nobsound amp, and do you have any recommendations on how I get rid of all this humming?

    -Paul
     
  3. Frank Sol

    Frank Sol Addicted Member

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    7,790
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    premington

    Could be your ICs

    Anyway I never had or have a hum with mine. Although the 1st or 2nd time I went inside I added a ground wire
     
  4. premington

    premington New Member

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    11
    Frank: Is your AC line cord shielded? I'm gonna try swapping out the line cord tomorrow with a shielded one.

    When you added a ground wire, where/how did you add it? I had the top off the amp when I got it (~8 months ago), and I remember it was simple point-to-point wiring. If necessary, I'll beef up the grounding. I'm just not exactly sure where and how to do that. Of course, there's no schematic for the unit.
     
  5. Frank Sol

    Frank Sol Addicted Member

    Messages:
    7,790
    Location:
    SoCal
    AC cable is not shielded but is grounded (3 prong)

    From memory there is a tab on the inside next to AC socket that is grounded. Soldered wire there

    @Tim64 ... Still no problem with unit and sounds very good.
     
    Pio1980 likes this.
  6. premington

    premington New Member

    Messages:
    11
    Great... Thanks for the info, Frank. What part did you solder the wire to the tab? I mean... from the ground tab to which part of the assembly?

    The AC cable is grounded, but without shielding, stray RF energy can still bleed into the wires. The amp is in front of my turntable with the amp AC cord running under the turntable and down the back of the computer table, around the computer and computer wiring. So I'll try a shielded AC cable and see if that clears things up.

    If it doesn't, I'll crack open the case and try soldering a ground wire. I just need to know what points to solder it to. The ground tab by the AC socket is a start.
     
  7. Tim64

    Tim64 Well-Known Member

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    870
    Location:
    North Central West Coast
    Thank you ,good to hear it is still working great for you, now to convince my wife.
     
  8. Frank Sol

    Frank Sol Addicted Member

    Messages:
    7,790
    Location:
    SoCal
    premington

    I usually have the preamp & amp grounded together with the added/mod ground wires - keep in mind this 'integrated' amp has been modded to just a power amp

    Pics from a thrown together office system (Notice white 'X')


    [​IMG]



    [​IMG]
     
    guiller likes this.
  9. Poultrygeist

    Poultrygeist Addicted Member

    that's a nice sounding preamp you've got there :)
     
  10. premington

    premington New Member

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    11
    Ahhhh... I see how you have your ground set up. You have a setup similar to mine. I have my tubed preamp (much cheaper and smaller than yours!) in the same spot, but my amp is moved forward with the turntable behind it. The preamp is to the left of the turntable.

    Where/how did you exit the ground wire out the back of the amp? I can do the same thing and connect it to my preamp--didn't think of that.

    Thanks for sharing this.
     
  11. Frank Sol

    Frank Sol Addicted Member

    Messages:
    7,790
    Location:
    SoCal

    Sounds better than it looks and its a beauty :hug:

    Add a modded PS 5501 then its a party
     
    Poultrygeist likes this.
  12. Nixxuz

    Nixxuz Active Member

    Messages:
    190
    Location:
    Minnesota
    To Frank:

    I was strongly considering pairing an NS-01p with either a used B&W ST2140, or possibly a new Behringer A500. Would that be an overall better combo than a Yaqin MC10T, considering the price difference? The NobSound and the B&W will run me about $540, while the Yaqin would be at it's usual list of around $650.
     
    Last edited: Sep 30, 2017
  13. Bob

    Bob AK Subscriber Subscriber

    Messages:
    1,498
    Location:
    West coast
    Mine is used daily. like others - no hum.

    try using a power strip for all units with three prongs, and if you can try reversing
    the 2-prongers in the strip. may help.
     
  14. KKnight

    KKnight Active Member

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    331
    Ill bet you $100 cash usd that you havent merely taken on the botton cover and verified the 'lytics and had them tested to spec and whether or not they are counterfeits.
     
  15. KKnight

    KKnight Active Member

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    331
    Ha. The only one that is worth a crap is the Yaqin. Anyone reading these posts needs to do a little research on AK about the truth of the Olchen, Nobsound, Douk audio, etc amps. The fact remains even in 2018, that ANY of the named amps are solely engineered to the cheapest Shaugan tubes in a hard core slave labor Chinese factory. Over 50% of the components, especially the 'lytics, are counterfeit (if not re-used from old stock), and the factory tubes are the worst on the planet. So mere tube rolling or 'lytic parts replacement with non-counterfiet verified tier 1 components is a null point, as the engineering and "tuning" at the dirty factory is for each amp's components on that days or hours run. These 3 main Chinese factories, using at least 12 different brand names, have been rusing the ignorant western "audiophile" since about 2005.

    I did a write up on AK about Olchen's EL-34 and the ONLY one thats worth a crap vs Yaqin.

    Seems this post, and many of the posters still live in a bubble where all that glitters IS gold, and ignorance is bliss.
     
  16. KKnight

    KKnight Active Member

    Messages:
    331
    PSvane, even their general (not audio music series) grade tubes are decent, IF you can verify the ones you get are not counterfeit.
    But its again a null point since your amp IS NOT engineered with components for anything but the factory tubes and that days or hours batch.
    You cant just roll tubes think youre going to achieve improvement, especially when over 50% of the 'lytics etc are counterfeit or waaaay out of spec. Even at best, the components and 'lytics are tier 4 and the worst.
     
  17. Poultrygeist

    Poultrygeist Addicted Member

    Your anti-Chinese gear comments add nothing to this thread.
     
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  18. mjw21a

    mjw21a Super Member

    Messages:
    2,546
    Location:
    Brisbane, Australia
    Seriously mate, I own a Yaqin MC10T, Oldchen K3 and the base model Oldchen SEP amp. Both Oldchen amps beat the crap out of the Yaqin in terms of sound quality, and the K3 has it beat for fit and finish as well.

    Replaced coupling and input caps on the Yaqin with Mundorf ZN and volume pot with Tocos Cosmos. Tubes are 12AX7 Amperex Bugle Boys, 12AU7 PsVane Treasure II and Soviet 6P3S-E coin base tubes. Before the Oldchen amps I loved the sound it prodoced.

    The Oldchen K3 received French Solen ZN coupling caps and Russian KY40-9 PIO's for input caps and an ALPS Blue volume pot. The improvement was far more subtle than the upgrade on the Yaqin, either way it's a better engineered and sounding amp. I ordered it custom wound for 240VAC, and no tubes. It's running 2x Shuguang CV181-Z Black Treasures, 1x Melz 6H8C hole plate metal base and 4x Tung Sol KT120 tubes. This is an amp deserving of more attention than it gets as it's at the same price point as the MC10T / MC13S though beats it silly in terms of sound quality and build quality. Part of that may be down to the KT120 power tubes, though let's face it, neither the MC10T or MC13S can run them without damaging the output transformers.

    The base model Oldchen SEP amp is what prompted me to try the K3 vs my MC10T in the first place. It's not much to look at, though it has point to point wiring and has Russian PIO's in it stock so I've not bothered replacing anything. It's a fantastic sounding little amp and also beats the Yaqin MC10T silly paired with some Dayton USA PS220-8 based speakers. I've a NOS RCA rectifier in there, 2x Melz 6H9C metal base tubes and 2x Soviet 6P3S-E coin base tubes.

    Maybe try commenting from experience rather than regurgitating negatives from others who've never seen or heard the amps in question? Your comments so far say more about you than the gear.
     
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  19. mjw21a

    mjw21a Super Member

    Messages:
    2,546
    Location:
    Brisbane, Australia
    There are some quite high end Chinese brands out there now too. I'd love a Line Magnetic or Prima Luna amp.... Cayin is also a well respected Chinese brand. All 3 make higher end gear than Yaqin or Oldchen though it costs more too. Basically you get what you pay for.

    Perhaps someday I'll own something from Line Magnetic, or made locally here in Australia by Western Accoustics or Falls Audio, though that's a fair way down the track. For now I'm really enjoying the sound I get from these entry level brands.

    The whole joy of these lower end brands is their price point is low enough to allow people to buy valve gear they could never otherwise afford and gain entry to valves in the first place.

    The simplicity of the circuits make them very mod and upgrade friendly, though frankly the Oldchen amps win in this category due to their point to point construction. Far far better than the circuit boards used in the Yaqin.
     
    Last edited: Dec 27, 2017
    bubba42 likes this.
  20. Funky54

    Funky54 Well-Known Member

    Messages:
    876
    I’m not 100% sure I understand what your comment means... but I’m Reasonably sure you owe me a $100 bucks.

    I’ve had the the “bottom” cover off. It’s point to point wired. Everything including the sador is neat and tidy. You shouldn’t spout things you don’t know anything about. It will make you sound less creditable.
     
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