Massdrop x Eddie Current ZDT Jr. (Official Thread)

Discussion in 'Headphone Amplifiers and Combo (DAC/Amp) Units' started by Hands, Nov 15, 2017.

  1. Orkney

    Orkney Acquaintance

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    Thanks for the update, The "fixed" units should have a white dot to the right of the SN. Very glad to hear you got a good 'un. It is a fun amp for sure, and a decent value for the pleasure it provides.

    Mine is not a good 'un, and is going back home. No more fixes or replacement units available, apparently. so with its departure I leave behind the world of ZDT Jr. Enjoy your amps, you lucky ones, and happy listening.
     
  2. Zampotech

    Zampotech Friend

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    If possible, try to break one power wire to include this circuit.
    This is a simple DC bias protection filter. Very useful thing for devices with toroidal transformers.


    [​IMG]
     
  3. Orkney

    Orkney Acquaintance

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    Hi,

    Thanks for the tip. I may give that a shot -- have tried something similar with an older amp and it worked. Disappointed that this fixed and tested version is worse than my original though, after that endless wait.
     
  4. Zampotech

    Zampotech Friend

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    Unfortunately, the amplifiers on the tubes are susceptible to interference.

    My NBM does not like cell phones, proximity of hands to the first tube and a bad source.
    But still it gives pleasure and comfort , like a fireplace compared to an electric heater.
     
  5. muckyfingers

    muckyfingers Rando

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    Just wanted to drop in and say I picked up a "New Open Box" ZDT Jr. from ebay. I barely noticed the hum with my Aeon Flow Open headphones, but the hum was very noticeable with my HD6XX.

    I did the transformer move mod as depicted by @AudioFriend and it eliminated the hum with the HD6XX by like 95%. I don't notice it at all while music is playing. Thanks for the mod info, I hope more people get a chance to hear this great desktop tube amp.
     
    Last edited: Jun 1, 2019
  6. Zed Bopp

    Zed Bopp Friend

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    Just got my 2nd ZDT Jr. running a while ago (after sending the 1st one back 'cos hum). The hum is basically gone altogether as far as I can tell. There might just be a real small hint of it left, but I really have to concentrate - and this is without music playing. So, everything's good there.

    Btw, when I first plugged in the amp there was a huge amount of channel imbalance, left channel was basically dead. (The amp had been on for about 30 min before.) Tried changing the tubes and cables around - nothing. Then, all of a sudden, everything was working a-ok. I guess these kinds of quirks are what you get with full-tube amps sometimes. Let's hope this is where these hums and imbalances stop, though. Sending stuff back overseas was a real pain-in-my-ass. I've had enough of this shit, thank you very much.

    The amp is sounding very nice through ADI-2 DAC and HD600s right now. Time to just enjoy stuff working.
     
  7. Ringingears

    Ringingears Honorary BFF

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    Glad to hear hum is gone and amp balance is good. New stuff can act weird but keep an eye. I really like this amp with HD600 and HD800. 300 ohm cans seem a bit better, but I am not yet sure. Amp is a slight bit on the warm side, but only a bit. IMO. Bass? I like it, but I listen to 50’s-60’s music a lot. Hoping it is just solder joints settling down for you @Zed Bopp .
     
  8. hikergrl

    hikergrl Friend

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    I have been enjoying using the ZDT Jr and noticed a couple of things.
    When I had both HD650 and Beyer T1 headphones plugged into the ZDT Jr (at the same time), the sound quality from the T1 out of the "Hi" output was degraded compared to having it as the only headphone powered (makes sense if the amp was struggling slightly to power both these phones simultaneously).

    Also I tried my Beyer T90s, they sound really quite nice from the ZDT Jr and are best from the "low" headphone output (the first 'phones I've tried that sound better from the "low" output). However comparatively the HD650s do have some special synergy with this amp.

    Also, I was curious about changing out the Voskhod 6N24P tubes. I found a pair of inexpensive Reflector 6N24P tubes from an ebay seller from the Ukraine (rather confusingly labelled as "rare '64's and '65's" and then later in description as "'70's").
    After these had 3-4 days to equilibrate in the amp. I prefer them to the Voskhod tubes, although the sound difference is small and certainly not dramatic (and its a little hard to compare since after switching tubes it seems to take the tubes about 36 hours to equilibrate). With the Reflector tubes the main differences I noticed are that the treble (cymbals) are less harsh (with more shimmer and detail and less of the harsh "shush") and the bass is more detailed (better defined). Also the vocals may possibly be a mite further away (so soundstage is possibly slightly less claustrophobic).

    The new tubes certainly improved the overall sound, since with the original Voskhod tubes, I did not enjoy using the T1 phones with music that had a lot of high-hats/cymbals (treble was too harsh). With the Reflector tubes, I'm currently preferring the T1 to the HD650 (as I prefer the wider soundstage). The improvements in bass from the Reflectors are also fairly evident using the HD650s. (The other tubes installed in the amp are GE 5654W JAN.)

    Although I definitely prefer the Reflector tubes, I'm perversely comforted that the sound is only slightly improved from Voskhod tubes. I prefer to enjoy listening to music than carefully focussing and trying to assess differences. So I'm now going to relax, not stress about tube rolling, and just enjoy the heck out of the ZDT Jr.
     
  9. Lyander

    Lyander Official SBAF Equitable Empathizer

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    Funny thing is I didn't think the ZDT Jr. particularly claustrophobic during my day with it. Then again, store conditions and weird headphones, never mind that I spent a half day listening to stuff I was familiar with. Or it could be that I'm used to poopy amps, more than likely in fact. Claustrophobic != poor layering though? That's the one thing that really had my jaw on the floor about the amp.

    Also, I notice having some ambient noise in the listening environment actually aids impression of wider stage/more room. Perception is fun, could also explain differing impressions.
     
  10. hikergrl

    hikergrl Friend

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    Oops probably expressed myself poorly, and over-stated by using term "claustrophobic" (also prob. very dependent on headphones being used). I find the hd650s to have a close soundstage (sounds like you are close to singers) and the zdt jr in my rig accentuates this (makes singers and instruments really very close) which can be unsettling for me.
    I agree with you, the zdt jr has good "layering" (significantly better layering than the jotunheim which to me sounded like a wide but very flat soundstage). I find the zdt jr. is good at conveying details (especially in the mid-range), and its got really a remarkably lovely timbre.
     
    Last edited: Jun 8, 2019
  11. Luge

    Luge Acquaintance

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    Hi

    I have recently contacted the Drop support regarding replacement of my ZDT jr. and this is their reply:

    Thank you for reaching back out. I can definitely understand needing a replacement amp. There was a similar issue with the replacement units so we are currently working on a fix for that and we will be in touch when we have more replacement units available.

    So it seems like even the replacement units were not ok (or only a part of the new amps was ok and they run out of them).
     
  12. Zampotech

    Zampotech Friend

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    What's the problem with your amplifier? I know this amplifier well enough to be able to help you.
     
  13. Luge

    Luge Acquaintance

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    It was the classic humming issue, I was just a bit late with sending the amp back for the replacement.

    Thank you for your help offer but the amp is now with the Drop and out of my reach, so no self repair is possible.

    EDIT: I am on the verge of asking for a refund and buying some Schiit.
     
  14. Zampotech

    Zampotech Friend

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    I see. This problem is solved in 20 minutes.
     
  15. msommers

    msommers High on Epipens

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    Am I reading that right? The replaced units still hum, and the fix only requires 20 minutes to fix?
     
  16. Hands

    Hands Overzealous Auto Flusher - Measurbator

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    What takes an individual 20 mins to fix, doing it themselves, is a much bigger logistical problem for a company to sort out for all products they shipped to customers. They probably have to consult with the amp manufacturer or find another third party to handle repairs. Then you have to arrange all that work, make sure the fix does what it's supposed to, figure out how to get it all in order with customers, etc. And that, I imagine, is a simplified version of the process.
     
  17. Dzerh

    Dzerh Friend

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    Could you elaborate, please?
     
  18. Zampotech

    Zampotech Friend

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    I've seen the real ZDT-JR twice. Both times it was at the manufacturer's plant.
    I do not know the Russian owners of ZDT-Jr, but I know a large number of NBM owners.
    I'm renovating right now, and this amp sometimes gets me on the table.
    After the appearance of ZDT-Jr I began to bring NBM in quantities larger than usual. Brought even amplifiers of production in 2010, with toroidal output transformatori. These amplifiers actually had a hum.
    The manufacturer recommended me the algorithm of refinement, and indeed it was a success.
    Probably Russian users covered "epidemic of suspiciousness" after reading SBAF. Otherwise I can't explain. Almost 10 years comfortably listen amp and all of a sudden detect the hum?
    My work certainly reduced the hum, and the money I took for the executed and effective revision.
     
  19. Zampotech

    Zampotech Friend

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    The manufacturer recommended me to make 2-3 turns of transformer steel around the power transformer. In all, the amp is silent like a fish.
     
  20. Zampotech

    Zampotech Friend

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    Yes, you are 100% right. I calculated the net work and did not take into account the side processes.
     

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