Massdrop x Eddie Current ZDT Jr. (Official Thread)

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

  1. Zampotech

    Zampotech Friend

    Friend
    Joined:
    Oct 15, 2018
    Likes Received:
    1,072
    Dislikes Received:
    0
    Trophy Points:
    93
    Location:
    Moskou
    If ZDT Jr. blew up the world market for tubes ECC 89 :), probably makes sense to make adapters ECC89->ECC88
    And pacify greedy sellers :)

    ECC88 abound

    It should probably look like this

    [​IMG]

    [​IMG]

    Instead of 6Z1P, you can apply a whole group of other tubes

    6AS6 (W), 6F33"Tesla", 5725, 409A, 6187, 7752, M8196, 6DB6, 6954
     
    Last edited: Jul 3, 2019
    hikergrl, gixxerwimp and tommytakis like this.
  2. jaker782

    jaker782 Rando

    Joined:
    May 6, 2019
    Likes Received:
    4
    Dislikes Received:
    0
    Trophy Points:
    3
    Location:
    Maryland
    That is great news! So how do you get the covers off to access the transformer? I don't see any screws anywhere...
     
  3. Ringingears

    Ringingears Honorary BFF

    Friend
    Joined:
    Sep 26, 2015
    Likes Received:
    3,473
    Dislikes Received:
    3
    Trophy Points:
    113
    Location:
    Northern Californium Valley
    It’s not as simple as just removing the hex screws on the bottom. There are other things that need to be removed as well. I think the headphone sockets and a PCB board IIRC. Best to see if someone has a copy of the instructions.
    Or see if there are instructions on here somewhere. Is your amp humming?? If not, it might be best to just leave it as is and enjoy some music. IMHO of course.
     
    hikergrl, Zampotech and Jinxy245 like this.
  4. tommytakis

    tommytakis Friend

    Friend
    Joined:
    Mar 22, 2018
    Likes Received:
    1,112
    Dislikes Received:
    1
    Trophy Points:
    93
    Location:
    Los Angeles, CA
    1.you need to first open the casing on the bottom first (removing 4 hex screws)
    2.Then you'll need to unscrew the 4 metric screws that are attached to the 4 corners of the PCB board.
    [​IMG]

    3. One of the 4 screws are obstructed by the 1/4 inch jack so u need to unscrew the 2 nuts from the front using a 11mm hex setter ( I used this one https://www.amazon.com/gp/product/B0017JX780/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1)
    *Credits to @Zampotech for the help
    [​IMG]


    4. Once the PCB Board is loose, you will be able to unscrew the 4 metric screws that are holding on to the box with the Eddie Current Logo.
    5. Now you will be able to access the transformer

    If you have follow up questions, feel free to message me. I will be more than happy to help :)
     
    Last edited: Jul 3, 2019
  5. Ksaurav402

    Ksaurav402 Friend

    Friend
    Joined:
    May 7, 2019
    Likes Received:
    370
    Dislikes Received:
    3
    Trophy Points:
    63
    Location:
    NY
    I received my unit few days back. I don’t hear any Hum.
    However I do hear imbalance at low volume. So I have to use SYS so that I can go up in the volume pot and remove the imbalance. imbalance goes down significantly once I’m around 9 on volume knob.
    I’m using HD600
     
  6. Dzerh

    Dzerh Friend

    Friend
    Joined:
    Apr 1, 2018
    Likes Received:
    235
    Dislikes Received:
    6
    Trophy Points:
    43
    Location:
    San Ramon, CA, US
    When checking your ZDT Jr. for hum please take into account:
    1. This particular issue was about the amp output transformers picking up noise from the amp power transformer. It was constant and was not affected by source, volume or positioning.
    2. Most amps humming/hissing in both channels proportionally to volume control setting. You just need cans sensitive enough to hear it.
    3. Output transformers may pickup noise from any EMI source, your DAC power supply, for example. So before sending ZDT Jr. back or trying to modify it - check it standalone, at least 1 meter away from walls or powered equipment.
     
  7. yotacowboy

    yotacowboy McRibs Kind of Guy

    Friend
    Joined:
    Feb 23, 2016
    Likes Received:
    1,796
    Dislikes Received:
    10
    Trophy Points:
    93
    Location:
    NOVA
    Home Page:
    This is pretty typical for lower cost volume potentiometers. consider decreasing the output of your source, either digitally if you're using a music app like roon (just cut the output by 3-6dB) or, by adding some inline RCA attenuators from harrison labs or the like to the input RCAs of the amp.
     
    hikergrl, Zampotech and Jinxy245 like this.
  8. Ksaurav402

    Ksaurav402 Friend

    Friend
    Joined:
    May 7, 2019
    Likes Received:
    370
    Dislikes Received:
    3
    Trophy Points:
    63
    Location:
    NY
    Thanks a lot, since I have Schiit Sys so using it to cut few dB. Inline RCA attenuators looks good.
     
  9. yotacowboy

    yotacowboy McRibs Kind of Guy

    Friend
    Joined:
    Feb 23, 2016
    Likes Received:
    1,796
    Dislikes Received:
    10
    Trophy Points:
    93
    Location:
    NOVA
    Home Page:
    In your particular case, what i'd probably recommend is to do all of your volume manipulation through one device only. So, run ZDT Jr. wide open, i.e., at unity gain, and do all volume adjustments through Sys since it has a bit nicer volume pot (ALPS).
     
  10. gixxerwimp

    gixxerwimp Professional tricycle rider

    Friend
    Joined:
    Sep 30, 2015
    Likes Received:
    2,260
    Dislikes Received:
    13
    Trophy Points:
    113
    Location:
    small island claimed by China
    How much were they before?

    I ordered a matched pair of GE 5654W from Riverstone @amazon for $36 for my incoming NBM. Guess I was too eager :rolleyes:
    https://www.amazon.com/gp/product/B01BFJDTW0

    But I just saw these on eBay for €15. Says 2 pairs available.*
    https://www.ebay.com/itm/372694341360

    *Edit: looks like it just ended.
     
    Last edited: Jul 4, 2019
  11. gixxerwimp

    gixxerwimp Professional tricycle rider

    Friend
    Joined:
    Sep 30, 2015
    Likes Received:
    2,260
    Dislikes Received:
    13
    Trophy Points:
    113
    Location:
    small island claimed by China
    Maybe @Zampotech can help us with where unity gain is on the volume pot. I remember @atomicbob measured it at around 1:00 on the MCTH.
     
    Last edited: Jul 4, 2019
  12. atomicbob

    atomicbob dScope Yoda

    Friend BWC MZR
    Joined:
    Sep 27, 2015
    Likes Received:
    9,779
    Dislikes Received:
    3
    Trophy Points:
    113
    Location:
    On planet
    hikergrl, edd, Lyander and 3 others like this.
  13. atomicbob

    atomicbob dScope Yoda

    Friend BWC MZR
    Joined:
    Sep 27, 2015
    Likes Received:
    9,779
    Dislikes Received:
    3
    Trophy Points:
    113
    Location:
    On planet
    Information about mods and results achieved were presented here
    The material is steel banding, maybe a high nickel content. Unfortunately it is usually only available in very large quantities.
     
    Dzerh and StageOne like this.
  14. randytsuch

    randytsuch Facebook Friend

    Joined:
    Oct 13, 2017
    Likes Received:
    93
    Dislikes Received:
    1
    Trophy Points:
    28
    Location:
    Los Angeles, Ca
    I bought a matched pair almost exactly a year ago for $12 shipped from a us seller.
    And they had been at that price since beginning of last year, or thereabouts.
    Supply drying up?
     
    Richgard likes this.
  15. Zampotech

    Zampotech Friend

    Friend
    Joined:
    Oct 15, 2018
    Likes Received:
    1,072
    Dislikes Received:
    0
    Trophy Points:
    93
    Location:
    Moskou
    There is another option.
    If you remove the jumper from the RCA connectors and put a resistor four times the nominal potentiometer instead of the jumper, you get two inputs. One with a attenuation coefficient of 1:1, the second with 1:5.
     
    Orkney and yotacowboy like this.
  16. Orkney

    Orkney Acquaintance

    Joined:
    Jul 15, 2016
    Likes Received:
    41
    Dislikes Received:
    0
    Trophy Points:
    18
    Those GEs are a nice fit with the ZDT. I hung onto mine and have tweaked it to be pretty much silent. It's a great little amp once it's sorted out. My fave for jazz and chamber of the amps I presently own, with enough resolution to show differences between recordings and instruments and a fairly neutral tonality.
     
    Zampotech likes this.
  17. jaker782

    jaker782 Rando

    Joined:
    May 6, 2019
    Likes Received:
    4
    Dislikes Received:
    0
    Trophy Points:
    3
    Location:
    Maryland
    Damn! I was really hoping it was a bit easier to access the transformer to apply the steel banding. My unit has a very slight hiss in the tight channel that really is only noticeable with no music playing. Maybe I'll just live with it. The perfectionist in me wants it to be dead quiet though! Thanks for the detailed response! Greatly appreciated!
     
  18. randytsuch

    randytsuch Facebook Friend

    Joined:
    Oct 13, 2017
    Likes Received:
    93
    Dislikes Received:
    1
    Trophy Points:
    28
    Location:
    Los Angeles, Ca
    Good article about magnetic shielding here
    https://www.kjmagnetics.com/blog.asp?p=shielding-materials
    I had heard about saturation in mag shield, but didn't really understand what it meant in this context until I read this.

    Based on the article, and the type of problem, I would expect mumetal would make a better shielding material. Mumetal has a high nickel content, so that matches what's been said here.

    BTW, a ways back in this thread, another solution was implemented. He moved the power tx a little bit, away from output tx's.
    Makes sense because field strength is inverse of distance squared, so a little farther makes the mag field weaker.
    You need to drill a hole in the chassis to move the tx mounting bolt, but requires no material to buy.

    Randy
     
    atomicbob, Jinxy245 and Zampotech like this.
  19. Zampotech

    Zampotech Friend

    Friend
    Joined:
    Oct 15, 2018
    Likes Received:
    1,072
    Dislikes Received:
    0
    Trophy Points:
    93
    Location:
    Moskou
    Of course, magnetic material with high mu will be effective protection. Maybe I'll try something like permalloy. In Russia it can be bought in tape and in small quantities.
    But permalloy has a flaw. If you hit him or not bending, he from a material with magical properties turns into a pumpkin. Just a regular piece of iron. To return its properties it is necessary to anneal it in vacuum or in hydrogen.
    Vacuum stove again I have there is. They gave it to me for my services ;)
    But I doubt that such a stove again there is have audiophiles.

    I'm making it easier. I use a hacksaw to remove the winding from the old dead toroidal transformer and wind off the required amount of transformer tape from the core.

    This steel can be used where electro-magnetic shielding is needed.


    Recently, I used such steel in the installation to test the tubes to protect the tubes from electromagnetic interference.

    [​IMG]
     
    Last edited: Jul 5, 2019
  20. atomicbob

    atomicbob dScope Yoda

    Friend BWC MZR
    Joined:
    Sep 27, 2015
    Likes Received:
    9,779
    Dislikes Received:
    3
    Trophy Points:
    113
    Location:
    On planet
    the modifications being described are for a mains HUM issue. HISS is a different problem. IEMs typically have greater sensitivity and may reveal hiss as will high sensitivity headphones. Obtaining tubes that have been selected for low noise might help.
     
    Leoi, Lyander, Jinxy245 and 3 others like this.

Share This Page