Massdrop x Eddie Current ZDT Jr. (Official Thread)

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

  1. StageOne

    StageOne Friend

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    I've had the ZDT Jr for a few weeks and I've been pleasantly surprised by it's performance. The old adage of under promise and over deliver.

    Background: I'm currently in the mid-fi realm learning and finding what sounds and styles I enjoy. At present I have a small handful of amps, Vali 2, mCTH, Gilmore MK2, BH Crack (stock) and a Mjolnir 2. My DACs are similarly varied but more focused, Modi 3, Modi MB, Bifrost MB and Gungnir MB (A2). But all play through a RPi/Allo DigiOne player fed via Roon. Headphones used for testing were ZMF Aeolus, Focal Clears, Senn 6XX and 600s.

    I purchased the ZDT Jr, used and from the original drop so I guessed that it was going to be afflicted with a small hum as others have noted. And after receiving it, that assumption was correct. But thanks to the members of this forum (@atomicbob, @Zampotech, @Dzerh) I was able to modify it and significantly minimize the hum to almost unnoticeable levels.

    As noted about, most of my amps have been tube hybrid, SS or with the BH Crack, OTL. The ZDT Jr was quite impressive in its depth and instrument separation. But as @hikergrl noticed, it did take a while for the stock tubes to settle down. The first few hours of listening were a little disjointed. But after a few days of leaving it on and listening it evened out and become more consistent.

    The first thing that just caught my attention was the depth and separation. Most of my amps presented music in a plane, with or without space. The ZDT did that and more, it gave depth and stage to the music. Though I did notice it was tightly focused. I don't want to say congested as there was space between the instruments, but it was more of a spotlight than a diffuse spread. Still, this sucked me in and I listened for hours sometimes way too late into the evening.

    For me, the treble and mids is where the ZDT shines, they are smooth and present and I can easily pick out details. Missing by Everything but the Girl, you can hear each breath and the guitar just sounds right. Buster Voodoo by Rodrigo Y Gabriela is the best I've heard as you almost hear each individual guitar string, and Hell to the Liars by London Grammar just sounds so ethereal. The piano parts just ring out, and I'm not really a piano fan, but damn. The into to "Lose Yourself to Dance" sounds incredible with those odd sparkly bits but this is where the amp starts to show its limits. Bass...

    Bass. I'm not a bass-head but I wish this had just a few more dBs down low. It rolls off pretty quick and you don't get that slam that other amps provide. I thought the mCTH was a little weak in this department but the ZDT is a step or two behind. The choice of headphones and tubes can help but this is still a limitation.

    Headphone synergy. This was the first amp that really showed what the HD6XX can do. With the other amps it always seemed nice but a bit congested. The ZDT allowed it to shine and I understand what it means when people say this headphone can scale. While the HD600 was my and maybe still is my preferred Senn, with this amp the bass rolloff just didn't work with it. I greatly preferred the 6XX and in the high Z mode as it gave it a bit more bottom end. The ZMF Aeolus was also solid on high Z but just not as smooth as the Senn though the mid bass bump helped with the deficiencies of the amp in this range. My favorites where the Clears and the 6XXs and it depended on what type of music I was listening too. For the Clears, in low Z, jazz, blues and acoustic guitar just excelled, while other genres the Senns performed better.

    Tube Rolling

    Stock - Very good sounding but narrow, tight focus but not congested as you can hear all the instruments. Wonderful texture to the sound as I can really hear and feel a guitar pick plucking a string.

    GE - Opens up the sound and reduces the 3 blob effect that you can get with some recordings and stock tubes. Adds a bit more bass and heft while smoothing the mids and highs. More forward mids and airy treble. Cymbals have a more natural shimmer instead of the dull sound of the stock tubes, almost as if someone is holding the cymbal. Loses that special texture.

    Raytheon - Similar to the GEs but has a touch more bass and air. Currently my favorite.

    cheers, nasdrovia
     
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  2. gixxerwimp

    gixxerwimp Professional tricycle rider

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    Can you be more specific?

    Great impressions, btw. Said things a lot better than I was able to. For me Clears help compensate for low-end shortcomings, but they can only do so much.

    Edit: I found mention of Raytheon 6AK5(W) in a Little Dot thread on HF, think it uses the same tubes as ZDT Jr.
     
    Last edited: Aug 7, 2019
  3. StageOne

    StageOne Friend

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    Not sure if you want more details on the sound or specific tube.

    The Raytheons I purchased were from ebay, and labelled 5654s, compatible with the stock tubes. To me they sounded just a bit better than the GEs most have recommended. But I'm talking small percentages not huge gains, but enough that it was noticeable.

    I bought these from the same seller:
    https://www.ebay.com/itm/RAYTHEON-5...-GTR-SWEET-TONE-1956-LITTLE-DOT/223611672632?

    There seems to be a few versions of this tube, I have the JAN red lettering version
    https://www.ebay.com/itm/One-Quad-o...-Tubes-By-Raytheon-Good-Ratings/372521861107?
     
    Last edited: Aug 7, 2019
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  4. Zampotech

    Zampotech Friend

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    Sometimes the potentiometers deliver a truly minute. A few years ago I was repairing a unique amplifier. This amplifier was a huge dual potentiometer with a diameter of 50-60mm. Some idiot advised the client to lubricate it with vaseline.
    When I opened the potentiometer, it was full of cockroaches. As I realized, small cockroaches crawled into the potentiometer on the smell of vaseline through a small slit. In the potentiometer they ate vaseline grew and could not get back.

    Lubricate potentiometers certainly useful, but not vaseline. Can be lubricated with silicone grease lubrication.
     
    Last edited: Aug 8, 2019
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  5. Baten

    Baten Almost "Made"

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    Oh god that's one thing I did not expect to read about today
     
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  6. gixxerwimp

    gixxerwimp Professional tricycle rider

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    The more you post, the more I realize what an interesting life you have :bird:
     
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  7. Zampotech

    Zampotech Friend

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    I'm just old but not yet stricken with sclerosis :D
     
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  8. bluebyte60

    bluebyte60 Acquaintance

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    Why people want to oil their potentiometer in the first place? Indeed, I will want to have some frictions to have better control tho :D
     
  9. hikergrl

    hikergrl Friend

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    Another manifestation to be worried about ;) Now we will all be worried about cockroach infestations in our amp transformers causing distortion (I'm having real difficulty erasing the unsettling image from my mind of @Zampotech 's encounter).

    Anyhow - almost all my 'phones sound better from the "Hi" output of the zdt jr.
    However, I acquired a HD600 and it sounded pretty harsh and unpleasant from the "Hi" output, and much better from the "Low" output (whereas I agree with @gixxerwimp that the HD650 sounds significantly better from "Hi" output).
    I wasn't expecting this difference between HD600 vs 650.
     
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  10. starence

    starence Facebook Friend

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    I noticed in the manual it says to turn off the ZDT Jr before plugging in headphones. Is there a good reason why we should do it this way?
     
  11. The Life

    The Life Almost "Made"

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    Shorts
     
  12. gixxerwimp

    gixxerwimp Professional tricycle rider

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    @Zampotech, from the developments with your Shortest Way amp, it would seem that the main limiting factor for bass extension and quality in OPT amps like the ZDT Jr is the output transformer. Is that what's holding back the bass of this amp (and the NBM)?
     
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  13. Hands

    Hands Overzealous Auto Flusher - Measurbator

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    The ZDT Jr, based on NBM tests, should be measurably flat down to 20Hz.

    Even to this day, I don’t know where people hear it as having lacking bass other than it being somewhat tubby. Having tested multiple units, some of which were called bass light, my best guess was luck-of-the-draw inferior tubes (or mismatched, or not fully warmed up or broken in) or pot channel imbalances causing a weird psychoacoustic perception of bass issues.

    Still one of the greatest mysteries of life in my mind.
     
  14. Zampotech

    Zampotech Friend

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    Shortest Way and NBM have different topology.
    The value of the bass depends on the internal resistance of the tube, the inductance and resistance of the transformers and the current of the transformer.
    For these criteria, there is no match between SW and NBM. They only match in one, they are both SET.

    It's like comparing a petrol and a diesel car. Superficially similar, but the design, principle of operation and characteristics of the engine are different.

    IMHO The bass in NBM is fine. With my favorite headphones, the Beyerdynamic DT770 bass is even too much.
     
    Last edited: Aug 10, 2019
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  15. wbass

    wbass Acquaintance

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    Yeah, I actually hear the ZDT Jr. (or my unit anyway) producing a mild bass bump with the two headphones I've tried it with (HD600 and Focal Elex). The HD600s are fairly new to me. I've read that they're a little bright/bass shy, but that seems mitigated by the ZDT Jr. I'm surprised how much I'm enjoying the combo. The ZDT Jr. is impressing me quite a bit so far (compared to the MCTH and Liquid Platinum I also run), especially in its layering of instruments.

    I'd agree that the ZDT Jr. bass is somewhat wooly--out of both Low Z and High Z, for me--but I don't mind that too much, at the moment.

    For whatever reason, I like the Elex pairing with the ZDT Jr. a little less. It seems to thicken up the Focals a bit, but also rob them of detail. The Elex and MCTH pairing is pretty fantastic though. Seems quite neutral, with just a hint of warmth, and reveals a lot in tracks I know quite well. Also a fun combo.

    The impressions of a rando/lurker, for what they're worth....
     
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  16. Hands

    Hands Overzealous Auto Flusher - Measurbator

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    Pairing the Focals with the right amp is very tough. They are generally lower impedance headphones but with a more concentrated impedance hump.

    It’s all too easy to make them sound too bassy and smear the high end in the process. It’s also not ideal to pair them with ultra low output impedance amps due to risk of not giving the low end more emphasis to slightly mask treble problems.
     
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  17. wbass

    wbass Acquaintance

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    Thanks, Hands. That's useful feedback. Yeah, I figured it's an impedance mismatch (if that's the right term) with the Elex and the ZDT Jr. The Focals are better with the tube hybrids, that's for sure. I tried the Elex once on an OTL (Decware CSP3), and it *really* didn't work. Far too wooly and warm.

    I've also got a pair of Utopia's (not with me at the moment, unfortunately), but I don't think they're going to be a great match with the ZDT Jr. either. I'd sort of hoped the OPT design would help tame the slight steeliness of the the Utopias, but I don't think it'll be worth the loss of detail/resolution.

    Utopias are a solid pairing with the Liquid Platinum, however. That seems to be a "do no harm" sort of amplifier and does a lot right. But I still wonder if it's getting the best out of the Utopias. Of all the lurking and reading I've done, I don't think I've ever seen any consensus gathering around a set of amplifiers (or general design) that's right for the Focals. Apart from the ECP stuff that seems specially designed (?) for their impedance characteristics?

    All said and done, however, the ZDT Jr. is wonderful with the HD600, and I'm keen to try it with HD650 and HD800S at some point.
     
  18. gixxerwimp

    gixxerwimp Professional tricycle rider

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    I don't remember seeing and haven't been able to find a proper FR measurement of either the ZDT or NBM (only distortion measurements at specific frequencies). Marv's comparison to Magni 3 is the closest to that I've found. It shows a very minor roll-off but I don't think the HD650K is the best tool to demonstrate bass response, especially down low.
    https://www.superbestaudiofriends.o...sdrop-x-zdt-jr-measurements.5424/#post-176571

    I don't find ZDTjr/NBM mid-bass response to be lacking though it can be tubby and woolly. I should have specified bass extension, tightness and impact. I don't have a measurement rig, but my ears tell me that bass drops just drop off into nothing. On tracks where I can hear sub bass notes with HD650Ms out of MCTH, there's practically nothing out of my NBM. The Clear's dry and extended bass help compensate, but there's still a lot lacking in the bottom octave. Sine sweeps and the bass shaker test give the same results.

    I've tried 2 sets of stock driver tubes and the GEs. The stock tubes sound the same and the GEs increase mid-bass somewhat, but not much in the sub range.

    This is just an observation, but I think @Hands places less importance on bass performance compared to my preferences (and perhaps even than the "average" listener). When you said about the Shortest Way, "There is a bit of roll-off in the lowest octaves. It's slight, but it's there," that was alarm bells for me personally that it wouldn't have the bass performance that I prefer.*
    Thanks for your explanation. Looking forward to comparing the MxZDT Jr and SW+.


    *Edit: Just thought I'd add that I think I can objectively say I'm not a bass head. If anything the opposite as I've been accused of being bass shy on occasion. I just prefer tight, extended bass.
     
    Last edited: Aug 10, 2019
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  19. atomicbob

    atomicbob dScope Yoda

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    A complete set of ZDT Jr measurements may be found here: Eddie Current ZDT Jr. Technical Measurements
     
  20. gixxerwimp

    gixxerwimp Professional tricycle rider

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    I knew you must have measured it at some point. Colour me dotard :confused:

    So how does one make sense of the flat FR measurement with perceived drop off in bass response?
     
    Last edited: Aug 10, 2019
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