Donald North Audio — Owners Thread

Discussion in 'Headphone Amplifiers and Combo (DAC/Amp) Units' started by Huxleigh, Aug 12, 2016.

  1. RestoredSparda

    RestoredSparda Friend

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    Does anyone have any experience using the Sophia Electric Aqua 274B rectifier? Donald mentioned on another forum it will work but I haven't found much on its sound.
     
    Last edited: Oct 20, 2022
  2. Clear Water

    Clear Water Friend

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    I have that rectifier, and it works well! It is inoffensive, does nothing wrong, and is incredibly boring.
     
  3. RestoredSparda

    RestoredSparda Friend

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    Just finished installing a Khzomo Shunt attenuator (50kohm). The stock TKD unit was getting noisy, even after multiple cleanings, so I decided to change things up and follow the success of an earlier friend here.

    I left the stock supplied 51kohm input resistors for now but have some 50kohm upgrades ready at a later date.

    The install went pretty easy. It's a big unit but it fit nicely in the Stratus. I chased down all the wires to make sure it was wired correctly. Basically imagine the stock pot flips 180 degrees and the wires were correct that way. The ground swapped sides basically.

    I did need to space the Khzomo a bit away from the inner chassis to get around the case screws, and also dremel off the tip of the Khzomo "stalk?" to get the knob to fit flush against the chassis.

    Haven't listened yet (besides ensuring it worked correctly), but will shared impressions later when I have time.


    20221123_143030.jpg

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    Last edited: Nov 23, 2022
  4. Clear Water

    Clear Water Friend

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    @RestoredSparda
    Amazing! Can't wait for impressions on how it has affected the sound.
     
  5. RestoredSparda

    RestoredSparda Friend

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    Ok, the stock input resistors sucked. Sounded hard and harsh. I ripped them out quickly and soldered in the two Charcroft z-foils.

    20221123_173012.jpg

    There we go. Much better. Here is what I noticed after listening to two albums back to back with HD650 KISS.

    • A very, very slight background hiss I used to have is completely gone. I guess the dirty TKD pot was the culprit all along. I assumed it was just tube related. Now the background is completely black with Yiggy LIM.
    • Perfect channel balance is nice to have at even stupidly quiet volume levels. There are also a lot of usable steps and plenty to find the perfect volume. I was on the fence with the 36 stepper kit for my past bottlehead kits, but this 48 stepper is perfect.
    • PLANKTON! Definitely hearing deeper into the mix with this attenuator. Noticing super faint background effects and background vocals that I did not notice on the previous 20 or so listens to these albums. More detail all around and slightly more extension up top and down low.
    Overall this was a worthwhile upgrade to me. I would equate it with the level of improvement from going with premium tubes. It is more of an upgrade than I was expecting to be honest.

    It still sounds like a v2 DNA Stratus, but with more clarity / resolution.

    Downsides - I wish it was blue.
     
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    Last edited: Nov 23, 2022
  6. RestoredSparda

    RestoredSparda Friend

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    Couldn't sleep so I decided to install some nice silver RCA jacks that match the same brand connectors on the Audio Envy cables I have.

    I was nervous to cut into the chassis to widen the holes a hair to accept the new jacks, so purchased a very nice stepper drill bit. Super clean cuts and an excellent result.

    Was it worth it? Idk, but it was fun and looks nice.

    I also ordered another Khozmo shunt attenuator, but this time with the best resistors Arek had on had. Should be here in a few weeks and I'll report back if it is an improvement over his cheaper offering.

    20221128_061559.jpg

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    Last edited: Nov 28, 2022
  7. RestoredSparda

    RestoredSparda Friend

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    The version with Takman REX resistors arrived finally. Took a little over a month from Poland. Just need to find time to install it and report back.

    Edit: just finished installing this new unit. It's been way too long to say if the Takman resistors are worth it, but it certainly sounds just as good as I remember. I've truly missed the Khozmo since I put the TKD back in waiting for this unit.

    FYI, if anyone else does this, the unit with Takman resistors has a different pcb layout than the vishay SMD unit. This one is identical to the stock TKD pot, so left, right input and grounds are in the same location. Much easier to install.

    I also only needed to trim the Khozmo stalk about 3 mm with a dremel, and add a 1 mm spacer on the inside of the chassis for everything to fit nicely.
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    Last edited: Dec 21, 2022
  8. jexby

    jexby Posole Prince

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    Can/Should attenuators of this quality be installed in a DNA Starlett?
    not that I own a Starlett, but might one day in future....
     
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  9. RestoredSparda

    RestoredSparda Friend

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    My vote would be yes. I've noticed pretty substantial upgrades with shunt resistor attenuators in all of the bottlehead kits as well as my Stratus.
     
  10. Inoculator

    Inoculator Friend

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    I am a big fan of the Khozmo/Hattor attenuators, have owned a couple of their switches/passive preamps. Currently running a Hattor The Big dual mono with AMRT resistors after I sold off my Holo Serene preamp. That being said, my vote wound be don't mess with modding your DNA amp. Instead just turn your amp all the way up (my Starlett ran dead quiet all the way up), and purchase a Hattor/Khozmo passive preamp. I actually asked Donald about potentially building a Stellaris without an attenuator for use with a preamp, and he suggested the just turn it all the way up approach as well.

    When it comes to these attenuators though, Arek of Khozmo/Hattor does amazing work:

    [​IMG]
     
  11. RestoredSparda

    RestoredSparda Friend

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    Yes, Arek is an artist!

    Different strokes for different folks regarding modifying amps. My thoughts are if it's easily reversible I don't have any qualms about it.

    A passive pre is also a great solution. Not that it's necessary, if I didn't already make it clear these amps sound stellar regardless of the pot. We are talking about the last 1 percent here.
     
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  12. bigjako

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    I've been tube-rolling the Stratus for the last couple months and forgive the stream-of-thought rambling but I thought some of it might be useful.

    I bought a used unit and it came with a National Union 5U4G, Fivre BQ7A and JJ 2A3s (I've seen a few JJ pairs up for sale recently, so this may be timely). Donald serviced the amp after I got it, and he complimented both the National Union and the JJs (but he had a 6n1p in when he serviced it). [side note, Donald is awesome, he picked up and delivered the amp in person]

    I normally don't like JJs, I think of them as the 'stock tube' company. But I'd read up on these 2a3's and understand they're manufactured on original equipment and are built like half-power 300b's. I listened to them and loved them and were really the defining sonic component of the Stratus in my first couple months. They do have a 300b-like sound: round-bottomed, maybe a little bloomy, but grand, spacious, full and strong. I picked up some used black plate Cunningham's (possibly RCAs) to have something to compare them to - I wasn't a fan. They were comparatively thin, though with a little more detail. It was more like there was less bloom so I could peer into the music deeper. I could see how some would go for that sound, though. I ordered a NOS NEC 2a3 pair from an eBay tube seller I like - there's not much to read on NEC 2a3's (or any of their tubes, really) but I have an appreciation for Japanese tubes - I think you can find good value there. My favorite tubes on the SW51 were a pair of Japanese-made Lindahls.

    I've only had a few days with the NECs but I really love them. They're full-bodied and detailed but have insane separation. I had numerous instances this week where I heard new details in a song that I'd never heard before. I've come to realize it's less about excavating never-heard-before details and more a case of instruments having such well-defined separation that I experienced instruments separately when they previously melded into each other. Keep in mind this is mainly on an Atrium, which can place the layers so well. I'm haven't abandoned the JJs but will stick with the NECs for a few weeks at least. I've also realized I just need to get some Linlai Elites, why postpone the inevitable.

    In the meantime, I was also testing input tube replacements (6n1p/6bq7a/6bk7b plus a CV4068 and (an attempted) ECC40). The Fivre 6bq7a was great, slightly ahead of a Brimar 6b7a. Many here recommended the CV4068 with adapter but I had to wait for a replacement adapter from Deyan, which gave me more time with the 6bq7a. The CV4068 was one level better, it opened things up even more. Next up was a Sylvania 6K7B and it opened things up even more, but added some extra heft in the bass (which works great for the NECs, but I don't think would work as well with the JJs). 6BK7Bs are so cheap that I splurged and bought a bunch - GE, RCA, more Sylvania and an Amperex. The Amperex 6BK7B stands out the most - I went through some others but came back to the Amperex. (GE was not as nice as the Sylvania).

    The Stratus cured any upgradeitis so now I'm just content to settle in and enjoy the tube rolling. It keeps me engaged with the amp in the long term, and the Stratus expresses the tubes' sonic differences so capably that rolling helps me discover the boundaries of the amp. Next up is an incoming Mullard GZ34 (I don't have the switch).

    Edit: updating this to note that I've since moved back to the CV4068 as I find it presents a more cohesive, musical sound. The 6BK7B had better dynamics, and they really stood out, but I feel like 4058 coalesces the macrodynamic into a cohesive experience. GZ34 has opened up and expanded the stage more than the 5U4GBs.
    Edit 2: back to the Amperex BK7B. Synergizes with the GZ34 opening things up, now feels like there's more placement options/room for the increased dynamics and they sound more natural.
     
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    Last edited: Jan 20, 2023
  13. ogharaei

    ogharaei New

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    Not to derail the thread as it, having read through parts, seems to focus on tube options - I put down a deposit for the Stratus V4 in November since I love the Starlett and am wondering about DAC options - any thoughts on, say, the Crane Song Solaris over AES from the source with the Stratus?

    I like the clean neutral-ish tone and slightly analytical nature of the Soekris dac2541 (not boring, though) with the Starlett, but feel better layering and detail are perhaps possible.

    However, consumer DACs that have the same tonality with better technicalities seem to be considerably more expensive, which has me looking at pro DAC options.
     
  14. earnmyturns

    earnmyturns Smartest friend

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    If you own the dac2541, it'd suggest you wait until you have the Stratus to decide whether to replace it. In particular, different filter choices may make enough of a difference to the overall result. I own a dac2541 for one small system, and a lot more expensive DAC setups for two larger systems, and I'd not put down the dac2541 technicalities without listening to it in combination with the rest of your intended chain.
     
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  15. ogharaei

    ogharaei New

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    Thank you, earmyturns. That makes a lot of sense as I do like the dac2541. My guess is that I inadvertently feel pressured to grab a DAC now because they have become considerably more expensive over the past few months. The pro DAC world seems a little more stable in that regard. That having been said, the Solaris, if I were to grab it, also has huge lead times here in Europe (and probably elsewhere), which does not help.
     
  16. earnmyturns

    earnmyturns Smartest friend

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    Some digital components like DSP and DAC chips are still in short supply, thus the higher prices and long lead times. But with higher interest rates across North America and Europe, demand may be slacking off a bit, so it's not obvious that prices won't moderate next year. Given how long it will take for your Stratus to arrive, in your shoes I'd take the bet to wait.
     
  17. RestoredSparda

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    It looks like you would need an xlr to rca adapter as well. The Solaris is XLR balanced out only, and the DNA Stratus has RCA single ended inputs only.

    An ISOMAX unit would work, but I'm not sure how hot the outputs are on the Solaris. The Stratus already has pretty high gain with single ended dacs rated at around 2vrms output. It sounds like the Solaris has adjustable levels on one set of its XLR outputs but I'm no expert with that unit. Just something to keep in mind when using a pro dac with a Stratus.
     
  18. ogharaei

    ogharaei New

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    I think the pad + attenuation in the Solaris would work, and it is purportedly a good implementation, but I need to look into it some more. I have the Jensen PI-2XR somewhere as well, but it is a 1:1 converter.

    I will post in the respective Solaris thread should any Solaris-specific conerns I can't figure out crop up.

    Huge thanks for the suggestions and help concerning DACs for the Stratus. I will probably hold off on a DAC for now.
     
    Last edited: Jan 15, 2023
  19. ColtMrFire

    ColtMrFire Writes better fan fics than you

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    FWIW/grain of salt, but I think the DNA amps work better (at least for me) with more linear/neutral/drier sounding DACs. When I owned the Starlett I did not like it with the Bifrost 2, but loved it with the NAD M51 (very neutral). I also thought @Erroneous ' Stellaris worked great with the Holo May and I consider the Holo DACs dry sounding. Haven't tried the 2541, but I've heard it is on the more linear side of the spectrum.
     
  20. ChaChaRealSmooth

    ChaChaRealSmooth SBAF's Mr. Bean

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    If I were you I'd actually keep the 2541 until the amp arrives. Then afterwards you can see if you still would like to change things up. Personally I think the 2541 has wonderful synergy with DNA amps.
     
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