The Mjolnir 2 thread

Discussion in 'Headphone Amplifiers and Combo (DAC/Amp) Units' started by maxedfx, Oct 11, 2015.

  1. winders

    winders boomer

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    My Topaz Isolation Transformer is a 120/240v version. Would that not be an option in the UK?
     
  2. SSL

    SSL Friend

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    I'll look around later when I have a moment because I'm pretty sure I saw something equivalent for 220v power.
     
  3. zonto

    zonto Friend

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    Randomly read through most of that thread this morning, so I'll save you the trouble:
     
  4. Kattefjaes

    Kattefjaes Mostly Harmless

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    Firstly, thanks for digging out the links!

    Sadly, none of that actually looks like an actual finished unit usable safely off-the-shelf, though. I don't have the space, or tools to start DIYing, either. I will continue trying to find a UK dealer with finished products to sell. I'm afraid I have the retail patience of @Torq though, which makes this whole exercise like pulling teeth :)
     
    Last edited: Jun 7, 2017
  5. mrflibble

    mrflibble Friend

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    I'm no expert, but I had a look on Amazon and Mains Cables R Us (MCRU). They carry the IsoTek, which seem to be well regarded but expensive. MCRU also have their own filters. They have a DC blocker (a standard and ultimate model):

    https://www.mains-cables-r-us.co.uk/mains-products/1128-mcru-in-line-dc-blocker.html

    Not sure if it is what you are looking for and no idea if it is any good.

    I've also read good things about the Surgex SX2213, but I'm not sure if you can purchase them direct from the UK dealer:

    http://www.rgbcomms.co.uk/products/...subcat_c=&subcat_d=&offset=&item_no=SG-SX2213
    http://www.rgbcomms.co.uk/products/...bcat_c=&subcat_d=&offset=&item_no=SG-SX2213RL

    They used to be available on Amazon and some chap (or chapess) really liked it:

    https://www.amazon.co.uk/Surgex-International-SX2213-Mountable-Eliminator/dp/B009M4ZI0M
    https://www.amazon.co.uk/Surgex-International-SX2213RL-Eliminator-Connectors/dp/B009M4ZI1Q

    EDIT: For some reason the read more link doesn't work on the amazon review, try this link instead:

    https://www.amazon.co.uk/review/R1FUQGGA8SNDRA
     
  6. Kattefjaes

    Kattefjaes Mostly Harmless

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    Yeah. the MCRU one might be a goer (if slightly overpriced), though it will involve cross-examining them on stuff like actual power rating, as they seem to have left all info off the page for that specific model. The £175 one is rated for 5 watts, which is a joke- not even enough for most DACs, let alone a headamp.

    Edit:

    So, it turns out that by "5 watts", they actually mean "5 amps". Mixing that up doesn't exactly inspire confidence. There appears to have been some hasty editing/deleting of web pages. The page with the "5 watts" device has now vanished. The remaining page showing a device using that same design doesn't mention any useful specifications, though.

    Edit the second:

    The £250 one is also on Amazon, for a whole 40p more, where it lists it as 5 amp, which means plenty of rated wattage.

    I guess it's an option, though it's a bit annoying that it has a short captive output lead- I've noticed some tube amps get funny if too close to other transformers, sometimes. I think I'll try to get the Edwards one, with a non-captive output, so I can at least have the box a meter away from the amp. However, I now have two pretty decent options - thanks for the MCRU suggestion.
     
    Last edited: Jun 8, 2017
  7. k1arg

    k1arg Facebook Friend

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    Not an isolation transformer, but I have a 230V DC blocker from ATL HiFi that has helped significantly with transformer hum. Are you aware of that and concluded that it's not appropriate?
     
  8. SSL

    SSL Friend

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    That's the one I was thinking of.
     
  9. BenjaminBore

    BenjaminBore Friend

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    So what are the pros and cons of having an isolation transformer vs an RFI/EMI filter and DC blocker combo?

    Hello @k1arg, That's great to hear. Do you feel that there are any audible differences?
     
    Last edited: Jun 10, 2017
  10. Kattefjaes

    Kattefjaes Mostly Harmless

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    (Can't quote, but in reply to both @k1arg and @BenjaminBore )

    That looks like a good option, at a decent price- using cap-fu does make sense. The explanation of the circuit:

    http://webcache.googleusercontent.c...tm+&cd=1&hl=en&ct=clnk&gl=uk&client=firefox-b

    --also looks reasonably sensible. It's probably not a bad option at all. That said, isolation transformers have some secondary benefits- especially if you sometimes like to poke at live circuits (but keep one hand in your pocket!). I'll see if that Edwards unit comes back into stock at a reasonable price, initially (given how terrible the MCRU website is at having actual info, and the fact that he doesn't really answer questions). However, that's a potentially good option- especially if the outgoing mains socket is mounted upside-down, so it could neatly sit in the floor under the desk with the cable run staying nice and neat.

    Thanks @k1arg - and apologies to the forum in general for the threadjack- but the info that has emerged is really useful. When the site doesn't look like hell, I will have a go at spaffing some of it into the power conditioning thread, if I remember.
     
  11. gaspasser

    gaspasser Flatulence Maestro

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  12. winders

    winders boomer

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  13. a44100Hz

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    The Emotiva CMX-2 seems to be making a difference. Before, after getting rid of the air purifier, the Mjo 2 with the WE396A tubes was non-fatiguing... now it seems that even the crisp Miniwatts are non-fatiguing (previously they were). I can actually use this amp now. :)
     
  14. Delayeed

    Delayeed Facebook Friend

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    Hell yeah, that is great to hear! After got my Gungnir Multibit few days ago it helped me a lot with fatigue. I'm still in disbelief every time I come back and put a song on. There's no fatigue anymore as the transients seem super resolved and not harsh slaps to the face and can even enjoy rock and metal now. It still seems to get better... :headbang:
     
  15. Darren G

    Darren G Friend

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    I also felt the MJ2 was slapping me upside the head at times using the balanced output. I made two changes near simultaneously; upgrade Bifrost Multibit to Yggdrasil, and I had moved both to a different 120V socket. A DC offset issue (as mentioned above) had never occurred to me, but I suppose that's possible. Can't say I was hearing any noise, but does anyone know if the Circlotron topology is above average adversely affected by DC offset?

    Either way, whether Yggdrasil, the socket, or both made a difference, the MJ2 has turned out to be a very pleasant (lush, clear, powerful) sounding amp.
     
  16. GoodEnoughGear

    GoodEnoughGear Evil Dr. Shultz‎

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  17. gaspasser

    gaspasser Flatulence Maestro

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    I think the MJ2 is resolves inputs to such a high degree that you are describing the change in DAC and possibly the change in quality of electricity.

    With HD650KM, moving from Valhalla 2 to MJ2 has really shown how much more Gungnir Multibit is providing. I don't believe I have any DC offset issues because I would describe the overall sound I am getting as "lush, clear and powerful" as well. Compared to Valhalla 2, there is a decrease in head stage but the MJ2 has a huge presence and drive from drums and bass that I sorely missed.
     
  18. zonto

    zonto Friend

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    I'm not an expert in these matters, but I think there's a lot of misdiagnosis of electrical system interference and noise as DC offset in this thread. From what I've read, DC offset issues most commonly present themselves as loud humming or buzzing coming directly from the audio equipment (i.e., its power transformer) itself, not through the speakers/headphones. One example: https://pooraudiophile.com/2015/03/how-to-fix-dc-offset-and-transformer.html.

    There are many noisy devices that when running may negatively affect the sound quality of your audio equipment. They may not be causing DC offset, but rather excessive distortion/load on the line or chopping up the signal with switching power supplies. The trick is to block this type of interference, and the interference pushed back on the line by audio components themselves, without unduly limiting current to your audio equipment.
     
    Last edited: Jun 14, 2017
  19. Garns

    Garns Friend

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    Agreed. I have both a Furman power conditioner and an ATL hifi DC blocker. The Furman makes a huge positive difference to the sound. The DC blocker doesn't seem to change the sound in any noticeable way, and may make it slightly worse. In fact this is not why I have the DC blocker; rather I use it on the linear power supply to my small form factor PC which hums quite a bit. It does an excellent job at that. But if you don't have an audible hum to fix and think you have power issues I would bet that 9 times out of 10 something with filtering would be preferable.
     
  20. AllanMarcus

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    My Mj2 and Bifrost Multibit are plugged into a cyberpower UPS (perfect sine wave, if it matters). No noise issues that I'm aware of, but is there any reason I shouldn't use a UPS?
     

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