Neurochrome HP-1

Discussion in 'Headphone Amplifiers and Combo (DAC/Amp) Units' started by Cspirou, Oct 26, 2016.

  1. Armaegis

    Armaegis Friend

    Pyrate BWC
    Joined:
    Sep 27, 2015
    Likes Received:
    7,461
    Trophy Points:
    113
    Location:
    Winnipeg
    I'd like to hear his thoughts against those who consider switch mode supplies (or even class d amps) to be the devil's anus.
     
  2. Hrodulf

    Hrodulf Prohibited from acting as an MOT until year 2050

    Pyrate
    Joined:
    Sep 28, 2015
    Likes Received:
    4,276
    Trophy Points:
    113
    Doubt that it's class-A, doesn't really need to be. For me class-A feels good, but I've never really seen the benefits. Class-AB when biased properly has no problem with IMD and let's you sweat about thermals less. Heck, half of the Schiit amps are class-AB and no one's complaining about the "clunk" when they go to class-B.
     
  3. chakku

    chakku Friend

    Pyrate
    Joined:
    Oct 13, 2015
    Likes Received:
    676
    Trophy Points:
    93
    Location:
    NZ
    Every time linear vs switching is brought up I'm reminded of this: (Skip to 7:50)



    On a more related note for the amp, it looks tempting but at the same time sourcing components over here isn't as easy.
     
    Last edited: Oct 27, 2016
  4. Hrodulf

    Hrodulf Prohibited from acting as an MOT until year 2050

    Pyrate
    Joined:
    Sep 28, 2015
    Likes Received:
    4,276
    Trophy Points:
    113
    Well, sure - the SMPS won't be audible. The question is how overall system performance changes with similar powered SMPS and linear supplies.

    Also keep in mind that not all SMPS'es are created equal.
     
  5. chakku

    chakku Friend

    Pyrate
    Joined:
    Oct 13, 2015
    Likes Received:
    676
    Trophy Points:
    93
    Location:
    NZ
    Of course, though if he's boasting specs like this and calling it 'ultra high end' he would be shooting himself in the foot using a bad SMPS.
     
  6. Armaegis

    Armaegis Friend

    Pyrate BWC
    Joined:
    Sep 27, 2015
    Likes Received:
    7,461
    Trophy Points:
    113
    Location:
    Winnipeg
    It's all fine and dandy to shove extra filter voodoo after the SMPS to clean it up, but what about the gunk that worms its way back into your mains? I'm not saying the HP-1 is guilty of this, but I'm curious if designers ever take this into consideration.

    I know there are regulations on how much emi/rfi devices are allowed to put out, and I know they are becoming more strict, but don't know any specifics beyond that.
     
  7. ultrabike

    ultrabike Measurbator - Admin

    Staff Member Pyrate MZR
    Joined:
    Sep 25, 2015
    Likes Received:
    8,960
    Trophy Points:
    113
    Location:
    Irvine CA
    I dunno the specifics of the IRM-20-24. But the datasheet does specify an EMI filter, which according to their website complies with EN55022 class B w/o any extra components.

    For more information about this standard, and the limits imposed on emissions this is a good read:
    http://www.digikey.com/en/articles/...lity-standards-for-switch-mode-power-supplies

    Is this good nuf? I dunno. But I would be surprised if this is an issue. Could be though.
     
  8. Cspirou

    Cspirou They call me Sparky

    Pyrate
    Joined:
    Sep 27, 2015
    Likes Received:
    8,200
    Trophy Points:
    113
    Location:
    Northwest France
    I don't think the power output of the switcher is an indication of how much power it consumes. SMPS modules can be extremely efficient for their size and it would be a given that they can output a lot of power. Rather I think he went for this because it's a high quality switcher with low emi/rfi radiation as well as the high voltage output. I think I've seen ECP Audio use them in a bunch of products. If he thinks like an engineer I am sure he considers SMPS/Class AB to have fundamental problems compared to linear/Class A, however those problems can be minimized to a point where it's below system noise.

    On the plus side this means universal acceptance of international voltages for us travelers. Which as long as we are comparing the T3 again, has fixed voltage settings.

    I remember reading that he runs a pretty high bias so their products run into class-A for most people. Which would explain power consumption when idle. Planar magnetics will run into AB but high impedance and IEMs will firmly be in the class A region, even for the Magni.
     
    Last edited: Oct 28, 2016
  9. ultrabike

    ultrabike Measurbator - Admin

    Staff Member Pyrate MZR
    Joined:
    Sep 25, 2015
    Likes Received:
    8,960
    Trophy Points:
    113
    Location:
    Irvine CA
    I actually prefer Class A/B. Because of efficiency and thermal considerations. But I don't necessarily feel strongly about it either. And my view of the world is not necessarily the only one. Other folks may feel strongly either way, and may want to know a bit more about the topology.

    I also noticed the IRM-24-20 Vin ranges from 85 to 264 V which indeed seems like a nice option for international situations. It's a pretty interesting design.
     
  10. Cspirou

    Cspirou They call me Sparky

    Pyrate
    Joined:
    Sep 27, 2015
    Likes Received:
    8,200
    Trophy Points:
    113
    Location:
    Northwest France
    Some more investigating on the volume. He also offers a differential preamp

    http://www.neurochrome.com/differential-preamp-8x2-r1-0/

    Even though all inputs and outputs are XLR he still uses a stereo pot. I have no reason to believe that he would use something different for the HP amp and it's very likely to be active. I'll read up what he has to say on diyaudio about this.
     
  11. Hrodulf

    Hrodulf Prohibited from acting as an MOT until year 2050

    Pyrate
    Joined:
    Sep 28, 2015
    Likes Received:
    4,276
    Trophy Points:
    113
    The preamp uses THAT differential summers/splitters. I believe that inside it's all SE.

    I mean, it makes sense if one believes that THAT IC's are fully transparent and balanced signalling is useful for external cables.
     
  12. Armaegis

    Armaegis Friend

    Pyrate BWC
    Joined:
    Sep 27, 2015
    Likes Received:
    7,461
    Trophy Points:
    113
    Location:
    Winnipeg

    Seems like that only applies to stuff into the MHz range. There's always bunk like CLF/LED lights and laptop bricks etc. I'm sure those pass whatever regulations there are, and yet there is a ton of gunk that modulates back down into the audible band.


     
  13. bazelio

    bazelio Friend

    Pyrate
    Joined:
    Nov 16, 2015
    Likes Received:
    3,417
    Trophy Points:
    113
    Tom sent me some design notes on the HP-1. Here they are:

    All signal routing and gain select is done with Kemet goldpoint relays to shorten the signal path as much as possible. The differential input is kept differential right up to the input selector relay. From there it’s single-ended to the volume pot and out. The opamps are OPA1611 and OPA1612. OPA2140 is used for the (four) DC servos - one servo per LME49600. I use two LME49600 sections in parallel to have enough output current drive for loads below 68 Ω. That’s how I get 3 W into 20-32 Ω from an IC… :)

    There’s no technical advantage but a lot of technical disadvantages of differential output drive. Thus, the 4-pin XLR is simply in parallel with the 1/4” phone jack. You do get the advantage of the separate ground leads per speaker if using the 4-pin connector, though.

    Also note that the amp is protected against DC on the output. In addition, the on-board voltage regulators are protected such that if one rail collapses, the other will be shut down. You will never end up with an unbalanced supply.
     
  14. ultrabike

    ultrabike Measurbator - Admin

    Staff Member Pyrate MZR
    Joined:
    Sep 25, 2015
    Likes Received:
    8,960
    Trophy Points:
    113
    Location:
    Irvine CA
    I think SBAF gates are closed temporarily. Once they are open, I would love to see the likes of Tom around here.

    The parallel current drive with the LME49600 sounds very similar to what was done in the O2 using the NJM4556 instead and makes sense to me given most op-amps have limited current drive capabilities. The idea seems to date back to this 2005 app note from Intersil:

    http://www.intersil.com/content/dam/Intersil/documents/an11/an1111.pdf

    But it maybe older than that. Note Rbm in the O2 is 1 ohm to limit offset current between the amps while still keeping a low output impedance.

    If I was doing my own stuff, I would definitively do that as well.

    Tom design seems to be a full TI implementation which makes sense given his background and possible experience with the parts. NwAvGuy seems to be more partial towards NJM (including the power management circuitry) which may also indicate he has more experience with such parts.

    It's good to see he added a servo for the DC offsets. Not all designs do this.

    I would love to see more discussion about the disadvantages of differential output drive. Is it due to mismatching?

    I think I understand that the amplifier is single ended and something is done to get balanced output out of it. But I don't know what is meant by "Thus, the 4-pin XLR is simply in parallel with the 1/4” phone jack". I think it means this:

    unbalanced_balanced.png

    (Output being the Amp output, Input being the Headphone input)
     
    Last edited: Oct 28, 2016
  15. Cspirou

    Cspirou They call me Sparky

    Pyrate
    Joined:
    Sep 27, 2015
    Likes Received:
    8,200
    Trophy Points:
    113
    Location:
    Northwest France
    I wonder if the SBAF policy can be changed to have a 'Friend' sponsor new members, at least for now. Sort of like how gmail started.

    I don't know too much about the technical aspects but I have read that it's better to get an amp that can can properly power your gear as opposed to getting two amps in the BTL configuration. The BTL is sort of a compromise to get to the power you need.

    To me my understanding is that the 4 pin jack is wired as if you are using a 4 pin -> 6.5mm adapter and plugging into the phono jack. However there are still benefits to using the 4-pin due to separate grounds.
     
  16. Armaegis

    Armaegis Friend

    Pyrate BWC
    Joined:
    Sep 27, 2015
    Likes Received:
    7,461
    Trophy Points:
    113
    Location:
    Winnipeg

    I'm sure parallel outputs dates back to the early days of tubes. Nothing new there.

    If you've got a bridged configuration and if everything is *perfectly* matched up, then you will get a reduction of some of the harmonics (evens I believe; my brain isn't working right now). If they aren't all magically aligned, you'll get more power but potentially just mush distortions into each other. Granted, having all the extra headroom and power available may in fact be sonically better (ignore distortion numbers which are probably insignificant anyways) so a couple blips on a THD chart isn't the end of the world. Or maybe your ground is so amazingly crapola that a bridged config is actually somewhat better.

    An inherently balanced topology like SuSy or Circlotron or Pivot Point is a different beast, but those topologies are very different and probably not compatible with the IC's that Tom is using in any meaningful ways, so perhaps outside the scope of this project of his.
     
  17. bazelio

    bazelio Friend

    Pyrate
    Joined:
    Nov 16, 2015
    Likes Received:
    3,417
    Trophy Points:
    113
    Yeah, I think Tom is interested in spreading the word about his products/designs, but just doesn't really spend much time doing so. I'd be thrilled to have him here and if we want to make exceptions or allow for sponsorships, I could extend an invite to him. I reckon his participation in the forum would be very similar in content to Doug's.

    PS I'm going to build one of these. I just have to hear it.
     
  18. ultrabike

    ultrabike Measurbator - Admin

    Staff Member Pyrate MZR
    Joined:
    Sep 25, 2015
    Likes Received:
    8,960
    Trophy Points:
    113
    Location:
    Irvine CA
    Ask Tom if he is interested in joining. Let him know about the vibe here. It is not 100% objective. More like 48.8128%, and tolerant to different views as long as they are not way out there and folks don't preach their truths as the only truth.

    If so, send a PM to the Matrix Architect, God Ex Machina, and Messiah: @Marvey and see what can be done to accommodate such request. I'm all for it BTW.

    Also, will be looking forward for your build and your impressions.
     
  19. Cspirou

    Cspirou They call me Sparky

    Pyrate
    Joined:
    Sep 27, 2015
    Likes Received:
    8,200
    Trophy Points:
    113
    Location:
    Northwest France
    He has tube amp builds. An objectivist that likes tubes is ok with me.
     
  20. M3NTAL

    M3NTAL Friend

    Pyrate
    Joined:
    Sep 27, 2015
    Likes Received:
    1,697
    Trophy Points:
    113
    Location:
    Arizona
    How much work is involved with installing the circuit board into the chassis? Buying the two separate would save quite a bit.
     

Share This Page