Neurochrome HP-1: Ultra-High End Headphone Amp
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bazelio

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I thought I'd start a thread dedicated to the new headphone amp design by Tom Christiansen (Neurochrome).  This can be ordered pre-built, or as a partial-DIY project where Neurochrome supplies the PCB, chassis, and BOM list.  I'd caught wind of this amp a while back, and preordered the PCB from Neurochrome before manufacturing had completed.  Now that Tom has notified me that boards are shipping imminently, I thought I'd get this thread started.
 
Full specs for the Neurochrome HP-1 are available here.  Tom seems to have set out to produce the ultimate "wire with gain" in the HP-1, delivering 3W/20Ω, 450mW/300Ω @ 0.000032% THD!  He's using the OPA1612 differential receiver and LME49600 output stage in a loop with an OPA1611.  
 
I've never heard this headphone amp, so am taking a flier on it based solely on my admiration for Tom's circuit design skills.  It has also been quite a long while since I've done any SMD soldering, so it'll be a fun project.  I'll post some pics of the build as I go and listening impressions at project completion.  Meanwhile, my box o' Mouser BOM parts is ready to go!
 
BTW, this proto unit built by Tom is also going to be making the rounds in the US among some hobbyists.  And it has been auditioned up in Canada at a local Head-Fi meet, from what I understand:
 

 
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tomchr

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Thank you for starting a build thread. I greatly appreciate it. It's always fun to see people's builds come together. Best of luck with the build process. Should you get stuck along the way, you know where to find me and I'll be happy to help.
 
Thanks,
 
Tom
 
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bluemonkeyflyer

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I've built several amps and other DIY projects. In order of easiest to most challenging to build:
 
Cavalli Bijou amp
AMB Epsilon 12 protection module
AMB-Cavalli CK2III amp
Meier Porta-Corda III Amp/DAC
Cavalli EHHA Rev A amp
Sjostrom QRV-08 amp and another PCB and BOM on the way
 
I've also built several Crossfeed modules and numerous headphone measurement kits with mics and phantom power supplies for myself and others. My next build will be Frans' Kameleon II amp and filter modules with all boards and BOMs ready to go. 
 
While reading on Sjostrom's site, I saw Christiansen's review and measurements of QRV-08. Reading a bit further, I learned that Christiansen has an amp of his own that looks interesting....Neurochrome HP-1 which looks much simpler to build than QRV-08. If possible, I'd like to participate in the Neurochrome HP-1 audition tour. I look forward to others' impressions and reviews.
 
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jh4db536

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I'll be building an HP1 along side bazelio. My PCB should be here next Friday if the holiday shipping madness permits.

Edit this is going to take longer than i thought, but im having a blast :). Build strategy for me will be start at the center of the dense component clusters and work outwards. I'll wait for Baz to post his impressions before mine, not to hijack.




All 804 sized SMD is complete. I deviated from the recommended build strategy, but I got to the same destination (I personally would do it the same way if I had to build another one). Just need to populate aluminum caps, relays, and the linear tech opamps. Through hole is cake...I could have this done in an hour or two.


 
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Armaegis

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I was the first one the leg of the tour and will hopefully have my writeup done soon (I was really hoping to get it done last week... and the weekend before that, but life gets nutty in December).
 
 
 If possible, I'd like to participate in the Neurochrome HP-1 audition tour. I look forward to others' impressions and reviews.
 
I'm coordinating on another site. I'll see about getting you on the list.
 
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tomchr

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I suggest the following assembly sequence:
 
1) Resistors and ceramic caps
2) Inductors L1, L2
3) Electrolytic caps
4) Diodes
5) ICs
6) Leaded parts
 
That way you work from least ESD sensitive to most ESD sensitive and from low to high in terms of size. The inductors do need to go on before the electrolytic caps, otherwise it gets difficult to get at the inductor terminals to solder them.
 
Make sure all connectors and switches are mounted perfectly perpendicular to the board and flush against the board. If you're getting board + chassis, I suggest using the front and rear panels as guides to get the spacing right on connectors and switches. It's not hard to do but does require a little attention to detail.
 
Tom
 
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Beng Yeow

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Appreciate feedback from people who have heard this amp.
 
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Armaegis

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  Appreciate feedback from people who have heard this amp.
 
Ask me something more specific and I'll do my best to answer.
 
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Beng Yeow

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If you were to gauge its performance in comparison with what's available on the existing market, which one would it be on par with? Is there any weakness to the design?
 
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bazelio

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I'll be building an HP1 along side bazelio. My PCB should be here next Friday if the holiday shipping madness permits.

Edit this is going to take longer than i thought, but im having a blast
. Build strategy for me will be start at the center of the dense component clusters and work outwards. I'll wait for Baz to post his impressions before mine, not to hijack.
 
 
Nah, don't wait for me, buddy.  I may not get to it before my Christmas break is over at this point.  Vinyl rigs and complete room reconfiguration is getting in the way of sitting down and soldering.  Because, literally, my soldering station is a temporary storage space at the moment.
 
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Armaegis

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  If you were to gauge its performance in comparison with what's available on the existing market, which one would it be on par with? Is there any weakness to the design?
 
In terms of measurements, I don't think anything else on the market touches it with the exception of perhaps the Benchmark AHB2.
 
The main weakness is masked simultaneously as its strength. It is a dry clean amp, which many people are not used to and may not necessarily like. Personally, I like the extra warmth of my Bryston amp, but it is not nearly as resolving as the HP-1. It was easier for me to tell dacs apart with the Neurochrome.
 
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Beng Yeow

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In terms of measurements, I don't think anything else on the market touches it with the exception of perhaps the Benchmark AHB2.
 
The main weakness is masked simultaneously as its strength. It is a dry clean amp, which many people are not used to and may not necessarily like. Personally, I like the extra warmth of my Bryston amp, but it is not nearly as resolving as the HP-1. It was easier for me to tell dacs apart with the Neurochrome.
 
Meaning to say its a clean amp to amplifier what it receives and as such it has to be paired with a good DAC.
 
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