Neurochrome HP-2

If you’re familiar with TCA Audio, he has several DIY projects available under the brand Neurochrome.

Type: Solid State Amp
Budget: $100 for the PCB, $150-ish for parts, add $200 for a custom chassis designed for the project

Balanced and RCA input, single ended output. Low and high gain can be changed via jumper on the PCB. Low gain is more than enough to destroy your hearing using your HD6xx.

Covid has me doing all kinds of projects at home and now I’m on a DIY kick. I just finished my build and the end product is quite nice. Building it took two evenings. The build of the HP-2 is very straightforward. It’s hard to say this is a good first project but definitely an easy second project. There are 2 surface mount chips and it’s helpful to know what to expect with a BOM and how to test DC on a board without pics.

Note that I feel new to the hobby and am a little unsure about my experience and being able to articulate it. Half an hour in, it is neutral and clean without being clinical. The Magni 3+ is a good amp but it goes to treadmill at the gym while this goes straight to the weightroom. 30 minute impression using a Bifrost 2 and Ananda).

Given the total kit for the Whammy is about half of this, I’m not 100% sure about the value. I’m interested in testing those side by side along with say my Asgard 3 and Magni 3+. The chassis is nice though.

I’m interested in loaning this out after I let it burn in and compare it to other things I have.


I just have a shitty iPhone 7, ok? :grinning:


Interesting DIY project. From their site:

Two OPA1656 headphone driver opamps form the output stage.

I think comparison-wise, this should be done against other chip-based driven amps. E.g.: Magni Heresy, L30, or others in the same category.

I don’t have much experience with op-amps either, but my gut-feeling tells me they “all sound the same” once the golden ears inside you kicks in. That is the reason why we tend to like the “colors” of fully discrete amps, such as Asgard, Magni 3+ and many others.

More parts. More colors. More risk of failures down the road. More fun. :stuck_out_tongue:


In general I think you’re right. I’ve had a Magni Heresy and ditched it because of the sound. This sounds nothing like it. The Heresy sounded clinical, sterile, acerbic. This is very clean but it doesn’t have the rough edge of the Heresy.


Note I’m not against op-amps. I’m just convinced that all we need is one of their specimen to taste their (lack of?) spice. :wink:

I could be wrong though, of course.

btw, if anyone is looking into this, the Panasonic 3300uF caps are out of stock. But you need them because any replacement is going to be too big for the chassis. so… i’ll be using mine without a lid for a month.

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Wanted to write some formal review thoughts. I have some time to play with this amp today.

About me: I’m not in a position to spend more than about $500 on a piece of equipment. Yet. Maybe when I get rid of some stuff and save up. “Why don’t you save up for…” I dunno. It’s a lot easier to justify to myself and my wife that I didn’t spend x on a single thing. I made an exception for the Bifrost 2 because of what it is. Also covid hobbies are a thing since I’m never leaving the house ever again. Remember concerts? Those were fun. Building things keeps me busy.

Cost: $99 for the pcb, less than $200 for parts from mouser, $200 for the custom chassis.

The HP-2 has balanced and single-ended inputs. Only single ended outputs. Low (+5db) and high (+15db) gain option can be switched using jumpers on the board. All listening impressions are on low gain. That’s more than enough to be too loud on the 6xx.

I do not have an opamp based amp to compare this to. I do have an iFi Zen and Hip Dac, but those are combo devices. I have a lot of Schiit gear and this is my 2nd DIY project that I’ve finished.

I don’t know what a “high end” Topping amp sounds like, and I don’t want to know. I had a Topping NX4 and sold it. I had a Heresy and sold it. I have other solid state amps to compare, but they are all discrete circuit. The HP-2 is an opamp based circuit. The recommendation is to use OPA1656, but those were out of stock at the time I built this so I have used the OPA1612.

Chain: Bifrost 2 → balanced cables → HP-2 → 6xx or Ananda

I don’t know what a “reference” amp would sound like, but this is the closest I have experienced to what I would think that sounds like. Little to no coloration, highlighting the music and every detail possible, but remaining musical. If you don’t want a tube sound, this is an excellent implementation.


  • The HP-2 is a detail monster. I feel like I’m hearing small details that I did not pick up on when using the Lyr 3, Asgard 3, or Vali 2+. I feel like I may be imaging things but every time I’ve said that someone on the forum has said, “No, I hear that too.”
  • The HP-2 is clean without crossing the line into clinical. It is not rough around the edges. The Heresy and NX4 were…kind of boring or even rough. Clinical to a fault. Harsh. My BTR5 isn’t my favorite probably for the same reasons. However, I do like the iFi products, probably because of the color the Burr Brown DAC gives the music. There is no harshness on the HP-2. It attempts to be neutral and clean and I think it succeeds. The HP-2 doesn’t alter the music, it lets the music shine through. I felt the other opamp designs I’ve heard needed some color in the chain. This lets the DAC and the headphones do their job. What I have learned is that even opamp implementation matters.
  • Sounds really damn good with the HD6xx


  • If you are pinching pennies, you can probably order a custom chassis elsewhere for less. All of the components on the back of the chassis are connected to the PCB. There are only 3 that are wired and one uses a ribbon (which is genius and fantastic). Knowing that, it would be easy to measure holes for the back of a chassis and customize the front to your liking.
  • Build time is straightforward, but stuffing the PCB may take longer than other projects. There are a shit ton of components. 70 resistors I think?

Why you want this: You want a really powerful clean amp that doesn’t add color but doesn’t detract from the music. You want an amp that highlights every detail and gets out of the way.

Why you don’t: You don’t like building things, that’s scary. You want the amp to color the music (tube, Asgard 2, etc.). You think all opamp amps are created equal (listening to this has me questioning this assumption - that most opamp amps are created equal but some may not be).

Value: From what I’ve seen on the market, under $400 (assuming you order your own custom chassis) for an amp like this is a very good value.


Sounds like it was money well spent, just from the experience of building it, so it’s a bonus that you also like the finished product.

I only have one op-amp amp (Burson Soloist) so I have no idea if all op-amps sound the same, but what you describe is very similar to what I hear from the Burson: clean and neutral, but very musical.

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Hey. Thank you for your writeup. I really appreciate it. It sounds like your build came together pretty well overall.

A couple of comments:

  • No, not all opamps sound the same. Some of them can deliver enough output current to make useful headphone amps, others can’t. It makes a difference. In the end what matters are the device characteristics and the end-to-end (and in-system) performance of the circuit. How you get there is really quite irrelevant (in my perhaps not so humble opinion).
  • You can certainly cook your own chassis. Many do. The one you find available on my website is from ModuShop in Italy. They do nice work. With the modifications I make to the stock chassis - especially those to the front panel - are pretty expensive. The cost of the chassis would be about $300 if you were to order QTY = 1 from ModuShop directly. I get a bulk discount because I order a year’s worth of inventory at a time. I share some of that bulk discount with you and pocket the rest.

Your point about my products being clean and powerful without colouration is spot on. That’s exactly what I design for (and I have the measurements to back up my claims). You wouldn’t drink good wine from dirty glasses, so why listen to good music through a dirty amp? That’s my take on it anyway. :slight_smile:

If you’re not up for building your own, you can always consider my Tom Christiansen Audio brand: The HPA-10 is not that much more than the HP-2.



I really appreciate how much you are involved in the forums. I really love the amp and I’m excited to keep using it. Zero regrets.


That’s heartwarming to hear. Thank you!


Tom did a recent interview too, quite lengthy but worth watching.