Review and Measurements of Neurochrome HP-1 High-Performance Amp

[JJB70]

T

If you google "Canada EU trade agreement" you'll find this: Canada-European Union Comprehensive Economic and Trade Agreement (CETA). It went into effect September 21st, 2017.

That won't affect the VAT. In the UK VAT is 20%, VAT is also payable on the postage costs and mail services levy a VAT collection fee for having to administer the customs check on behalf of our actual customs service. On something this expensive that adds up to a very significant additional expense if buying from overseas (it's a major reason I don't find many bargains on Drop compared to buying stuff from regular channels, we can buy Sennheiser HD650 and even HD660S headphones for not much more than the HD6xx if we shop around).

 

[Yviena]

The amp starts to clip at 250 mW into 300 Ω. I could probably play the specmanship game and claim 300 mW (or maybe more) at 10% THD, but that's not how I operate.

Tom

I see so would you say 250mw is enough for transients peaks of 100+db on a HD800?

 

[Azeia]

Exactly, all RCA connectors should be connected to the chassis at the connector. Neil Muncy (RIP) wrote about this some 25 years ago.

This is interesting, do you have an article I can read on this? I'm actually curious how this works, because my understanding was that if you ground the connector this way, you risk creating a ground loop if the device has an earth plug. (In this situation for example, the loop could be from the earth ground on the amp, to the earth ground on a PC, since the DAC would be plugged to PC through USB which has an earth shield).

 

[tomchr]

I see so would you say 250mw is enough for transients peaks of 100+db on a HD800?

1 mW is enough to produce 100 dB SPL in the HD-800, so, yes, 250 mW is plenty. 250mW is enough for 124 dB peaks in the HD-800 - enough to cause permanent hearing damage.

Tom

 

[JohnYang1997]

One thing i have to say is the returned broken d30 must be the issue of Amazon, not a product being cheap.....

 

[tomchr]

One thing i have to say is the returned broken d30 must be the issue of Amazon, not a product being cheap.....

Yeah. It's a vendor issue. But it's the manufacturer's responsibility to select good vendors ... at least if they want to preserve the value of their brand.

Tom

 

[bequietjk]

One day I will find one of these for sale. And I will snag it up! My dream amp!

 

[tomchr]

Yeah... The Neurochrome HP-1 does show up occasionally on the used market. There aren't a lot of them in the world.

Tom

 

[Yviena]

@tomchr Will you make more measurements of the new HP-1 when final PCBs arrive like the 32 tone, IMD 5.5khz, and transient response test that you did for the HP-2?

Also is the HP-2 a higher performing version of HP-1 or...

 

[deafenears]

Also is the HP-2 a higher performing version of HP-1 or...

Way less power though?

 

[Yviena]

Way less power though?

Seems like it has way less power at lower impedances, while higher impedances are a tiny bit better, 10mW difference, the HP-1 seems better for planars due to the higher power output.

 

[tomchr]

@tomchr Will you make more measurements of the new HP-1 when final PCBs arrive like the 32 tone, IMD 5.5khz, and transient response test that you did for the HP-2?

Also is the HP-2 a higher performing version of HP-1 or...

So let's clear up a few things here:

• The Neurochrome HP-1 (now discontinued) was a DIY headphone amp. Many requested it fully built, which is how this thread came into existence.
• The Neurochrome HP-2 (just launched) is a DIY headphone amp. It will not be available as an assembled product. Ever. Not assembled by me anyway. If you can find someone to assemble it for you, great! The HP-2 provides about the same performance as the HP-1 with high-impedance loads. It provides slightly worse performance into low-impedance loads. It also provides much lower output power into low-impedance loads. Those were the tradeoffs I had to make to make the amp all-DIY (and not compete with my TCA products). The HP-2 is currently on into special. The first 10 buyers will save 10%. You can find more information about the HP-2 here: https://neurochrome.com/products/hp-2
• The Tom Christiansen Audio (TCA) HPA-1 is a retail headphone amp. It will never be available as a DIY product. It has been optimized for low-volume mass production (batches of 100-250 amps at a time). My intent was to keep as much of the HP-1 performance as possible while making the amp mass-producible. This required a drastic reduction in BOM cost, and it required the design of a chassis and volume control that provided a better user experience. I was able to meet or exceed many of the HP-1 specs, but I had to trade off some output power. The Neurochrome HP-1 provided 3 W into 32 Ω, the TCA HPA-1 provides 1 W into 32 Ω. Many want 5 W for their planar headphones and neither amp would satisfy those needs. I would also invite those who believe they need 5 W into a headphone to reevaluate need vs want. You can read more about the TCA HPA-1 here: https://www.tomchr.com/products/hpa-1 Note that the first 40 of these are on early-bird special ($649). I've sold 20 of them while hardly doing any advertising. The chassis is in production and the PCBs will go into production by Wednesday. I expect to be able to ship the amps starting around December 20th. At that time (or when 40 amps have sold), the price will go up to $899. You can see the AP test report (with graphs) of the prototype build on the "specifications" tab. I will add all the plots on a "performance graphs" tab once I get the first production batch in. Expect the graphs to show in early December. I will also send a sample to Amir for review.

Some may wonder about all this TCA vs Neurochrome stuff. So here's the deal: DIY is by many perceived as cheap. It turns out it's hard to command a good price for a premium product if your brand is perceived as cheap. Thus, I launched TCA as my retail brand. There are other factors in play as well:

• I increasingly find myself hamstrung with my DIY designs. From my past experience, supporting builds that use surface mounted parts is a nightmare. Using only leaded parts degrades performance as I don't have accesses to the higher performing parts, and it drives up cost as the PCB area grows significantly when leaded parts are used. Thus, expect my Neurochrome products to provide lower performance than my TCA products.
• With my TCA retail designs, all options are open, which allows me to optimize for performance. The main challenge there is to keep the cost under control. Distributors generally take about 30-40% commission. If I use an agent or representative to get in with that distributor, there goes another 5-6%. I need to eat periodically, so I need to keep my margins up in order to survive. That said, I think I can bring to market some very high-performance products at a quite reasonable price.

Anyway. That was a 1000-word response to a yes/no question.... I guess I was in the mood for writing.

Tom

 

[JohnYang1997]

"Distributors generally take about 30-40% commission."
Holy shit. Wasn't expecting that. I thought 20% is about as much as you can get.

Also about 1W from HPA-1, is it limited by thermal? Or something else? 1W into 32ohm is only about 180ma rms and 250ma peak.

 

[bequietjk]

"The Neurochrome HP-1 provided 3 W into 32 Ω, the TCA HPA-1 provides 1 W into 32 Ω. Many want 5 W for their planar headphones and neither amp would satisfy those needs. I would also invite those who believe they need 5 W into a headphone to reevaluate need vs want."

Im interested in this. If i am to build HP2 i will need to dig deeper into this statement, as i was planning to buy a used HP1 at some point to satisfy at least 2-3W of the 4W max my T50RP have.

 

[tomchr]

Also about 1W from HPA-1, is it limited by thermal? Or something else? 1W into 32ohm is only about 180ma rms and 250ma peak.

It's limited by how much clean output current swing the output stage can generate. "Clean" is the important term here. I specify the output power at the point where the THD+N vs output power graph starts shooting up.

Tom

 

[tomchr]

Ugh... This is not the kind of post I enjoy writing: The HPA-1 will be delayed until mid-January. I apologize for the delay. I pulled out all the stops to be able to get these under the Christmas trees world wide, and all was going well until yesterday, when my chassis manufacturer let me know that they had a production issue that affected the surface finish of the chassis and would have to start over. They expect to be able to ship in middle of January, which pushes my shipping date out similarly.

I find it insanely frustrating to have invested an amount of money that's well into the five digits by now only to have the project come to a screeching halt like this. This means I'll miss the Black Friday, Cyber Monday, and Christmas sales. Grr!! Unfortunately sh...tuff happens and this event was completely beyond my control.

I do understand if those who have preordered the HPA-1 are getting impatient. I am too. At least the end result will be well worth the wait. I apologize for the delay.

Onward!

Tom

 

[tomchr]

On a more positive note: The question about the differences between the Neurochrome HP-1 and Tom Christiansen Audio HPA-1 popped up in my brain. I realized some important differences between the HP-1 and the HPA-1 that I haven't touched on previously:

With the Neurochrome HP-1, the chassis was honestly a bit of an afterthought. The HPA-1 chassis design took place concurrently with the PCB layout, which allowed me to optimize the PCB+chassis to enhance the reliability of the final product. Thus, the HPA-1 offers the following improvements:

• Integrated sub-panel/bracket for the headphone jack and volume control. This drastically reduces the stresses on those components and their solder joints for better reliability and durability.
• The TCA HPA-1 uses an Alps RK271-series pot, which offers better channel matching and better durability than the RK097 used in the Neurochrome HP-1.
• The switches used in the TCA HPA-1 are sealed and of higher quality than those used in the Neurochrome HP-1.

Tom

 

[tomchr]

So far the market response to the HPA-1 has been excellent. I've now sold over 20 of them on preorder even though my only advertising has been through word of mouth. I'll push harder on the advertising once I get closer to having amps in stock.

I'm toying with the idea of a Dutch auction inspired pricing scheme for the preorders. My preorder discount is my way of thanking those who are willing to support my business and I early in the project. I think it's completely fair that those who wait the longest get the biggest discount. So I'm thinking to nudge up the pricing to $749 by December 15 and $849 by January 15. I expect to have the amps in stock by the third week of January. At that time, the pricing will be $899 and no further discounts will be available. I'll take a page from Schiit's playbook and just not have sales as they increase prices for everybody. That's also the only thing of Schiit's that I'll copy.

Tom

 

[solderdude]

@tomchr
Your HPA-1 doesn't happen to the 'mystery amp' in a specific, not to be mentioned voldemort type of forum that uses the name of NwAvGuy in vain to make ASR and its owner look bad by any chance ?

 

[tomchr]

I think I know the forum you're referring to. I'm not a fan of the culture there either. I much prefer the culture here. As I wrote in another thread, I firmly believe in science and the self-correcting nature of the scientific method.

If the Forum to Remain Unmentioned is what I think it is, I'm not surprised if an undertow is developing to throw me and my products under the bus. That's happened there before. One of their "trusted ears" didn't like the Neurochrome HP-1 as it didn't include cross-feed. The TCA HPA-1 will be no different, and I suspect the Forum to Remain Unmentioned's reaction to it will be similar. After all, my HPA-1 completely lacks glowing light bulbs sticking out of it, and I actually fundamentally believe in science, the scientific method, and measurements and use this to back up my product claims. Apparently that rubs some the wrong way. Oh, well... I have no plans to advertise any of my TCA products there.

If someone is referring to the HPA-1 as a "mystery amp", they've seriously missed the memo. There's nothing mysterious about it. I demoed it at RMAF and it was well-liked there. I've posted the specs and AP test report on my website (here, to be specific). Here're some pictures of what the final version will look like. Doesn't look very mysterious to me.

Tom