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

[Azeia]

I dinked around in Fusion 360 earlier... Attached should give you a sense of scale.

Really stupid question, but is this just another small testing prototype like the last pic?

I ask because it looks way smaller than I'd have expected the final unit to be; pretty interesting

 

[JohnYang1997]

Really stupid question, but is this just another small testing prototype like the last pic?

I ask because it looks way smaller than I'd have expected the final unit to be; pretty interesting

10cm*13cm approximately according to the grid. Maybe it's about twice the size of o2. I don't see any issues. The unbalanced input may be put in the front. and basically all looks good.
And smaller chassis is probably why it could be made cheaper.

 

[tomchr]

Really stupid question, but is this just another small testing prototype like the last pic?

I expect the only change between this and the final rev. will be a silk screen change from "PROTO 1.1" to "Rev. 1.0". I'm also hoping to reduce the CLCLC filtering to CLC, thereby, shaving a few bucks off the BOM cost. It'll all depend on the measurements.

The previous prototype was more of a proof of concept.

10cm*13cm approximately according to the grid.

I'm expecting to fit into a 140 x 190 x 50 mm chassis.

The unbalanced input may be put in the front.

Nah. All inputs will be on the rear.

Tom

 

[Azeia]

I'm expecting to fit into a 140 x 190 x 50 mm chassis.

Ah, ok. I measured that IRL just now; for some reason the picture gives the impression that it's a bit smaller than that, maybe some sort of optical illusion or something. Like the power and XLR connectors look huge so it made me think the whole thing was smaller, maybe my eyes are playing tricks on me or something.

 

[tomchr]

Ah, ok. I measured that IRL just now;

Yeah. It's about the size of a hardcover book.

Like the power and XLR connectors look huge so it made me think the whole thing was smaller, maybe my eyes are playing tricks on me or something.

IEC C14 power connectors are monstrous. The one I plan to use in the HPA-1 is the smallest I could find and it's still 33 mm wide! The XLRs probably look huge because the model from Neutrik isn't all that detailed. There's a plastic overhang at the top of the connector that extends pretty far back. That's probably the dimension they used for the model. That said, there is no empty space on the rear panel. The connectors are packed about as tight as possible. I left the most room between the IEC inlet and the XLRs. There're some metal bits in the bottom of the chassis that I need to stay away from (1/4"/6.3 mm clearance needed for electrical safety!). That severely constrains the connector placement.

I did consider going with the IEC C2 (shaver plug) as the Mean Well supplies I will use are Class II medical switchers, thus feature their own isolation between primary and secondary, but I don't like the idea of having mains voltage inside a non-grounded metal chassis. I could have used the IEC C6 (Mickey Mouse plug), but that's starting to get large and people wouldn't have the opportunity to geek out over power cords without using an adapter. So IEC C14 it became.

I definitely wanted a compact high-performance amp. As we've discussed before, I'm aiming for the $500-600 price point. That's remarkably hard to hit if you want a high-performance product that's safe to use, enclosed in a pretty box, has a large volume knob that feels right, etc. that is manufactured at western wages. One of the knobs I can turn is the size of the box. Large box -> higher cost. So minimize the size of the box. Reducing the feature set is another knob. So two gain settings instead of three (saves a $6-7 relay plus a few other sundry items and the cost of their assembly and test).

Another knob I could have turned to reduce price would be the performance knob. Lower performance -> lower cost. I left the performance knob cranked to 11. Okay... Maybe 10.5. But still... I know I charge more than the eBay vendors. I have to. I like to eat periodically! Thus, my products have to be better.

I should have a handle on the cost within the next few days. That'll allow me to figure out what the amp should cost. At the very least I think I can do something like $549 for the early birds who are willing to preorder (and wait for stock to arrive). Once I have amps in stock, the price will go up. I'm not planning to have any sales after that. I've arrived at the same conclusion as Schiit regarding sales: They suck for everybody and result in higher prices.

Tom

 

[Azeia]

I did consider going with the IEC C2 (shaver plug) as the Mean Well supplies I will use are Class II medical switchers, thus feature their own isolation between primary and secondary, but I don't like the idea of having mains voltage inside a non-grounded metal chassis. I could have used the IEC C6 (Mickey Mouse plug), but that's starting to get large and people wouldn't have the opportunity to geek out over power cords without using an adapter. So IEC C14 it became.

C2 seems to be limited to 0.2 amps though, the C8 one seems more common out there for ungrounded AC power plugs (you see it a lot on laptop power bricks) and supports 2.5 amps. In any case, C14 seems like a great choice since most people have such a cord in their house from like an old PC, so it's easy to replace.

The thing about Class II isolation is something I've been wondering about lately; I've noticed a lot of smaller production run products tend to use C14, and they'll ground the case, whereas bigger companies will often make large AV receivers, blu-ray players and other products with built-in power supplies in a metal case, and only have two-prong ungrounded plugs (often hard-wired to the device). I've been wondering if these devices are just inherently unsafe, or if they're doing something special to avoid the risk, I looked up a disassembly video and saw a blu-ray player that had a little plastic sheet under the power supply board; is this all it takes to qualify as class II and clear safety regulations around the world? seems kind of odd to me.

The reason I started wondering about it is because it seems like grounding adds the risk of ground loops for unbalanced connections, whereas an ungrounded device wouldn't have that issue, but if it's in a metal case then obviously that could be a problem, so I started wondering what would be the ideal design for unbalanced connections. I don't know enough about circuit design to figure all of this out though.

In any case, everything sounds great so far regarding the amp, I'm starting to get on the hype train. =)

 

[tomchr]

C2 seems to be limited to 0.2 amps though

That's still 24 W (or rather 24 VA) at 120 V, though.

I've been wondering if these devices are just inherently unsafe, or if they're doing something special to avoid the risk, I looked up a disassembly video and saw a blu-ray player that had a little plastic sheet under the power supply board; is this all it takes to qualify as class II and clear safety regulations around the world? seems kind of odd to me.

Class I devices require a grounded chassis. Class II devices are double insulated (or use heavier insulation between mains conductors and the chassis). Class II (not to be confused with Class 2, which is something else) devices are designed such that it requires the failure of more than one part before anything that can be touched by the user becomes energized with mains voltage. A Class II power supply will feature extra insulation between primary and secondary, for example. For a switching supply, where the secondary voltage is controlled by a switching circuit on the primary side, the feedback from the secondary to the primary side commonly goes through an optocoupler. And, as you've noted, additional insulation is used between exposed mains connections and the chassis. So it's a lot more than just a simple sheet of plastic.

I'll have to use extra insulation between the mains connections and the chassis as well. Ironically, that's driven by the volume control. I want the volume knob centred vertically on the front panel. This defines the vertical location of the PCB, which in turn defines the maximum length of any mains-connected pin that pokes through the PCB. While my PCB assembly folks are awesome, I don't want to rely on them to accurately trim the component leads to length. I'm sure they can do it, but I'm also sure it'll increase the assembly cost. So I'll use a sheet of plastic or maybe fibreglass glued to the bottom of the chassis.

My goal is to design a Class II compliant device with a grounded chassis. Some may find this overkill. To me, it's fundamental risk management. Something tells me that electrocuting my customers isn't the best strategy for growing my business.

The reason I started wondering about it is because it seems like grounding adds the risk of ground loops for unbalanced connections, whereas an ungrounded device wouldn't have that issue

True. That's probably why the big players don't ground the chassis. They can probably also afford the lawyers to fight the product liability lawsuits.

The solution to the ground loop issue is simple: Use a differential connection. I also help you out by leaving the signal ground floating relative to the chassis safety ground. I actually use the differential receiver even when you select the RCA inputs. The signal path is differential all the way to the volume control.

Tom

 

[amirm]

My goal is to design a Class II compliant device with a grounded chassis. Some may find this overkill. To me, it's fundamental risk management. Something tells me that electrocuting my customers isn't the best strategy for growing my business.

You will certainly garner praise from our little corner of the Internet for that!

 

[Azeia]

The solution to the ground loop issue is simple: Use a differential connection. I also help you out by leaving the signal ground floating relative to the chassis safety ground. I actually use the differential receiver even when you select the RCA inputs. The signal path is differential all the way to the volume control.

Ah! That makes a lot of sense. I've actually noticed in some pictures of various amp designs that sometimes they use these little plastic washers/discs, specifically for RCA screw-type connectors that're designed to be fastened through holes on the chassis (example on the little dot mk3), I'm guessing maybe that's why. Although there are other RCA connector types like the ones on the khadas tone board that seem to have a plastic screw-portion, so those wouldn't be making contact with the case obviously.

Thank you for all this info by the way, I really appreciate all the detailed explanations. I love learning about this stuff. =)

 

[Barce]

I've been waiting for a real competitor to the THX789 - don't feel like buying one badly enough because I love my DX3 Pro. So a practically bespoke contender unit that is partly made in Canada in the $500-600 range sounds pretty damn nice right about now. Purple PCB looks rad as hell!

 

[tomchr]

The purple is what OSH Park is using. If you want a low-cost prototype board, they're the best around. For the next prototype and the final production version, I'll go with red solder mask and white silk screen.

The HPA-1 will be as "made in Canada" as you can get with a modern electronic product. The bare PCB will be manufactured in Ontario. The assembly will be done in Calgary. Some mechanical bits will come from Nova Scotia. The design was done by me, in Calgary. However, the chassis will come from Japan and the components are from various places, including the US.
It turns out that countries care about how their names are used, so "Made in..." is a bit of a protected term. I can probably argue that the components undergo a "significant transformation" to become a headphone amp. That's technically enough for a "Made in..." label. However, should someone get a bee in their bonnet about it, I'll have to fight a legal fight. I can avoid that altogether by using the term "Designed and Assembled in Canada", so that's what I'll do.

Tom

 

[tomchr]

Front and rear panels. I suppose I should get a logo designed or something... This is likely what I'll go with for the prototype.

Features in orange will be printed in white on the black chassis. I included the outline of the volume knob. The volume knob outline will not be printed.

Tom

 

[amirm]

Tom, why not use English for the front labels? You have that in the back and people know the few English words regarding audio.

 

[tomchr]

I like the simplicity of pictorials. Text looks tacky on the front. I also find text labels get really crowded - even with 2 mm tall text (as shown below).

Tom

 

[Azeia]

I think the icons for "power" and "headphones" are pretty universal, but the gain and input ones actually threw me off the first time I saw them a few weeks ago, I had to look up what they were. I'm guessing it would be the same with most people, I think those two are probably the more ambiguous ones.

 

[tomchr]

So now I'm curious. I've put together a survey with one (1) question. If you have a split second, I would greatly appreciate your input here: https://forms.gle/GnDPFA8f2pnu3Neb6

Now, I'm not planning to outsource every design decision, but sometimes what I prefer is rather different from everybody else's preferences. That's not a big deal, except there are a lot more of you (who are hopefully looking to buy my amp) and only one of me.

Thanks in advance.

Tom

 

[maxxevv]

Front and rear panels. I suppose I should get a logo designed or something... This is likely what I'll go with for the prototype.

Features in orange will be printed in white on the black chassis. I included the outline of the volume knob. The volume knob outline will not be printed.

Tom

As someone who has dabbled in both the printed page and heavily into machining work, I have to ask, are those letters going to be printed or engraved?

Aesthetically, they don't look their best as they are imo. If they are printed, then the sky is the limit, ask your local namecard shop for some help if they are willing. Or some budding graphic design student and pay him/her a reasonanble fee.

If they are engraved, ask your vendor what kind of engraving and machining / CNC software they use; point engravers or endmill cutters ?
Some of the newer CNC software will actually allow the use of Truetype fonts and even CGM format vector lines. But will require point engravers and have a size limit proportionate with depth of engraving.

If they allow Truetype and CGM vector lines, similarly, you can do a more fanciful faceplate design with the help of the graphic designers.

Graphic layout makes a very big difference in aesthetics. Likewise the choice of fonts .

 

[tomchr]

Thank you. I really appreciate your input. The text will be printed. My vendor wants vector graphics with the text as outlines.

Can you shed a little more light on what you don't like or how you would improve it? I agree that the current design is very utilitarian. Maybe it needs not to be? Get rid of the ALLCAPS?

If I look at something like the Pass HPA-1 (didn't realize until a moment ago that we both use HPA-1), all I see is Arial or Helvetica. No fancy fonts here...

Unfortunately my hands are pretty much tied with the locations of the components. I went for as symmetrical a layout as I could get and was able to get there without compromising performance.

Tom

 

[maxxevv]

Thank you. I really appreciate your input. The text will be printed. My vendor wants vector graphics with the text as outlines.

Can you shed a little more light on what you don't like or how you would improve it? I agree that the current design is very utilitarian. Maybe it needs not to be? Get rid of the ALLCAPS?

If I look at something like the Pass HPA-1 (didn't realize until a moment ago that we both use HPA-1), all I see is Arial or Helvetica. No fancy fonts here...

Unfortunately my hands are pretty much tied with the locations of the components. I went for as symmetrical a layout as I could get and was able to get there without compromising performance.

Tom

Try experimenting with different fonts for the text for starters if you like to keep the aesthetics to be minimalist utilitarian.

Also, vary the line thickness of the different symbols. It doesn't have to be uniform and usually being completely uniform in thickness can make things pretty boring looking. I have nothing against the placement of your various switches and knobs. Not much can be done with them really from the engineering point of view.

As said, engage a budding graphic design student that you can trust as its not a complicated design to begin with, they don't cost much.

Also, invest time on design of your signature name , it will go a long way.

 

[tomchr]

As said, engage a budding graphic design student that you can trust as its not a complicated design to begin with, they don't cost much.

That would probably be time/money well spent. I happen to have one of the better Art & Design schools within an easy bike ride of my house.

Also, invest time on design of your signature name , it will go a long way.

That's a really good point.

For now, I'll have to do it myself, though. What I've shown so far will be for the prototype. The idea being that if the prototype works, I just go make more of them. If I have to change the graphics between the prototype and the final product, that's no big deal. I could even go without the graphics for the prototype. It would be nice to get it kinda/sorta right for the prototype, though. After all, I'll be showing it off at RMAF and need to make a good impression. I also want to submit the design to my manufacturer within the next 48 hours or so, so I can actually have a prototype to show at RMAF. Decisions, tradeoffs...

Tom