This Homemade Headphone Amplifier Is A Work Of Art

> and it's not pure form, it's also functional

Understandable, honest, unobtrusive, thorough, and useful. Really good design by D.Rams definition.

Of course you need fixturing: that's a given. Remember to account for the time and materials making up fixtures.

I would price the labor at around $15-$30 per hour minimum. You aren't going to farm this out to an assembly shop (not enough volume) and there isn't enough money in it to hire employees and deal with that overhead, so you're down to finding a FOAF or a student who can solder and is reliable. Factor into that that the person must be supervised.

Next, this isn't just assembly that has to work; it has to look good, so the assembler needs the skill and attention to detail to provide that. That means either you get lucky or you have a lot of rework, or you watch him closely. Soldering is not enough: need to pay attention to the cut ends of those thick conductors. The component lead terminations must look good and the components themselves should be fairly regularly placed and not look sloppy. Remember, you're selling primarily on looks. Also, if this assembler isn't always available, you have to make enough inventory to handle orders that may come in until he can make more if you don't have the time to do it yourself.

Volumes are uncertain, but the parts are cheap, so let's assume he buys enough to make 100 units at a time. The selling price has to reflect the risk that all those parts won't be used. Buy higher inventory levels and your parts cost goes down, but risk of "dead stock" goes up.

Having a small electronics mfg business on the side, I live this on a daily basis. Luckily I don't sell to price sensitive hobbyists :-)

But in the end, the price I'd try to sell it for has nothing to do with how much it cost to build: it's cool looking. That's where the price comes from.

I've performed as well as supervised manual circuit board assembly. I know what it's like to get in the zone of doing something like this all day.

My experience teaches me that it takes on average soldering a few dozen units of anything unusual before the assembler gets the hang of it. Unusual being anything besides stuffing a PC board and manually soldering. This is not likely to ever be a high volume product, and I probably (admittedly only knowing the size of the market from what other posters have said) would not be comfortable doing production runs of more than 50 at a time, so you lose a lot of the benefits of doing long runs.

That said, I think your estimates are a bit optimistic. Once the entire time is accounted for: from kitting up the run, setting up the work area, actual assembly and testing, my guess would be closer to 30 minutes per unit.

Slightly OT, but if you can point me to any good resources for setup and manual assembly of cable harnesses, it would be much appreciated. It's an area I find myself getting involved in and I don't have much experience, so it's pretty much "learning by error."

You aren't really addressing his main point about market size other than saying there are people that would pay quite a bit for this, even if they're not audiophiles. I have no idea what this does, or why I would want it, and I'm fairly confident I'm not alone there.

How many people want or even know what this thing does?

How many of those people will think this product is so much better than what they have that a clear version is worth spending $100s of dollars on?

It could be that the market is huge and I just do not understand it, but you didn't really help us understand how big it is either. To me, "a killing" seems like a stretch.

Where did I say there aren't people who would pay for this? I said he couldn't make a killing. Depending on the price-point... if he offered it at $500, there's probably a market of 25 people. $300, probably 50. $150, probably a couple hundred. I've owned about 20 headphone amps over the years that cost between $50 - $2500. Some of these amps have serial numbers in the double digits, many hand-built PTP tube amps, and the designers tend to be pretty transparent about the numbers sold, as many are headphone enthusiasts themselves and they come from the DIY-world then transition into small businesses. Very few of the small shops make anywhere close to a killing - most are just barely making a living doing what they love. There have been tons of Kickstarter-esque pre-orders threads on head-fi, where a well-known designer has a goal of selling something like 100-500 amps before beginning production and offers early-bird discounts. Usually the product in question changes the game in some way whether it comes to sonics/power/battery life/portability (if we're talking about portables).

It's a poor assumption that novelty-factor is high on the list of an audiophile. As cool as this design is, what it does does not add any functionality or utility to the amp. At the extreme upper end sure novelty may become more of a factor. But even when you get to kilobuck amps the component and labor costs are still quite high, ie. the designer of a $5000 amp usually has $2500 sunk into the amp, and he might sell a dozen of them. And to do that, the company has to have a ton of cachet in the industry.

There is a very large and active community around headphone audio if you're interested in this field... in excess of a quarter million members with about 10M posts - http://www.head-fi.org/. I've been an active member there for over 7 years and into this hobby for over a decade. I've hosted a meet with about 30 members w/ almost $100k in equipment. I personally have owned over $20k in equipment over the years. I think I can speak with some authority on this.

Oh come on, the only thing transparent about this design is the resin. It's an integrated circuit connected to a few passive components. The only way you'll have a chance of understanding it is by reading the datasheet.

Buy a mint-tin cmoy amp and you'll see the same thing. The circuitry is very simple. Wires from the input connect to an op-amp chip, which is connected to the output. Some resistors feed the output back into the input, controlling the gain. Finally, a big beefy capacitor sits between the power supply and op-amp to provide some extra current for sudden loud parts of the music. That's it. Everything cool happens inside that little IC.

Here's a bog-standard amp which looks almost exactly the same as the encased-in-epoxy variant http://electronics-diy.com/electronic_schematic.php?id=797

Here's the information for the op-amp they choose:

http://www.ti.com/product/opa2132

Note that they don't even give you a schematic for the op-amp because it's so complicated.

Oh, my. Why did you have to bring that up? And provide a link?

A blown electrolytic cap is not hard to diagnose. The top of it pops open and crap comes out of it.

I figured out both what they are and how to tell if one has been blown when I was a teenager, all by myself, sans internet.

Even fewer would have the equipment to fix it and the determination to source the part. A fraction of those would have the skill to pull off a successful replacement.