John Curl's Blowtorch preamplifier part II

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SE, it looks to me like you've gone from defending steel to defending mumetal, I suppose because...

ahhh, it's really not that important to me.

They each have their use.

MuMetal has a much higher permeability than steel, but it saturates sooner than steel, so it may not be practical at high levels. Steel can take a lot more before it saturates but its permeability isn't as high making it less effective at magnetic shielding. Though you can use the two together, using steel on the interference side to help knock the level down to a level that the MuMetal can handle.

se
 
Again, please look at the skin depth of copper at 60 hz... it's 8mm. We're talking in the context of a case machined out of a solid billet (goodness, that'd be awful with Cu), so it wouldn't be surprising if the Blowtorch's case is greater than 1 cm all the way around, which is right about the skin depth of pure Al at 60 Hz.

We're not talking material efficiency here...

But you could achieve the same thing with a lot thinner steel chassis.

se
 
Given the volumes involved, pennies on amortization costs.

Sure, but you're not guaranteed those volumes starting out.

Dr Dre's are a rip-off technically and sonically.

Have you listened to the current versions across all of the models?

Here is a classic case of 'brand equity'.

But equity is something that it built. It's not something you're guaranteed from the start.

But, they are also smart because the distribution and retail channels are well taken care off. Plus, they know their target demographic well - young males with with small brains, no appreciation of fine sound and too much testosterone.

Much the same can be said of older males in a different market, where they are known to spend massive sums of money on that which technically, is garbage.

As in all these things, it seems to me the greater the bs, the greater the ability to leverage outrageous, confiscatory pricing models.

And that's different from "high end" audio how exactly?

se
 
BTW -- shielding effectiveness as frequency increases becomes one of reflection rather than absorption (low freq).

We're talking about shielding against magnetic fields. And absorption loss is the primary mechanism here. That's really the only way materials like copper can provide any real shielding at all of magnetic fields. It is the absorption loss due to skin effect that copper can be effective at higher frequencies.

se
 
Titanium is usually only used for the leading edges, not for the entire wing surface. It is very hard to machine and form, we used titanium for the leading edges of most rotor blades for helicopters. Much of the machining of titanium was actually done with surface grinders, it was not a nice thing to have to do and forming those machined surfaces was another issue without cracking the material.

ps. The common tolerance on those parts was to +/- 0.0002"
 
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Everyone: just check out [ dr dre headphone breakdown] on Google and look at the article from the Huffington Post. That should be enlightening! Then Demian, we can discuss where I went wrong. '-)

That is an estimate but way off. And estimates like those have bankrupted several headphone startups. Its true, you can get some knock-offs for those prices but they will have a lot of problems that will bite when you are doing large volume.

If I did a similar BOM estimate for the cost of a Blowtorch I would come up with maybe $100 for the BOM. As you know not all resistors and transistors are interchangeable.

Many of the parts prices are way off. I'm not sure (no link) which headphone this is a breakdown of (most likely the solo) but even the cheapest Beats costs significantly more for the parts. They are all done "open BOM" plus a standard multiplier for profit so there is not much room for price fudging at the vendor. I don't think the largest volume products would not have really sharp purchasing/supply chain people involved and the negotiations are brutal.

Don't always trust the internet.
 
Going along with what Demian was just saying if you have ever worked with injection molds you would understand that the costs are much more involved than it seems. Finding someone who can actually build the tooling, vetting those vendors, first article parts and qualification don't come for free. By the time you have completed tooling before any production you have sunk a large amount of money just to get a first article part. If you have a successful product then the final amortized costs may be low on a high volume production item but there are never any guarantees going in. When you just look at the final manufacturing costs there are so many other cost factors to consider that the common thinking is just very short sighted. If it was only that easy and cheap there would be lots more competition in many things we purchase, try it sometime, some of us know better what is truly involved in starting a new project for a new product.

In Johns defense you also have to consider that his high end products are very limited in quantities and that is going to make the effort to produce a product that much harder. Selling a commercial product is so disconnected from a diy project, the comparisons are just not fair.
 
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