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Old 28th February 2013, 12:46 PM   #11
marce is online now marce  United Kingdom
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The Vulcan Bomber re-born
Its a nice design and I think you have a design that would sell quite well, when you look around at some of the offerings on e-bay.
It would apeal to my son...I may have to break the habit of a lifetime and actually get around to building somthing other than speakers.
How many layers is it?
I would be interested in having a look at the gerbers, out of interest.
One of the best concieved projects I have seen on here for ages
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Old 28th February 2013, 08:56 PM   #12
Big Gig is offline Big Gig  United Kingdom
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Hi Marce,
Thanks for your comments, yes that Delta Wing flies again
I thought about manufacture but I'd need to mass produce it for it to compete with other designs on the market which requires a lot of investment.

The board is a 6 layer design with 0.15mm track and gap. Layer 1 and 6 is really just component pads with Ground fill. All routing is done on the internal 4 layers.
So the PCB itself is quite a high cost. I could possibly get this down to 4 layers if I compromised the ground shielding.

I can send you the Gerbers if you are interested to take a look. Just send me a PM with your e-mail and I'll send them over. Cheers!
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Old 28th February 2013, 09:00 PM   #13
Big Gig is offline Big Gig  United Kingdom
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I finally managed to get hold of a half decent sound card (iMac running Parallels Win 7 and RMAA). The low frequency jitter in my previous plots was worrying me so thought I would re-measure with a better card. I'm sure that the THD results will improve further on an AP but I think this is good enough for now.
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Old 28th February 2013, 09:45 PM   #14
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Ian,
What do you approximate it would cost to produce the pcb board as you designed it? If you were to do a run of one hundred what do you estimate would be the cost? Molding the housing would be something else but that could be a simple mold to make the two halves in a few different processes.

Steven
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Old 1st March 2013, 05:28 AM   #15
qusp is offline qusp  Australia
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a 6 layer PCB in this price bracket in smallish numbers would be unworkable commercially IMO, particularly using a lesser known dac chip. the WM8740 would definitely be a better choice commercially too. you can get reasonable pricing on 4 layer these days, but 6 layer isnt usually found on special anywhere, unless you have a facility that you know, such as where you got these done.

Last edited by qusp; 1st March 2013 at 05:30 AM.
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Old 1st March 2013, 10:22 PM   #16
Big Gig is offline Big Gig  United Kingdom
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Hi Steven,
I just costed the BOM for 100 pieces and buying through UK distribution it works out at $165 (US Dollars) per board inc taxes (20% here) for the components. The PCB would be about $30 and SMT assembly would be about $60 plus the enclosure.
With these costs I think it would need to handle 24/96 Audio over USB and use a better DAC as Qusp mentions.

Qusp: I agree 6 layer PCBs are significantly more expensive than 4 but the extra layers are useful as an EMI shield. The unit is housed in plastic which can be more challenging to pass EMC compliance compared to using a metal enclosure. That's not say it can't be done in 4, and yes the prototype boards were expensive.
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Old 1st March 2013, 10:31 PM   #17
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Ian,
Are the components less expensive in the US? On the plastic housing I imagine that they could be metal sprayed if you needed more shielding, it would probably need flame retardant material also? I could get materials that would me the UL V0 to V5 rating we use here for housings if you wanted me to hand make the parts. It sounds like you are already thinking of an upgraded design with the different dac chip?
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Old 1st March 2013, 11:03 PM   #18
Big Gig is offline Big Gig  United Kingdom
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The components may be slightly cheaper in the US but it's probably more beneficial for me to do a cost down of the design.
A plastic case can be sprayed with conductive coating so that may help if emissions are found to be too high.
Thanks for the offer to make the enclosure parts. Flame retardant material would be required and it's good to know that you know about that stuff.
For now though I think I need to revisit the design and change the DAC and go with an Asynchronous USB chip to be competitive in the market. This could take some time though as I have other priorities at the moment. But we'll see what the year brings!
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Old 1st March 2013, 11:14 PM   #19
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Don't worry about it Ian, we will still be here when your ready to take another look at your design.

Steven
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Old 2nd March 2013, 04:13 PM   #20
Big Gig is offline Big Gig  United Kingdom
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marce, I've sent the Gerber files over, feel free to comment.

Steven, That's the good thing about audio it doesn't move at such a fast pace, Silicon devices that were produced 10 years ago can still hold their own today if they were designed well. So I think I'll try and re-spin this product as time allows. I've started looking at the XMOS devices which have Eval Boards available from Digikey. Has anyone tried these parts? I guess I can search this Forum for advice.
My aim will be to get to single sided placement in 4 layers and use fewer components. The current component count is ~350 parts, 25 of which are 0R resistors for debug which can all go, so lots of work to do......
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