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Old 30th August 2010, 12:36 PM   #11
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Yurk, I recommend you see Multi-Channel Mixer project available in Altium Designer software. That project I've attached below:
Mixer_Routed.pdf - 1.82MB
There is a very useful tutorial for placing electronic components audio mixer. That project uses the THT components, which you could also use.
Secondly, at home is quite difficult to work with SMD, especially when it comes to large projects PCBs.
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Old 30th August 2010, 03:06 PM   #12
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Quote:
Originally Posted by marce View Post
4+ layers tend to be the norm for a lot of commercial stuff.
Not for baseband analog stuff, even in surface mount. 2 layers is plenty if the layout engineer is not inexperienced or lazy. If you have a load of digital stuff racketing away in there in the same box that is subsequently discovered to cause problems, then the usual resort is an internal compartment.

Quote:
Originally Posted by Yurk View Post
a 20 dollar difference between 2 and 4 layer boards from that company.
Commercial = cost sensitive.

To put it in perspective, that's $20,000 dollars on a production run of 1000.

I've rarely encountered an audio board I couldn't route on ONE layer with a few wire links or 0 ohm resistors, and the ones that really require two have multi-pin power devices whose positioning is constrained by the need to bolt them to large heatsinks, or as in the case of the Altium mixer, multiple channels and space constraints.

EMC is generally only a problem with switch-mode PSUs and digital boards with a fast clock or short rise-times. Radios generally have the critical bits compartmentalised with feed-through capacitors anyway.

When you design a DAC or other mixed-signal device is the time to reach for a 4-layer board.

w
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Old 30th August 2010, 04:18 PM   #13
marce is offline marce  United Kingdom
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i'll agree for simple designs, and cost sensititive. I think using the term commercial is to broadband as it covers a wide span. I have somewhere the Printed Circuit Design & Fab yearly surveys that show how PCB design is evolving, they show some interesting trends, and if I am correct I belive that this years had multi layers just piping double and single sided, by only a couple of percent. That said there are still lots of designs done on double sided, I've just done a Class D amp for Savu, on two layers which was a fun challenge.
Still for anything digital these days I'd prefer multi-layer, as I belive that EMC is a wider problem than just SMPS's etc. Also for SMD it depends on the size of the devices, as they shrink its getting harder to get everything on even 4 layers. Again on a comercial basis having four layers can be cheeper than having to place and solder a few zero ohm links, it depend on the design.
We have found that our layer count for more complex boards is up from an average of 4 - 6 to 8 - 12, due device size and BGA's with multiple voltages, quite often the extra layers are for getting the various supply voltages to the required place, not just for extra routes. These ar mainly digital boards or digital with a bit of analogue, I still prefer to have different boards for digital and analogue circuitry where ever possible.
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Old 30th August 2010, 04:50 PM   #14
Yurk is offline Yurk  United States
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Well, as far as cost goes, I'm doing this is a home project. I can see saving money in a commercial environment being paramount, not that I want to spend a mint here. I'm a long way from a professional pcb designer, too!

I'm using all old technology, PTH, not SMT. I actually work in a plant that builds both all day long, so if I did SMT I have access to a reflow oven. I just like the PTH for playing with at home.

Looking at that commercial mixer, I'm going to say I think my board looks neater than that, so far (as 2 layer). I may use some jumpers on top for some of my traces that cross planes, but I'm not sure about the traces that go straight to a pin. I'm probably going to have to leave those in. Most of the ones I have on the top layer look like jumpers anyway, only being .5" long or so.

I'll be feeding my analog board with a filtered/regulated DC supply, so no SMPS to cause noises. I guess the worst looking aspect of this build is going to be wiring up all those slide pots! Nothing to be done about it though, I'm using every bit of available space (under 21sq" per board, 4 boards) to keep my cost down some. (over $100 difference).

Lot's of good ideas to think about.
Thanks!
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Old 31st August 2010, 02:34 PM   #15
marce is offline marce  United Kingdom
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FYI
the PCD&F annual survey, it gives a good induication of technology trends etc.
Printed Circuit Design & Fab Magazine Online
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