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Old 14th December 2008, 08:51 PM   #61
rhysh is offline rhysh  United Kingdom
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Here is the 'dirty' version of the schematic.

Note, it is correct, but hard to understand maybe.

http://www.cdupload.com/files/42436_...raft%20SCH.pdf

Sorry the values are not on the schematic, all the values are on my paper diagrams at the moment.

Rhys
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Old 14th December 2008, 09:07 PM   #62
rhysh is offline rhysh  United Kingdom
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I forgot to mention, rerember to use capacitors on the input, and on the single ended outputs. High quality films a must.
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Old 15th December 2008, 05:59 PM   #63
rhysh is offline rhysh  United Kingdom
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Hi Everyone,

To save me some trouble, could you please order your boards thru my online shop here. .

Also, i added a bit of info about the preamp here.

Cheers.
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Old 16th December 2008, 07:27 PM   #64
rhysh is offline rhysh  United Kingdom
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Are people still intrested?
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Old 16th December 2008, 07:46 PM   #65
Dr_EM is offline Dr_EM  United Kingdom
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Still interested, might be a week or two buying, got a few things to sort out. Your online shop looks like it will charge postage even though I'm in the UK?
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Old 16th December 2008, 07:47 PM   #66
rhysh is offline rhysh  United Kingdom
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Quote:
Originally posted by Dr.EM
Still interested, might be a week or two buying, got a few things to sort out. Your online shop looks like it will charge postage even though I'm in the UK?
If you are the bottom, you will see there is a option to remove postage if prior discussed, or if you are in the UK.

Rhys
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Old 17th December 2008, 11:19 PM   #67
rhysh is offline rhysh  United Kingdom
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Put this on the backburner for a while. No money left.
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Old 19th December 2008, 08:41 PM   #68
gfiandy is offline gfiandy  United Kingdom
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Rhys,

You design is not optimal in some ways. Would you like me to describe them or just shut up and go away :-)

Andy
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Old 19th December 2008, 10:55 PM   #69
rhysh is offline rhysh  United Kingdom
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Quote:
Originally posted by gfiandy
Rhys,

You design is not optimal in some ways. Would you like me to describe them or just shut up and go away :-)

Andy

Hi andy. Feel free to describe my mistakes.
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Old 20th December 2008, 06:14 PM   #70
gfiandy is offline gfiandy  United Kingdom
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Hi Rhys,

The most significant problem is decoupling. You have no decoupling capacitors on the 5V rail at all. This will mean there is lots of noise on it.

There should be a bulk decoupller of 100uF at least. then 100nF caps shoudl be placed close to the micro controller and the 5V supply to the pre amp chip. I would also use an inductor to reduce noise from the Micro controller getting into the pre amp chip via the PSU.

I recomend re-reading the 7805 data sheet you should have some input and output decoupling on this part, however I can't remeber the optimal parts.

I'd recomend an input filter on the opamps to reject RF noise say 100pF to GND. However this is one of those value judgements as in a sirtuation where these is very little RF noise the system may sound better without them, however if there is noise about it will upset the input to the opamps.

I would recomend much more decoupling on the +/- 15V rails to ensure all th opamps and the output of the preamp as completely stable. 4.7uF to 10uF for each chip would be optimal with a seperate 100nF cap for each chip as well. However there is clearly some decoupling alread there and this will rpobably be ok.

I can't see where the +/- 15 comes onto the PCB it doesn't seem to have a connector, but I may have just missed it.

Regards,
Andrew
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