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Sjöström Diamond Buffer group buy

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#42
Interested in 8 boards.

One note regarding parts - I think that Per-Anders did a really good job on BOM. For EU diy-ers: Farnell used to have everything in stock, bit higher prices but flat 5EUR shipping cost.

Question: does it matter when the board is mounted horziontally (up to 1cm over the mother board) or is it recommended to mount it horziontally? I am curious about the heat dissipation. For a line driver this is probably not an issue, for the headphone amp it could matter.

Daniel
 
#48
BigE said:
Perhaps using C-channel?
Click to expand...

do you mean like a tube with a piece cut away 😕

ehh, maybe use something with 'slits'
 

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#49
Actually, a rectangle with part of a side cut away. It would probablyh be better to use UHMW edge wear strips for conveyor belt use. You can get them with a 1/8" slit. Make them longer and you can mount by bolting through the ends. Instant standoffs! I may use this approach on my DCB1, and avoid using standoffs entirely.
 
#54
peranders said:
About your question, it can be rather hot until you have a real problem. What temperature are we talking about?
Click to expand...

Sorry, I need to do some math homework in advance next time.

bcp56 has thermal resitance (j-a) of 125 K/W (considering 1cm2 mounting pad). That would theoretically give us 150oC junction temperature when 1W is dissipated, 87,5oC for 0,5W dissipated, 50oC for 0,2W dissipated or 37,5oC for 0,1W dissipated, all for 25oC ambient temperature.

You have published 6mA quescient current for the ouptut stage on your web, that would give not more than 50mW per output transistor in idle. This is far on the safe side.

I am not good at circuit math but for low impedance headphones we could expect a dissipation of few hundreds of mW per output device - seems to be still ok for the chip. Are my calculations correct?

Kind regards,

Daniel
 
#55
tried to 'copy and paste' a few of the Farnell parts numbers from your BOM list over to Farnell site
looks like the parts numbers still work

also appears we should be prepared to buy minimum 10 component kits
but I guess that will be ok

will try to go through them all to get a complete cost figure
 
#57
Actually I realise now that J5, J6, J7 are 2.54mm pitch apart so can use male /female pcb headers to a carrier board that can also contain the psu. I also need to stack them to save space.

Peranders, what's the minimum VA transformer you recommend for a pair of these. Would 1.5VA do?
 
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#60
I'm going ahead with the group buy and I will also offer parts as a service not cheap I'm afraid.

I will start sending out Paypal invoices this weekend. Don't forget to send me your email address for those of that have "No" in the column "P-A got email addr."
 
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