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sammich power consumption


Davo

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thanks for posting this! i was wondering about power consumption...reason being i've noticed the sammich runs nice and hot after a little while, and had the crazy idea of installing a tiny fan inside the case.

would i, theoretically, be able to plug this:

http://www.xsfans.com/index.php?main_page=product_info&products_id=809

into the 5V/G pads underneath the 7805 and not bust my amp budget?

[using 2 6581s, 12VDC regulated supply @ 500mA, high power LCD with brightness trimmed all the way down]

i guess the second consideration would be whether plugging a fan into the system might screw with the audio quality...

would love to have an expert opinion! sorry for the hijack...

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Tudy: Thanks :) So 350mA at 12V makes the power consumption of your sammichSID 4.2 Watts.

Technician4: Well... Obviously a fan is a good idea. Then again, it pulls power (0.6W) from the very rail you are trying to cool with it. So it's kinda hard to tell if it'll actually make the whole situation worse rather than better :) Also, electrical motors tend to be very noisy and give you a fairly big amount of noise on the 5V rail... It won't kill the 7805, but I am not sure if it'll actually improve anything in the bigger picture ;)

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Technician4: If you absolutely must add a fan, note that the amount of noise the fan adds to the power rails (and thus the audio output) will vary a lot. For me, the nicest looking 40mm translucent fan with red LED inside was a real noisy bitch compared to the simple and cheaper black one. Also, it's probably best to get one that runs at slow revs on 12V and power it directly from your regulated 12V power supply (i.e. take power at J1 header). This will mean the current used is not supplied from the regulators inside the sammichSID, just like using JBL set to "12V" to supply the LCD backlight with power from the input, not via the regulators.

I think you would be better served attaching some heatsinks to your 6581 SIDs to keep them cooler, it's unlikely you'll cook the regulators with only ~300mA passing through them at a regulated 12V DC input (i.e. rough calc. of 12V-5V=7V, 7V*0.3A=2.1W heat dissipated through heatsinks, this calc. is a guestimate, some heat is dissipated through the two power diodes).

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Thanks guys. It looks like the 1amp supply I've been eyeballing would have been overkill. Have you specced a power supply for the sammichFM? I'd guess that it would be 5 volts, but if it can use a 12V supply, that would help avoid mixups.

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Wilba, do you have a suggestion on heatsinks inside the Sammich? Clearance seemed to be an issue there. I have some of FuzzyLizards sinks but it didn't look like they would fit in the Sammich.

I have some too. They look like they might have enough clearance with the top PCB, but then not with each other or with the filter caps. So you'd need to fold the fins up a bit and then trim them short, and also maybe chop off fins that have clearance issues with the caps, or bend the caps down a bit.

It might be easier to just stick some other kind of heatsinks onto the SIDs.... these aren't permanent, it's just a layer of double-sided tape holding them on.

http://www.zalman.com/ENG/product/Product_Read.asp?idx=136

ZM-RHS1_02_b(1).jpg

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