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Old 25th November 2005, 09:42 PM   #1
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Default How do I box a Skynet 8080 SMPS

Newbie post - apologies for sins of commission and omission !

I've got one of NUUK's Skynet 8080 SMPS for my T-amp. I need to box it to stop the kids poking their fingers in and getting a shock (!)

I'm thinking of using a Maplin aluminimum diecast box because its robust, and it will keep in some of the switching RF. However, I am concerned about where all the heat is going to go in a sealed box.

Has anyone boxed a Skynet 8080 ? If so I'd be very interested in you experience.

Should I drill holes in the box to let the heat out ? How big do the holes have to be before they let too much of the RF out as well ?!

Should the box be on the end of a long wire to keep the nasties away from the T-amp, or can it sit on the shelf next to the T-amp, and enjoy the benefits of a short power cable ? Pros & cons ?

Finally, what sort of DC plug and socket should I use on the T-amp ?
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Old 25th November 2005, 10:27 PM   #2
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dont worry about the heat, it's a T-amp and it's gonna need a lot of abuse to get to that level!
Pop a few drill holes in the base plate to get some convection currents flowing but dont worry about RF as it will be absorbed by the case dispite the holes.
My PSU is in the same case as the T-board and there is no interference at all, as long as there is some kind of earthed metal wall between them.....I think his may be overkill as well!

Plugs, sockets and Power cords....now there's another topic...... have a search!
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Old 27th November 2005, 01:41 PM   #3
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Default Hot Stuff

Did you use one of NUUK's Skynet 8080 SMPS and put a 10 ohm 10Watt resistor across the 5V outputs as he recommends ? It gets too hot to touch !

Has anyone else done this ?
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Old 27th November 2005, 06:18 PM   #4
KASUMI is offline KASUMI  United Kingdom
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Hi
I've mountd Nuuks Psu in an aluminium case bought from Rapid electronics.The resistor I've mounted on the SMPS enclosure there are some holes that the resistor can be fixed to
Input is via IEC to a on/off switch.O/P is via 2.1mm DC socket from Maplins
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Old 27th November 2005, 06:18 PM   #5
KASUMI is offline KASUMI  United Kingdom
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Here is a PIC
Attached Images
File Type: jpg img_0635.jpg (79.8 KB, 504 views)
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Old 27th November 2005, 06:18 PM   #6
GJF is offline GJF  United Kingdom
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Just done it!

Used a Maplin alloy box and a 10 ohm 10 watt resistor as per Nuuk's instruction with a pair of 10,000 mf caps.
Yes the resistor gets hot, but well within it's operating limits.
The box I used was well oversized and I have not drilled any ventilation holes, it stays within sensible temperature level and barely gets warm.
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Old 27th November 2005, 08:09 PM   #7
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Default Hot resistor

Quote:
Originally posted by GJF
Just done it!

Used a Maplin alloy box and a 10 ohm 10 watt resistor as per Nuuk's instruction with a pair of 10,000 mf caps.
Yes the resistor gets hot, but well within it's operating limits.
The box I used was well oversized and I have not drilled any ventilation holes, it stays within sensible temperature level and barely gets warm.

I hope you did not attach the resistor to the caps. This would heat the caps up enough to be a potential problem. I would recommend remote mounting it against the chassis to dissipate the heat and use additional wire to couple it into the circuit.
Roger
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Old 28th November 2005, 01:05 PM   #8
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Default Hot Boxing

Thanks All.

Using the box as the heat sink for both the SMPS and the resistor is a good idea. Plaited cables look impressive too !

Anyone tried heat sink paste on a ceramic resistor to improve the heat transfer ?!

BTW Kasumi - where did you get such a huge IEC connector ? Presumably you've got shielded mains cable ?

GJF - I assume the 10000mF (m=milli ? do you mean mu, or micro ?) cap was across the +12V and 0V ? I've been following the "cap or not to cap" debate in other threads with interest. Did you hear a difference ?
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Old 28th November 2005, 10:56 PM   #9
GJF is offline GJF  United Kingdom
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Yes, that should have been 2 X 10,000 micro farads.

To be honest with you I am not sure if I don't prefer the 12v linear regulated supply I was using previously. It somehow sounded 'warmer', for want of a better description.

As for switch mode versus switch mode and caps, well the jury's still out on that one. With caps I detect a slightly deeper bass but strangely some of the swing has gone out of Sinatra.
Everything is still there but its too analytical.
Maybe the 2 caps need more running time, I used a couple of ALS 20's and they have no hours on them as yet.

The one thing I have noticed with these Tripath amps is that like tube amps they are very revealing of supporting component quality and its dead easy to upset the tonal balance by changing just 1 or 2 components for same values but different makes.
Or is that just me?
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Old 28th November 2005, 11:57 PM   #10
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Quote:
Originally posted by GJF
Yes, that should have been 2 X 10,000 micro farads.

To be honest with you I am not sure if I don't prefer the 12v linear regulated supply I was using previously. It somehow sounded 'warmer', for want of a better description.

As for switch mode versus switch mode and caps, well the jury's still out on that one. With caps I detect a slightly deeper bass but strangely some of the swing has gone out of Sinatra.
Everything is still there but its too analytical.
Maybe the 2 caps need more running time, I used a couple of ALS 20's and they have no hours on them as yet.

The one thing I have noticed with these Tripath amps is that like tube amps they are very revealing of supporting component quality and its dead easy to upset the tonal balance by changing just 1 or 2 components for same values but different makes.
Or is that just me?
Electrolytics are notorious for needing long break in times. I suspect most of that warmth will come back.
You are right in that the amp revels other deficiencies and when you get all that worked out you will find about 95% of your recordings are junk! I can usually listen past a poor mic selection but I draw the line when I hear the mixer pots being tweaked or a piano that covers the whole back wall. I think some of the big name artists have a mic preference that is truly awful and they insist on these being used while the engineer uses the good stuff on the instruments and they really shine. At least this has been my experience on a lot of different disks.
Roger
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