Controlling regulator heat via sinking/shielding

[AndrewT]

Originally posted by hollowman
but a 5VAC xformer is not kosher.

that's why post9 says 6Vac to 7Vac.

[00940]

Originally posted by hollowman
Thx for that info. Earlier you noted: "If you have a good idea of the amount of heat you want to burn off use a resistor ahead of the regulator ..." By "ahead" do you mean: before the reg and in series with the input, or after the reg?

The 10R/2W resistor must be before the reg.

This being said. If you have really 9.2VDC before the reg (which, on second thought, is quite possible on average with 11.7VAC p2p and only 1000uF), you're only dissipating around 0.84W. There are plenty of small heatsinks with about 18°C/W that would fit on your board. Assuming an ambiant at 30°C, you're still under 50°, which is quite ok. "Stacking" the heatsinks won't help much, you have to find a taller one.

I'm just saying that because a 10R resistor drops your voltage a tad too much. I would use a 5R/1W + taller heatsink.

[hollowman]

Originally posted by 00940
The 10R/2W resistor must be before the reg.

This being said. If you have really 9.2VDC before the reg you're only dissipating around 0.84W. There are plenty of small heatsinks with about 18°C/W that would fit on your board. Assuming an ambiant at 30°C, you're still under 50°, which is quite ok. "Stacking" the heatsinks won't help much, you have to find a taller one.

... because a 10R resistor drops your voltage a tad too much. I would use a 5R/1W + taller heatsink.

I only had 5R/3W resistors on hand, so I installed one in series betw. rectifier and Vin(reg). This worked well: the reg now runs only mildly warm.
As far as the heat sinks, I used double-sided thermal tape to add more sinks (see below).

[luka]

Why aren't you using switching? like lm2576, for this load you would even need heatsink, doesn't care what wold be input voltage,... can you use something like that or not, or you need to use what you did?

Here is my

[Eva]

Use a switching regulator like LM2574, 2575 or 2576 and forget about heat problems. Input may be as high as 20V or 30V without much performance degradation. They can work with as little as 4 external components.

I would even recommend an off-line SMPS but building one from scratch is way too complex and dangerous for most people. Recycling some 5V 200mA switchmode power adapter (or old mobile phone charger) may be an interesting option, though.

[luka]

Originally posted by luka
you would even need heatsink

you WOULD NOT need any heatsing, sry for typo... and yes some old wall adaper would be even better

[hollowman]

SMPS are, soundwise and IMO, better-performing than what a lot of so-called audiophiles give them credit for. E.g., certain okay-performing Toshiba CD/DVD players use them. But that said, and in my albeit limited and statistically-insignificant experience, none have yet matched the SQ of traditional shunt or linear PSUs.

Further, I don't see them frequently recommended in the DIY community or represented in the marketplace or incorporated in "serious" manufactured audio products compared to "std." types. E.g. in myriad DIY projects, kits or products-for-sale sites:

http://www.borbelyaudio.com/psshunt.asp
http://www.audiocom-uk.com/control/n...asp?a=158&z=15
http://sjostromaudio.com/_unsql/hifi/index.html
http://www.paulhynesdesign.com/
http://www.at-view.co.uk/alwsr.htm
http://www.gammaelectronics.com/powe...hi-fi-diy.html
...etc.

Bottom line: There's an overarching consensus -- statistically-significant -- that non-SMPS PSUs are still the way to go. This may one day change as technology evolves.

All that said, I do think the ideas SMPS promoters present -- as in posts above -- are interesting and worth noting WRT PC-based audio systems.

[Eva]

Switching amplifier and power supply technologies, together with digital audio processing, are one or two orders of magnitude more complex than older and more rudimentary linear technologies.

Most of the circuits themselves don't contain much more parts than linear ones, but understanding the inner working requires a much deeper understanding of electronics. Most audio designers don't have that understanding and they are either too old or too lazy to study electronics deep enough, not to mention the specific switching and DSP techniques.

They are stuck to the more straight solutions, the ones that require less brain at the expense of wasting more space, resources and heat.

If these technologies started to rule the market from one day to another, 90% of current audio designers would be completely incapable of learning them and would be out of business immediately. This explains everything.