12v to 5v

[audiogeekess]

Hi I have a really nice 3amp 12v (13.8v) regulated power supply that I'd like to use with my FIIO D3 DAC which expects a 5V input.

Can someone point me to the right voltage regulator to buy? I want the best possible power for this DAC. If it is better to make my own circuit versus buying an integrated voltage regulator, please let me know.

Thanks!

[N-Brock]

For simplicity you can use this 5V regulator, does a good job and has few extra parts.
LM78M05 - 3-Terminal Positive Voltage Regulators

-Nelson

[apoopoo999]

salas shunt or bobken 5v will do, pm me if u want schematics

[ChrisA]

Originally Posted by audiogeekess

Hi I have a really nice 3amp 12v (13.8v) regulated power supply that I'd like to use with my FIIO D3 DAC which expects a 5V input.

Can someone point me to the right voltage regulator to buy? I want the best possible power for this DAC. If it is better to make my own circuit versus buying an integrated voltage regulator, please let me know.

Thanks!

In terms of noise, the best you can do is a battery that is bypassed by a small film cap. Yes even a battery has noise because of it's internal resistance, the small cap will take care of that. The battery is your "gold standard."

The next bet thing you can do is use a 7805 three terminal regulator, also with the caps to bypass the noise

If you want to test your power supply for noise then rig an A/B switch so that your supply is swapped with a battery. Then have a buddy flip a coin and move the switch randomly based on the coin flip. (He MUST use a coin) You guess the switch position. If your PS is good you should guess wrong 50% of the time. Getting this 50% score proves to yourself that there is zero room for improvement and you will not have to wonder if it could be better

[audiogeekess]

Thanks, does the LM78M05 come with those input/output caps or do I need to buy those? Looks like they are outside the chip, but N-Brock said it had a few extra parts.

Chris, what capacitor would I use with a 5v battery? The same one used with that LM78M05? .1 uF?

This is the power supply I have: http://www.amazon.com/Pyramid-PS3KX-.../dp/B0002JTD2K

I need 5v 500ma for the DAC.

[stratus46]

Originally Posted by N-Brock

For simplicity you can use this 5V regulator, does a good job and has few extra parts.
LM78M05 - 3-Terminal Positive Voltage Regulators

-Nelson

The 'M' chips aren't rated for much dissipation. It won't take much current to get the regulator pretty hot. Consider the TO-220 package where you can attach a heatsink.

G²

[sofaspud]

You're planning to use a 41.4 watt supply to power a 2.5 watt device. I just wanted to get that out here. It'll work, but IMHO it's akin to bringing home six bags of groceries in a dump truck.

[audiogeekess]

So order this 7805 from mouser? :

LM78M05CT/NOPB National Semiconductor (TI) Linear Regulators - Standard

It is the LM78M05CT/NOPB TO-220.

[audiogeekess]

Originally Posted by sofaspud

You're planning to use a 41.4 watt supply to power a 2.5 watt device. I just wanted to get that out here. It'll work, but IMHO it's akin to bringing home six bags of groceries in a dump truck.

I might use it to power other things as well.

I also go this cause a lot of people are using it for the V-DAC on Amazon. It got good ratings. I didn't know what else to buy--it's the smallest Pyramid available (2.5A continuous).

It makes my 12v phonostage sound a lot better--better than the switching power supply it came with. I find it interesting that I can turn off the power supply and it runs for about 7 seconds before going out.. So must be a big capacitor in the supply I guess?

I was going to try and run both the DAC and phonostage off the same power supply in parallel if it worked well enough alone for the DAC--don't know if this is a good idea or not as far as noise is concerned.

Does it use a lot of watts idle? --This 3A power supply. (Just put my hand on it while it is running.. it vibrates.. no fan I don't think though.)

[sofaspud]

Yes. capacitor(s) discharging into the load. I don't know about a V-DAC, but I've had a 13.8V/10A Pyramid supply for about 20 years and am happy with it. The vibration you feel is just the transformer behaving normally. Running multiple devices from it ought to be okay; just keep the total draw within the output capability of the supply. I couldn't say what the idle dissipation is. A few watts will be lost just in the regulator circuit. But you're in good shape running the supply through a regulator (get the TO-220 package) to power your FIIO. There's help here on the forum if you need it.