Getting +15/-15V and +48V from 9V

[nordine]

Hi there, i dont know if this is very "stompbox" related, but its very diy related so here i go  :

i want to get what i stated in the topic title, 15/15 and 48V from a 9VDC supply

should i even bother? should i get a toroidal transformer and forget chip solutions? ive read some threads but im not sure which option is best, and gives me the cleanest voltage

im all eyes 

[armdnrdy]

The cleanest voltage by far would be had with a properly filtered power supply using a toroidal transformer.

What may I ask are you powering?

[nordine]

sure, i want to power the $5 mic preamp

already have the chip, but this phantom power bussiness is starting to get troublesome

[knutolai]

Wouldn't using a 48V power supply be better? If this isn't supposed to be a pedal and there's no chance you will mix their power supplies, why obey to that standard?

[nordine]

Wouldn't using a 48V power supply be better? If this isn't supposed to be a pedal and there's no chance you will mix their power supplies, why obey to that standard?

because 9V is what i have at hand
any pointers to get clean 48V? also +15/-15 for that matter. being it transformers, ics, whatever.. i want to get into hifi and synth territory, so i need to learn these new tricks

[samhay]

how much current do you need?

[nordine]

how much current do you need?

is a bipolar powered mic pre and phantom power for the condenser mic

[samhay]

ok - perhaps 10mA of each.
You might be able to get away with using a charge pump like a 7660S or TC1044S. The data sheets have a lot of useful examples.

[Seljer]

That datasheet for the INA217 lists the acceptable supply voltage range from +-4.5V to +-18V.

I'd just go and use two batteries for +-9V and call it a day


Use a charge pump to get the phantom power supply.

[blackieNYC]

Very few mics require the full 48.   There are little boxes that add phantom, and have two 9v batteries inside. I don't recommend that particular box, but it works.   If you have a variable DC supply you could check out what your mics require. 

[TheWinterSnow]

Very few mics require the full 48.   There are little boxes that add phantom, and have two 9v batteries inside. I don't recommend that particular box, but it works.   If you have a variable DC supply you could check out what your mics require. 

Mics don't use the full 48v but that is because there is a large voltage loss across the biasing resistors and thus a mic that draws more current will get less supply voltage.  Phantom power is usually limited to just above 14mA, if mic pulls exactly 14mA, it will only have a supply voltage of 1.8v.  Typical mics draw 5mA to 10mA so they usually are supplied with 15V to 30v.

To the OP, your best bet is to use a pump charge IC in a voltage multiplying configuration to get the 48v (will actually be ~49v) and use some of the voltage taps to get 30v and use that 30v as a single ended supply rather than a bi-polar supply.  For such high voltages and as such I expect higher current draw than 10mA, you should look more into the LT1054 which allows up to 100mA.

You could use two DC to DC converters but unfortunately they are not easy for beginners to design.

[garcho]

Synth modules? You'll want a power supply that can handle current to all the modules you'll fit in your rack/cab whatever. Know what you're gonna build? No? Then over shoot.
Don't mess with mains unless someone who KNOWS what they're doing is watching you closely while you work. Death, pain, fire, etc.
A number of us have had good and bad luck with 1044 style chips. They usually work for me.

[tombaker]

Check out the JLM Audio website. Joe makes a mono mic pre thats portable and runs off two 9V nimH batteries.
I'm not saying you should buy one, he has all the schematics available in the build thread section. Like its been said most mics dont actually need 48V to run, thats just optimum headroom level.
Ive got one and it sounds great, the schematic also has a hook up for a 48V power supply so you can go the full voltage and it also recharges the batteries. But from memory he creates a single 18V rail instead of a dual +/-9V