How to power these boards on DC?

[mkv]

Hey guys,

Forgive my beginner questions, I'm learning as I go along.

I'm putting together a little DIY audio project, and I found this great preamp board which I want to use. The problem is though that the board specifies that it requires an AC supply, however the project is mobile and will be running on DC. Am I able to run this board on DC somehow or do I have to find another preamp?

The preamp is pictured here:
NE5532 Preamp DIY Treble Mediant Bass Blance Volume Board Aseeembled $20.73 Free Shipping @GoodLuckBuy.com

It seems alot of these preamps using the NE5532 require an AC aupply. How can one get around this?

Thanks for your help!
Mark

 

[DF96]

You could try feeding in a DC supply, say 20-0-20V. The AC probably goes straight to a bridge rectifier so you can feed DC through it. This device probably will not function from a single DC supply without some reworking - would be easier to start again if that is your aim.

 

[mkv]

I have had a quick look around for an off the shelf dc to dc supply, say 12V DC to 6-0-6, or 24V DC to 12-0-12.

Haven't found anything...

It's easy to find DC powered class D power amps for what I'm looking for, but I can't seem to find any volume/bass/mid/treble preamps which run on DC for my needs... Can anyone suggest something?

Thanks for the help!

 

[Minion]

The board has on board rectifiers , regulation and filtering for turning AC to filtered DC .....
If this is going to be a mobile you can use 2 x 9v batteries in series to get a +/-9v dc supply , You would need to mod the Rectifier/regulator section of the pcb to accept a DC supply , it could be as easy as installing a couple jumpers .....

 

[wwenze]

I see 3-pin regulators... likely to be 12V or 15V...

 

[MarianB]

That board requires AC suply because it has it's own bridge rectifier and filtering caps, and stabiliser just after them, the stabilisers seem to be 7812/7912 so it would be as simple as feeding the DC supply voltages directly on the capacitors pins ( the 2200uF/25V ones ), no modification needed, just be careful to respect the polarities. If DC supply voltages are smaller than 12V ( or equal ) but they are from some battery so stable than you need to bypass the stabilisers, just remove them and with a jumper feed the voltages from the caps to the Vout of the stabilisers, it's sound complicated but in fact it's verry easy.

 

[DF96]

You can't simply apply a single supply to a circuit designed for a dual supply. Single supply is less popular now, but I would have thought that the internet still has lots of simple preamp circuits for 12V. Just look for them. There is a 12V based tone control being discussed in another thread on here right now.

 

[MarianB]

I do not remmber saying that he should use single supply, ofcourse it should be a simetrycall DC supply ( i sayd voltages, not voltage ), so as someone else sayd use two 9V batteryes and all should be ok, just bypass the stabilisers.

 

[DF96]

No, he implied he wants to operate from a single 12V or 24V DC supply - presumably a battery? See post 3. He can of course use two batteries.

 

[MarianB]

Ok sorry then... as i see he sayd that he was looking for some DC to DC converter from a sigle supply to simetricall one ( for example 24Dc in <=> +/-12VDc Out...) , but he did not find anyting ( he might try floating ground..), i might be wrong but this is what i understud from message #3.

Two 9V batteries are more than ok, the power consumption for that board is verry low so the batteryes should last long time, and they are cheap.

 

[mkv]

Hey guys,

Thanks for the replies. To answer your questions, I am trying to run it from a single DC supply, namely a battery. From what I understand I could use 2 batteries in series, then take a tap off their join for the '0V'?

I guess I could use a 24V charger across the two 12V batteries if I wanted to charge without removing them?

Single source preamp/tone control circuits aren't THAT easy to find, however I have found a fairly easy one to make using the TDA1512A. That will solve all my needs, and I think I'll just use Class D amps for battery based applications.

Thanks!
Mark

 

[whizgeek]

I think that cct is using 12v regulators.
If you are using 12V batteries, remove the regulators and fix a jumper across in to out.
those regs probably use more power than the rest of the board

 

[MarianB]

...I think that cct is using 12v regulators...

I've already sayd it does on the other page, so it's nothing new

..those regs probably use more power than the rest of the board...

Not likely, they have a quiescent current of les than 10mA ( about 6,5 to be exact ), the OA on the ather hand requiers more than that, ( about 20mA each ), but anyway, that is NOt the reason why he should bypass the regulators ( sayd that too myself ) but thing is the regs need some minimal Vin-Vout difference to work properly, you cannot power a 12v regulator with 12V and espect it to perform well, on the other hand, powering an OA from batteryes makes the regs useless cus the voltage is already fairly stable.

@mkv that board requires split supply so eyther 9 or 12V battery you still ned 2 of them, connect them in series and take the 0 point ( ground ) from the batteryes joyning point, connect them directly on the filter caps pins and bypass the regulators as i say before, that is all you need to do.

 

[alayn91]

Hello,

It's written on the ad:
"- Input voltage:AC15V-0-AC15V"

So, you only need a transformer.

Regards.
Alain.

 

[MarianB]

@alayn91 didn't you read anything? @mkv specified that he wants to power the board directly from DC supply, he wants it to be mobile so a transformer is out of the question here.

 

[mkv]

Hello,

It's written on the ad:
"- Input voltage:AC15V-0-AC15V"

So, you only need a transformer.

Regards.
Alain.

Hi Alayn91,

Thanks for the reply. But I'm looking to power from a DC source, like a battery. I'm going to do the twin 12V batt setup though, then charge across them with a 24v charger.

M

 

[DCPreamp]

You could try this: Switching boost Power Supply board DC12V to DC±32V 180W | eBay I bought one of these from this guy and it works just fine! The component quality is actually quite good and it operates pretty cool powering a load (when properly heatsunk).

Because the preamp board you're looking for has a bridge rectifier on the input, you can apply AC (naturally) or DC and it will work fine. With +/-DC voltage applied, the current will just flow through two diodes only, but still work fine.

Next, because the preamp board you're looking at uses input regulators, most likely 7812/7912 (or 9V, 15V), and they can handle up to 37Vin, so applying the +/- switching regulator with an output of +/-32VDC, it will work just fine.

Plus, there should be enough power left over to run a power amp along with the preamp all from the same supply.

You'll have to check on shipping to your location, but this is a reputable seller and a great price for the complexity and quality of the supply.

 

[spwalek]

Do you need the 24v swing? If not I would suggest bypassing the regulators and building a negative voltage pump with a 555 timer. If it's just opamps you shouldn't need a ton of current and it will keep the weight down if it's portable. just a thought