Convert AC Power Supply to DC?

[michaywood]

Hey!

So I've got a homemade pedal board with 3 components. A preamp, tuner, and some LED lights. Now that I've got them on the board, I'm wanting to power them all at once. Thus lies the problem..

Preamp runs off 9V AC
Tuner runs off 9V DC
LEDs run off 12V DC

I spent over an hour with the manager at my local radio shack who helped me figure this out as well as helped me figure out the polarity of the LEDs. Turns out, I can run the LEDs off 9V DC, but it's a positive polarity (compared to my tuner which runs off a negative polarity). So I've already cut the wire and flipped it so the wire going to the LEDs are the correct polarity.

So, now I have the lights daisy chained to the tuner, since they are both running 9V DC right now.

So that gives me 2 components are 9V DC and 1 component is 9V AC.

What I can't figure out, is there some sort of inline option where I can power the 9V AC component, then daisy chain out of that power supply and somehow convert it to DC power? That way I could have all 3 daisy chained running off 1 power supply (a 9V AC power supply).

Thanks in advance!

[g1]

What is the preamp? May be fairly easy to convert it to run on DC.

[J M Fahey]

*Maybe* the preamp needs 9VAC to run some tube, or to get split rails.

[michaywood]

What is the preamp? May be fairly easy to convert it to run on DC.

It's an ART Mic Tube PreAmp . Here's the link: ART Tube MP Studio Mic Preamp | Musician's Friend


The perfect scenario would be just to have something wired inline since the daisy chain cable was $5 and there is room for error.

[eschertron]

It's an ART Mic Tube PreAmp . Here's the link: ART Tube MP Studio Mic Preamp | Musician's Friend


The perfect scenario would be just to have something wired inline since the daisy chain cable was $5 and there is room for error.

So clarify things if I don't seem to understand:
you have a mic pre that came with a 9vac adapter
you have a tuner that did not come with an adapter
you have a couple of LEDs and interconnecting wires

before I jump in and give advice, is that it? Also, the specs for the mic pre in the MF ad did not give power requirements for the unit or any specs for the power supply. If you can find those numbers in the docs that came with the parts (or possibly printed right on the devices), it would be helpful to know how much excess capacity the adapter has.

[michaywood]

So clarify things if I don't seem to understand:
you have a mic pre that came with a 9vac adapter
you have a tuner that did not come with an adapter
you have a couple of LEDs and interconnecting wires

before I jump in and give advice, is that it? Also, the specs for the mic pre in the MF ad did not give power requirements for the unit or any specs for the power supply. If you can find those numbers in the docs that came with the parts (or possibly printed right on the devices), it would be helpful to know how much excess capacity the adapter has.

I just took a photo and tried to illustrate how I hope to have things hooked up.

The white box in the middle is the hook up for the LEDs.

Thoughts?

[eschertron]

If you have the capacity available from the 9vac adapter, you can make 'something' that will provide power to the tuner. What I still don't get:

What are the LEDs for? How many do you have, and are they going to ba a significant current drain?
With all the hours you've already spent and will spend additionally on this ac-to-dc project added to the cost of parts, why don't you get a 9vdc adapter and be done with it? I'm not being snotty, I'm suggesting a "next best" analysis might be employed here.

[Enzo]

The LEDs are not really an issue. You can run them on most any voltage, just change the current limit resistor. And polarity? If they want positive, just turn them the other way, now they want negative.

Most of those units using AC adaptors are doing so because they will make a split supply from it. You probably COULD come up with a DC-DC converter that makes negative 9v from positive, but really that is a very complicated way to solve the simple problem of two power adaptors.

[52 Bill]

If the 9vac power supply is big enough to supply all of the current that you will need for the other items, it can be used to build a 12dc and a 9vdc supply. The 9vac rectified and filtered will give you about 12vdc unregulated, which in turn can be reduced down to a 9vdc regulated.

You need to figure out how much current the 9vac supply can carry and what the total current needs of the three items plus the added power supply circuit will draw. Basic power supply rectifier bridge with a filter cap and either a transistor or Zener diode based regulator circuit should be easy to design or find online.

[J M Fahey]

Here it is in the simplest implementation:

[michaywood]

Thanks so much for the replies! I really am a simplistic person so would love if I could get this down to just one power supply! You can practically take the LEDs out of the picture, because I've already tested by hooking them up to the power out on the BOSS pedal and they powered up just fine since I rewired the cable to flip the polarity going to the LEDs. Running the lights off 9V is bright enough for me. So that part is figured out, so we can remove that from the equation.

So that drops the question to: I have a PreAmp and a Tuner that I want to run off 1 power supply. Preamp is 9vAC. Tuner is 9vDC. How can I run them off 1 power supply?

In my mind, I would love a simple solution like the below picture (without the switch). But I imagine just a little box with a female in and male out that takes an AC signal and sends out a DC signal.


Any ideas? Thanks again!

[52 Bill]

In my mind, I would love a simple solution like the below picture (without the switch). But I imagine just a little box with a female in and male out that takes an AC signal and sends out a DC signal.

I did a quick search, and I could only find one power supply that did both ac and dc voltages. And that one only did 12 volts ac and cost $500.00.

Juan's circuit is what you need, and could be built in a small box like the one that you showed. Maybe you have a local shop that can build it for you?

[olddawg]

I did a quick search, and I could only find one power supply that did both ac and dc voltages. And that one only did 12 volts ac and cost $500.00.

Juan's circuit is what you need, and could be built in a small box like the one that you showed. Maybe you have a local shop that can build it for you?

That Art. Preamp not only runs on AC but also draws more current. Just use it's own separate dedicated AC supply. On my pedal board I actually have a 120v AC terminal strip at the top. Although most of my pedals are daisy chained off of a OneSpot supply. It gives me versatility for any oddballs or anything else that needs power near my pedal board. I have a black removable 8 ft power cord that plugs into it.

[michaywood]

That Art. Preamp not only runs on AC but also draws more current. Just use it's own separate dedicated AC supply. On my pedal board I actually have a 120v AC terminal strip at the top. Although most of my pedals are daisy chained off of a OneSpot supply. It gives me versatility for any oddballs or anything else that needs power near my pedal board. I have a black removable 8 ft power cord that plugs into it.

Yea, I had a feeling that preamp was a power sucker. And don't really have much room on my pedal board for much more! I don't know any local electricians, but maybe I can find someone who could make that thing that Juan drew up. Thanks for that, Juan.



The way I run things now, is I power the Preamp with the power supply, then run the BOSS Tuner of a 9V battery. I guess if I wanted to, I could run the Tuner AND the LEDS off a 9V battery, then just have 1 power supply for the preamp. Then I'd just have to remember to always bring batteries.

I did some searching (not an electrician I am) and from googling, it looks like a rectifier is something you can wire in place that converts AC to DC? So couldn't I find some rectifier and just put it inline? Or do they not work that way? haha.

[eschertron]

Yea, I had a feeling that preamp was a power sucker. And don't really have much room on my pedal board for much more! I don't know any local electricians, but maybe I can find someone who could make that thing that Juan drew up. Thanks for that, Juan.



The way I run things now, is I power the Preamp with the power supply, then run the BOSS Tuner of a 9V battery. I guess if I wanted to, I could run the Tuner AND the LEDS off a 9V battery, then just have 1 power supply for the preamp. Then I'd just have to remember to always bring batteries.

I did some searching (not an electrician I am) and from googling, it looks like a rectifier is something you can wire in place that converts AC to DC? So couldn't I find some rectifier and just put it inline? Or do they not work that way? haha.

D1 in Juan's schematic "is" the rectifier. the rest is filtering and current limiting. Google or Wiki should take you to some time/voltage traces that show how 1 or more diodes act to rectifier AC. Different configurations produce different results, bottom line. If you're a visual learner (I am) you might understand how it works from those few examples.