2016 July 7    Audio   How-To

Introduction


A reader emailed me, asking how to wire the Bellari VP-130 phono preamp to work with the PS-1501 power supply.

This article applies to any other phono preamp that takes a "wall-wart" power supply, as long as you mind the correct voltages and polarities

DISCLAIMER:  I accept no responsibility for what may happen if you try any of this.  Careless soldering or wiring can cause serious repercussions.  Use the info at your own risk!


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In This Article


Before You Do Anything Else

Soldering, Or Not

Testing It All Out

Conclusion




Before You Do Anything Else


Find out the correct voltage and polarity that your pre-amp takes.  Look at the power supply that came with your pre-amp.  Somewhere on that power supply, or on the pre-amp itself, there should be information about the correct voltage.  For example, "15V, 0.3A" would be 15 volts, 0.3 amps (i.e., 300 milliamps).  Before you do anything else, you need this information.

On a unit like the VP-130, the stock power supply has a weak current output (300 milliamps).  The max current output on your new supply can be higher (in this case it should be), but you must get the voltage correct.  On most audio power-supplies, two-tenths of a volt either way is not going to fry anything, but you should get it as close as possible.

Next, the polarity.  You must get this right, or you will probably ruin the electronics instantly.  Getting it wrong may also create a dangerous situation.

The power supply usually has a little diagram showing the polarity.  Look for a small circle that goes around an even smaller circle or solid dot.  The central dot should have a line coming from it, showing either "+" or "-" depending on the polarity.  The Bellari VP-130 also shows the correct polarity right on the casing:



Watch that polarity.  The Bellari VP-130 is CENTER NEGATIVE, which is kind of unusual.

Don't mix it up with another connector that's wired center-positive... bad things could happen.


Soldering, Or Not


Some people don't like to solder.  It does take some skill.  The most difficult part is getting the solder to "tin" the metal.  Clean copper wire tins fairly easily with rosin-core solder.  If you solder stuff, you should have a roll of this for sure.  Don't forget the respirator.  (See this article for more about that.)

If you just use the DC output cord from the stock power supply, you won't need to solder.  You know that little round connector that goes from the wall-wart into the pre-amp?  You'll want that, with at least eight or ten inches of wire attached to it  Leave a couple inches of wire at the wall-wart junction, in case you have to solder it back on later....)

Once you have the connector and some usable length of wire still attached to it, just figure out which wire is positive and which is negative. 
(USUALLY the one with the white stripe or dotted line is positive...)  Then attach the leads to the corresponding terminals of the PS-1501.

Sometimes the wire leads on a cheap power supply are too thin.  Wouldn't you hate for that to be the limiting factor in your whole audio system?  If you are inclined to solder, you could attach the DC power plug to a set of thicker wires; that's what I did.  Again, make sure you use the correct polarity.  I strongly suggest using a digital multimeter with "continuity check" to make sure you get it right.

I used an orange wire for positive and a black wire for negative, but usually people use red and black.






Testing It All Out


Once you have the DC power connector attached to the wires, and the wires attached to the linear power supply, you should test the voltage before you plug it into the pre-amp.

At this point I should also advise you that if you have a two-year-old who likes LED lights and electronics, he or she is probably going to turn that voltage knob on the power supply when you least want that to happen.  I would keep that power supply somewhere safe when you're not directly using it.

However, it is a happy coincidence that the PS-1501 has a maximum voltage of 15 volts.  That means it is unlikely to burn out your Bellari VP-130 even if someone cranks it up to the max.  Other pre-amps, I don't know;  depends on their maximum input voltage. 

Now, test the voltage with your multimeter.  Do you know how to do a polarity check?  Most any digital multimeter will show a positive voltage when you have the red lead to positive and the black lead to negative; meanwhile, it will show a negative voltage if you have them reversed.  Test this to your own satisfaction, using the linear power supply with no wires attached, before you test out your power connector wires.  And of course you should always test every power supply anyway, just to make sure they put the right colors in the right places at the factory.....



         



Conclusion


Upgrading the power supply can improve the audio response of your audio equipment.  In fact, it's often one of the most cost-effective improvements you can do.

Connecting a linear power supply to your pre-amp is generally quite easy.  If the pre-amp uses a "wall wart" with DC output, you probably won't even need to do any soldering.

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