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Transformer voltage issue

T

tonynoriega

Jun 26, 2004
637
45
Tampa, Florida
www.
#1
My wall wart for the Sadowsky DI/Pre tested 12.35volts when I put it on the meter today. It's a 9 volt transformer. Before I plug it in to the unit I want to learn what, if any, problems this may present (I've been using an alkaline battery up to now). I have tested 9v batteries in the past - new - and some of them have been in the 9.8v range so I'm made to wonder if it's a big deal or not.

Thanks!
 
#3
Once you put a load on the wall wart, the voltage will drop considerably, anywhere from 9-11v. In any case, this isn't a big deal anyways. The standard capacitor voltage tolerance for 9v pedals is 16v before they start to strain. Most opamps actually usually run with a wee bit more headroom on 12v.
 
#4
Well, I never really got to find out how much of an issue the voltage variance matters because last evening when I plugged in the Sadowsky with the transformer, it made a steady and loud amplified noise, which of course prompted me to immediately unplug it and insert a 9v battery which worked fine.

The transformer I was using is a Radio Shack adjustable model (the voltage is adjustable) and it seems to fit appropriately in to the jack on the DI. I don't know what the problem is but maybe it has to do with being regulated/not regulated? I was trying to save the 25 bucks that Sadowsky charges for theirs but it looks like I'm going to have to cough it up anyway.

Have any of you Sadowsky users been able to use a generic transformer without troubles? By the way, I'm going to post a seperate question about it since this will probably not catch the attention of Sadowsky owners without the name in the post heading.
 
#5
Be warned, just because it fits into the jack socket means absolutely nothing! And all warrantys are void if you plug in the wrong power supply.

First, get the recommended specs direct from the horses mouth. Either by checking the manual for the preamp, or by finding the specs on the recommended power supply.

You should get two figures, one is the voltage (obviously 9VDC) and the other will be the current requirement. It's also vital to get the correct polarity. This should also be specified.

Now, you want a good quality, DC regulated supply that meets the voltage specs exactly, and meets or exceeds the current spec. Also ensure the connector polarity meets the requirements of the preamp.

A couple of possibilities that might explain your troubles:
  • insufficient current rating of the supply
  • incorrect polarity of the connector
  • AC supply instead of DC
  • poor filtering or lack of regulation
 

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