I have four 14v SMPS's that I put in series to make a 28-0-28 supply for some 41hz.com AMP-1B's. The problem is when I connect my bulk capacitors to the supplies there is a strange buzzing that comes from them that doesnt stop until there is a load of a couple amps applied.
The setup works perfectly fine with and without the caps attached, but the supplies only buzz when they are connected😕 . Voltages between the supplies vary about 0.2v, is this a problem?
Oh, and they will also make the noise if I connect just one cap to one supply.
The setup works perfectly fine with and without the caps attached, but the supplies only buzz when they are connected😕 . Voltages between the supplies vary about 0.2v, is this a problem?
Oh, and they will also make the noise if I connect just one cap to one supply.
Ok I fixed the buzzing but in a very strange way, and I have no clue what it did to actually fix the problem.
I just put a very low resistance in series with the power wire to the cap.
I dont have any low value high wattage resistors so I used a piece of NiCrome wire. The piece of wire is 2" and has a resistance of about 0.5 ohms.
If no one sees a problem with the way I'm doing this I guess this will be my solution. The NiCrome wire can handle hundreds of watts of heat so I dont have to worry about it burning up like a resistor would.
I just put a very low resistance in series with the power wire to the cap.
I dont have any low value high wattage resistors so I used a piece of NiCrome wire. The piece of wire is 2" and has a resistance of about 0.5 ohms.
If no one sees a problem with the way I'm doing this I guess this will be my solution. The NiCrome wire can handle hundreds of watts of heat so I dont have to worry about it burning up like a resistor would.
This buzzing is probably due to control loop instability or discontinuous mode operation. Sometimes some SMPS have a hard time working with very light loads, so adding dummy load resistors in paralell with the output of each SMPS will probably be a better solution.
Thank you for the reply Eva. A dummy load across the output requires quite a bit of current before the buzzing stops.
Will having 0.5 ohms of resistance in series before the bulk caps have any negative effect on the amplifiers?
Will having 0.5 ohms of resistance in series before the bulk caps have any negative effect on the amplifiers?
Thanks Eva, a simple statement from you like "nothing bad" is extremely comforting to me.
The DIY resistors seem to be doing the trick. After playing a 20hz sine wave near clipping the makeshift resistor gets pretty warm, but it doesn't glow red so thats good. I still don't know why such a small amount of resistance in series with a cap fixed whatever was wrong, but I guess it doesn't really matter why as long as it works.
Here's a pic of my DIY resistor and the complete test setup....... on the carpet no less.
don't tell Mrs. Anonymous, shes away for the weekend.
The DIY resistors seem to be doing the trick. After playing a 20hz sine wave near clipping the makeshift resistor gets pretty warm, but it doesn't glow red so thats good. I still don't know why such a small amount of resistance in series with a cap fixed whatever was wrong, but I guess it doesn't really matter why as long as it works.
Here's a pic of my DIY resistor and the complete test setup....... on the carpet no less.
don't tell Mrs. Anonymous, shes away for the weekend.
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