Hum in Standel Hybrid

Jerry Roller · Post by **Jerry Roller** » 11 Sep 2004 8:11 am

I have one that has a hum even with nothing plugged into it. The hum is there even with the volume control turned to zero and gets louder as you crank the volume. Does anyone have an idea where to start to correct this?
Jerry

John Daugherty · Post by **John Daugherty** » 11 Sep 2004 8:18 am

Probably the filter capacitors in the power supply need to be replaced. This is a common problem with aging amplifiers.
Defective filter caps will cause the exact symptoms you described....JD

Gene Jones · Post by **Gene Jones** » 11 Sep 2004 8:23 am

Jerry, I'm not sure about your hybrid, but I played a Standel Custom "tube" amp for several years with an EchoPlex and a CordOVox, and always had to be careful with my settings on everything to avoid "hums".

I only had my "solid-state" custom Standel for a brief period before some low-life burglarized it from our bandstand, but during our short association I never had a "hum" or any problems with it.

www.genejones.com

Ken Fox · Post by **Ken Fox** » 11 Sep 2004 9:14 am

I fixed one about a year or so ago Jerry, same problem. Filter caps were bad. There is a cap on the plus voltage rail and one the minus supply voltage rail. They phase cancel what hum is left after filtering. If one is weaker than the other, the difference in hum that is not cancelled is amplified by the power transistors. As the transistors are after the volume controls, the noise is there at any volume setting.