Aboutcleggsan Expertise Consumer Electronics of all kinds. Audio, esoteric audio systems and components, video, tv. Digital equipment for consumer use. Ham radio and automotive electronics.
Experience Electrical Engineering; recording, broadcasting, design, international standards, tv and radio theory and practice.
Organizations FELLOW of AES (Audio Engineering Society)
Senior Life Member of IEEE (Institute of Electronic and Electrical Engineers)
International Consulting Organization
Publications IEEE Spectrum
Various Consumer Electronic publications
Education/Credentials BSEE
MSCS
MBA
Awards and Honors Famous Engineer for Digital Audio
Expert: cleggsan Date: 7/10/2008 Subject: Sony STR-SE501 dreaded buzzing
Question I've read many posts on this topic but I couldn't find one that did what mine does. I'll try to explain as much as possible.
Vol. at 0 = no buzz
Vol. at 1 = buzz (not 60Hz hum)
Buzz gets louder with vol. up to MAX
Doesn't matter what "Input" I select (DVD, Tuner, Video, Aux, etc.)
No sources connected to receiver, different outlets don't help, buzz comes from all speakers (L, R, C, Sub)
Sub is connected using RCA to powered sub unit.
I've swapped speakers to different channels, swapped speaker wire (short, long, small gauge, large gauge)
I am a 20 year vet of 12 volt goods in cars but I don't do much at all with home stereo stuff. I have built C-Moy headphone amps and even a headphone amp for my bass guitar using a schematic from a guy on the web.
Also, the tuner part has not worked in a few years. I get nothing but static. Antenna not the problem.
Answer Let me make sure: The buzz is there even when there are no input connections of any kind? Right? And, the buzz is heard as soon as the volume control starts coming up? Right? And, the level of the buzz continues to increase as you increase the volume control (until is saturates out)? Right?
The buzz is power supply ripple buzz and it is at 120 Hz, twice the frequency of the 60 Hz line. It is a buzz because it is a voltage coming out of the full-wave bridge rectifier which is NOT a sine wave but has many harmonics in it and therefore the buzzing sound.
The cause is the loss of one or more filter capacitors in the section of the power supply that feeds the amplifier section ahead of the volume control. The solution is to replace all the electrolytic capacitors in the power supply. The fact that one or two have gone means the others are likely on their way out as well.
