Actually I believe I'm good at this point, I've ruled everything else out after getting this (new to me) Panasonic SE-405. I really believe some of my issues may be with my home power; maybe some kind of grounding issue, but I just don't get any hum with newer gear like the Surround Master on the same power lines. I may need to call in a electrician to diagnose and nail down the problem.
Back now to CD-4 test LPs, I also have 2 or 3 different ones I plan on locating today and I'll post their discogs page here for others. I know some are better than others, and IINM it was
@Doug G. that mentioned somewhere that one of those LPs has some incorrect tests on it?
The way I figure, the more we discuss CD-4 "fun" LOL we're having and solving problems for others here, we'll drive those CD-4 prices up with new users and it may make a small comeback like a CD-4 board in an upcoming Involve Master Pre-amp
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I have become an expert on eliminating hum after 50 years of doing stereo repairs and live sound systems. There are many causes of hum. Here are some ideas for eliminating it:
Hum is caused by audio equipment picking up the 60 Hz or 50 Hz power line frequency (which one depends on where you are). The problem is that there are many ways for power line frequency to sneak in. Here are some of the ways:
- Defective power supply in a component (hum is always there with that component).
- Defective ground connection in the power cord to a component.
- Multiple paths to ground for the same component (ground loop acts as antenna).
- Missing ground connection between components.
- Missing or disconnected shield in signal cable.
- Circuitry picks up a hum field from a transformer or lamp ballast.
- Noise coming in on a power line (unlikely).
- Radio noise for other sources picked up by equipment.
- The pickup cartridge is in a hum field.
- The pickup cartridge has a bad internal connection.
- Another hum producer making a humming sound in the room.
- Open circuit in balanced line.
Here are some of the strangest solutions I have seen to hum problems:
1. A homemade cable had the signal and ground connections traded at both ends.
2. The cable used for signal was intended for speaker use and had no shield.
3. There was still hum with the system off. A new clock was on the other side of the wall.
4. An AC adaptor was placed next to the balanced line transformer for a guitar.
5. Adding a new component created a ground loop.