I ran into a little problem while providing some vintage audio sounds for the season. In the room with the Christmas tree is a Marantz SR-820DC receiver with Akai GX-400D SS and GX-747 DBX reel to reel decks connected. I have been listening to some tapes I picked up from a radio station and also transferring some formats over to the more common 7.5 IPS quarter track format. Some of the tapes are 15 IPS and others are old half track mono. The GX-400D handles the 15 IPS speed and with its 4 channel capability it also does a good job with the old half track tapes. All was happy with the vintage stuff.
The problem occurred when I hooked up an XM receiver for the Radio Classic channel. I noticed after a few minutes the receiver volume control had gotten noisy. Switching to either of the tape decks made the problem disappear. I checked the XM receiver and it puts about half a volt of DC on the audio output. This one doesn't have a line out so I was using headphone out to line in. Adding blocking capacitors took care of the problem and after Christmas I will do some surgery and add line output to the XM receiver. I imagine with dynamic headphones connected the DC isn't an issue but with the high resistance/impedance line inputs it was. So with a tip of the hat to "madman Muntz" I added a couple of capacitors
Now I can enjoy Dragnet and Johnny Dollar without a crackle.