Hello,
I finally got around to building my Crack, which I ordered July last year. Yes, it has been a busy 11 months, I got married, and diagnosed with ADD, and those two things probably go a long way in explaining why it took me so long.
So I have completed the build, and there is a loud buzz in both channels, with the following characteristics:
- 55Hz fundamental, with harmonics at every +100Hz (ie. 155Hz, 255Hz, 355Hz, etc) - I did a quick test with an iPhone app by placing the end of my phone inside my headphones.
- Hum is at a low level when I power on and remains like that for around 20-30s, at which point it ramps up fairly quickly to a loud level and remains there.
- Hum is independent of volume control
- Hum is present both with and without a source plugged into the RCA jacks
- I am using Sennheiser HD600 headphones
I've triple checked the connections, re-done most of the solder joints (my soldering is pretty decent), I've tapped/pushed all of the wires, components, lugs, tubes, everything many times with a chopstick , and the hum does not change.
Oh and my voltages and resistances checked out okay.
I should also add, the output tube is a 'special 6080' that was the weekly special at the time of my order. It says "JAN-CAHG-6080WA CHATHAM ELECTRONICS 5933".
I am in Australia, so it is 240V.
I've played music through it, and behind the horrible hum, it sounds great (ie. playback at a high level with music that is dense enough in the low end to drown out the hum) Any ideas?
Cheers,
James
