Gilbert Posted August 19, 2007 Share Posted August 19, 2007 Yesterday afternoon when I arrived home from work I found a note from the wife stating that her and kids had gone to a birthday party, and wouldn't be home for a few hours. During this time I did some quality listening, and experimented for the first time with VRDs and BBX crank-up a bit. <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /> I do not know the maximum level at which I played the system (maybe near 50% or a little less), but loud enough to mildly vibrate the brick veneer on the outside of the house. So, pretty loud IMO. Anyway, when I increased the LEFT & RIGHT line level adjustment controls of the BBX, I noticed a low level Hum. It sounds like transformer Hum. It might also be important to note that when I adjusted the line level adjustments, I did so when switching LP's, so no music was playing at that moment. I'm not sure if this means I've got a faulty 12AT7, or other tube, or maybe it's my system component configuration. As currently setup on top of my bedroom dresser, my stereo components line-up from left to right as follows: VRD's next to Thorens TD124 next to BBX next to MR71 Tuner w/ Ah! CD player on top of tuner. Now I know that placing my VRD's and Thorens adjacent one another with only 3 inches of distance between them is not the smartest arrangement, but I had done this at the time due to cable length limitations. Can anyone give me some insight or suggestions as to what might be the source of the HUM, and what is the most effective way to troubleshoot and pin-point this condition with minimal hassles. The hum is not present at an audible levels during normal listening volume. It is only detectable when cranked up, and especially when the TTs tonearm is lifted up. Thanx guys, Gilbert Quote Link to comment Share on other sites More sharing options...
pauln Posted August 19, 2007 Share Posted August 19, 2007 If the volume knob is at 50% you are really in the full power area, and if the hum is not heard with music playing this is normal. Because of the additional gain in the phono signal path, even systems that have no sound through the speakers at full volume with no signal in the source (line level like CD) will show some "blow" with the phone at 1/2 volume. The gain in the phono stage is typically quite a bit more than in the preamp and main amp stages combined. There may be a couple of actions you could try to lower the level of the hum... component positions, wiring placements, and ground verification. Since the position of the cartridge makes the sound vary, is it possible to lay the stylus in the lead in groove of a stationary record and see if the sound is less when CAREFULLY cranked up? Be carefull!!! The record does not have to turn for there to be acoustic feedback. If your exterior brick was vibrating the room interior was probably not a feedback free environment for your turntable. Quote Link to comment Share on other sites More sharing options...
sparrow Posted August 26, 2007 Share Posted August 26, 2007 Good discussion in the earlier post. However, if the hum is louder when touching the tone arm, it could be a ground loop. Do you have more than one grounded equipment plugged into the electrical socket? Try lifting the ground except for one piece of equipment. Everything would be grounded anyway via the patch wires. The hum may go away. Not sure if this will work, but you could try? Quote Link to comment Share on other sites More sharing options...
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