My Audible Illusions Modulus 3 has significant phono stage hum at the moment. The tonearm, turntable subchassis, and lundahl transformers are grounded to the preamp. One thing I noticed when checking the grounding connection was that the hum decreased significantly whenever I touched the grounding jack on the preamp. I double checked the connection there, and it became clear that the difference came from adding me to the ground.
Other data point: I just installed new tubes in the preamp. They were rigorously tested by Upscale Audio.
Any ideas about next diagnostic steps?
Other data point: I just installed new tubes in the preamp. They were rigorously tested by Upscale Audio.
Any ideas about next diagnostic steps?
First replace them with the old tubes. If the hum is gone, that"s your answer.
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No! Just much quieter white noise - tube noise I guess? On a hunch, I removed the step-up transformer and the hum was not present. Not quite enough gain for a low output mc, and of course you hear the tube noise a little with the volume way up.
I just did a search on google, step up transformers are prone to introducing noise and hum. I guess my next step is to look into the positioning and grounding of the step-up.
No they are not . I use a 3a with a Cotter transformer and it adds nothing.
Sounds like you have a cable/ tonearm issue that needs sorting or a bad transformer
Regards
David
Sounds like you have a cable/ tonearm issue that needs sorting or a bad transformer
Regards
David
Check there is nothing in the room contributing noise.
I traced "hum" to a phone base. Even moving the base to the opposite side of the room I could still induce hum in the turntable and change the level by waving the base around. Dead silent when I moved the phone to another room.
I traced "hum" to a phone base. Even moving the base to the opposite side of the room I could still induce hum in the turntable and change the level by waving the base around. Dead silent when I moved the phone to another room.
?? Is your cotter your only data point? Other people have traced problems to transformers....
One last data point: I disconnected the transformer from the ground and ran the ground wire direct from the turntable to the preamp. Hum is now much quieter - pretty much masked by below the surface noise of an LP.
You could always switch to an active headamp for the extra LOMC gain - rather than a (passive) SUT!
Andy
On a more serious note, I'm not sure it's even cost effective to mate LOMCs with tube preamps. Step ups and head amps can get expensive. Soundsmith makes very well regarded high output cartridges at various price points. I'm wondering weather to have my Dynavector overhauled for three or four hundred dollar or bite the bullet and get a thousand dollar Soundsmith Carmen. It's a big investment, but cartridges tend to last a long time if you're nice to them.
I'll try that and report back. Both my phono IC is designed to ground to the table, and the table (Sota) has grounding post on the subchassis, so I assumed that the "correct" configuration was to ground there.
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