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Welcome to the LOMC twilight zone. When I went from Rosewood Signature to Urushi (same company and all with 5ohm internal impedance) I got a humming issue that sure sounded like ground loop. It look me months to work on it. I checked all the connections, repositioned wires, rearranged plugs and what not. The grounding wire from the tone arm affected the loudness of the hum. I went to a balanced tonearm wire into my phonostage (no grounding needed) and problem was solved. I don't know why I had hum issues with one cart and not the other.
I don't either...it's like when I am touching the metal part of the tonearm with the Ruby Z on at those loading, the grounding is going through me...but the weird thing is, others that have this cartridge load theirs at those values fine! my Shelter 901, a .5mV output has no issues at all?Hm...should I send the cartridge back to be checked up just in case?
Does it do the same thing with the other phonostage? If you can't convince yourself that the cart is not defective, the lingering doubt will eat at you until you won't like the cart. Send it back to have it checked out. Let them fix it or give you a new one. For the money you are paying you have to be sure you are getting a good one, IMHO.
if u need to send it out,be prepare to wait.u probably have a another baby before the Cartridge arrive .lapsan
That's interesting, it just seems unlikely that the slightly bent pivot could be the switch. The arm is probably grounded closer to the base and the wiring doesn't go through the pivot. I guess it's somehow possible. I don't have a better explanation, but an unshielded wire touching the armtube and a resonant circuit at those loads would be more likely? I don't know but the problem is with the Xono IMO.
So, the underlying mystery still remains: why does this only happen with certain loads, the Xono , and the Benz? Where's the fault?There are a bunch of things at play here. One of them probably explains why this is happening.First, consider the circuit hooked up to the preamp. Tuan's body is capacitively coupled to the tonearm: he is one plate, the plastic tonearm lift cover is the insulator, and the tonearm lift and body are the other plate. The tonearm plate is grounded to the preamp ground via the bearing cup and unipivot needle (and ground wiring) when the arm isn't in motion. When the arm is moving, the bad bearing acts as a switch that is opening and closing both randomly and quickly as the metal surfaces chatter against each other. The other capacitor plate (Tuan) is either grounded to the floor or is acting as an antenna -- we don't know which. Either noise from the antenna Tuan, or removal of ground through Tuan, is causing noise to be injected into the ground of the Xono. The rustling characteristic follows the "switch" opening and closing as the metal surfaces chatter.Next, the tonearm/cartridge circuit connected to the first gain device in the Xono consists of the cartridge's resistance and inductance, the wiring capacitance, the load resistor, the ground, and Tuan. With certain load resistors, the first gain stage amplifies the noise injected into the ground when Tuan holds and moves the tonearm. Why with only certain loads? Yesterday, I had two possible explanations: There's either a resonant circuit formed by these particular component values that's coincidentally tuned to something going on mechanically, or the first gain stage of the Xono is rectifying the high frequency noise from Tuan the antenna when this particular combination of values is added to the circuit.Another possibility that's come to mind is that there may be a DC offset between ground in the Xono and Tuan the capacitor. Inductive coupling between the preamp's power supply transformer and the ground/chassis could be raising the ground voltage, or the charge on Tuan or whatever he's standing on could be raising the Tuan capacitor plate's voltage. The "switch" in the pivot would then cause the DC voltage to turn on and off rapidly, changing the operation conditions of the first gain stage or just showing up as plain noise. I've seen hundreds of volts from transformer leakage inductance before, which would drop to zero when the transformer body is properly grounded. The amount of current when making the ground connection was miniscule, so this was not an actual fault where the AC or DC grounds were shorted to the chassis.The only way to know for sure what the actual cause is would be to measure for DC offsets and to scope the signal that's going into the Xono. Unfortunately, trying to measure either of these would change the grounding and loading and stop the noise! At least we now know that Tuan can double as a capacitor or an antenna when needed.- Eric
I look forward to your regular posts here!
I think Tuan is a switch, capacitor, and antenna.Once you start hearing things that make you think something is not right it is a tough path. Hope my tonearm upgrade isn't another round of audio Russian roulette.
Tuan, don't want to get off topic.But, have a four point on order. Before I move up the cartridge food chain I want to end game my tonearm.
