I am using muffsy phono stage kit https://www.muffsy.com/mobile/ with Thorens TD160 turntable. This turntable does not have any ground wire. It is making hum and buzzing sound when I use. I tested the Thorens Td160 with other integrated amp but there is no hum or buz, even at the highest volume level. I have checked the gournd scheme of the turntable , it is ok. When I disconnect the phono stage from the turntable, while the phono stage (muffsy) is connected with pre and power (no turntable is connected with phono stage muffsy) it is making huge hum sound. The hum reduces when the turntable is connected with Muffsy. The speaker is absolutely silent when I use the CD or DAC, so this is not a problem of my pre or power amp. Please help. My system is First watt M2 (DIY), DIY tube preamp, DIY speaker (Finalist). Best regards
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Firstly double check all the cable connections, esp. from the preamp to the amp - phono connectors can sometimes fail to have good ground connection, and may need a little careful squeezing with pliers to regain good grip on the ground ring.
Does shorting the input to the muffsy make any difference from having them unconnected?
Does shorting the input to the muffsy make any difference from having them unconnected?
I have checked all connections and there is no problem. I have a big casing to match all other equipments. I have used a ei core transformer which is at least 11 inch way from the main circuitry. I have connected the ground by a wire both with the chassis and the RCA negative side. Checked the ground and other connections by meter, it is ok. There is no loose connection. Still the buzzing and humming sound prevailing. It is auditable from 3 meter distance when the volume is full. At 3/4 of volume it can be heard from 1 m distance. Can anyone help. I wrote to the vendor, there is no reply! I am attaching pictures showing all connections , dip switch and setting.
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Check if there is a line filter in the input plug. If there is such a filter, many of them has two Y capos between line (Live and Neutral) to chassis (Normally earthed), and then current flows from line to chassis to audio amplifier ground causing hum.
This also may be caused by some resistor usually wired between line or neutral to chassis, or the transformer itself (Leakage to chassis).
In any case I suggest a wire to earth the chassis, including your safety, and the amp.
This also may be caused by some resistor usually wired between line or neutral to chassis, or the transformer itself (Leakage to chassis).
In any case I suggest a wire to earth the chassis, including your safety, and the amp.
The transformer is properly isolated from the chassis, no possibility to have leakage with chassis. Your first point is beyond my knowledge and idea how to check. It will be helpful if you kindly guide me.
This also may be caused by
This also may be caused by
All kind of thansformer has some leak from the windings to chassis: one is capacitive (From the winding to the core and then to the chassis if it isn't galvanicaly isolated. The other is resistive, the plastics and the varnish in the winding establish a high value resistive leak that may be amplified by the high gain amplifier inside the TT.
As Osvaldo asked, what does the hum do when the inputs are shorted to ground?
I have a muffsy (I actually have 3...) and I have found it to be somewhat susceptible to induced hum from the transformer, in my experience, 11” is not anywhere near enough distance. Do you have a 15v AC wall wart you can try? When the phonostage is far from the transformer, my circuit is silent.
Your grounding looks like it may need a change, but it’s not entirely visible in the photos. Can you draw it out for us? All chassis and PCB connections.
I have a muffsy (I actually have 3...) and I have found it to be somewhat susceptible to induced hum from the transformer, in my experience, 11” is not anywhere near enough distance. Do you have a 15v AC wall wart you can try? When the phonostage is far from the transformer, my circuit is silent.
Your grounding looks like it may need a change, but it’s not entirely visible in the photos. Can you draw it out for us? All chassis and PCB connections.
Since you have this in an uninsulated chassis you must have a fuse on the live side of your AC after the IEC before the transformer, and an attachment to the mains safety earth.
Do you have an Earth ground connection somewhere in the system? Usually the amplifier or linestage has a 3-prong power cord. If not, your entire system is floating...
http://www.hagtech.com/pdf/eliminatingnoise.pdf
http://www.hagtech.com/pdf/eliminatingnoise.pdf
I would try a CL-60 between the chassis ground and the phono amp RCA's ground. Easy to try, just unbolt the chassis ground from the chassis and install the CL-60.
I agree that the chassis should be connected to the ground pin on the IEC, just in case.
I agree that the chassis should be connected to the ground pin on the IEC, just in case.
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