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Muffsy phono stage hum problem

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Daniel4381

New Member
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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Should learn something here ... I have a Mk 1 TD160.
I losed some hum on TT when I put in nylon cartridge screws.......weird.
 
Reliving. said:
Should learn something here ... I have a Mk 1 TD160.
I losed some hum on TT when I put in nylon cartridge screws.......weird.
Click to expand...
Maybe not so weird as steel screws may have made an electrical connection between the tonearm and one of the negative terminals of the cartridge. As always, the devil is in the detail.
 
Daniel4381 said:
Thanks for the reply, there is no ground wire from muffsy to integrated amp, so as my main system that tube pre.
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Sounds like a grounding issue with the muffsy to Pre Amp. Or a ground loop within the muffsy itself. Ground it to the pre amp and see if it helps. If not, recheck your work, or contact muffsy.
 
I agree with Skywatcher, put in your own ground wire. I don't remember seeing a turntable without a ground and the amplifier would always make noise until I grounded that black turntable wire to the amplifier case.
 
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. The noise reduces to half when connected with turntable.
 

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Daniel4381 said:
I wrote to the vendor, there is no reply!
Click to expand...

No surprise there. It's a "kit" made in China.. Some of the solder joints look "dry", meaning it looks like they may not be making the best contact. Try shorting the inputs + to - (center to ground on the RCA connectors) with about a 1k-3k resistor in the muffsy and see if the hum gets better. You can buy "shorting plugs" for RCA inputs. I use them on unused inputs to eliminate stray hum. Don't short the outputs though. :D
 
Daniel4381 said:
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. The noise reduces to half when connected with turntable.
Click to expand...

I looked at each picture. I did not see any connection to the amplifier chassis shown??
 
ironcoder said:
I looked at each picture. I did not see any connection to the amplifier chassis shown??
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The yellow wire is bolted to the metalwork.

Are all those phono sockets isolated from the chassis? They should be. Also, the input and output sockets' earth tags are linked together - try cutting the link between the inputs and outputs. They should be linked on the PCB and the extra link is causing a small ground loop.
 
rothwellaudio said:
The yellow wire is bolted to the metalwork.

Are all those phono sockets isolated from the chassis? They should be. Also, the input and output sockets' earth tags are linked together - try cutting the link between the inputs and outputs. They should be linked on the PCB and the extra link is causing a small ground loop.
Click to expand...
RCA negative of all output and input along with ground are soldered together.
Then, a wire is connected to the chassis with the RCA negative tag. If I separate the input and output tag, how those will be connected to chassis? Should I only connect chassis with the input tag or chassis connections for input and output to be separated. Please suggest.
 
Daniel4381 said:
RCA negative of all output and input along with ground are soldered together.
Then, a wire is connected to the chassis with the RCA negative tag. If I separate the input and output tag, how those will be connected to chassis? Should I only connect chassis with the input tag or chassis connections for input and output to be separated. Please suggest.
Click to expand...

Connect a wire from your turntable internal ground to your phono amplifier case and another to the case of your amplifier, then show us a picture. Please. BTW, don't use rca grounds instead of case grounds. Drill a hole in the case if you must to put in a self tapping screw to make these connections. The only time this did not work for me was when I had a bad connection between a wire and the crimp on connector.
 
Daniel4381 said:
RCA negative of all output and input along with ground are soldered together.
Then, a wire is connected to the chassis with the RCA negative tag. If I separate the input and output tag, how those will be connected to chassis? Should I only connect chassis with the input tag or chassis connections for input and output to be separated. Please suggest.
Click to expand...

You have a "loop" with the grounds starting in the power supply that goes through the preamp board and across all the inputs/outputs (RCA), then finally makes it's way to the chassis. Any hum produced by the power supply will be amplified. It should probably have it's own ground to chassis, or at the very least a snubber cap to ground.
 
You know, long ago I had a turntable and amplifier that had a pesky hum problem. The amplifier and turntable sat next to a window. I ran a wire out the window and hooked it to a ground stake. Presto, all hum gone. That log cabin in the woods did not have any ground hooked to the power outlets or anything else. However, if you have not connected the ground for the turntable to the case of the phono amp (not the rca shield connectors) and connected the phono amp case to the amplifier case, then you have not properly grounded it. The case or chassis of each must be hooked together. If you connected the phono amp board rca shields to the case, disconnect them. I believe your setup can be made to work well even if it has a cheap phono amp.
 
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