How silent should my phono input be?

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El Sergento

Active Member
I have a technics table hooked into a Yamaha CR-620. At relatively high volumes, like 5 +, I get some humm from the phono input. All my other inputs are dead silent, and at normal volume, the phono input is also very silent.

Is this humm normal or should it be dead silent like my other inputs? Like I said, it’s not bad at all, I have to really crank the volume to hear the humm.

Btw, the TT is grounded to the receiver, but the receiver itself is not grounded.

Cheers
 
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If you play a record at normal listening volume, or even a bit loud, then lift the tonearm, you should hear no hum or hiss. Make sure you have the ground wire connected from the turntable to the preamp. See if the hum is on one channel or both. Try moving the turntable audio cables away from AC cords and the back of the preamp.
 
MRL_Audio said:
If done correctly with proper grounding and operating equipment it should be dead silent.
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No, nothing is dead silent - all amplifiers have a signal-to-noise ratio and that ratio is never infinite.
Phono circuits are inevitably noisier than line inputs and some hum and hiss is usually audible if you max out the volume control. What matters is the signal-to-noise ratio. The noise shouldn't be audible when the volume control is at normal listening levels and it should be well below vinyl surface noise.
You can put shorting plugs into the phono inputs to hear how low the noise can be with your amp. If there's more noise when you connect the turntable, any extra hum is due to the turntable/tonearm wiring. Any extra hiss is due to the cartridge resistance - there's nothing you can do about that.
 
My point was that at any thing on the left side of 12:00 on the volume control there should be no audible hum or hiss. If there is, there’s a problem somewhere.
 
A tiny bit of noise at 5+ on the volume control with no signal to mask it might not be ideal but I wouldn't consider it a major concern.
 
My Technics and Kenwood integrated does the same thing. If I unhook the ground it gets really loud so I don't think it a ground problem
 
El Sergento said:
I have a technics table hooked into a Yamaha CR-620. At relatively high volumes, like 5 +, I get some humm from the phono input. All my other inputs are dead silent, and at normal volume, the phono input is also very silent.

Is this humm normal or should it be dead silent like my other inputs? Like I said, it’s not bad at all, I have to really crank the volume to hear the humm.

Btw, the TT is grounded to the receiver, but the receiver itself is not grounded.

Cheers
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The CR 620 has a very good phono stage and a great S/N ratio. If you are getting some noise you may have a problem.
 
If there’s a 60 cycle hum then I’d be looking at the power supply smoothing caps, grounds, AC plug polarity and cables routed near AC sources.
A bit of hiss at high volume settings with no signal is normal.
 
Thunderbox said:
The CR 620 has a very good phono stage and a great S/N ratio. If you are getting some noise you may have a problem.
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w1jim said:
If there’s a 60 cycle hum then I’d be looking at the power supply smoothing caps, grounds, AC plug polarity and cables routed near AC sources.
A bit of hiss at high volume settings with no signal is normal.
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Could grounding the receiver help? Man, that would be annoying, as my whole system is set up in the only part of the house without grounded outlets :(

Oh, forgot to mention, the TT is plugged into the back of the receiver. But I tried plugging it into a wall socket and the problem persisted. Actually, the “problem” occurs weather the TT is plugged into AC or not.
 
Disconnect the turntable from the receiver and see how silent it is, I'm willing to bet it's much quieter lol. Think about it, you have a pickup hanging in the air, your room is not soundproof, the stylus is picking up movement in the air and you're cranking the output lol.
 
Grenadeslio said:
Disconnect the turntable from the receiver and see how silent it is, I'm willing to bet it's much quieter lol. Think about it, you have a pickup hanging in the air, your room is not soundproof, the stylus is picking up movement in the air and you're cranking the output lol.
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Yeah that’s what I figured, although connecting the ground cable to the receiver more securely made the problem far less severe.

From what I’ve read, if it were a true ground loop the 60h hum would be audible at lower volumes.
 
rothwellaudio said:
No, nothing is dead silent - all amplifiers have a signal-to-noise ratio and that ratio is never infinite.
Phono circuits are inevitably noisier than line inputs and some hum and hiss is usually audible if you max out the volume control. What matters is the signal-to-noise ratio. The noise shouldn't be audible when the volume control is at normal listening levels and it should be well below vinyl surface noise.
You can put shorting plugs into the phono inputs to hear how low the noise can be with your amp. If there's more noise when you connect the turntable, any extra hum is due to the turntable/tonearm wiring. Any extra hiss is due to the cartridge resistance - there's nothing you can do about that.
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Once again, an educated voice in the forest. I have noticed that to be the norm with you, and I have come to really respect and value your input.

I have never heard a dead quiet phono circuit on any piece of gear I have ever owned. Perhaps @rothwellaudio who manufactures a phono section can explain just how much noise a person can expect with a well designed phono section. I know some are more quiet than others, but I have yet to hear one that is dead quiet.

I must say I am impressed with this battery powered SOTA head amp that I recently purchased as it has helped lower the background noise quite a bit.
 
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El Sergento said:
Yeah that’s what I figured, although connecting the ground cable to the receiver more securely made the problem far less severe.

From what I’ve read, if it were a true ground loop the 60h hum would be audible at lower volumes.
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Unless you’ve gale force winds in your house the cantilever isn’t causing any signal to be produced hanging in the air.
 
If everything else is quiet, the problem is likely not the 620. You can make up a pair of shorting plugs and short the phono inputs to see if the hum is still present. That said, the CR-620 is a great receiver but it does have a small grounding error. It's been a while so I don't remember if this shows up more on phono or just everywhere. It's also my belief that nearly all CR-620s will have severely degraded caps on the power side of the unit by now. Recap it or get it recapped. The fix for the grounding error is quite easy involving a short piece of enameled wire.
 
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