arcorob
Addicted Member
A debugging course
So your turntable has a mystery hum that is driving you nuts. It may be in both channels, one channel, slight or overwhelming. This short guide should help with some standard steps to debug and rid you of annoying hums. Will it work 100%? No, but I am sure 90 to 95% will be corrected.
First basics stepsYou should always be sure with any turntable that the contact points are clean and free of tarnish as are the RCA connections. For head shell wires, there are several recommended methods of cleaning (deoxit, lighter fluid, alcohol, etc.). My preference is liquid TARN-X. I just dip the ends in a small saucer of the liquid and watch the tarnish disappear. I then take them out and clean off any residue with a swab and alcohol.
For RCA jacks (male end) you can again use a liquid to get the oxidation off. Do the male stud and the surrounding outer rim (inside ands out). If they are not gold or silver plated and slated to be scrapped some time, you may also use a light emery cloth, 1200 grit sandpaper, etc. but any coating on the plugs will be lost. You could also make new RCA ends (cut wire, new ends, etc) but that is beyond the scope of this guide - plenty of information available on the web.
For RCA connections (female as in the receiver end), I would only use a deoxit or alcohol and a q-tip to be safe.
And of course, if your cartridge pins are not clean, carefully address those also. Work carefully and stay away from the stylus.
So you are off to a good start and all points are clean, you hook everything up and it hums. Uggh. Of now we come to more advanced steps, let’s call it level II.
Level II steps
First, have you made sure your turntable ground wire is properly connected to the amp? If not do so. Conversely, if it is connected, try it without. Did the hum go away? It might because there are many cases where ground can actually introduce hum.
Is the ground wire correctly connected to the turntable? Check that.
Does your amp or turntable use a 3 prong plug in any way (directly or via a power strip)? Well, many house grounds are not phased correctly (split phasing in a room not in sync..look it up). So switch out the 3 prong for a 2 prong cheater plug. SERIOUS SAFETY NOTE : This is not the safest method in the world as it may cause harm to the devices or pose a safety hazard. How ? Well, it takes a unique set of cirumstances but you should be aware and only do at your own risk. The 3rd pole ground gives the device a path of least resistance. So if a "HOT" wire broke off or was rubbing on the metal case of the unit iniside, then the case itself is hot and if you touch it, guess who becomes the ground ?
More info - In the professional audio and video fields, the cheater plug has been identified as a serious safety problem. Its casual use as a method for avoiding ground loops in analog audio and video signals (to eliminate hums and buzzes) is dangerous. Bill Whitlock, president of Jensen Transformers, writes, "never, ever use devices such as 3 to 2-prong AC plug adapters, a.k.a. 'ground lifters', to solve a noise problem!"Whitlock relates how an electrical fault in one device that is connected to its electricity source through an ungrounded cheater plug will result in dangerous, high current flowing through audio or video cables. Whitlock notes that in 1997, consumer audio and video equipment electrocuted nine people
"Geeze Rob, you just said use a cheater plug and now scared the bejesus out of me that next time I spin the Partridge Family Christmas album I could get toasted if I do. So what do I do ? Check with an electrician on the phaseing of the outlet (if you find that a cheater plug solves it then you know its that outlet so correct the issue) - DONT STAY with the cheater plug. It was a diagnosis tool.
If you are only using 2 prong, reverse the plug (turn it 180 degrees) and try it. Still hums? Time to move to level 3.
Level III steps
The level 3 steps should be pretty standard to help you determine do you have a bad RCA wire set, bad cart, bad headshell wires, or bad tonearm wires. Many folks will say “Use a multi-meter, measure the capacitance”. Uh huh. Well, I don’t own one and if I did, don’t know how to use one and if I did, would not be writing this…lol..or maybe I would to help those like me…who don’t own one.
First, is the hum in one channel or both(hope it’s in one). If in both you most likely have a general grounding issue and hopefully, level I or Level II steps cured it. If not, it says some aspect of parts is bad for both channels that we did not address. This would be rarer as it would mean one of the following:
• BOTH RCA’s are bad
• BOTH headshell wire sets are bad
• Both cartridge channels are bad
• Tonearm wires or tonearm ground are bad
Like I said, a bit harder to debug and rare that the first steps didn’t correct it (maybe that 5 or 10% ?)
So one channel hums and before you start ripping out tonearm wires, lets narrow down the problem.
First, disconnect BOTH RCA’s from the amp. Still have a hum? It’s the amp phono stage. Get service.
No hum, well, it’s definitely in the TT or the RCA’s.
So let’s do process of elimination. Let’s assume the RIGHT channel hums (just reverse instructions if it’s the left). If the RIGHT Channel hums and the LEFT channel is fine, it means our LEFT channel is our TEST set of connections because we know from AMP to CART, LEFT side works. What we have to determine is it the RCA plugs, tonearm wiring, headshell wiring or the cart itself.
Now if you have removable RCA’s (from the TT side) this will work. If not, we have to do something else and bypass this step.
• Remove BOTH RCA’s from the turntable side and connect the RIGHT SIDE RCA plugs to the LEFT side of the turntable (the side that is working). Plug into the LEFT side of the AMP. No hum? Then your RCA’s are good. If it hums, RCA is bad and replace.
• So RCA is good, what now? Again, we will use the LEFT SIDE channel to tell us where the problem is. Take your LEFT side headshell wires and connect to the RIGHT side cart pins. If it hums, it’s the CART because we know the LEFT SIDE wiring is good. If no Hum, then you have now narrowed it down to either the RIGHT SIDE Headshell wires or RIGHT side Tonearm wires back to the connection inside
If you DON’T have removable RCA’s on the turntable side
• As in many pre-wired setups, you may not be able to remove the TT side RCA plugs. But we can still do the next steps to at least eliminate the cart as the culprit.
• Again, we will use the LEFT SIDE channel to tell us where the problem is. Take your LEFT side headshell wires and connect to the RIGHT side cart pins. If it hums, it’s the CART because we know the LEFT SIDE wiring is good.
If no Hum, then you have now narrowed it down to either the RIGHT SIDE Headshell wires or RIGHT side Tonearm wires back to the connection inside, or the right side RCA wire. If this is the case, I would make sure the headshell wire (RIGHT SIDE) is very clean, tarnish free and connected well. I would also check inside the table for connection to where it becomes the RCA cable and replace the RCA cable if necessary (may take some soldering).
Okay so does this guide fix EVERY HUM? No. Did it fix MANY hums? You bet.
Q: Besides where you listed can hums be caused by other things.
A: Yes. Electronics in the table, dirty pots, bad caps, etc. can wreak havoc. But again, if you were to take hum issues in order of prevalence, these would be that 1 in 10 (or last 10%) type issues.
Hope this helps…Rob
So your turntable has a mystery hum that is driving you nuts. It may be in both channels, one channel, slight or overwhelming. This short guide should help with some standard steps to debug and rid you of annoying hums. Will it work 100%? No, but I am sure 90 to 95% will be corrected.
First basics stepsYou should always be sure with any turntable that the contact points are clean and free of tarnish as are the RCA connections. For head shell wires, there are several recommended methods of cleaning (deoxit, lighter fluid, alcohol, etc.). My preference is liquid TARN-X. I just dip the ends in a small saucer of the liquid and watch the tarnish disappear. I then take them out and clean off any residue with a swab and alcohol.
For RCA jacks (male end) you can again use a liquid to get the oxidation off. Do the male stud and the surrounding outer rim (inside ands out). If they are not gold or silver plated and slated to be scrapped some time, you may also use a light emery cloth, 1200 grit sandpaper, etc. but any coating on the plugs will be lost. You could also make new RCA ends (cut wire, new ends, etc) but that is beyond the scope of this guide - plenty of information available on the web.
For RCA connections (female as in the receiver end), I would only use a deoxit or alcohol and a q-tip to be safe.
And of course, if your cartridge pins are not clean, carefully address those also. Work carefully and stay away from the stylus.
So you are off to a good start and all points are clean, you hook everything up and it hums. Uggh. Of now we come to more advanced steps, let’s call it level II.
Level II steps
First, have you made sure your turntable ground wire is properly connected to the amp? If not do so. Conversely, if it is connected, try it without. Did the hum go away? It might because there are many cases where ground can actually introduce hum.
Is the ground wire correctly connected to the turntable? Check that.
Does your amp or turntable use a 3 prong plug in any way (directly or via a power strip)? Well, many house grounds are not phased correctly (split phasing in a room not in sync..look it up). So switch out the 3 prong for a 2 prong cheater plug. SERIOUS SAFETY NOTE : This is not the safest method in the world as it may cause harm to the devices or pose a safety hazard. How ? Well, it takes a unique set of cirumstances but you should be aware and only do at your own risk. The 3rd pole ground gives the device a path of least resistance. So if a "HOT" wire broke off or was rubbing on the metal case of the unit iniside, then the case itself is hot and if you touch it, guess who becomes the ground ?
More info - In the professional audio and video fields, the cheater plug has been identified as a serious safety problem. Its casual use as a method for avoiding ground loops in analog audio and video signals (to eliminate hums and buzzes) is dangerous. Bill Whitlock, president of Jensen Transformers, writes, "never, ever use devices such as 3 to 2-prong AC plug adapters, a.k.a. 'ground lifters', to solve a noise problem!"Whitlock relates how an electrical fault in one device that is connected to its electricity source through an ungrounded cheater plug will result in dangerous, high current flowing through audio or video cables. Whitlock notes that in 1997, consumer audio and video equipment electrocuted nine people
"Geeze Rob, you just said use a cheater plug and now scared the bejesus out of me that next time I spin the Partridge Family Christmas album I could get toasted if I do. So what do I do ? Check with an electrician on the phaseing of the outlet (if you find that a cheater plug solves it then you know its that outlet so correct the issue) - DONT STAY with the cheater plug. It was a diagnosis tool.
If you are only using 2 prong, reverse the plug (turn it 180 degrees) and try it. Still hums? Time to move to level 3.
Level III steps
The level 3 steps should be pretty standard to help you determine do you have a bad RCA wire set, bad cart, bad headshell wires, or bad tonearm wires. Many folks will say “Use a multi-meter, measure the capacitance”. Uh huh. Well, I don’t own one and if I did, don’t know how to use one and if I did, would not be writing this…lol..or maybe I would to help those like me…who don’t own one.
First, is the hum in one channel or both(hope it’s in one). If in both you most likely have a general grounding issue and hopefully, level I or Level II steps cured it. If not, it says some aspect of parts is bad for both channels that we did not address. This would be rarer as it would mean one of the following:
• BOTH RCA’s are bad
• BOTH headshell wire sets are bad
• Both cartridge channels are bad
• Tonearm wires or tonearm ground are bad
Like I said, a bit harder to debug and rare that the first steps didn’t correct it (maybe that 5 or 10% ?)
So one channel hums and before you start ripping out tonearm wires, lets narrow down the problem.
First, disconnect BOTH RCA’s from the amp. Still have a hum? It’s the amp phono stage. Get service.
No hum, well, it’s definitely in the TT or the RCA’s.
So let’s do process of elimination. Let’s assume the RIGHT channel hums (just reverse instructions if it’s the left). If the RIGHT Channel hums and the LEFT channel is fine, it means our LEFT channel is our TEST set of connections because we know from AMP to CART, LEFT side works. What we have to determine is it the RCA plugs, tonearm wiring, headshell wiring or the cart itself.
Now if you have removable RCA’s (from the TT side) this will work. If not, we have to do something else and bypass this step.
• Remove BOTH RCA’s from the turntable side and connect the RIGHT SIDE RCA plugs to the LEFT side of the turntable (the side that is working). Plug into the LEFT side of the AMP. No hum? Then your RCA’s are good. If it hums, RCA is bad and replace.
• So RCA is good, what now? Again, we will use the LEFT SIDE channel to tell us where the problem is. Take your LEFT side headshell wires and connect to the RIGHT side cart pins. If it hums, it’s the CART because we know the LEFT SIDE wiring is good. If no Hum, then you have now narrowed it down to either the RIGHT SIDE Headshell wires or RIGHT side Tonearm wires back to the connection inside
If you DON’T have removable RCA’s on the turntable side
• As in many pre-wired setups, you may not be able to remove the TT side RCA plugs. But we can still do the next steps to at least eliminate the cart as the culprit.
• Again, we will use the LEFT SIDE channel to tell us where the problem is. Take your LEFT side headshell wires and connect to the RIGHT side cart pins. If it hums, it’s the CART because we know the LEFT SIDE wiring is good.
If no Hum, then you have now narrowed it down to either the RIGHT SIDE Headshell wires or RIGHT side Tonearm wires back to the connection inside, or the right side RCA wire. If this is the case, I would make sure the headshell wire (RIGHT SIDE) is very clean, tarnish free and connected well. I would also check inside the table for connection to where it becomes the RCA cable and replace the RCA cable if necessary (may take some soldering).
Okay so does this guide fix EVERY HUM? No. Did it fix MANY hums? You bet.
Q: Besides where you listed can hums be caused by other things.
A: Yes. Electronics in the table, dirty pots, bad caps, etc. can wreak havoc. But again, if you were to take hum issues in order of prevalence, these would be that 1 in 10 (or last 10%) type issues.
Hope this helps…Rob
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