Phono hum and no ground wire!

[QuarterCuban]

My Kenwood KA-8100 is not playing well with my turntable. When I select phono-1 or phono-2 without the turntable plugged in, there is a slight hiss. And it's only really noticeable when I turn it up past three quarters max volume. When I plug my turntable into either phono1 or phono2 inputs, there is a very noticeable humm that starts at low-volume. There is no ground wire on the turntable.

I have recently connected a sub woofer to the system using speaker wire connections. This seems to have made the humm worse.

The other input selections are very clean. Whether I have components hooked to them or not, there is no hiss or humm at any volume.

What tricks can I try!?

 

[JamVal]

The AT-LP120-USB that I have does not exhibit that behavior. Yes, no ground wire.

Just some trouble shooting ideas though, do you have another amp/receiver with phono input? If you have ground hum also on another amp, then problem is probably with the turntable, but probably with the cartridge. What cartridge are you running on the AT-LP120?, doesn't look like the stock AT-95E. If you have the stock AT-95E or another cartridge, try a different cartridge to see if it still makes the ground hum. Some cartridges can cause the problem. Does that cartridge have metal or plastic mounting brackets where it comes in contact with the headshell? I have a Shure M93E that has metal mounting bracket and made the ground hum noise. I had to make sure those little mounting screws and bracket were insulated from the headshell. Some cartridges have a 'ground' lug tab on the backside where the wires are connected that can be removed.

Also, there is a switch on the back of your turntable to utilize the internal phono-preamp in case a customer does not have phono inputs on their amp. Try running your RCA's to AUX in on your amp with the AT-LP120 switched for use of the internal phono-preamp. Just make sure you don't use that setting when switching your RCA's back to Phono-In on the amp, because that is Line Level output from your turntable and you won't like the results running that into the Phono input on your amp.

Good luck!

 

[QuarterCuban]

The AT-LP120-USB that I have does not exhibit that behavior. Yes, no ground wire.

Just some trouble shooting ideas though, do you have another amp/receiver with phono input? If you have ground hum also on another amp, then problem is probably with the turntable, but probably with the cartridge. What cartridge are you running on the AT-LP120?, doesn't look like the stock AT-95E. If you have the stock AT-95E or another cartridge, try a different cartridge to see if it still makes the ground hum. Some cartridges can cause the problem. Does that cartridge have metal or plastic mounting brackets where it comes in contact with the headshell? I have a Shure M93E that has metal mounting bracket and made the ground hum noise. I had to make sure those little mounting screws and bracket were insulated from the headshell. Some cartridges have a 'ground' lug tab on the backside where the wires are connected that can be removed.

Also, there is a switch on the back of your turntable to utilize the internal phono-preamp in case a customer does not have phono inputs on their amp. Try running your RCA's to AUX in on your amp with the AT-LP120 switched for use of the internal phono-preamp. Just make sure you don't use that setting when switching your RCA's back to Phono-In on the amp, because that is Line Level output from your turntable and you won't like the results running that into the Phono input on your amp.

Goo

 

[QuarterCuban]

The AT-LP120-USB that I have does not exhibit that behavior. Yes, no ground wire.

Just some trouble shooting ideas though, do you have another amp/receiver with phono input? If you have ground hum also on another amp, then problem is probably with the turntable, but probably with the cartridge. What cartridge are you running on the AT-LP120?, doesn't look like the stock AT-95E. If you have the stock AT-95E or another cartridge, try a different cartridge to see if it still makes the ground hum. Some cartridges can cause the problem. Does that cartridge have metal or plastic mounting brackets where it comes in contact with the headshell? I have a Shure M93E that has metal mounting bracket and made the ground hum noise. I had to make sure those little mounting screws and bracket were insulated from the headshell. Some cartridges have a 'ground' lug tab on the backside where the wires are connected that can be removed.

Also, there is a switch on the back of your turntable to utilize the internal phono-preamp in case a customer does not have phono inputs on their amp. Try running your RCA's to AUX in on your amp with the AT-LP120 switched for use of the internal phono-preamp. Just make sure you don't use that setting when switching your RCA's back to Phono-In on the amp, because that is Line Level output from your turntable and you won't like the results running that into the Phono input on your amp.

Good luck!

I do have a Shure cartridge. Not sure of the model number and I'm not at home right now to check. I'll switch that one out for the original and see how that works. I have tried connecting the turntable to other amps and have gotten a similar humm.

 

[JamVal]

If you can get the Shure Cartridge number, go to vinylengine.com. (if you haven't done so already). Sign up for a free account. Go to their 'Library' page and see if you can find the user manual for your cartridge. There might be a diagram of where that ground lug tab is. If you are getting the same ground hum on other amps, my bet would be that your cartridge isn't insulated from the headshell. The stock AT95E cartridge has plastic mounts to the headshell so no ground hum with that one.

I just used some black electric tape to insulate the metal mounting bracket on my Shure cartridge from the metal headshell. Not the best solution, as that can throw some things off, VTA, Azimuth, etc, but it worked fine for me. There are also nylon/plastic washers that can be used for mounting to insulate.

 

[dahoo]

it is a shure v15 type IV. as JamVal suggests, try isolating the metal headshell with something not conductive. or use nylon screws. check the metal body of the cartridge if there is any scratched paint.

 

[sKiZo]

Try touching some metal on the table and a piece of wire hooked to the receiver's ground terminal. If that helps, nothing saying you can't ADD a ground to the table using a convenient bolt or some such.

Also might be worth a wiggle of the audio interconnects. Those can get stretched and strange with abuse.

Oh. Can't imagine this helping much with a newer design, but maybe the designers were having an off day, eh. Old timer trick to reduce hum is to simply reverse a two prong plug in the socket. Only works if you've got a non-polarized plug ... or a set of tin snips. <G>

 

[QuarterCuban]

The AT-LP120-USB that I have does not exhibit that behavior. Yes, no ground wire.

Just some trouble shooting ideas though, do you have another amp/receiver with phono input? If you have ground hum also on another amp, then problem is probably with the turntable, but probably with the cartridge. What cartridge are you running on the AT-LP120?, doesn't look like the stock AT-95E. If you have the stock AT-95E or another cartridge, try a different cartridge to see if it still makes the ground hum. Some cartridges can cause the problem. Does that cartridge have metal or plastic mounting brackets where it comes in contact with the headshell? I have a Shure M93E that has metal mounting bracket and made the ground hum noise. I had to make sure those little mounting screws and bracket were insulated from the headshell. Some cartridges have a 'ground' lug tab on the backside where the wires are connected that can be removed.

Also, there is a switch on the back of your turntable to utilize the internal phono-preamp in case a customer does not have phono inputs on their amp. Try running your RCA's to AUX in on your amp with the AT-LP120 switched for use of the internal phono-preamp. Just make sure you don't use that setting when switching your RCA's back to Phono-In on the amp, because that is Line Level output from your turntable and you won't like the results running that into the Phono input on your amp.

Good luck!

Ok. So I plugged into the tuner input and switch to the turntables preamp... Clean as a whistle..

Does the phono preamp circuitry in the Kenwood need servicing? I'm tempted to leave it plugged into the tuner and be done with it.... I haven't sat down and listened to the radio in years.

 

[JamVal]

Ok. So I plugged into the tuner input and switch to the turntables preamp... Clean as a whistle..

Does the phono preamp circuitry in the Kenwood need servicing? I'm tempted to leave it plugged into the tuner and be done with it.... I haven't sat down and listened to the radio in years.

I think you mentioned earlier that you were getting the same hum when using other amps, so I don't think it's an issue with your Kenwood amp.

I still suspect it has something to do with your shure cartridge. But it is puzzling that the hum is gone when by use of your turntable's phono pre-amp out.
I don't have a v15, but from what I have read it is very well regarded.

 

[QuarterCuban]

I think you mentioned earlier that you were getting the same hum when using other amps, so I don't think it's an issue with your Kenwood amp.

I still suspect it has something to do with your shure cartridge. But it is puzzling that the hum is gone when by use of your turntable's phono pre-amp out.
I don't have a v15, but from what I have read it is very well regarded.

To experiment I used tape around the cartridge mounts. It made no difference. I have a Kenwood KA-4002 that had a similar humm.

What is the v15?

 

[Djcoolray]

If the power plug on your unit is two prong......

You need to ground the receiver to a pipe, then ground the turntable to the receiver ground.

 

[JamVal]

To experiment I used tape around the cartridge mounts. It made no difference. I have a Kenwood KA-4002 that had a similar humm.

What is the v15?

dahoo, in post #6 above identified your cartridge as a Shure v15 Type IV. if that is what you have it is a well regarded cartridge.

 

[Rock_nut]

Use a length of speaker wire from either a motor mount screw, or chasis skew and twist the other end around the ground plug on your amp.

 

[JamVal]

Read this from Shure Customer support - sounds like exactly what you're up against:
http://shure.custhelp.com/app/answe...ground-loop-buzz-or-hum-with-metal-headshells

Take a look at the back of your cartridge where the green wire is attached. There is a ground tab that the above link is talking about.

The reason I didn't remove the ground tab from my cartridge is that I didn't get the ground hum on all my decks. I had the hum on my AT-LP120 and a Sony PS-4750, but not on my Pioneer PL-530. Careful insulation of the mounting plate and screws took care of the problem on all my decks. The warning here is that once you remove the ground tab, I'm not sure if you can get it back on.

In the Shure v15 iii instruction manual on page 16 it says:
"Note: Some installations may require the cartridge shield to be electrically isolated from the RG (right ground - green) terminal. This can be achieved by removal of the ground tab. The tab may be straightened and reinserted to provide an independent cartridge shield ground if required."

 

[JamVal]

Use a length of speaker wire from either a motor mount screw, or chasis skew and twist the other end around the ground plug on your amp.

According to Shure Customer support article: http://shure.custhelp.com/app/answe...ground-loop-buzz-or-hum-with-metal-headshells
"the problem is likely a ground loop caused by the cartridge body being grounded in two places"
If that is what's going on, I think the hum will persist even if the TT is grounded to the amp. I had a similar problem with a shure cartridge and had the hum regardless of the TT being grounded. After I insulated the cartridge from the metal headshell the hum was gone.

 

[bimasta]

Take a look at the back of your cartridge...

Jamval, good pic — and nice clips! Are those headshell leads, or the tips of internal tonearm wiring (eg fixed h'shell)? I'd like to get some, I need some spare leads, was going to make them, but those look very well made, with a very secure contact....

 

[WaynerN]

If the power plug on your unit is two prong......

You need to ground the receiver to a pipe, then ground the turntable to the receiver ground.

Not

 

[JamVal]

Jamval, good pic — and nice clips! Are those headshell leads, or the tips of internal tonearm wiring (eg fixed h'shell)? I'd like to get some, I need some spare leads, was going to make them, but those look very well made, with a very secure contact....

Sorry, I should have mentioned that is not my cartridge and not my photo. I found it on the net when researching the problem with my Shure cartridge.

 

[WaynerN]

Here is some things to think about. The Shure cartridge body is grounded to the right channel shield pin (the green wire), and the tonearm (and the rest of the table) is grounded to your receiver via its RCA interconnects. If you have a metal headshell and use metal screws, now the cartridge body is also grounded to the receiver via the interconnects shield. You have 2 paths.........Hummmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmm

 

[WaynerN]

Sorry, I should have mentioned that is not my cartridge and not my photo. I found it on the net when researching the problem with my Shure cartridge.

Photographs on the internet are copyrighted.