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Help! Amp humming!

Niklas S

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Hello,
I’ve spent days roaming the internet for a solution, so I really hope you can help!

I have an Harmon/Kardon HK3270 RDS and an old BSR turntable.
When I just plug in my turntable to the amp, it sounds awesome. BUT my turntable is 15 feet away from my amp, so I have to use a 15 ft RCA extender cable, and when I plug that into my amp, it starts humming very loudly, even when it’s not plugged into anything at the other end. It keeps humming when I hook up the turntable to it, and I almost can’t hear a thing because of the loud hum.
The thing is, when I plug it into my pc through the RCA extender it also keeps humming until I play something - then it kinda cancels out the hum so the music plays just fine. Like the pc can activate something to cancel out the hum or something.
Does anyone know how to fix this??!
Remeber the turntable plays just fine directly into the amp. It’s just the extender cord that messes it up. I’ve tried other cables it’s the same thing.
Please help!
 

staticV3

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Hi @Niklas S! Welcome to ASR.

I would search for a phono RCA cable with the correct length, so you can avoid using that extender cable.

Phono RCA cables have an additional GND wire with which you can ground the turntable to the Amp. In many cases, that fixes the hum.
 

RayDunzl

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Here's an example of RCA with additional ground wire, but you might need to make/have one made, for the distance you need.

Maybe just try running a third wire from the turntable to the case of the preamp, see if it helps.

shopping
 

sergeauckland

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Bear in mind also that 15ft (4.5m) of cable will add a lot of extra capacitance which will royally screw up the frequency response of the cartridge, assuming it's a Moving Magnet cartridge. The distance between the turntable and the phono stage (either separate or built-in to the amplifier) should normally not exceed 5ft, ideally less.

If you can, try and move the turntable (or amplifier) so they are a lot closer. Failing that, you can always use a small external phono stage and then run the longer cable to a line input on the amplifier.

S.
 
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MaxwellsEq

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Hello,
I’ve spent days roaming the internet for a solution, so I really hope you can help!

I have an Harmon/Kardon HK3270 RDS and an old BSR turntable.
When I just plug in my turntable to the amp, it sounds awesome. BUT my turntable is 15 feet away from my amp, so I have to use a 15 ft RCA extender cable, and when I plug that into my amp, it starts humming very loudly, even when it’s not plugged into anything at the other end. It keeps humming when I hook up the turntable to it, and I almost can’t hear a thing because of the loud hum.
The thing is, when I plug it into my pc through the RCA extender it also keeps humming until I play something - then it kinda cancels out the hum so the music plays just fine. Like the pc can activate something to cancel out the hum or something.
Does anyone know how to fix this??!
Remeber the turntable plays just fine directly into the amp. It’s just the extender cord that messes it up. I’ve tried other cables it’s the same thing.
Please help!
Hi and welcome to ASR.

Just to reiterate what others have said, there is only one cable in an analogue setup that must be as short as possible and that's the cable between the cartridge and the phono preamplifier. Long cables are susceptible to noise, but they can also significantly degrade the frequency response of the cartridge.

The phono preamplifier needs to be adjacent to the turntable. If you can't move your main amplifier or the turntable closer together, consider getting a cheap phono preamplifier like the Art II and plugging that via a long cable into a line level socket on the amplifier.
 
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Niklas S

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Thank you guys for your help! I will try a shorter cable.
The thing is just that the humming sound already appears before I even connect the turntable in the other end. So, it’s not the turntable making the sound.
Just the long cable in itself is enough to make the hum. And I’ve tried two, it’s the same.
 

MaxwellsEq

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Thank you guys for your help! I will try a shorter cable.
The thing is just that the humming sound already appears before I even connect the turntable in the other end. So, it’s not the turntable making the sound.
Just the long cable in itself is enough to make the hum. And I’ve tried two, it’s the same.
That's correct . The problem is not the turntable.

Phono preamplifiers have tons of gain because the output form the cartridge is so tiny. At these levels of gain, hum and radio pickup are very likely.

There's lots of nonsense talked about cables, but there is one cable that must always be short and properly earthed - the wire between a cartridge and a phono preamplifier.
 
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Niklas S

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That's correct . The problem is not the turntable.

Phono preamplifiers have tons of gain because the output form the cartridge is so tiny. At these levels of gain, hum and radio pickup are very likely.

There's lots of nonsense talked about cables, but there is one cable that must always be short and properly earthed - the wire between a cartridge and a phono preamplifier.
That’s a very good explanation. Thank you. That might explain everything. And it can’t be bypassed by buying a more expensive cable?
 

DVDdoug

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And it can’t be bypassed by buying a more expensive cable?
It's possible that your cable isn't shielded. In that case any "proper" audio cable should help, but it's still a long-run between the phono cartridge and preamp.
 

JeremyFife

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Hum is annoying?

Move your Amp closer to the turntable (0.5m). If that's not possible then I second the suggestion to get a phono preamp, not expensive, into your Amp's line in
Borrow one and try it?
 

egellings

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Hello,
I’ve spent days roaming the internet for a solution, so I really hope you can help!

I have an Harmon/Kardon HK3270 RDS and an old BSR turntable.
When I just plug in my turntable to the amp, it sounds awesome. BUT my turntable is 15 feet away from my amp, so I have to use a 15 ft RCA extender cable, and when I plug that into my amp, it starts humming very loudly, even when it’s not plugged into anything at the other end. It keeps humming when I hook up the turntable to it, and I almost can’t hear a thing because of the loud hum.
The thing is, when I plug it into my pc through the RCA extender it also keeps humming until I play something - then it kinda cancels out the hum so the music plays just fine. Like the pc can activate something to cancel out the hum or something.
Does anyone know how to fix this??!
Remeber the turntable plays just fine directly into the amp. It’s just the extender cord that messes it up. I’ve tried other cables it’s the same thing.
Please help!
It doesn't know the words so it just hums along with the music! Is the ground connection good at both ends of the cable?
 

MaxwellsEq

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That’s a very good explanation. Thank you. That might explain everything. And it can’t be bypassed by buying a more expensive cable?
If your cable is very cheap and poorly screened, then a properly screened cable with earth lead could improve things a bit, but the high frequencies will still be affected by the cable capacitance.

You MUST have a very short cable between a turntable and phono preamplifier. It's a "law of physics" and no amount of hyper expensive cable can fix it. Put the turntable next to the amp or buy a phono preamplifier and put it next to the turntable.
 
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Niklas S

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If your cable is very cheap and poorly screened, then a properly screened cable with earth lead could improve things a bit, but the high frequencies will still be affected by the cable capacitance.

You MUST have a very short cable between a turntable and phono preamplifier. It's a "law of physics" and no amount of hyper expensive cable can fix it. Put the turntable next to the amp or buy a phono preamplifier and put it next to the turntable.
Thank you very very much for your advice! It makes good sense.
 

GXAlan

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Is the hum 50/60hz? Or like a radio signal? If it is a radio signal a ferrite choke could help. Long cables can affect the frequency response but it’s weird that you get hum if the extension cables are well shielded.
 
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Niklas S

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Is the hum 50/60hz? Or like a radio signal? If it is a radio signal a ferrite choke could help. Long cables can affect the frequency response but it’s weird that you get hum if the extension cables are well shielded.
It’s about 50hz. But my cables are not well shielded. They’re the cheapest I could find..
 

Zapper

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It’s about 50hz. But my cables are not well shielded. They’re the cheapest I could find..
Cables don't matter, until they do. The cheapest available cables have poor or no shielding and are susceptible to hum. As several others have said, no cable is suitable for your use unless you use a phono preamp between the turntable and the long cable.

FYI: if you add a pre-amp, its outputs need to connect to a line-in input on your receiver like AUX, CD, or TAPE PLAY, not the PHONO input.
 
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Niklas S

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Thank you guy for your help! This is much more useful than the radio guy in town was!
 

Zapper

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GXAlan

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It’s about 50hz. But my cables are not well shielded. They’re the cheapest I could find..
Sometimes the cheapest cables are OK. Just look for a ~$8 extension cable on Amazon that lists "double shielded"

Take a look at this person's experience where the $400 cable didn't fix his hum but the cheap shielded ones did

Everyone is right about the long cables affecting capacitance, etc. But it's a pretty minor trade-off is you need to have your turntable that far from your amp.
 
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