TT Hum

[cpd]

You said that the tuner in your Marantz stereo receiver does not suffer from the hum problem. That further suggests the hum problem you hear during phono playback is caused by AC power line hum and not radio frequency (RF) interference from the LED lights and/or the dimmer.

Where is the antenna and antenna line for FM radio reception located? Is it near the Marantz receiver, or is some distance away? The antenna line probably does not run near the LED light power line, or it might also pick up that hum.

I don't have an antenna line hooked up. It grabs the signal on its own.

 

[highfigh]

Like I sai


Accessing and fishing an RCA cable is not going to be a huge issue. Unless these tubes provide shielding from the interference, I don't think there is much need for them in my application. I assume the answer to that question is that they do not shield from interference.

They're used to make fishing cables easier in the event that they fail or become obsolete. We install them during pre-wire, to establish a path, to be filled later. You could use flexible conduit, too- it's not terribly hard to install and if it's grounded at the AVR/receiver, it can reduce interference to some degree.

 

[highfigh]

You said that the tuner in your Marantz stereo receiver does not suffer from the hum problem. That further suggests the hum problem you hear during phono playback is caused by AC power line hum and not radio frequency (RF) interference from the LED lights and/or the dimmer.

I doubt any AM/FM tuner will pick up 60Hz interference.

 

[Swerd]

I don't have an antenna line hooked up. It grabs the signal on its own.

Your receiver grabs signal on its own, without an antenna and without hum. And your photo (thanks) shows how close the receiver is to the LED lights. Because of all that, I feel more confident in concluding that the source of hum during phono playback is the close proximity of the electrical power line and the RCA cable between the Marantz and the turntable.

 

[Swerd]

I doubt any AM/FM tuner will pick up 60Hz interference.

Only because all tuners are properly shielded from RF or EM interference.

 

[cpd]

Your receiver grabs signal on its own, without an antenna and without hum. And your photo (thanks) shows how close the receiver is to the LED lights. Because of all that, I feel more confident in concluding that the source of hum during phono playback is the close proximity of the electrical power line and the RCA cable between the Marantz and the turntable.

Thanks. I'll try to rerun the RCA cable tonight. If that doesn't work, I'll take the cabinet off and figure out how to wire everything so they are kept separate. How much distance should I endeavor to keep?

 

[Swerd]

Thanks. I'll try to rerun the RCA cable tonight. If that doesn't work, I'll take the cabinet off and figure out how to wire everything so they are kept separate. How much distance should I endeavor to keep?

If memory serves me right, six inches apart might be OK. But I wouldn't bet on that. Keep them as far apart as you can. I hope that solves the hum problem.

A more cautious answer would be: far enough apart so that there is no more hum.

 

[TLS Guy]

Only because all tuners are properly shielded from RF or EM interference.

I wish that were true. The RF interference from LEDs and dimmers sounds just like the hum and buzz from ground loops. I now think that hums and buzzes from RF is more common than ground loops and is a serious and pervasive problem.

I took extreme measures in this home to minimize it, but if I turn on lots of lights, especially those on dimmers I can get a low buzz coming through. Although the bulbs and dimmers actually emit more noise directly than through the system, but it is a low enough level to not be a problem.

However if the OP separates the AC line and the signal cable he will reduce EM and RF radiation at the same time by the square of the distance he separates them.

 

[cpd]

You can use Lutron Caseta, too- these work well if you want to automate your lighting with the AV system.

Yes, you can use that Maestro switch because it's made for most kinds of lights but it won't guarantee eliminating the hum- that's probably a proximity issue between the Romex and RCA cable.

If you can't get rid of the hum in a reasonable way ($$$), you could consider using an analog to digital converter and then connecting the output to one of the digital coax inputs on the AVR, via the same coax cable (only one of them).

I reran the RCA from the Marantz to the Denon on the path that would keep it as far away from lighting wires as possible without removing the cabinet to get behind it. There is still a hum. I want to believe it is better but that’s a pretty hard A B comparison.

I’m going to try the switches tomorrow hopefully. If that fails, you mentioned an ADC. Downsides? Recommendations on models?

 

[TLS Guy]

I reran the RCA from the Marantz to the Denon on the path that would keep it as far away from lighting wires as possible without removing the cabinet to get behind it. There is still a hum. I want to believe it is better but that’s a pretty hard A B comparison.

I’m going to try the switches tomorrow hopefully. If that fails, you mentioned an ADC. Downsides? Recommendations on models?

Before you spend money on a new dimmer, replace the dimmer with a straight switch. I have a feeling that will eliminate the problem. If that does not solve it then try another brand of light. If eliminating the dimmer stops it then it is worth spending money on the maestro dimmer.

One other question, do you have other dimmers on the same circuit as that dimmer?

LEDs and dimmers can cause terrible headaches. I just had an issue where the lights for the family room next door and the lights for the staircase were on the same circuit. The dimmers where back to back on the same wall. This created an unholy amount of RF that made a wicked racket when both sets of light were on. I found this is a known issue. It was only solved by running a new circuit from the panel so that the family room lights and the stair lights had their own circuit.

You really have to keep LED lighting circuits as short as possible and limit the amount of wire on the circuits if you want quiet audio. That means not having lighting circuits also power wall outlets, as that increases the "antenna" length from each dimmer and circuit.

I can assure everyone that current audio gear especially receivers and pre/pros do not reject RF to anything like the extent they should.

I put my speaker leads in metal conduit as speaker wires are great antennas for feeding RF back to the voltage gain circuits via negative feedback.

As I said issues like yours are now common place, especially in houses like mine which have a large number of LED light bulbs and dimmers. These present much tougher issues than dealing with ground loops.

 

[cpd]

Before you spend money on a new dimmer, replace the dimmer with a straight switch. I have a feeling that will eliminate the problem. If that does not solve it then try another brand of light. If eliminating the dimmer stops it then it is worth spending money on the maestro dimmer.

One other question, do you have other dimmers on the same circuit as that dimmer?

LEDs and dimmers can cause terrible headaches. I just had an issue where the lights for the family room next door and the lights for the staircase were on the same circuit. The dimmers where back to back on the same wall. This created an unholy amount of RF that made a wicked racket when both sets of light were on. I found this is a known issue. It was only solved by running a new circuit from the panel so that the family room lights and the stair lights had their own circuit.

You really have to keep LED lighting circuits as short as possible and limit the amount of wire on the circuits if you want quiet audio. That means not having lighting circuits also power wall outlets, as that increases the "antenna" length from each dimmer and circuit.

I can assure everyone that current audio gear especially receivers and pre/pros do not reject RF to anything like the extent they should.

I put my speaker leads in metal conduit as speaker wires are great antennas for feeding RF back to the voltage gain circuits via negative feedback.

As I said issues like yours are now common place, especially in houses like mine which have a large number of LED light bulbs and dimmers. These present much tougher issues than dealing with ground loops.

Yeah my house is an “updated” house from 1929. Updated is in quotes because two owners before me did everything themselves and there’s all sorts of weird electrical.

There is another dimmer in the adjacent room. I will have to check what circuit that is on.

I’ll try the switch tomorrow.

 

[cpd]

Thanks for all the help everyone!

 

[TLS Guy]

Yeah my house is an “updated” house from 1929. Updated is in quotes because two owners before me did everything themselves and there’s all sorts of weird electrical.

There is another dimmer in the adjacent room. I will have to check what circuit that is on.

I’ll try the switch tomorrow.

Well it is worse than you think. Up until 2013 code allowed you to daisy chain neutrals. Now it is illegal. The reason is that in times past loads were continuous, that is to say loads were drawn evenly throughout the AC cycle. Now loads have become to a large extent discontinuous and power drawn preferentially at the peak of the cycle. All LED and LED and dimmer circuits are discontinuous, as are all TVs, computers and anything with a switching power supply. That is a lot of loads. The problem is that these loads cause what is known as neutral gouging. In times passed the neutral took little load, but not any more. I am one who personally believes that all homes prior to 2013 should be rewired and neutrals separated. Also arc fault breakers will not stay closed on any circuit that shares a neutral, precluding this added measure of safety being used in most homes constructed prior to 2013.

This daisy chaining of neutrals by the way makes RF interference worse.

I witnessed a serious and dangerous incident from neural gouging in a home the opposite side of Lake Benedict when I lived there. I moved in May,

Things are not what they used to be, not by a long shot.

 

[highfigh]

Only because all tuners are properly shielded from RF or EM interference.

No, it's because they operate in the RF range, not AF.

 

[TLS Guy]

No, it's because they operate in the RF range, not AF.

So it is clear now that this post has created a highly teachable moment. You are an experienced guy highfigh but you are seriously in need of further education on this one.

Your above statement is correct and dead wrong at the same time.

You are correct that a turntable is an analog device. So I maintain LEDs and dimmers generate a lot of RF and thought that likely this was the cause of the buzz from his turntable. You thought it was AC EM induction, not an unreasonable hypothesis. But the obliging OP moved his cables and the buzz was still there. So how does this RF interference way, way above the frequency of human hearing make an audible buzz to come out of his speakers?

So now I have have to don my professorial hat again. I will try and make it as entertaining as I can. The points I'm going to make are now more important then ever in the design and installation of AV systems.

Now this old man is going to go back to his early childhood and the building of a crystal set with my father age 5. I remember it like yesterday and still actually have the book that explained it in a way a young child could understand. "Wireless works like this."

So lets go back to my nursery in the OP.

As I remember it this was the circuit.

There is no battery. The power to drive the headphones bought from the army surplus store are powered from the energy in the radio signal. The antenna connects to a coil in parallel with a variable capacitor and forms a variable tuning circuit for the different frequencies of the stations. The detector circuit is completed by the diode D1 which is, guess what? It is a semiconductor junction. This is the detector and circuit that converts the RF signal into an audio signal the headphone wearer can hear. Now remember this simple crystal radio circuit as it is key to really understanding the OP's buzz, and lot of others.

Now lets look at a transistor. It is a sandwich of two diodes, like in the crystal set but made so that two of the junctions share a common semiconductor material. Note there are two semiconductor junctions.

The vertical line is the base, and the middle of our sandwich. The one with the arrow is the emitter. The one without the arrow is the collector. Now the signal is connected across the base emitter junction which is low impedance. The base collector junction is high impedance. The signal sneaks electrons onto the base and allows current to flow across the high impedance junction. This is how amplification occurs when a power source is added.

Now the really important point is the base emitter junction is a diode just like the diode in our crystal radio set and can detect an RF signal and make it audible. BUT it is now powered, and has gain that our crystal radio does not.

So now lets look at a simple transistor voltage amplifier, it could be IC or even tube for that matter it makes no difference.

Just look at those semiconductor junctions. The base emitter junction of the first 2N3904 junction has any RF it detects and rectified amplified all the way up the chain.

Now lets look at how speaker wire can and does become an antenna for RF noise to be detected and amplified. You will now see the reason I place my speaker cables in metal conduit.

So this is a very simple power amplifier. Now VO would be the speaker terminals.

Now look at the negative feedback circuit from C4 and R2. The speaker wires create an antenna for feeding back RF hash right into the early voltage gain circuits. Again it does not matter whether it is solid state or tube these devices are able under many conditions to detect and rectify RF signals and make them audible.

Now my contention is that this is something we all have to understand. I hope I have presented it in a way the least technically inclined members can understand.

Now that we have much more RF hash in homes this is a pressing issue made even more manifest by the number of channels we are using. This makes me the poster boy as my system has 18 amp channels.

So a buzz in four channels rather then 2 gives us a 3db increase, going to 8 gives is 9 db and going to 16 gives us 12 db compared to two channels.

So in my rig I really have to pay attention to this as if I get RF penetration have 13.5 db more noise than from a 2 channel rig. So that means I have to really carefully plan and install everything and pay close attention and participate fully in the design and wiring of the home.

Lastly lets just return to the OP and his turntable LED light and dimmer. I will put back up my crystal set from the nursery once more. I will show you how a turntable becomes a worst case scenario.

So the cartridge coils can substitute for the inductor L1 and the cartridge loading capacitance for capacitor VC1 and the first base emitter junction of the phono preamp the diode D1. Now we have our crystal radio, but now with amplification!

No wonder the OP has a buzz from his LED light and dimmer.

 

[cpd]

So it is clear now that this post has created a highly teachable moment. You are an experienced guy highfigh but you are seriously in need of further education on this one.

Your above statement is correct and dead wrong at the same time.

You are correct that a turntable is an analog device. So I maintain LEDs and dimmers generate a lot of RF and thought that likely this was the cause of the buzz from his turntable. You thought it was AC EM induction, not an unreasonable hypothesis. But the obliging OP moved his cables and the buzz was still there. So how does this RF interference way, way above the frequency of human hearing make an audible buzz to come out of his speakers?

So now I have have to don my professorial hat again. I will try and make it as entertaining as I can. The points I'm going to make are now more important then ever in the design and installation of AV systems.

Now this old man is going to go back to his early childhood and the building of a crystal set with my father age 5. I remember it like yesterday and still actually have the book that explained it in a way a young child could understand. "Wireless works like this."

So lets go back to my nursery in the OP.

As I remember it this was the circuit.

View attachment 33527

There is no battery. The power to drive the headphones bought from the army surplus store are powered from the energy in the radio signal. The antenna connects to a coil in parallel with a variable capacitor and forms a variable tuning circuit for the different frequencies of the stations. The detector circuit is completed by the diode D1 which is, guess what? It is a semiconductor junction. This is the detector and circuit that converts the RF signal into an audio signal the headphone wearer can hear. Now remember this simple crystal radio circuit as it is key to really understanding the OP's buzz, and lot of others.

Now lets look at a transistor. It is a sandwich of two diodes, like in the crystal set but made so that two of the junctions share a common semiconductor material. Note there are two semiconductor junctions.

The vertical line is the base, and the middle of our sandwich. The one with the arrow is the emitter. The one without the arrow is the collector. Now the signal is connected across the base emitter junction which is low impedance. The base collector junction is high impedance. The signal sneaks electrons onto the base and allows current to flow across the high impedance junction. This is how amplification occurs when a power source is added.

Now the really important point is the base emitter junction is a diode just like the diode in our crystal radio set and can detect an RF signal and make it audible. BUT it is now powered, and has gain that our crystal radio does not.

So now lets look at a simple transistor voltage amplifier, it could be IC or even tube for that matter it makes no difference.

Just look at those semiconductor junctions. The base emitter junction of the first 2N3904 junction has any RF it detects and rectified amplified all the way up the chain.

Now lets look at how speaker wire can and does become an antenna for RF noise to be detected and amplified. You will now see the reason I place my speaker cables in metal conduit.

So this is a very simple power amplifier. Now VO would be the speaker terminals.

Now look at the negative feedback circuit from C4 and R2. The speaker wires create an antenna for feeding back RF hash right into the early voltage gain circuits. Again it does not matter whether it is solid state or tube these devices are able under many conditions to detect and rectify RF signals and make them audible.

Now my contention is that this is something we all have to understand. I hope I have presented it in a way the least technically inclined members can understand.

Now that we have much more RF hash in homes this is a pressing issue made even more manifest by the number of channels we are using. This makes me the poster boy as my system has 18 amp channels.

So a buzz in four channels rather then 2 gives us a 3db increase, going to 8 gives is 9 db and going to 16 gives us 12 db compared to two channels.

So in my rig I really have to pay attention to this as if I get RF penetration have 13.5 db more noise than from a 2 channel rig. So that means I have to really carefully plan and install everything and pay close attention and participate fully in the design and wiring of the home.

Lastly lets just return to the OP and his turntable LED light and dimmer. I will put back up my crystal set from the nursery once more. I will show you how a turntable becomes a worst case scenario.

View attachment 33528
So the cartridge coils can substitute for the inductor L1 and the cartridge loading capacitance for capacitor VC1 and the first base emitter junction of the phono preamp the diode D1. Now we have our crystal radio, but now with amplification!

No wonder the OP has a buzz from his LED light and dimmer.

So I didn't understand much of that, but that's ok. I replaced the dimmer switch with a non-dimming 15A toggle. No more buzz when the lights are on! So I tried hooking up a Maestro next. Unfortunately, the buzz came back. While it would be ideal to have a dimmer switch controlling the units, it is not necessary as the lights are not bright anyway (and the cabinets are dark and deep).

Long story short, the buzz is gone so tonight I can finally enjoy it without worrying that I'll never get rid of the buzz. Thanks again to everyone for all the help. I learned a lot (mostly that I have a lot to learn).

 

[TLS Guy]

So I didn't understand much of that, but that's ok. I replaced the dimmer switch with a non-dimming 15A toggle. No more buzz when the lights are on! So I tried hooking up a Maestro next. Unfortunately, the buzz came back. While it would be ideal to have a dimmer switch controlling the units, it is not necessary as the lights are not bright anyway (and the cabinets are dark and deep).

Long story short, the buzz is gone so tonight I can finally enjoy it without worrying that I'll never get rid of the buzz. Thanks again to everyone for all the help. I learned a lot (mostly that I have a lot to learn).

Thank you for your reply. Yes, LED lights plus a dimmer means a lot of RF interference, even with a high end dimmer. Also it confirms that turntables are sitting ducks to be badly affected by said RF radiation.

If I could trouble you for a favor and ask you to document what parts of my post you don't understand. If you don't understand it, then others won't either. I do try my best to make important technical points understandable and that presents challenges.

This is a topic I fear will be the subject of increasing problems from posters on these forums. The basic problem understanding this is that it is hard to believe that interference from something way above the range of hearing comes out of their speakers as an audible nuisance. On the other hand people should consider we have been listening to detected and rectified radio waves by semiconductors and thermionic valves (tubes) for a century now. So some downsides of that fact should really not be surprising.

 

[cpd]

So I didn't understand much of that, but that's ok. I replaced the dimmer switch with a non-dimming 15A toggle. No more buzz when the lights are on! So I tried hooking up a Maestro next. Unfortunately, the buzz came back. While it would be ideal to have a dimmer switch controlling the units, it is not necessary as the lights are not bright anyway (and the cabinets are dark and deep).

Long story short, the buzz is gone so tonight I can finally enjoy it without worrying that I'll never get rid of the buzz. Thanks again to everyone for all the help. I learned a lot (mostly that I have a lot to learn).

Thank you for your reply. Yes, LED lights plus a dimmer means a lot of RF interference, even with a high end dimmer. Also it confirms that turntables are sitting ducks to be badly affected by said RF radiation.

If I could trouble you for a favor and ask you to document what parts of my post you don't understand. If you don't understand it, then others won't either. I do try my best to make important technical points understandable and that presents challenges.

This is a topic I fear will be the subject of increasing problems from posters on these forums. The basic problem understanding this is that it is hard to believe that interference from something way above the range of hearing comes out of their speakers as an audible nuisance. On the other hand people should consider we have been listening to detected and rectified radio waves by semiconductors and thermionic valves (tubes) for a century now. So some downsides of that fact should really not be surprising.

As you said in your post, you tried to write it in a manner easy enough to understand at least for the technically inclined. When it comes to circuits, I fall squarely in the technically un-inclined group of the population. I understood the larger point, and you proved your merit with your advice. You were spot on. I just did not understand the analysis of the different circuits. But I'm a lawyer, so you can't blame me for being dumb.

 

[Swerd]

I’m glad to see that cpd, the original poster, was able to eliminate the hum problem without requiring major rewiriing or drywall work. As it turns out, the solution took more than one single modification. Not surprising.

I’m also put off by TLS Guys tone in his last response. It was offensive. The rest of my comments are directed at him and not the OP.

First, let’s reiterate the known details of the OP’s problem. (Pay close attention to the sectons I've bolded.)

• The OP had audible hum through the loudspeakers during phonograph playback. He explained that his phonograph cartridge was connected to an older Marantz stereo receiver’s phono input, using it as a phono pre-amp, and then out from Tape Out jacks to a Denon AVR via RCA interconnects.
  
  
• Those RCA cables, containing line level audio signals, exit the back of the cabinet where they ran behind drywall adjacent to an electric power line for the LED lights. This inaccessible space was between the wall and the back of the cabinet.
  
  
• A photo showed the turntable, three LED lights, and Marantz receiver (containing the phono pre-amp and FM tuner) were close to each other. It did not show where the dimmer light switch was located. Nor did it show the Denon AVR, speaker cables, or speakers.
  
  
• The hum occurred only during phono playback, and only when the LED lights were on. The OP did not mention what other sound source devices he used, but he did say an FM tuner built into the nearby Marantz receiver did not suffer from any hum with or without the LED lights. Furthermore, this tuner operated without any antenna. I assume the antenna connection jack was left unoccupied. This suggests the OP lives in an area with strong FM signals, strong enough to dominate over many sources of interference. But it also suggests the unoccupied antenna jack could allow RFI to interfere with FM radio playback from a shielded radio receiver.

How to fix the problem? First try #1, and if it doesn’t eliminate the hum, try #2 and #3.

1. Relocate the RCA interconnects running between the Marantz stereo receiver and the Denon AVR, such that they don’t run nearby the power line for the LED lights.
2. Replace the dimmer switch for the LED lights.
3. Replace the LED lights themselves.

The OP first, relocated the wires described in item 1. This may have partially reduced the hum, but did not eliminate it. The OP next replaced the dimmer switch with a standard on/off wall switch, and that did completely eliminate the hum. His results suggest that RFI generated by the LED dimmer, entered the system by the phono level cable between the turntable and the Marantz pre-amp, by the line level cable between the Marantz pre-amp and the Denon AVR, or both.

TLS Guy's lengthy explanation indicates how RF interference, such as that generated by LED dimmers, could generate an audible hum in the presence of unshielded solid state amplifiers driving loudspeakers. If so, the OP would hear that hum regardless of the sound source. Yet, while using the FM tuner in the Marantz receiver, no hum could be heard while the LED lights were on. TLS Guy's lengthy explanation fails to address that.

But your efforts at schooling the readers of this thread does succeed at insulting their intelligence. I speak for myself. But I wouldn’t be surprised if others felt as I do.

 

[flippo]

It's offensive to try to explain something?