Please help me with this noise! (Solved)
I have bought a little dot mk2 tube amplifier for my HD6XX about 1 1/2 years back. It has 4 gain settings that can be changed by jumpers inside. It sounds wonderful but it does have this annoying noise which I cannot figure out where it is coming from. I tried moving from the electrical outlet to another, isolating it from ground, changing tubes, keeping it away from other devices, etc and nothing helps. It is worse at night. However, the gain stage 4 which is the lowest it is almost inaudible unless you listen to it in silent passages. Other gain stages it is there and at gain stage 4 it is very audible. This however is worst on small IEM's and low impedance headphones including monk plus. HD6XX is the least effected headphone I have from this noise/hum.
Could this be something wrong with my A/C supply from the grid?, I checked the polarity as well and everything seemed to be in order. I will upload sound samples with the hum along with this post. Please let me know what you think it is according to hum. Could it be filter capacitors?
Amplified audio file Vocaroo | Online voice recorder
Unamplified audio file Vocaroo | Online voice recorder
I have bought a little dot mk2 tube amplifier for my HD6XX about 1 1/2 years back. It has 4 gain settings that can be changed by jumpers inside. It sounds wonderful but it does have this annoying noise which I cannot figure out where it is coming from. I tried moving from the electrical outlet to another, isolating it from ground, changing tubes, keeping it away from other devices, etc and nothing helps. It is worse at night. However, the gain stage 4 which is the lowest it is almost inaudible unless you listen to it in silent passages. Other gain stages it is there and at gain stage 4 it is very audible. This however is worst on small IEM's and low impedance headphones including monk plus. HD6XX is the least effected headphone I have from this noise/hum.
Could this be something wrong with my A/C supply from the grid?, I checked the polarity as well and everything seemed to be in order. I will upload sound samples with the hum along with this post. Please let me know what you think it is according to hum. Could it be filter capacitors?
Amplified audio file Vocaroo | Online voice recorder
Unamplified audio file Vocaroo | Online voice recorder
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It sounds like a ground loop to me. Which would be strange as you have isolated it from ground already!
Thank you so much for your reply. Yes, this is how I Isolated it from it. Just took off the ground pin of the power plug. I did it correctly right...?
At the moment I was experimenting with this noise and you're right I have a feeling that it has something to do with my electricity. The only way to make it 100% sure is to connect it to a power filter or isolation transformer. I live in a wasteland of these kind of stuff so it's going to be hard for me to find it.
Also, I just realized that plugging some extra RCA jacks to the output (when used as a preamp) and plugging them to something that has power and running RCA actually takes the noise off completely but reduces the sound of headphone jack. Could it be something faulty in the amplifier? I have a feeling that this noise is generating from the preamp section. When I go higher in Gain settings it gets worse and worse which I believe alter the output power of the preamp section. I tried changing the tubes but didn't help. Could it be the capacitors responsible to operate in preamp stage? (Gain stage).
Sorry for my English!
If there is no direct mains earth connection and the earth is "floating " and there is no earth connection through an ancillary piece of equipment then its radiated RF interference .
You say -quote- "its worse at night " that backs up my point .
First turn off all electronic devices in the room including putting your mobile phone elsewhere .
The same with a DECT phone ,keep it away from your router .
If its still there check out your fridge/freezer and other electronic equipment , if it continuous then turn off ALL LED lights in the house .
If that doesn't stop it then is this "annoying noise " a HUM or a BUZZ ?
If a hum that could be a fault in your equipment , if a buzz which implies varying frequency oscillations then an external source is causing it .
That could be a local transmitter/power lines transformer near you.
I spent years with the public helping them trace out this type of fault,
number 1 in the modern cause was LED lighting .
Get a portable FM radio tune it across the waveband does it pick up a buzz or does the buzz disable various stations ?
You say -quote- "its worse at night " that backs up my point .
First turn off all electronic devices in the room including putting your mobile phone elsewhere .
The same with a DECT phone ,keep it away from your router .
If its still there check out your fridge/freezer and other electronic equipment , if it continuous then turn off ALL LED lights in the house .
If that doesn't stop it then is this "annoying noise " a HUM or a BUZZ ?
If a hum that could be a fault in your equipment , if a buzz which implies varying frequency oscillations then an external source is causing it .
That could be a local transmitter/power lines transformer near you.
I spent years with the public helping them trace out this type of fault,
number 1 in the modern cause was LED lighting .
Get a portable FM radio tune it across the waveband does it pick up a buzz or does the buzz disable various stations ?
Thanks a lot for all the help. I just tried what you recommended. I turned off the entire house and left the power on for the amplifier. The buzzing noise is still there. I don't have a router or any wifi generating equipment in my room. I kept the mobile phone outside as well. Still there. I think this is more of a buzz than a hum. You can give it a listen to those audio links I gave above. To me it is more of a buzz, My next step is to take it to my mother-in-law's house who she lives around 15KM away from where I am and then try it there.
FM Doesn't pick up anything odd, anyways the reception is pretty bad at my place but I am sure it doesn't pick anything out ordinary.
Here's another thing. I do have two more tube amplifiers. One is 6N3 Matissle clone preamp connected to a cheapo chip amp (lepy), and the other is Qinpu Q2 which is a small hybrid 6n3 tube amplifier. I tested them out today with headphones V.E Monk Plus, V.E Bonus Iem, KZ ZS5 and KZ ATR. Although they sound different than LDMK2 , All of them has that strange buzzing noise in the background and they are worse on these amps than on my LD MK2. However HD6XX doesn't get any buzzing on these amps probably because they cannot push it hard enough i guess.
The only amplification that is not affected by this is my Solid State Amplifiers.
Here's another thing. I do have two more tube amplifiers. One is 6N3 Matissle clone preamp connected to a cheapo chip amp (lepy), and the other is Qinpu Q2 which is a small hybrid 6n3 tube amplifier. I tested them out today with headphones V.E Monk Plus, V.E Bonus Iem, KZ ZS5 and KZ ATR. Although they sound different than LDMK2 , All of them has that strange buzzing noise in the background and they are worse on these amps than on my LD MK2. However HD6XX doesn't get any buzzing on these amps probably because they cannot push it hard enough i guess.
The only amplification that is not affected by this is my Solid State Amplifiers.
*** Update ***
I must mention that the buzzing in 6N3 Matisse clone went away soon after I plugged the input side to a Bluetooth receiver and powered the BT Receiver. (Strange)
I must mention that the buzzing in 6N3 Matisse clone went away soon after I plugged the input side to a Bluetooth receiver and powered the BT Receiver. (Strange)
I think you just have a little capacitive pickup on the input. Could be something external or from the heater supply. Does it go if you ground the input. Does it disappear immediately when you turn the power to the unit off but before the HT has time to collapse. Could you include the heater supply in your schematic.
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#1. Yes sir! it does go off immediately after switching off the amplifier. Even if i disconnect the power chord it goes off immediately (The tubes are still glowing and the sound is slowly playing and fading away)
#2. It does get minimize to inaudible level if I connect the preamp outputs to another small power amplifier or something while using LD MKII as a headphone amplifier to HD6XX.
I also found out a post and here are the text from it. I don't understand much of but someone with LD MK1 amplifier fixed this problem by doing this.
Right now I am searching the internet for heater supply schematics.
"soo, i finally got to fix this problem.
i followed a hint from a comment on amazon, regarding the heater filament wiring of the tubes.
then i desoldered the wires on one of the tubes, twisted them nicely around eachother and resoldered them.
this helped a bit, but the humming was still quite audible.
i kept on researching the topic of correct heater filament wiring between tubes, and found out about the so called "artificial center tap".
this "artificial center tap" is built by soldering one 100Ohms resistor to each of the wires. those resistors have to be connected to ground later on.
i did exactly that. After i was done the humming was almost non audible. i hope this can help others who have the same issue."
#2. It does get minimize to inaudible level if I connect the preamp outputs to another small power amplifier or something while using LD MKII as a headphone amplifier to HD6XX.
I also found out a post and here are the text from it. I don't understand much of but someone with LD MK1 amplifier fixed this problem by doing this.
Right now I am searching the internet for heater supply schematics.
"soo, i finally got to fix this problem.
i followed a hint from a comment on amazon, regarding the heater filament wiring of the tubes.
then i desoldered the wires on one of the tubes, twisted them nicely around eachother and resoldered them.
this helped a bit, but the humming was still quite audible.
i kept on researching the topic of correct heater filament wiring between tubes, and found out about the so called "artificial center tap".
this "artificial center tap" is built by soldering one 100Ohms resistor to each of the wires. those resistors have to be connected to ground later on.
i did exactly that. After i was done the humming was almost non audible. i hope this can help others who have the same issue."
Sorry AllenB!
By the way, this is all I found when I search as schematics for EF95.
I am not an electronics professional but I can solder. If soldering 100ohm resistors to each cable that connects to heater filament and The other end to ground, I can do it. I just want to make sure I got this right...!
By the way, this is all I found when I search as schematics for EF95.
I am not an electronics professional but I can solder. If soldering 100ohm resistors to each cable that connects to heater filament and The other end to ground, I can do it. I just want to make sure I got this right...!
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Hi nofacemonster,
You can use pins 3 and 4 and place a resistor from both pins to ground.
Alternatively you can elevate the filaments from ground. This means you don’t connect the resistors to ground, but to a positive voltage (lower than max. Grid-Cathode voltage), say for example 30 volts.
Read more on this topic so you will know what you’re doing, before you actually try this.
Regards, Gerrit
You can use pins 3 and 4 and place a resistor from both pins to ground.
Alternatively you can elevate the filaments from ground. This means you don’t connect the resistors to ground, but to a positive voltage (lower than max. Grid-Cathode voltage), say for example 30 volts.
Read more on this topic so you will know what you’re doing, before you actually try this.
Regards, Gerrit
Sir...! One single question remains. Should I do this to all the four tubes or just the Gain preamp tubes? 6J1 (EF95) family is the gain tube, and 6N6 (6H6P) are the power tubes. I think i will be able to solder one resistor to 3 and then 4 then both other ends connect to the ground. I will definitely read up on this topic musch further before trying anything by myself. I am not an electronics expert but I gotta do this somehow otherwise it is really annoying with the buzz.
You do know the EF95 is an RF amplifier valve specially designed to amplify RF signals ?
Its designed that way , I have several in one of my old UK ex-WD communications receivers and a good job it does under those design conditions.
Its listed in Mullard,s own industrial guide as - SQ /industrial receiving valve.
Also used in VHF communication.
Its designed that way , I have several in one of my old UK ex-WD communications receivers and a good job it does under those design conditions.
Its listed in Mullard,s own industrial guide as - SQ /industrial receiving valve.
Also used in VHF communication.
If it immediately disappears when turning off the unit its internally generated. If it disappears if you ground the input or connect to another unit switched on then that's reducing the input impedance to the first grid. So is probably cap coupling to the grid. Sometimes these valves have the grid pin next to the heater supply. In any case the heater supply should be balanced i.e. a CT transformer with the CT to ground or two resistors as the text above shows. Failing that DC heater supply.
Just looked at your waveform on audiocity - definitely cap coupling. There's also some LF variation < 2Hz.
Just looked at your waveform on audiocity - definitely cap coupling. There's also some LF variation < 2Hz.
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What I was getting at its designed to pick up even the slightest RF signal .
The two RF stages in that Navy receiver can pick up micro-volt signals.
The same does not apply to normal ---designed for audio valves which need a larger RF input to be amplified by the grid.
I realize the meaning of "tube rolling " used extensively by head-fi website which I was on till it changed its web software but physics are physics and cant be ignored.
Of course it will disappear when turned off but the EF95 is designed to amplify ANY RF signal at one or two micro-volts.
The two RF stages in that Navy receiver can pick up micro-volt signals.
The same does not apply to normal ---designed for audio valves which need a larger RF input to be amplified by the grid.
I realize the meaning of "tube rolling " used extensively by head-fi website which I was on till it changed its web software but physics are physics and cant be ignored.
Of course it will disappear when turned off but the EF95 is designed to amplify ANY RF signal at one or two micro-volts.
It's OK I did understand that is may be oscillating at VHF. It could amplify the buzz, and may explain the DC moving around in the mp3 file. Hard to tell. Usually you get a radio station or two!
Wow! you guys know so much! I feel like a total idiot in a PhD class. lol....! I am sorry, I don't know so much deeper about the tubes. So according to my understanding EF95 amplify even the slightest signal. It is designed to do that and that's what it is doing... amplifying that noise as well.
So if I do this trick with Resistors soldering them on to the tube pins and grounding them, this will go away right...? I will be doing this to the EF95 gain tubes. in my case mullards.
So if I do this trick with Resistors soldering them on to the tube pins and grounding them, this will go away right...? I will be doing this to the EF95 gain tubes. in my case mullards.
I am really sorry if I sound like a total Noob...! thanks a lot for all the help. What does it mean by cap coupling? will this "Artificial Center tap" will work on my issue? or should I do something else?....