Actually, we don't focusing in HUM sound. When the HUM sound not audible, we forget that problem.
Many people said that we must use toroidal trafo's, star grounding techique
but i think, that's technique only reduce hum sound not removing HUM sound.
If we look another branded amplifier, in their output sound don't contain any HUM sound, how they do that??
Do i need to build ground loop breaker??
Any idea?
If we can remove this HUM sound, ur GC sound become more professional,
There is an excellent paper from Jensen about hum:
http://www.jensen-transformers.com/apps_wp.html
Take a look at their AN004 - Hum & Buzz in Unbalanced Interconnect Systems (94KB PDF)
From my experience, if you have hum with your amp's input disconnected, then it comes from your amp.
If you only have hum when you connect your amp to the source, then the hum comes from the current flow in the shield of the interconnect.
http://www.jensen-transformers.com/apps_wp.html
Take a look at their AN004 - Hum & Buzz in Unbalanced Interconnect Systems (94KB PDF)
From my experience, if you have hum with your amp's input disconnected, then it comes from your amp.
If you only have hum when you connect your amp to the source, then the hum comes from the current flow in the shield of the interconnect.
> Many people said that we must use toroidal trafo's, star grounding techique but i think,
> that's technique only reduce hum sound not removing HUM sound.
Amplifiers don't by nature hum. They amplify electrical signals. If there is an unwanted hum in the signal, the amplifier with amplify it.
So, the trick has nothing to do with reducing or removing hum, the trick is simply to not introduce any hum.
Toroidal transformers help because their electromagnetic field is well-contained. EI transformers have a larger external magnetic field, which is also quite directional. If you pass a wire through a magnetic field, that field causes electrons in the wire to move -- introducing hum. So, using a toroid, you don't have to worry as much about routing your wires.
Another source of hum is current travelling through your ground wires -- grounds will be at slightly different potentials due to the imperfect nature (non-zero resistance) of non-superconducting wire. So, we use star ground technique so that the ground potentials are all the same.
Remember: don't introduce hum into your amp, and it won't hum.
Wes
> that's technique only reduce hum sound not removing HUM sound.
Amplifiers don't by nature hum. They amplify electrical signals. If there is an unwanted hum in the signal, the amplifier with amplify it.
So, the trick has nothing to do with reducing or removing hum, the trick is simply to not introduce any hum.
Toroidal transformers help because their electromagnetic field is well-contained. EI transformers have a larger external magnetic field, which is also quite directional. If you pass a wire through a magnetic field, that field causes electrons in the wire to move -- introducing hum. So, using a toroid, you don't have to worry as much about routing your wires.
Another source of hum is current travelling through your ground wires -- grounds will be at slightly different potentials due to the imperfect nature (non-zero resistance) of non-superconducting wire. So, we use star ground technique so that the ground potentials are all the same.
Remember: don't introduce hum into your amp, and it won't hum.
Wes
Actually,I use El transformer, and i know about flux magnetic which can induced to GC cable. But i still, hear a 50Hz hum sound in my GC although the Hum sound is very low. But, i still hear if my ear close to the loudspeaker (about 10cm), without any input of course. 
It's not audible when i sit about 1 metre from my loudspeaker.
The HUM sound is not bother me but i want my GC free from Hum sound, so our GC become more professional
I'm sure all of the DIYers has the HUM problem, although the HUM is not audible/very low but almost of them tolerated this problem
.If the branded amplifier can remove the HUM, why we can't?
Toroidal and El are not the main reason in producing HUM sound because i know that many branded amplifier using El transformator, and they don't produce any HUM sound.So, we can remove the HUM sound although we use El transformator.
But, it need a some technique.
thomgun_lc said:[BI'm sure all of the DIYers has the HUM problem, although the HUM is not audible/very low but almost of them tolerated this problem
My GC has no hum, zero, zilch, even with my ear stuck in the speakers so the side of my head touches the cone and the volume turned up.
I have had hum in one or two GCs but has has always turned out to be an issue with earthing or cables.
Regards
Why are you sure all DIYers have hum?
If the hum is not audible, there is not hum. This applies to store-bought and DIY amps. There is no magic difference between the two.
Your problem is either wiring or ground. Find the source of your hum, and you can eliminate it. Why not post a picture of your amp? Somebody may be able to help.
Wes
If the hum is not audible, there is not hum. This applies to store-bought and DIY amps. There is no magic difference between the two.
Your problem is either wiring or ground. Find the source of your hum, and you can eliminate it. Why not post a picture of your amp? Somebody may be able to help.
Wes
You know where you need only 1" of wire they will have like 6" wraped around something. Bapak,
I've built GCs, a discrete amp, class-D, opamp preamps all with NO hum. Where there have been problems, they've clearly been because of grounding issues, and tracing the ground connections and ensuring a clean star ground scheme have removed the hum. I'm sure there is residual 50Hz ripple on the supplies, except for the battery powered pre, but there's no audible hum at all. Good luck in your trouble shooting.
I've built GCs, a discrete amp, class-D, opamp preamps all with NO hum. Where there have been problems, they've clearly been because of grounding issues, and tracing the ground connections and ensuring a clean star ground scheme have removed the hum. I'm sure there is residual 50Hz ripple on the supplies, except for the battery powered pre, but there's no audible hum at all. Good luck in your trouble shooting.
No HUM sound at all??That's very interesting for me, because i always have hum problem although i use star grounding, but the hum/buzz sound not too loud. It occur, but not audible in 1 metre. When my head close to the loudspeaker i can hear the "buzz"sound like a bee sound . I have used star grounding technique, but the buzz sound still there. The HUM sound doesn't bother me, but it can make my GC not professional look alike.
Or it because i use a poor potensio?The Hum sound is audible when i turn the volume to minimum(no sound).
Or, the buzz sound because of my home electricity. Because my mains power supply is 220v/60Hz and only use 2 cable (Active & Neutral+ground), without separated ground wire. So, ground wire is joined with one of hot wire.
Is that causing HUM?
Attachments
But, in branded amp although they don't use "prong"connection, HUM sound already gone, how they do that?
I'm not sure if i use toroidal transformer and the HUM is gone. It's about 50Hz injecting to our amp.
Or,Maybe i get a "ground loop" problem because the chassis ground don't go anywhere because i don't have a separated earth wire. The earth wire is joined with one of the hot wire.
Do i need to add ground breaker??
Maybe if I have separated earth wire,the HUM sound will gone.
I'm not sure if i use toroidal transformer and the HUM is gone. It's about 50Hz injecting to our amp.
Or,Maybe i get a "ground loop" problem because the chassis ground don't go anywhere because i don't have a separated earth wire. The earth wire is joined with one of the hot wire.
Do i need to add ground breaker??
Maybe if I have separated earth wire,the HUM sound will gone.
Mr.mb thanks for ur attention.If u see my wiring schematic,I have connect Signal ground (input signal gnd and out signal gnd) with power ground in PCB, but the HUM still there.
Should i use the shortest way to star grounding from each ground point like u said?
My be i will try to connect every ground point to chassis(starground point).
U said that, i must connect"mains earth"to star ground point, but i only have 2hot wire.I don't have "mains earth" wire.Almost home electricity in my country only have 2 wire(the "mains earth" joined with one of the hot wire).
So, i don't have mains earth and i'm sure the HUM will be loop in my GC. I don't know how to remove the HUM if i don't have separated mains earth.
Please help me, i'm frustated with this HUM problem
Thanks
regards
---------
TomZ
I have a 4ch dual mono kit and had a few problems with hum from 2 of the channels.
I have just recased the amp boards into a seperate 1U chassis and redone a lot of the wiring - I used to get more hum if I touched the input wire - I used 2 core shielded HQ cable (in and ground) before but have swapped it for single core shielded now with just the center wire used in the in and std wire on ground.
I touched up the soldering on the bits I didn't rewire too.
I have only connected the channel grounds via a 100r resistor and 0.1 uF cap to the chassis and....
Totally silent, no hum, no hiss - nothing. There is a bit of crosstalk from the preamp but I can't do anything about that.
It's a std rev 3 3875 kit with the addition of a 22uF cap from R3 to ground to reduce DC offset.
I reckon I may have had a dodgy solder joint and I certainly used the wrong type of cable on the input the first time.
<<edit - I have done some stuff with the PSU but that didn't have anything to do with the hum - it was the same afterwards.>>
I have just recased the amp boards into a seperate 1U chassis and redone a lot of the wiring - I used to get more hum if I touched the input wire - I used 2 core shielded HQ cable (in and ground) before but have swapped it for single core shielded now with just the center wire used in the in and std wire on ground.
I touched up the soldering on the bits I didn't rewire too.
I have only connected the channel grounds via a 100r resistor and 0.1 uF cap to the chassis and....
Totally silent, no hum, no hiss - nothing. There is a bit of crosstalk from the preamp but I can't do anything about that.
It's a std rev 3 3875 kit with the addition of a 22uF cap from R3 to ground to reduce DC offset.
I reckon I may have had a dodgy solder joint and I certainly used the wrong type of cable on the input the first time.
<<edit - I have done some stuff with the PSU but that didn't have anything to do with the hum - it was the same afterwards.>>
Hi,
Connecting the signal ground to the power supply ground is not a good idea. Although "ground", there are large currents around that area as the power caps are constantly being charged.
Try the connections I've listed, but skip the earth. Remember that power supply ground should have just a single wire connection to star point. All other grounds should also have just a single path to the star point.
Connecting the signal ground to the power supply ground is not a good idea. Although "ground", there are large currents around that area as the power caps are constantly being charged.
Try the connections I've listed, but skip the earth. Remember that power supply ground should have just a single wire connection to star point. All other grounds should also have just a single path to the star point.
Hi, Mr Mb
Would u like to send me a wiring diagram, so i can do the same wiring with ur amp?I'm very glad if the HUM from Gc is gone. Need ur help please.
Actually, i used 3 trafo, for amp,loudspeaker protector and fan. can a cooling fan causing HUM sound too?
Where to join signal ground and power ground?i'm joined that two ground to the PCB, and i draw some wire to connect to the chassis.I have connect every ground point, trafo, PSU,PCB to chassis,is it right?
Here is my GC's picture with a slight Hum.
Would u like to send me a wiring diagram, so i can do the same wiring with ur amp?I'm very glad if the HUM from Gc is gone. Need ur help please.
Actually, i used 3 trafo, for amp,loudspeaker protector and fan. can a cooling fan causing HUM sound too?
Where to join signal ground and power ground?i'm joined that two ground to the PCB, and i draw some wire to connect to the chassis.I have connect every ground point, trafo, PSU,PCB to chassis,is it right?
Here is my GC's picture with a slight Hum.
Attachments
That's a lot of stuff in your case! I'm afraid I'm not in a position to help.
There are a number of good articles to look up if you search "ground loop", "star earth", "audio amplifier". Here are a couple:
http://www.aikenamps.com/StarGround.html
http://www.dself.dsl.pipex.com/ampins/groundloops/grndloop.htm
Good luck!
There are a number of good articles to look up if you search "ground loop", "star earth", "audio amplifier". Here are a couple:
http://www.aikenamps.com/StarGround.html
http://www.dself.dsl.pipex.com/ampins/groundloops/grndloop.htm
Good luck!
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