Are your input jacks insulated from the chassis?
Try disconnecting the fan and see if the noise goes away. Motors can generate a lot of noise that can find its way into a lot of the wrong places via the power leads. In general, these chips run cool. I am surprised you need a cooling fan...
When you are testing for hum and noise, you should disconnect anything from the input jacks and short them. Maybe your noise is coming from elsewhere in your system.
Can you post a schematic of your amplifier, showing how you have connected the various boards together and how they connect to ground?
I_F
Try disconnecting the fan and see if the noise goes away. Motors can generate a lot of noise that can find its way into a lot of the wrong places via the power leads. In general, these chips run cool. I am surprised you need a cooling fan...
When you are testing for hum and noise, you should disconnect anything from the input jacks and short them. Maybe your noise is coming from elsewhere in your system.
Can you post a schematic of your amplifier, showing how you have connected the various boards together and how they connect to ground?
I_F
Ok some thoughts ... I didn't get a chance to read every post completely so sorry if some of this is already covered.
1. No you can't just call the chassis the star ground point and then go about attaching wires to the chassis all over the place where ever is convenient. A star ground is exactly that, all wires meet at the same location.
2. As has already been stated, you must short the inputs while testing for hum within the amplifier.
3. Assuming this is a stereo amp then you really need to isolate the inputs from the chassis.
1. No you can't just call the chassis the star ground point and then go about attaching wires to the chassis all over the place where ever is convenient. A star ground is exactly that, all wires meet at the same location.
2. As has already been stated, you must short the inputs while testing for hum within the amplifier.
3. Assuming this is a stereo amp then you really need to isolate the inputs from the chassis.
Mr.I forgot, i have tried many connection to remove my slight HUM.This slight HUM sound liked buzz sound.I have tried to disconnect the fan and speaekr protector, and the result is the same,slight HUM(buzz) sound still occur.
When i disconnect SG&PG then meet them at the star ground, a slight HUM become Very loud HUM+very loud Hizz sound (like white noise sound).
I though this is must be wrong, and then i connect SG&PG using a piece of a short cable and slight HUM occur again.
I use digital multi meter (UNI-T)to measure my 3886amp(using 10r between output), and the result is:
DC offset: -0.7mV
AC offset: 5mV
I still don't know why i get this AC offset too much. I have add a 220pF between two opamp input (+&-). I have located Rfb close to the pin.My zobel using 2.7r+100nF.Or maybe i should increase 2.7r to 10r to decrease the bandwidth of my amp?
I set the gain to 33x (Rfb 22k,Rin 680).U can see the pcb which i post.
In listening position i only hear a cooling fan sound, but when my ear close to the ludspeaker i can hear a buzzing sound.Although this slight hum not very audible but this HUM make me sick and frustated.
Maybe i need some reports from GC's DIYers which using El transformator!!Do the GC's DIYers which using El transformator get a Zero HUM?
Mr. I forgot, would u like to check my wiring? I'm sory for poor/bad drawing
regards
---------
TomZ
Attachments
Hello there thomgun!
I used cheap EI in the old days and there are EI that simply create hum. Try to touch the body of the EI and check if it needs grounding. I used to ground at its leg.
Toroid is a bit quiter (nicer highs) but I still love EI more for it's quality bass. I don't have hum with Sony/Panasonic EIs.
You keep saying that the hum is okay because it is inaudible from a meter or so. No it is not okay. You can't hear the hum with full music, but the hum is there with your bass, making your bass not clean and tight.
Have you tried connecting each of the speaker negatives to the starground? Or have you moved the starground to the power supply (between positive and negative capacitor legs), maybe with floating ground? Have you used thick ground cables? Do you have good connection to the chasis? If I were you I would try to locate the problem by removing most of the parts, starting from one channel.
I used cheap EI in the old days and there are EI that simply create hum. Try to touch the body of the EI and check if it needs grounding. I used to ground at its leg.
Toroid is a bit quiter (nicer highs) but I still love EI more for it's quality bass. I don't have hum with Sony/Panasonic EIs.
You keep saying that the hum is okay because it is inaudible from a meter or so. No it is not okay. You can't hear the hum with full music, but the hum is there with your bass, making your bass not clean and tight.
Have you tried connecting each of the speaker negatives to the starground? Or have you moved the starground to the power supply (between positive and negative capacitor legs), maybe with floating ground? Have you used thick ground cables? Do you have good connection to the chasis? If I were you I would try to locate the problem by removing most of the parts, starting from one channel.
thomgun_lc said:
Mr. I forgot, would u like to check my wiring? I'm sory for poor/bad drawing
The only thing that jumps out at me is the minus-speaker connections are made at the AMP PCB and not at the star ground. They should definitely be connected at the star ground.
EI or toroid shouldn't really matter because you should keep audio wiring away from the transformer anyway. Millions of commercial amps have EI transformers and manage to be hum-free.
Your DC offset number looks good.
I_F
Slightly off topic,
does anybody have problems with buzzing coming from GSM cell phones? Everytime the cell tower sends some locating signal or when i receive or dial a call, my speakers buzz like crazy. Is it my GC that's amplifying this? or my speakers (which aren't magnetically shielded)? I have googled about this problem and have found that the buzz is 217 Hz.
does anybody have problems with buzzing coming from GSM cell phones? Everytime the cell tower sends some locating signal or when i receive or dial a call, my speakers buzz like crazy. Is it my GC that's amplifying this? or my speakers (which aren't magnetically shielded)? I have googled about this problem and have found that the buzz is 217 Hz.
I have this problem with my computer speakers, and every cheap radio in the house when the phone is nearby (~12" or less). But I have never noticed it when I set my phone on my stereo speakers.
Conclusion? The noise is probably coming from the amplifier. Improve amplifier and interconnect shielding; if that doesn't help, move to balanced inputs.. the noise should be rejected as it would be common to both leads.
It's kind of neat knowing ahead of time when you're getting an SMS, though!
Wes
Conclusion? The noise is probably coming from the amplifier. Improve amplifier and interconnect shielding; if that doesn't help, move to balanced inputs.. the noise should be rejected as it would be common to both leads.
It's kind of neat knowing ahead of time when you're getting an SMS, though!
Wes
Any other suggestion/solution to remove HUM based on my wiring?Mr.Jay can i PM u?I need to speak in Indonesian.
Mr.Jay do u ever try with a cheap EI transformator?I never use SOny/Panasonic.I know the buzz sound will make my bass sound become a little bad.But, i still don't know how to kill that buzz sound.
Mr.I forgot, do you have any suggestion?Or can anyone help my problem. Let's kill the HUM together
regards
---------
TomZ
Hi there.This is my progress report.Last night until 2am, i check my wiring especially in PSU wiring.
I think there is no problem with my PSU.I also check the PCB and there is no problem.All ground are connect.
I try disconnect SG&PG again and meet them at starground, the HUM sound louder than before. I have check all off floating ground, i found a cooling fan's trafo have a floating ground because it's doesn't have CT, i connect 0v to starground, and a slight HUM still occur.
I still looking for slight HUM sound which make me frustated but i never give up.I have tried to attach the minus speaker to starground and the slight HUM still there.I test all above with input short to ground (by turn a pot max to left).So,what must i do now?Please help me.
regards
---------
TomZ
(^3^)V
I think there is no problem with my PSU.I also check the PCB and there is no problem.All ground are connect.
I try disconnect SG&PG again and meet them at starground, the HUM sound louder than before. I have check all off floating ground, i found a cooling fan's trafo have a floating ground because it's doesn't have CT, i connect 0v to starground, and a slight HUM still occur.
I still looking for slight HUM sound which make me frustated but i never give up.I have tried to attach the minus speaker to starground and the slight HUM still there.I test all above with input short to ground (by turn a pot max to left).So,what must i do now?Please help me.
regards
---------
TomZ
(^3^)V
hi tom,
i had this @#$%^&* hmmm in my tda8563.that was when i soldered the board very hastily.this resulted in dry solders that i didnt notice in the first place.i used EI supply,greatly filtered,but still hmmm persisted.
i took out desoldering gun,desoldered all joints and resoldered everything.it took jus 30 min for every thing but the hummm,it dissappeared!!!
yeah its true,dry solderjoints cause hummm bec they dont make proper contacts b/w pins and board tracks,so currents flows like tiny sparks(u getting me) b/w pins and tracks.these sparks create alternating waves that is ac which gets out at o/p as @#$%^&* hmmmm.
if u have patience,check all the joints individually or else resolder board
.use flux cored solder wire and thin tip 30w iron.joints must be round and shinny.
rest as u deem good
i had this @#$%^&* hmmm in my tda8563.that was when i soldered the board very hastily.this resulted in dry solders that i didnt notice in the first place.i used EI supply,greatly filtered,but still hmmm persisted.
i took out desoldering gun,desoldered all joints and resoldered everything.it took jus 30 min for every thing but the hummm,it dissappeared!!!
yeah its true,dry solderjoints cause hummm bec they dont make proper contacts b/w pins and board tracks,so currents flows like tiny sparks(u getting me) b/w pins and tracks.these sparks create alternating waves that is ac which gets out at o/p as @#$%^&* hmmmm.
if u have patience,check all the joints individually or else resolder board
.use flux cored solder wire and thin tip 30w iron.joints must be round and shinny.
rest as u deem good
OK, here are a few more checks:
Be sure to disconnect anything connected to the amplifier input...
1) make sure that the volume pot casing does not connect to any of the pot terminals - it will connect to the "ground" side but that connection should be made through the SG-star ground-chassis connection. You'll need to lift the ground wire off the pot terminal when you check this.
2) make sure that the input jacks only get ground from the SG or star ground, not directly at the chassis. Disconnect the ground wire and check the reistance between the ground terminals and the chassis. It should be open.
2) Simplify. Connect one channel directly to power supply and star ground- leave out the speaker protection stuff, and disconnect the power supply for that circuitry. Also leave the fan power off (meaning no AC to the transformer that powers the fan). Check for hum after checking DC offset into a resistor, before connecting your speaker.
3) Do you live near high power radio/tv broadcast antenna systems? My parents live near a park with multiple TV/fm radio broadcast towers and their computer speakers dribble out audio from the broadcasters all the time. You may have something coming in via the speaker input, being rectified (detected like a crystal radio set) in the nonlinear output transistor junctions, and presenting itself as buzzing to your speakers.
4) Don't set you amp on top of/under/next to some electronics with a large motor or transformer. You can't practically shield against magnetically induced hum- you can only separate the pieces. TV and CRT computer monitor's horizontal oscillators can induce noise into nearby electronics. Make sure you're not close to one of those.
I_F
Be sure to disconnect anything connected to the amplifier input...
1) make sure that the volume pot casing does not connect to any of the pot terminals - it will connect to the "ground" side but that connection should be made through the SG-star ground-chassis connection. You'll need to lift the ground wire off the pot terminal when you check this.
2) make sure that the input jacks only get ground from the SG or star ground, not directly at the chassis. Disconnect the ground wire and check the reistance between the ground terminals and the chassis. It should be open.
2) Simplify. Connect one channel directly to power supply and star ground- leave out the speaker protection stuff, and disconnect the power supply for that circuitry. Also leave the fan power off (meaning no AC to the transformer that powers the fan). Check for hum after checking DC offset into a resistor, before connecting your speaker.
3) Do you live near high power radio/tv broadcast antenna systems? My parents live near a park with multiple TV/fm radio broadcast towers and their computer speakers dribble out audio from the broadcasters all the time. You may have something coming in via the speaker input, being rectified (detected like a crystal radio set) in the nonlinear output transistor junctions, and presenting itself as buzzing to your speakers.
4) Don't set you amp on top of/under/next to some electronics with a large motor or transformer. You can't practically shield against magnetically induced hum- you can only separate the pieces. TV and CRT computer monitor's horizontal oscillators can induce noise into nearby electronics. Make sure you're not close to one of those.
I_F
Hi. Mr_Jay. Please contact me at thomgun_lc@dbzmail.com because i can't PM u from this forum .Would u like to contact me?When i separated SG&PG, i draw a piece of cable then contact to starground.When i contact to starground, there is a little spark. I check the voltage between SG and PG and there is no difference, but why the spark can occur?
Mr. I_F:1. my gnd's pot connect directly to the pcb.I think the pot doesn't make a HUM sound, because i have tried not use a pot and the result is still slight HUM.Maybe i will try to disconnect all of the other transformator supply(FAN+Protector).
2.If i touch the pot, very loud HUM will appear.Why ?
3.All of my input/output terminal are isolated from chassing.
4.Yes, i live near BTS(GSM base station tower) about 30 metre from my house.If this can make a buzz sound, so my pioneer amp should be buzz too, but my pioneer amp didn't buzz.The only buzz sound in my home is my computer loudspeaker and my GC.
5.I don't set this amp near electronic amp.I tested this amp without any input.
6. I have try to re-soldering my pcb junction, the HUM still there.
7. I notice if the HUM sound very loud there must be fault wiring or disconnect one of the gnd.But when slight HUM occur, there is no disconnect gnd and i don't know what to do.
regards
---------
TOmZ
Can you power up one channel without haveing the other plugged in at all?, I noticed my one input resistor was a dud actualy measuring 2k instead of 10k, giving me massive gain, strangely enough this channel will play by itself, but oscilates easily when I plug both into the powersupply...
I only traced this error just now, so I still need to get a replacement resistor before I can say if it fixes the problem...
I only traced this error just now, so I still need to get a replacement resistor before I can say if it fixes the problem...
I haven't try to analyze HUM using 1 channel. Maybe i will try to analyze 1 channel.My last progress:
1.I tried to remove the transformator from chassis--->slight HUM still there
2.I disconnect fan&protector->slight HUM still there
3.I tried to change the transformator with other EI transformator-->the sound of slight HUM become more higher than before.
NB:The sound of the slight HUM which i mean is not audible in 1 metre. In quite room , i only hear the sound of the cooling fan.Cooling fan sound's louder than the slight HUM.If the HUM sound louder than cooling fan sound, there is a fault wiring.
Only times I had hum was with bad solder joints, they looked pretty from the outside, but after some wriggling they came loose... especialy the feedback resistor.... caused a massive noise when it looked pretty but had dry joint...
I do think you will trace your error much quicker working with one channel at a time... Worked for me, even if it took 3 days....
I do think you will trace your error much quicker working with one channel at a time... Worked for me, even if it took 3 days....
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