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Topic # 165872 23-Feb-2015 14:29
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Hi There!

I am looking for someone pretty experienced but reasonably cost effective  to help me troubleshoot a buzz I can hear in a home made headphone amp I have been trying to complete for far too long. 

It's been difficult to do this over the provided forums with the supplier, as I have very little free time right and would rather spend it listening to than fixing this AMP. 

If you know someone who may be able to assist. Please let me know. It's AC mains Powered.

Cheers


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  Reply # 1245062 23-Feb-2015 18:26
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Send me a schematic, I have done one or two electronic designs from time to time (major understatement).  Also draw up how everything is interconnected.




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  Reply # 1245304 24-Feb-2015 00:13
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What is the audio source for your headphone amp? Is the buzz still there if you disconnect the audio source? Is the buzz 50Hz mains hum or something completely different? Im also interested in the schematic and connection diagram.





 
 
 
 




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  Reply # 1245508 24-Feb-2015 13:15
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Sorry for the delay, I'll get this together and PM it (It's a propriety design). The Buzz is source independent if I recall correctly. I'll double check all the parameters and confirm.

One thing I can confirm is that the buzz is not louder as I increase the volume on the amp or source.

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  Reply # 1245515 24-Feb-2015 13:27
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What is the power supply for the amp? A switchmode brick or an oldschool iron transformer?

Former is likly to be a ground loop, latter poor filtering, but pictures and stuff are good.

I have a cheap ebay headphone amp that has an annoying hiss on it. So quiet you dont hear a his, its more like feeling pressure on your ears that goes away when you unplug the headphones, but its so low that it doesnt show on my friends cheap oscilliscope. Headphones are crazy efficiant at making the tinyest voltages into the slightest of sounds that you can hear.




Richard rich.ms



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  Reply # 1245556 24-Feb-2015 14:03
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Hi. 

This is actually a continuation of this thread: 

http://www.geekzone.co.nz/forums.asp?forumid=73&topicid=147293&page_no=3

I never got back to it after that, but I did determine the PC wasn't causing the problem as I disconnected it. 

Someone in that thread begged me to get some assistance, so I thought I might just give in and let it beat me this one time as I'd rather get it going than never use my HP's as a result of it not working nicely. 


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  Reply # 1245773 24-Feb-2015 18:23
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Oh, that thing.

It could use some smaller capacitors in parallel with the electrolytics to remove high frequency noise for a start.

Some small caps across the RCA inputs to try to remove any RF coming in there. Perhaps some small inductors in series with it to again remove any high frequancy components would be the first few things I would try to remove noise. Is there any more schematic etc for this available?

Making something like that noisefree will be hard, as the large spaced out design gives it more area for noise to get into it. Also when its in wood not metal thats more room for RF interference to get into it.




Richard rich.ms



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  Reply # 1245784 24-Feb-2015 18:29
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richms: Oh, that thing.

It could use some smaller capacitors in parallel with the electrolytics to remove high frequency noise for a start.

Some small caps across the RCA inputs to try to remove any RF coming in there. Perhaps some small inductors in series with it to again remove any high frequancy components would be the first few things I would try to remove noise. Is there any more schematic etc for this available?

Making something like that noisefree will be hard, as the large spaced out design gives it more area for noise to get into it. Also when its in wood not metal thats more room for RF interference to get into it.


Hi

There are hundreds of these kits in the market and this noise doesn't fall within "normal". There is obviously a fault with a component or solder or something I have wired incorrectly (Though all voltages and resistances are within the "normal" range and it sounds perfect except for this buzz). 



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  Reply # 1245788 24-Feb-2015 18:34
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So take it somewhere else and try it in a different environment and see if the noise problem is any different.




Richard rich.ms



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  Reply # 1245798 24-Feb-2015 18:41
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richms: So take it somewhere else and try it in a different environment and see if the noise problem is any different.


Yup ok I'll try that tomorrow. 


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  Reply # 1245910 24-Feb-2015 20:59
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Ah, your new post should state from the start that it relates to the old one.  So how did it go with the ground loop isolator in the RCA cable?

Are the RCA sockets supposed to be isolated from the metal plate (earth), or are they supposed to connect to the metal plate?

What does the noise sound like?




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  Reply # 1246767 26-Feb-2015 02:08
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  Reply # 1259872 15-Mar-2015 21:30
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Well this is turning out to be very puzzling! I took it to the office and I could hear the buzz in one ear and the following day I can't hear it any longer! It's the first time since I owned it it's been working perfectly and I really really like it. 

I am going to try and narrow down the difference between day one and two. 


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  Reply # 1261233 17-Mar-2015 18:19
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networkn: Hi There!

I am looking for someone pretty experienced but reasonably cost effective  to help me troubleshoot a buzz I can hear in a home made headphone amp I have been trying to complete for far too long. 

It's been difficult to do this over the provided forums with the supplier, as I have very little free time right and would rather spend it listening to than fixing this AMP. 

If you know someone who may be able to assist. Please let me know. It's AC mains Powered.

Cheers



Quick guesses.
1. Earth loop
2. Not enough filtering of the DC rails
3. Poor Earthing 



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  Reply # 1261250 17-Mar-2015 19:41
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I would bet on the earthing. I had a similar problem with a sub-woofer amp. Everything seemed properly earthed but when I ran a new wire between the sub and the main amp a few metres away the buzz magically disappeared.

 





I reject your reality and substitute my own. - Adam Savage
 




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  Reply # 1261252 17-Mar-2015 19:49
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sir1963:
networkn: Hi There!

I am looking for someone pretty experienced but reasonably cost effective  to help me troubleshoot a buzz I can hear in a home made headphone amp I have been trying to complete for far too long. 

It's been difficult to do this over the provided forums with the supplier, as I have very little free time right and would rather spend it listening to than fixing this AMP. 

If you know someone who may be able to assist. Please let me know. It's AC mains Powered.

Cheers



Quick guesses.
1. Earth loop
2. Not enough filtering of the DC rails
3. Poor Earthing 




I am pretty sure I don't have enough experience to work with information that non specific. All the Voltages are within the margin of error as were the resistances and other than the buzz it sounds wonderful, so I am unsure how to troubleshoot further. 

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