Hello everyone,
I have just finished building Aleph5, It seem to work fine even though the supply voltage is a bit low at 32V as I have previously posted.
After I power it up. I got DC offset at output 50mV for Left channel and 38mV for right. It is ok? since I have read the in several posting before.
Then I connect the speaker everything fine No noise observed.
And Finally, I introduced the preamp. Then it hum or buzz like crazy 😕
I try to be patient and observe the condition of buzzing.
- No hum or buzz observe when only connect to speakers.
- No hum or buzz observe when connect to speakers together with introducing preamp one channel.
- Hum or buzzing start when introduce both channel of preamp. I notice that it start hum when the center of second channel RCA is connect. No need to be fully connect with ground.
- I did some experiment. I connected the speaker, then I attached the single end cable (RCA). At the other tip, I brought the center pole to touch the ground connection on the PCB itself, I heard slightly hum. My understanding, this is short input to ground. It should be silence?
More info on my aleph 5.
I have used output mosfets per channel and bring up the bias to 2.8A
I observe that my PCB use a ground plane scheme, not the star ground. Is it cause this problem?
I have tried several ground schemes but the problem is still there. The currently one is as the picture.
Any suggestion would be appreciate. I am loss now.😕
I have just finished building Aleph5, It seem to work fine even though the supply voltage is a bit low at 32V as I have previously posted.
After I power it up. I got DC offset at output 50mV for Left channel and 38mV for right. It is ok? since I have read the in several posting before.
Then I connect the speaker everything fine No noise observed.
And Finally, I introduced the preamp. Then it hum or buzz like crazy 😕
I try to be patient and observe the condition of buzzing.
- No hum or buzz observe when only connect to speakers.
- No hum or buzz observe when connect to speakers together with introducing preamp one channel.
- Hum or buzzing start when introduce both channel of preamp. I notice that it start hum when the center of second channel RCA is connect. No need to be fully connect with ground.
- I did some experiment. I connected the speaker, then I attached the single end cable (RCA). At the other tip, I brought the center pole to touch the ground connection on the PCB itself, I heard slightly hum. My understanding, this is short input to ground. It should be silence?
More info on my aleph 5.
I have used output mosfets per channel and bring up the bias to 2.8A
I observe that my PCB use a ground plane scheme, not the star ground. Is it cause this problem?
I have tried several ground schemes but the problem is still there. The currently one is as the picture.
Any suggestion would be appreciate. I am loss now.😕
An externally hosted image should be here but it was not working when we last tested it.
Use 10R resistors to connect each input RCA ground shell to the amplifier ground.
This will break the ground loop.
Good point Mr. Happy 🙂
My recent A5 build had a bit of hiss (not buzz) into my Klipsches. I had always used a lower power/ gain amp and never heard a problem. Single ended RCA in.
I pulled the Negative XLR to GND shorting jumper, which lowers the gain - no other harm if using original A5 circuit.
Hiss gone. 🙂
My recent A5 build had a bit of hiss (not buzz) into my Klipsches. I had always used a lower power/ gain amp and never heard a problem. Single ended RCA in.
I pulled the Negative XLR to GND shorting jumper, which lowers the gain - no other harm if using original A5 circuit.
Hiss gone. 🙂
Measure the voltage with an oscilloscope across the L and R RCA ground with every thing disconnected, just the amp powered up. There should be no signal. However, looking how your power supply is built, the charging current is going through the copper plate from top to bottom, and your connections are made on the side, along the direction of the current. This could introduce hum on the ground. Somehow you only notice it once the preamp is connected.
I had the same thing with my F5. It is specifically a problem with class A amps as the steady state current through the power supply is relatively large. The Elco's only charge during a small percentage say 10% of the mains cylcle (60Hz in the US), so if you're drawing 3A DC from your PSU, the charging spikes will be in the order of 30A (!). This causes potential even across a copper clad ground plane.
I had the same thing with my F5. It is specifically a problem with class A amps as the steady state current through the power supply is relatively large. The Elco's only charge during a small percentage say 10% of the mains cylcle (60Hz in the US), so if you're drawing 3A DC from your PSU, the charging spikes will be in the order of 30A (!). This causes potential even across a copper clad ground plane.
I forgot to mention that hum happen when plug both chennel of preamp even the preamp was turned off. So, I don't think the problem come from the gain structure. Anyway it was a interesting article. I put in my book mark , Thank you very much.🙂
Not sure I understand correctly, but the connection is made at the opposite side (end side) of the copper plate.
An externally hosted image should be here but it was not working when we last tested it.
How can I get rid of that problem?😕 any suggestions?
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Instructive article about ground loops and interconnections,
scroll down the page to see a different configurations schematics :
Audio Component Grounding and Interconnection - diyAudio
Have a nice day 🙂
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Your 0v connection seems to be too large , you'd better try to do this way 😉
in audio , the shorter and the simpler , is very often the better 😉
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in audio , the shorter and the simpler , is very often the better 😉
.
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Thank you. But where should I connect to the psu ground?
Useful link Thank you very much.
Your 0v connection seems to be too large , you'd better try to do this way 😉
in audio , the shorter and the simpler , is very often the better 😉
.
Interesting, will try this. Thank you.
I have tried it, it was no change in Buzz. Are there any other step of testing? Thank you
More information, I also have a small buzzing from transformer itself. Does it affect to this problem?
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