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Old 8th May 2006, 06:15 AM   #61
jleaman is offline jleaman  Belgium
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Quote:
Originally posted by The Saint
Ok Jason

I have modified the Bmp of your PCB overlay
and I have had a look at the schematic you sent me.
The schematic is mostly correct, but as I suspected there is a
small error on the PCB layout.

You need to cut the SG track where shown on the overlay
and run a link wire from SG to the node of R0 and Z4
This will connect the Signal ground as shown on the schematic
and correctly isolate signal ground from power ground.
also increase the value of R0 to 10 Ohms.

Thats it!

Right on. Thank's Ill try this tomorrow. Do i have to change R0 to 10 Ohms. Or can i keep it at 3.Ohms
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Old 8th May 2006, 06:17 AM   #62
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I Would change it to 10 Ohms
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Old 8th May 2006, 06:22 AM   #63
jleaman is offline jleaman  Belgium
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Quote:
Originally posted by The Saint
I Would change it to 10 Ohms

I only asked because i don't have any 10 Ohm @3watt
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Old 8th May 2006, 06:32 AM   #64
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A 1 Watt resistor will do just fine. in fact a 600mw metalfilm
with back to back diodes across the resistor as I showed you before will work just great
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Old 8th May 2006, 07:49 PM   #65
jleaman is offline jleaman  Belgium
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OK this did not fix the problem.. Now what to do.
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Old 8th May 2006, 08:36 PM   #66
Cortez is offline Cortez  Hungary
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Hey boys, lets now fix this humming bear already !

To Post #56:
http://www.diyaudio.com/forums/attac...amp=1147029082
If you connected your wires like this, lets firstly forget all of
the the power and speaker cables and the red signal wire.
I guess, we can state surely, that the problem is somewhere else...!

Namely:
- ground traces on the PCB
- and the heatsink's grounding

My questions:
Is it necessary to connect the signal GND with the power GND on the PCB ?
If its not, please cut off every unneeded gnd trace, and do not connect
the 2 different gnd on the PCB, because they are already connected at the PS,
and if there is a redundancy, there is a ground loop, and there will be a humming...
So lets clearify the grounds on that PCB finally!

Think through every ground wire, and draw it for us, now without the power and speaker wires !

You should also try to shortwire one of the RCA and try to leave the other chanel alone.
If the humm is gone, the ground loop is created between to 2 side.

And now the heatsinks: try the main possibilities, like:
- unconnected (no earth, no ground, etc on the 'sinks)
- connect the 'sinks directly to the power GND
- connect the 'sinks to the power GND through a (1k sesistor || 100nF)

If these doesnt work, I will eat my hat...
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Old 8th May 2006, 08:42 PM   #67
Cortez is offline Cortez  Hungary
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Oh, just one last thing:
If you have only a passive preamp (a pot) after your source,
the wire section after the pot is specially sensitive to collect
humm from the environment, particulary when the pot has a
high value, like 50k-100k and/or its a long wire after the pot.
But you check this easily, if you grab that section after the pot,
and the humm is getting louder, thats the main reason.
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Old 8th May 2006, 08:43 PM   #68
jleaman is offline jleaman  Belgium
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When each wire to a source is removed the hum is gone.. BUT to help with this thread and close it..

I have just fixed the problem.


http://gallery.zorby-audio.com/main....m&g2_itemId=87

This picture shows all..

A little hint the input wires are ABOVE the psu and not along the base of the amp.
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Old 9th May 2006, 04:32 AM   #69
Cortez is offline Cortez  Hungary
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> A little hint the input wires are ABOVE the psu and not along the base of the amp.
So you just had to place the input wires away from the PSU and the trafo ?
You should route it then right next to the heatsink with the builtin RCAs.

Otherwise I really suggest, that you route the speaker wires as I told you.
Now, you have a great and high current loop formed by them.
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