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Old 2nd April 2013, 12:05 PM   #11
Zen Mod is offline Zen Mod  Serbia
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CRC or not, principle is here (see first pic)

with proper and tight wiring there will no be any hum

then - if you have some hum with input cabled connected , add bridge shown on sec. pic
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Old 2nd April 2013, 12:30 PM   #12
wazzy is offline wazzy  Zimbabwe
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Correct me if I'm wrong but your transformer seems to have a three wire secondary, and you seem to have two bridge rectifiers one for each amplifier board not so? In a form of dual mono power supply but from a common transformer, in my limited experience when trying this scheme always resulted in hum, try using one bridge rectifier for both boards and just use your existing caps for the smoothing, worth a try. And as Andrew T said twisted pairs, always.
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Old 2nd April 2013, 01:29 PM   #13
Zen Mod is offline Zen Mod  Serbia
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oups

I missed that from pic
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Old 2nd April 2013, 02:21 PM   #14
6L6 is offline 6L6  United States
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Wazzy - Good eyes! Bravo!

3GGG - Wazzy's suggestion is spot on - use one bridge to feed the PSU, like this - (please excuse the crude sketch)

Click the image to open in full size.
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Old 7th April 2013, 08:14 PM   #15
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Thank Mod Zen for the wiring diagramm of the ground. In summary:
1) Main Audio Ground "L" and "R" are on the amp boards.
2) The power thermistor between MAG and chassis.
3) With Arta verify if the FAT WIRE BRIDGE lowers the noise.
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Old 8th April 2013, 10:15 AM   #16
AndrewT is online now AndrewT  Scotland
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Quote:
Originally Posted by claudio52 View Post
...........
2) The power thermistor between MAG and chassis..............
will the Power Thermistor pass Fault Current?

That Fault Current can approach and even exceed 1kApk.
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Old 8th April 2013, 06:13 PM   #17
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I do not understand. Under ordinary condition the thermistor provides some isolation against ground loops. If the leakage becomes large current, then the thermistor heats up, providing a more efficient path. Why it is not a good solution? It best to connect the thermistor between the PSU and chassis?
Thank you for your patience.
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Old 8th April 2013, 06:56 PM   #18
Zen Mod is offline Zen Mod  Serbia
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power thermistor will certainly pass greater current than fuse , be it on secondary or primary side

if that's good solution for PL and FW products , which certainly have all necessary trading/safety/regulatory permissions ..........
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Old 8th April 2013, 09:32 PM   #19
AndrewT is online now AndrewT  Scotland
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Quote:
Originally Posted by Zen Mod View Post
power thermistor will certainly pass greater current than fuse , be it on secondary or primary side ..........
are you sure?
a fault current prior to the fuse blowing can be 1kApk.
Can a Power Thermistor pass this current?
Or will the power Thermistor reduce the current such that the fuse does not rupture?
Have you tested any Power Thermistor to see if they survive longer than it takes for the fuse to rupture and the arc to extinguish?
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Old 8th April 2013, 10:16 PM   #20
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did you ?
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