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DIY For Audio
Power amp diagnostics / earthing advice: help needed
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<blockquote data-quote="ludo" data-source="post: 73504" data-attributes="member: 691"><p>I think the 10 Ohm resistor is just there so one can do a basic test of the main poweramp pcb in isolation. It gets bypassed by the ground wiring on K601/K602 ribbons to signal gnd. The humm disappears when you switch to balanced because there is low impedance drive to the poweramp input then, and that drive is referred to signal gnd. So the problem is probably only at the RCA socket or in the ribbon from K601/602 and the ribbons further on. Not sure how those ribbons find their way to signal gnd.</p><p></p><p>With 10 Ohm there inside the feedback loop, and the input resistor terminating on it as well, you get funny stuff. The 10 Ohm has to be bypassed. So the junction of the 10 Ohm and the 25v/100u cap is at signal gnd.</p><p></p><p>Edit x2: clarification, I hope</p></blockquote><p></p>
[QUOTE="ludo, post: 73504, member: 691"] I think the 10 Ohm resistor is just there so one can do a basic test of the main poweramp pcb in isolation. It gets bypassed by the ground wiring on K601/K602 ribbons to signal gnd. The humm disappears when you switch to balanced because there is low impedance drive to the poweramp input then, and that drive is referred to signal gnd. So the problem is probably only at the RCA socket or in the ribbon from K601/602 and the ribbons further on. Not sure how those ribbons find their way to signal gnd. With 10 Ohm there inside the feedback loop, and the input resistor terminating on it as well, you get funny stuff. The 10 Ohm has to be bypassed. So the junction of the 10 Ohm and the 25v/100u cap is at signal gnd. Edit x2: clarification, I hope [/QUOTE]
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DIY & Tutorials
DIY For Audio
Power amp diagnostics / earthing advice: help needed
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