Well...the low level scrungy sounds from a source non-selected is now improved on my Hafler D110 preamp.
The separated grounds from input to output IS A PROBLEM WITH THE SOURCE SELECTOR SWITCH GROUNDING UNSELECTED
INPUTS!
I fixed it by almost 30db, by adding a very heavy common wire ground from both sets of input jacks shield points, to the Selector switch shield ground point. Amazing improvement!
The separate ground traces way to thin, at 2.5 Ohms measured through the ribbon connectors. The added heavy wire, now 0.1 Ohms bypassing the connectors and thin traces through the rubber grommet. Calculate 20 X Log 2.5 / 0.1 to gnd = 28.9 dB
Wow. What a design blunder.
Scope trace...only 27 mV.
Over 50db isolation from 10 volts. Not a perfect world, but much better!
The separated grounds from input to output IS A PROBLEM WITH THE SOURCE SELECTOR SWITCH GROUNDING UNSELECTED
INPUTS!
I fixed it by almost 30db, by adding a very heavy common wire ground from both sets of input jacks shield points, to the Selector switch shield ground point. Amazing improvement!
The separate ground traces way to thin, at 2.5 Ohms measured through the ribbon connectors. The added heavy wire, now 0.1 Ohms bypassing the connectors and thin traces through the rubber grommet. Calculate 20 X Log 2.5 / 0.1 to gnd = 28.9 dB
Wow. What a design blunder.
Scope trace...only 27 mV.
Over 50db isolation from 10 volts. Not a perfect world, but much better!
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