After home-building such an amp for the purpose of connecting to the LS outputs of my laptop and tablet to enhance music quality (which is great from bookshelf speakers mounted on the wall by the way), I tended to leave the amp permanently powered for convenience.To date, I am on my third stereo dual control pot, as the tracks had become extremely noisy and so were unusable. A track on the second pot was even o/c at the bottom end. This annoyance merited further investigation and admittedly should have been done much earlier when first discovered. It appears that at IC audio input pins 7 & 6, derived from the chip's internal transistor network, there are standing voltages of +2v dc directly connected to each pot wiper in the traditional circuit. To mitigate this intrusion, I have added a re-designed input circuit and attached this to view for your interest and reference. The two 33 ohm loading resistors simulate a pair of stereo headphones plugged in the pc LS socket. Left and right channels have fixed loading resistors for the +2v dc mentioned. Each +2v dc is blocked by electrolytic caps to protect the pots. Note the polarities. The two 3k9 resistors act as audio current feeds rather than audio voltage feeds, to stop shrieking instability at high inputs. The two 33k resistors limit maximum audio output level.
Hopefully my third dual pot will remain in pristine condition. I trust the above comments might be helpful to your readers and constructors, to not fall into the same cycles of puzzlement as myself.Please Note
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