I quickly threw together a gainclone using the TI OPA548. I just tested it using a portable CD player and an old 4 ohm 3 way car speaker. I have the whole thing powered with a table top power supply (BK precision 1650). Here are the strange findings:
wideband distortion even at low input levels from the portable CD player (although I cannot quantify the input level as I do not have a scope yet).
When I check the current draw from the PS meter its only like
100-200mA. I am using +/-10v rails and my gain is only set at 10x.
Thanks for any help,
Mike
wideband distortion even at low input levels from the portable CD player (although I cannot quantify the input level as I do not have a scope yet).
When I check the current draw from the PS meter its only like
100-200mA. I am using +/-10v rails and my gain is only set at 10x.
Thanks for any help,
Mike
Problem solved
My problem turned out to be a simple one. Using the OPA548, I had forgotten to connect the enable pin (7) to V+ (5) and the current limit pin (3) to V- (4). Also, some of my aligator clips must be on the frits leading to intermittent lose ground connections. This seems to result in a full excursion of the speaker at a very low current draw. I am very surprised by how this little chip drives my 6x9 speaker with authority. Of course, I have yet to really push it... and will.
Mike
My problem turned out to be a simple one. Using the OPA548, I had forgotten to connect the enable pin (7) to V+ (5) and the current limit pin (3) to V- (4). Also, some of my aligator clips must be on the frits leading to intermittent lose ground connections. This seems to result in a full excursion of the speaker at a very low current draw. I am very surprised by how this little chip drives my 6x9 speaker with authority. Of course, I have yet to really push it... and will.
Mike
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