I built LJM's p7 mini preamp circuit and I'm very happy with it. I'm now going to wire a power switch before the 12v transformer. I would like to include an "on" status led in the circuit. I understand that led's need a resister in line in order to limit the mA they receive. However, I'm not sure where in the circuit I should add this little guy.
The transformer is 12 0 12. Do I add the led before the circuit or after or what?
(Thanks diy'ers for answering my basic questions. Sometimes the smallest first steps are the biggest thrusts into a hobby)
The transformer is 12 0 12. Do I add the led before the circuit or after or what?
(Thanks diy'ers for answering my basic questions. Sometimes the smallest first steps are the biggest thrusts into a hobby)
You are best adding the LED and its series resistor across one of the DC rails produced by the power supply, in other words, connect across one of the big caps in the power supply.
The resistor needs to be in the region of 3.9k and upwards depending on the LED and how bright it is.
(Adding LED's to the AC side... the transformer... would give noticeable flicker and would also need an additional diode to protect the LED from the negative cycles)
The resistor needs to be in the region of 3.9k and upwards depending on the LED and how bright it is.
(Adding LED's to the AC side... the transformer... would give noticeable flicker and would also need an additional diode to protect the LED from the negative cycles)
Ok. So I would insert it between the smoothing cap and the op amp and then ground it?
And will this cause one channel of the preamp to receive less power?
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