Use Amplifier Phono Input as Line Level
Input: Inverse RIAA Filter - The circuit does two
functions: signal level attenuation and inverse RIAA filtering. The signal attenuation is needed to convert the
500 mV signal to 2. 5 mV signal. The inverse-RIAA filtering is needed to make the frequency response of the
system flat (same equalization that is used when music is transferred to vinyl in the studio). The picture. . .
[Tomi Engdahl]
Variable AC Power Supply - In electronics, it is often handy to have a fully isolated variable AC power supply. With
such a device you can safely test various AC powered circuits and even probe around in the circuit with an
oscilloscope. The hobby circuit below was designed to . . . [Hobby Circuit designed by Dave Johnson P.E.,
07/08/00]
Variable Isolated AC
Voltage Spans 0Vac to 280Vac - I designed and built
this circuit about 25 years ago. It came in handy for many projects that were powered from 120 VAC, 240 VAC and
277 VAC. It provides complete isolation from the power line. It uses two 1:1 isolation transformers that are
wired in parallel . . . [Circuit by David Johnson P.E., 07/09/00]
Voltage Boost to
Series Regulator provided by Capacitor - This circuit
adds some capacitors and diodes to a traditional transformer type series regulator circuit to extend the normal
operating range. It can insure regulation during low line voltage conditions or it can squeeze a few more watts
out of a plug-in-the-wall power adapter power supply . . . [Hobby Circuit designed by Dave Johnson P.E.,
01/01/98]
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