The LM334 does a great job in regulating DC. But it also can be used in pairs to produce a regulated current AC.
I put two LM334 three-terminal devices in parallel but in opposite senses, and set their currents with a 75 ohm set-resistor on each. The resulting sub-circuit is a two-terminal device. I put this in series with the silver electrodes and a 15VAC output used to power toy trains. The regulated current in each branch of the LM334 pair can be monitored by a micro-ammeter. But an oscilloscope could be used to monitor the constant currents in both directions. My pair of LM334s levellled off at 300 micro-amperes. The CS that resulted was very clear and more tasteless than CS brewed with DC constant current. The silver electrodes were cleaner too. matt
