Amplifier Power Consumption

“Please Standby, We are Experiencing Technical Difficulties”: This should have been the headline that began the notification from the EU when it enacted its current standby circuit regulations. And it affects many in North America as well.

We at REL have always adopted a design stance that favors efficiency wherever possible. This approach extends to our amplifier designs. Recently, a customer wrote to me stating that he so enjoyed the purchase of his new REL Tzero MKIII that he wanted to purchase a larger unit, our T/9x but he would only do so if we offered a Standby circuit. I wrote him back explaining that in North America we don’t offer Standby circuits on anything except our Tzero MKIII and our larger Class D amps (in the EU and UK we do so by requirement but perhaps if more gear were designed like ours, it would never have become necessary).

Back in the not-so-distant olden days of 2010, standby circuits were employed on all sorts of low level audio gear. When I say low level, I mean items like source components such as CD players, tuners, and also preamps that don’t draw much by their very nature. It was also pretty common, and still is today, for tube equipment to feature a standby circuit as well as an audio mute circuit to allow the heaters on their tubes to warm up quietly and eliminate possible noise during startup.

These circuits were great because they allowed enough power, say 5 watts or so, to keep the sensitive low level circuits warm, which cut the warmup time from an hour or so down to a few minutes. Solid state preamps and even amps featured these too because the input circuit for a large power amp can take hours and sometimes even days to arrive at their best sound. But the European Union’s draconian requirement to limit current draw at idle (standby) to just ½ watt changed all that.