Carbon Copy' is a wonderful allusion to the all-analogue signal path of this retro-style delay pedal from MXR. This is an old-school delay pedal featuring 'bucket brigade technology' – a phrase which refers to an analogue delay line that was developed in the late 1960s by Philips Research Labs. It uses capacitance to store the analogue signal, which is then moved along a line of capacitors one step at each clock pulse, much like a line of people passing buckets of water to extinguish a fire.
Just about every classic delay, chorus and flanger employed Bucket Brigade Devices (BBDs), and many enthusiasts maintain that the digital signal processors that superseded BBDs can't achieve the same warm tone. Mind you, they can't achieve the same crystal clarity either, so it's horses for courses. In this case BBDs are an appropriate choice.
Maximum delay time is quoted at 20ms to 600ms, which is pretty impressive for an analogue delay. It's the same size as a Phase 90, but MXR has managed to squeeze on three knobs: Regen (number of repeats), Mix, and Delay (time), as well as a Mod switch. Mod modulates the pitch of the delay signal to mimic the small fluctuations in speed that are typical of tape echo devices. The speed and width of the modulation can be adjusted internally using a small screwdriver. The footswitch is true bypass and you can run the Carbon Copy from a battery or a negative centre 9v power supply.
Controls: Regen, Mix and Delay, with modulation switch and true bypass footswitch