http://www.maxonfx.com/Realtube_II_RTO700.php --
The best tube overdrive / Distortion pedal on the market.
The RTO700 Tube Overdrive Pedal has no clipping diodes in the signal path - All distortion comes directly from the dual triode preamp tube and hi-gain amp circuit. This design makes the RTO the best tube overdrive pedal for use with clean and semi-clean amps to effectively add a 2nd or 3rd channel of pure tube tone to your rig.
Every aspect of the RTO700 has been re-thought and redesigned to provide a lifetime of trouble-free performance. As soon as power is applied to the pedal, an In-Rush Current control begins heating the tube at a very low voltage (much like a tube amp standby switch) to dramatically extend tube life. When the pedal is engaged, a charge pump circuit bumps incoming voltage to feed the tube with 12.6 VDC.
Unlike other tube overdrive pedals, the RTO700 places the tube AFTER the OD / Distortion circuits, making it the best tube overdrive pedal to recreate an authentic tube-amp tone.