Guitar-cable-amplifier. If this describes the rig you use, then the Sovtek 6L6WXT+ is one of two modern vacuum tubes you should consider. This is not a repackaged 5881. Extremely low noise and a lack of microphonics combine with excellent ratings for detail and harmonic content to provide an audio tube of exceptional quality. These 6L6 tubes can be used in any tube amp. Plenty of power and great tone. We have tested these tubes with plate voltages ranging from 425 to 500 volts without problem. Biasing can be set from conservative to hot; again, no real problem and great tone will be delivered from most settings.