Jim Kelley Power Attenuator w/ Carrying Case

Availability: In stock now!
The L-Pad Attenuator
The Jim Kelley Power Attenuator utilizes a time-proven engineering standard L-Pad design. An L-Pad is an infinitely variable power divider that, when combined with a speaker, maintains constant load impedance over its range of adjustment.   L-Pads have been used to adjust the volume of high fidelity music systems with complete transparency for more than 50 years.  At the heart of our device is a pair of 100 watt rheostats wired in an ‘L’ arrangement. A rheostat is a large, power dissipating, wirewound potentiometer. Increasing the amount of attenuation moves the rheostats in unison such that as the impedance of the series rheostat increases, the impedance of the shunt rheostat decreases.  As attenuation is increased, more power is diverted to the rheostats and less is conveyed to the speaker.   Maintaining constant load impedance at all attenuation settings allows the natural tone of your amplifier to come through at virtually any power level. This is a rugged, good looking, high power device with 30 years of performance tested experience on stages around the world.          
Resistance vs. Reactance
There are two perspectives from which to view impedance: from the perspective of the amplifier, and from the perspective of the speaker.  Generally, the perspective of the amplifier is taken, and it is argued that in order to best preserve the integrity of the signal, the attenuator should present a reactive load to the amplifier. This has the effect of shaping the frequency response.  However, from the perspective of the speaker, the way it responds to a given signal is primarily a function of its own frequency-dependent impedance characteristics.  With a reactive attenuator, the frequency response is a combination of both the response of the speaker and the response of the attenuator.  The logic for using purely resistive elements in the attenuator is that they are neutral with regard to frequency, and can thus provide optimal signal transparency.  Although there are other effective means for accurately attenuating a signal, and some may be well suited in a bedroom environment, players have found that ours is simple, practical, reliable, and great sounding on stage, and in the studio.
The ‘Loudness Effect’
Ever notice what happens when you listen to music at low volume? The high-end and low-end become less prominent.  Stereo systems have a Loudness switch to compensate for this, and now due to popular demand the Jim Kelley Power Attenuator also has 3 levels of Treble Boost compensation:  0 dB, +3dB, or +6dB.  The exact amount of compensation varies as needed with the amount of attenuation. Webster's dictionary defines dynamic range as the ratio of the strongest to the weakest sound intensity reproduced by an audio system. Turning down the volume on your stereo reduces the dynamic range of the sound by reducing the strongest sound intensity. This is what a power attenuator does - the advantage being that it allows you to utilize your amplifier to its full capacity. 
The Optional Footswitch

True bypass footswitching allows you to restore full power in an instant.  The optional attenuator footswitch also provides an auxiliary jack which, depending on your amp, can be used to simultaneously boost gain, or select channels whenever you switch.  With the Jim Kelley Power Attenuator you can adjust for both a clean sound, and an overdriven output sound - both at the same volume.  An internal selector switch allows you to optimize the auxiliary switching for your particular amplifier.


  • 100 Watts Maximum Input
  • Footswitch Input for remote IN/OUT switching
  • Variable Line Output
  • Headphone and External Speaker Jack
  • Continuously Variable Power Control
  • Constant Load Impedance (+/- 1 ohm)
  • Weight: 7lbs
  • Dimensions: 6" Wide x 4" High x 7" Deep