RND 5025

Over fifty years in the making, the Shelford mic preamp is the definitive evolution of the original technologies in Rupert’s classic console modules. The 5025 contains two of these preamps in a single rack space.

While the majority of the harmonic richness found in Rupert’s designs is a product of the output transformer and surrounding class-A amplifiers, this step-up input transformer also imparts a unique musical enhancement of its own. The technical reasons for this are primarily a result of the reactive impedance characteristic of the input transformer and how that interacts with the connected microphone, resulting in subtle, non-linear harmonic enhancement of the lows and an unmistakable sweetness in the high frequencies.

Mic Gain
This 12-way precision rotary switch controls gain from 0 to 66 dB in 6 dB steps.

Trim
This rotary switch provides further continuous gain adjustment over a range of +/– 6 dB.

48V
This push button switch engages phantom power on the microphone input.

Polarity
This push button switch inverts the polarity of the signal path. It illuminates when engaged. (The symbol “Ø” is often used to denote opposite polarity.)

HPF / HPF FREQ
The HPF switch engages a 12dB per octave high pass filter. The HPF FREQ potentiometer is variable from 20Hz to 250Hz, and can be used to filter out unwanted low frequencies, or in conjunction with the EQ to help shape source material. Note that engaging the HPF to S/C switch moves the HPF from the primary signal path to the compressor side-chain signal path.

Silk / Texture
Pushing the Silk button cycles the Silk modes from Red to Blue to OFF. Silk reduces the negative feedback on the output transformer, adding harmonic content as the texture is increased. Red Silk accentuates the musical harmonic saturation from the mid and high frequencies, while Blue Silk accentuates harmonics from the low and low-mid frequencies. By manipulating the Texture control, the amount of Silk can be changed from essentially absent, to roughly 4-5% THD (mostly second order) depending on how hard the output transformer is being driven.

VU Meters
The VU Meters are calibrated to display average (RMS) output levels.

Peak LED
Red indicates near clipping of the output stage.

Dual Tap Output
In addition to the MAIN full-headroom output, the -6dB output creates a rich harmonic character while reducing the risk of clipping the next device in the chain.

Gnd Lift
This switch separates the direct connection from audio signal ground to chassis earth.

Universal IEC Power Input
Works worldwide, accepting voltages from 100-240VAC.