Requisite Audio PAL Preamplifier and Limiter MK III


The original PAL (Preamp And Limiter),introduced in 1998, was based on a combination of our original Y7 microphone preamplifier and our L1 optical limiter. Within a year, the PAL was outselling all four versions of the Y7 and L1 combined. For us, this established the PAL as a permanent platform for continued development and refinement. Components and construction are the highest quality seen in the audio industry today. Each unit is point-to-point hand-wired to solid Teflon terminal strips and oxygen free copper post. All audio transformers are based on classic designs, upgraded wherever appropriate, and made to our specifications.
High-grade polypropylene capacitors are used exclusively in the signal path. Polypropylene caps are also used for B+ filtering, making the PAL Plus MkIII the only pro audio product that does not use electrolytic caps for filtering. Allen-Bradley carbon composition resistors, gold switches, gold and ceramic tube sockets and special solid-core audio wire are all selected for their tonal character and reliability. This design approach has yielded characteristics that include wide bandwidth, low noise, low distortion, reliability and truly high fidelity performance making the PAL Plus MkIII a “must have” for any professional recordist.



  • Mic/DI – Line Select
  • Mic/DI Gain – Continuosly Variable
  • Hi-Pass Filter
  • Mic/DI Feedback – Continuosly Variable
  • -20dB Pad
  • Output Level – Continuosly Variable
  • +48V Phantom Power
  • VU Meter (upper meter)
  • VU Meter Adjust
  • Hi-Z Input
  • Limiter Response – Continuosly Variable
  • Mic Link
  • Limiter Feedback – Continuosly Variable
  • Limiter Link
  • Peak Reduction – Continuosly Variable
  • Ratio 10:1 & 3:1
  • GR Trk – Gain Reduction Tracking Calibration
  • Peak Reduction Meter (lower meter)
  • VU Meters


  • Ground Connector – Chassis and/or Circuit Ground
  • Power Supply Inlet (choice of Tube or Solid-State Supply)
  • Transformer Balanced XLR Output (pin 2 HI)
  • Limiter Link – 1/4″ Jack for linking additional PAL Limiter (not included)
  • Tube Channel – Protective Structure for easy Tube replacement and Ventilation
  • Transformer Balanced XLR Mic Input (pin 2 HI)
  • Transformer Balanced XLR Line Input (pin 2 HI)


  • Solid-Core Copper/Silver Wire with Teflon Dielectric
  • Handwired, Point-To-Point Throughout (only Meter/Phantom on PCB)
  • Custom Input and Output Transformers
  • Overbuilt – using highly rated, quality components



    Left to run freely, vacuum tubes tend to exhibit a considerable amount of harmonic generation and other forms of distortion. For over half a century, negative feedback has been engineered into circuits to “improve” the linearity of vacuum tubes when used in audio gain stages. However, best readings on a meter don’t always equate to the ideal sound (whatever that happens to be). By making MIC/DI FEEDBACK an adjustable feature, harmonic content and texture are in the creative hands of the audio engineer and not the guy with the THD meter.


    The Pal Plus MkIII features a full-time VU Meter and Gain Reduction Meter. This allows the user to monitor both actions simutaniously whitout needed to switch between the two functions.


    Unique to the PAL Plus MkIII, the Mic Link switch allows for inter-connection between two PAL microphone preamplifiers (a second PAL and inter-connect cable is required). Because of where (within the circuit) the connection is made, the microphone only “sees” one preamp and is loaded as it would normally be, using just one preamp. Having one mic drive two mic-pres offers many sonic and creative possibilities, especially when one considers the broad range of tonal variation of the PALs variable gain structure, variable feedback circuitry and limiter functions. Layering from a pair of PALs is encouraged.



The RTS-4A is built on classic, no compromise design and techniques. It is tube regulated, tube rectified and capable of powering any Requisite Audio vacuum tube audio processor in current production. It is expandable from one to four channels. Filtering is accomplished using custom made poly/oil capacitors and a heavy duty audio frequency choke.


Standard with the RTS-4A is the GZ34 (5AR4) tube rectifier. DC filtering is via custom AF Choke input & custom made oil & polyprophylene capacitors.


Power Supplied: B+, Heater, Meter Driver, Lamps. Power Required: The RTS-4A can operate on 115V or 230V mains.

  1. Single channel RTS-1A
  2. Dual Channel RTS-2A
  3. Three Channel RTS-3A
  4. Four Channel RTS-4A



The OPS-2D is a single or dual-channel solid-state power supply designed to power all current production Requisite Audio vacuum tube audio processors: L2M MkIII, PAL Plus MkIII, OS1, SM 162 Summing Mixer and the SMX 1748 Summing Mixer Expander. The OPS-2D can be configured for single or dual-channel operation.


Standard with the OPS-2D are ultra-fast, soft-recovery diodes with balancing resistors and polypropylene bypass caps. DC filtering is via Nichicon audio capacitors with polypropylene bypass caps. Power Supply coupling is via AF Chokes.


Power Supplied: B+, Heater, Meter Driver, Lamps. Power Required: The OPS-2D can operate on 115V or 230V mains.

  1. Single channel
  2. Dual Channel