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SW1X Audio Design™ PRE III

Performance Level 3
EL84 OPT Phono & Line Pre-Amplifier


The PRE III is a pure class A, zero negative feedback (global or local) line pre-amplifier with a signal output transformer (OPT) de-coupled valve output stage. Signal OPT of highest quality not only increases transparency (superior to any kind of capacitors) but also lowers the output impedance of the line pre-amplifier further close to 4 Ohms, capable of driving any load of power amplifier input. That virtually unlimited driving capability of PRE III (as well as the DHT version PRE IV) line pre-amplifier acts as a supercharger to a source (DAC Phono, Tape or Radio). It is a great enhancement to any tube power amplifier, driving a sources (DAC or Phono), which has a weaker small signal (high output impedance) tube based output stage. With a help of a PRE III, any source becomes unleashed to drive subsequent power amplifiers to its full potential.

Essentially, the design of PRE III valve line pre-amplifier is akin of a power amplifier, which instead of driving high load of a speaker drives line level output. The PRE III line pre-amplifier utilises 6N6P or 5687/E182CC as a driver and a pair of triode connected EL84 is a classic power valves, which were popular in electric guitar amps and most radios in the 50s and 60s and are known for their articulate character. Altogether, the combination of powerful driver and output tubes & Signal Output Transformer (OPT) results in tonal purity, incredible transparency & the dynamic driving ability, which in turn provides an added dynamic expressiveness as the ability to dig deep into musical presentation. In combination with finest materials & component, the sound of the PRE III is transparent, characterised by scale, authority and dynamic bite.

Available with a supercharged LPU Phono stage denoted as PRE III LPX and can be ordered with our range of signal OPTs: M6 EI core (STD version), all Copper wound Double C-core Super HiB Signal OPT (Special version) or with partial Silver wound Ultra HiB (Classic version) or as all Silver wound Ultra HiB, limited production Signature version.

SW1X Audio Design™ PRE III Line Pre-amplifier Features:

  • Specially Selected and Harmonically matched Component & Material Quality
  • Anode follower, zero NFB, Signal Output Transformer (OPT) de-coupled Valve Output Stage
  • SW1X Audio Design™ Double C-core Super (Cu/CU or Cu/Ag windings) or Ag/Ag wound Ultra HiB Signal OPT transformers
  • 1 x Double triode 6N6P or 5687 driver, 2 x EL84 Triode Connected Power Pentode Valve Amplificaton Design
  • 2 x SW1X Audio Design™ Mono, 24 Way, discrete resistor Stepped Attenuators made from the Finest Materials and Specially Selected Resistors
  • Hybrid Point 2 Point Hardwiring Technique for the most consistent production results
  • 5Y3/5U4GYB/5R4GYB Directly heated Tube rectified CLC2LC (choke filtered) B+ power supply
  • For maximum transparency & dynamics, the circuit is hard wired with of a specially selected conductors (single strand or Litz)
  • Internally wired exclusively with our SW1X Magnum, Genesis and Opus conductors


Tube Compliment:  2 x EL84, 1 x 6N6P or 5687, 1 x 5U4



PRE III is avaiable in 4 Versions with following output transformer (OPTs) specifications:

  • Standard : SW1X Audio Design all Copper wound, orient grain M6 EI Core OPTs
  • Special :  SW1X Audio Designall Copper wound Super HiB DC Core OPTs
  • Classic : SW1X Audio DesignCopper/Silver Windings, Super HiB DC Core OPTs
  • Signature : SW1X Audio Design™ Silver/Silver Windings, Super HiB DC Core OPTs


SW1X Audio Transformers




Optional Extras:

  • Fully Hardwired Tube Output Stage on the Bakelite Board
  • Fine Silver wiring on the Input, Bakelite Board and Output
  • SW1X Audio Design™ Custom Designed & Fully or Partly Silver wound Super HiB DC core Signal Output Transformers


Note: Due to SW1X Audio Design’s ongoing research and development process, specifications are subject to change without notice.


SW1X Audio Design products were designed for maximum performance and also to ensure compatibility with majority of audio systems. However, pairing different audio systems may result in impedence or sensitivity mismatch. For maximum musical pleasure, we recommend to pair our products only with our harmonically matched system components. To achieve best possible results, the matching system component should be on equal performance level or alternatively within one level below or above.


Dimensions: Height (mm) 150 x Width (mm) 440 x Depth (mm) 400

Weight (kg): 17 (with LPX Phono, 22kg)

Max Power Consumption (W): 180

Output Noise, Unweighted (mVrms): < 0.5

Output Impedance (Ohms): 4


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