SW1X Audio Design™ PRE IV Performance Level 4

6V6 OPT Line Pre-Amplifier


The PRE IV is a signal output transformer (OPT) de-coupled 6V6 tube output stage based, zero negative feedback (zero NFB global or local), line pre-amplifier design. It is a further development of the PRE III power line stage pre-amplifier. The difference in line stage design to power amps is that our goal is the preservation of the signal integrity while minimizing the output impedance and not really signal amplification and reduction of output impedance. Consequently, PRE IV offers the sound akin of DHT tubes plus has very powerful output to drive any power amp, with output impedance below 10 Ohms.

The sound is mature, large & holographic with scale, authority and a lot dynamic bite but above everything very transparent comparable to a great passive volume control. It is a great enhancement to any tube power amplifier, driving a sources (DAC or Phono), which has a weaker small signal, indirectly heated tube based output stage.

Available in either double C-core Super HiB transformer version or Pemalloy core version (Special version) and the limited production Signature version on request.

SW1X Audio Design™ PRE IV Line Pre-Amplifier Features:

  • Specially selected and harmonically matched component & material quality Performance level 4/5
  • Copper wound Super HiB DC-core Signal Output Transformers (OPT silver wiring is optional)
  • Zero NFB, 2 x 6J5 driver tubes and 2 x 6V6 Power Output Valve Output Stage
  • 5Z3/5U4G/274B or 80 Directly Heated double diode tube rectified C2xLC (choke filtered) power supply
  • Vintage, out of production AB 2W & 1W resistors
  • Dual Mono Stepped attenuators with AB carbon resistors and AN 2W Niobium or non magnetic Copper Tantalum at input
  • XLR Balanced and RCA Single Ended outputs
  • Matte silver or black aluminium top (pure copper top is optional)


Tube Compliment:  2 x 6J5, 2 x 6V6 , 1 x 5Z3/5U4



Optional Extras:

  • Fully Hardwired Tube Output Stage on the Bakelite Board
  • Fine Silver wiring on the Input, Bakelite Board and Output
  • SHiB double DC-Core mains transformers and chokes


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


Dimensions: Height (mm) 250 x Width (mm) 440 x Depth (mm) 400

Weight (kg): 23

Max Power Consumption (W): 80

Output Noise, Unweighted (mVrms): < 0.5

Output Impedance (Ohms): <10

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