SW1X PRE IV DHT Line Pre-Amplifier

SW1X Audio Design™ PRE IV Performance Level 4 Power DHT Line Pre-Amplifier


The PRE IV is a signal output transformer de-coupled 71A/45/300B tube output stage based, zero negative feedback (global or local), line pre-amplifier design. The DHT tube output stage is similar to the output stage as found in our DAC V. 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. Therefore PRE IV only uses a single 6SN7  double triode instead of 2 x 6SL9/6SN7 tubes to drive the DHT stage. Consequently, PRE IV offers the sound of DHT tubes plus has very powerful output to drive any power amp, with output impedance below 10 Ohms while having only a very modest gain of 3.

The sound is mature, large & holographic (as one would expect from DHT) 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.

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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 C-core signal output transformers (silver wiring is optional)
  • zero feedback, choke loaded 2x 6F6 driver tubes and 2 x 71A or 300B Directly Heated Triodes valve output stage
  • 5Z3/5U4G/274B or 80 Directly Heated double diode tube rectified C2xLC (choke filtered) power supply
  • Inter-stage signal decoupling capacitors are Audio Note Copper Foil in Oil
  • Mundorf/Nichicon copper lead B+ power supply capacitors
  • Vintage, out of production AB 2W & 1W resistors
  • 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)


Optional Extras:

a) Black Gate capacitors in the power supplies

b) HiB double C-Core mains transformers and chokes

c) Fine silver wiring

d) AN 2W silver, non-magnetic, tantalum resistors

e) Fine silver windings on the signal output transformers


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

Tube Compliment:  1 x 6SN7, 2 x 45 or 2 x (71A/45/AD1/300B) , 1 x 5Z3/80


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We do not recommend purchasing a key system component without first auditioning it carefully, which is why we have demonstration rooms and a flexible home loan policy.

However in certain situations it can be difficult for people to get to our showroom and for those instances we can offer our mail order service.


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