SW1X Audio Design® Range of Phono Pre-Amplifiers
It is all about Quality and not Quantity.
All SW1X Phono products are made to order, are available on different Performance/Price Levels and specified according to a variety of versions.
An articulate sounding Phono Pre-Amplifier is one of the key components in the analogue playback
LPU I, LPU II and LPU III family of Phono Pre-Amplifiers share similar tube input stage- a pair of EF86 pentode tubes. Due to the brilliant sound character of the EF86 those tubes were commonly used in many radios and RTR tape recorders in the early 60s. The idea of their circuit design was borrowed from the input stage of early Reel to Reel (RTR) tape recorders, which were used in the mastering studios and radio stations. Maybe that is one of the reasons as why most recording from the 60s are sounding at their best, much better than from the 70s and 80s? In a way, the EF86 input tube design closes the loop and makes all our LPU Phono Amps range a time-less classic.
All our LPU Phonos are 2 gain stage, MM level input designs, share the rich & lush sounding 2 x EF86 pentode tubes for the input and RIAA EQ stage in between two gain stages.
What different is a) the tube output stage topology, b) power supply and c) the components & materials employed across the LPU Phono range.
In the LPU I (entry, performance level 1, small chassis), there is a powerful 1 x 6N6P/5687 double triode as the output tube with indirectly heated 6X5 tube rectification.
In the LPU II (performance level 2) there are 2 x 6S3P/EC86/6CM4 single triodes (one per each channel) in the output stage but on a larger circuit board design, so we can use larger capacitors & resistors and also improved Directly Heated (DHD) tube rectified power supply. The sound is expressive & seductive similar to LPU I, while LPU II sounds larger and has more authority & scale.
Special version of LPU II comes in a larger chassis (DAC III Balanced chassis), same LPU II circuit board, DHD tube rectification and with inductively (choke) loaded tube output stage with 2 x 5687/E182CC/6N6P tubes. Relative to the basic LPU II, the Special version adds even more scale and authority but most importantly more dynamics to the sound.
If one wanted to take a step further, LPU III (level 3) is based on LPU II Special (larger, DAC III Balanced chassis) but uses 2 x EL84 power tubes just like on the DAC III Balanced with inductive loading. Those tubes increase power, grunt and authority & dynamics further. The Balanced version of the LPU III takes it a notch further by employing signal output transformers and one gets maximum dynamics and transparency over any LPU III/ II & LPU I. The LPU III and LPX (PRE III without the volume control and input selector) are the best possible noval tube phono pre-amplifier money can buy, especially if implemented as Special, Classic or Signature with silver wound OPTs, Bakelite board & hardwiring.
In addition to Signal Output Transfomer (OPT) de-coupled Balanced design as employed in the LPU III and PRE III LPX, the circuit design of the LPU IV and LPU V Phono is basen upon larger octal base valves. Instead of 2 gain stages of the LPU I, II and III, LPU IV and LPU V Phono are a 3 gain stage designs. The input stages of the LPU IV and V employ the 6SJ7- the octal version of the superb sounding EF86. The interstage/driver is based on the musical and well known 6SN7 double triode. The output stage of LPU IV is based on the 6F6 (predecessor to 6V6 as in DAC IV and PRE IV) power valves. The LPU V empoys 45 DHTs instead of the 6F6 at the ouput. This makes both the LPU IV and LPU V larger & bolder sounding Phonos relative to the already vivid and bold sounding LPU III. Just like with all our Balanced versions, highest Quality Signal OPTs further improve transparency & dynamics. The Special, Classic and Signture versions take this design to the limit with more chokes, higher grade transformers and even more matched and higher specified components & materials.
While all our LPU Line of Phono Pre-Amplifiers have Musicality in their DNA, the higher performance level Phonos add more Holography, Expression and Power to the Presentation.