Wow that is bold to list this as being built with used caps...

The ARC LS22 uses eight tubes compared to the four in the PA-03 so not an exact clone:

More detailed specs from Alibaba (note the mention of this pre-amp using second hand caps 😱) : Leaf Audio PA-03 MKII Tube Preamplifier with VU Meter 6N11 Standard Balanced Version Refer To ARC LS22

Product Description Description: Standard Balanced Version features transformers for input and output, with a set of balance interfaces for input and output separately. It uses 4 pieces of thin film alloy + oxygen-free copper wire winding, the package is shielded by copper foil for 3 layers, the frequency response is flat. The measured frequency response is 20Hz -22KHz ±0.1DB (better than most audio transformers). The sound through the audio transformer is detailed and clear, dynamic and wide, and very friendly to ears. Referring to the circuit for American Audio research LS22, it adopts a balanced dual mono design. The sound of this preamp is smooth and durable, high frequency extension is good, middle and low frequency mellow, deep dive, it gives people the feeling that it is very quiet and suitable for listening for a long time at a moderate speed. The even harmonics of -60dB make the sound more rounded and durable! Sound Characteristics: Use thin-film alloy transformer for conversion, the dynamics are better than the single-ended version, and the voice is sweet Functional Features: 1. Optional power supply upgrade kit (refer to German power black box for OCTAVE tube amplifier) 2. RCA ports are changed to rhodium-plated RCA 3. Potentiometer for ALPS27, with good sound quality and better reliability 4. Increase the partition between the circuit board and the transformer to prevent interference 5. The specially designed relay input selection circuit will not cause the sound of other groups to crosstalk the current channel (this problem will occur in many machines) 6. Output delay design to prevent the DC output impact of power amplifiers and speakers 7. Two groups of high voltage adopt op amp servo + FET for voltage stabilization, low temperature wave, high speed, quieter background, better sound quality reproduction 8. The hand swing can turn off (only the hand swing can be turn off, not the light) 9.Filament power supply AC and DC switching (note: filament AC power supply is temporarily cancelled, please contact us if you need filament AC power supply) 10. Equipped with treble and bass adjustment function, which can also be turn off (relay switch). The tone circuit has no common bass mixing and treble harshness 11. The electrolysis of the power supply part and the red for WIMA are consistent with the parameters of the original machine, and the sound is neutral and balanced 12. Transformer: Japan Z11 EI86 iron core 90W 13. Chassis: All aluminum standard size: 430*330*100mm, with VU meters, weight 10KG, upper cover without screw, large R angle at the edge, perfect CNC technology, there is no better case than ours at the same price 14. Standard electron tube: Chinese 6N11 electron tube x 4 can be replaced by E88CC, 6922 and 6DJ8 15. Output: Balanced version boasts 2 groups of RCA+1 group of XLR balanced output at the same time 16. Input: Balanced version with 1 set of XLR + 3 sets of RCA More Details: - With transformers for input and output - With a set of balance interfaces for input and output separately - Four thin-film alloy input voltage transformers and output voltage transformers, with flat frequency response, low distortion and good dynamics - Input Interfaces: three groups of RCA and one group of XLR balance - Output Interfaces: Two groups of RCA, one group of XLR balanced output at the same time - Each machine is shipped after passing software test, and the tubes are installed in the best position. Please not change the tubes casually, otherwise it will affect the sound Parameters: - Signal-to-noise ratio: filament DC power supply 100dB (when the output is 2V, the volume is about 2 o'clock position) - Magnification: 6.5 times - Frequency range: 10HZ-100K (±0.5dB) - Bass adjustment range: 50HZ±6.5dB - Treble adjustment range: 15KHZ±6.5db - Input impedance: 100KΩ - Output impedance: 200Ω - Maximum output undistorted voltage: 25V RMS - Distortion: 0.2% (when VU meters are closed, no negative feedback) Package Included: - 1 x Tube Preamplifier Note: - It is assembled. - The position of each tube is specific (tested with the instrument in the best condition), please not insert it randomly, otherwise it will affect the effect. - Full balance requires 2 machines. - Components for WIMA and coupling capacitors are second-hand. Please make sure that you don't mind before purchasing. - Filament AC power supply is an optional function (cancelled by default). If you need to retain the AC power supply, please contact us, but noise level is not guaranteed. - Only the machine is included, accessories are not included in the package.

There seems to be at least three versions available:

The "Normal Version" with Mundorf caps:

The "Upgrade Version" has a remote control and uses a stepped attenuator volume control in place of a potentiometer. Not sure if this relates to the additional circuit board:

Close up of that circuit board: