268C: 58,000 yuan, including a complete audio part, linearized EQ, ARC acoustic environment processor.
268: 52,000 yuan, including the complete audio part and linearized EQ.

Package express, send massive non-destructive resources. Ledi directly engraved Swiss FM268, 268C preamp; including a complete audio part, linearized EQ, ARC acoustic environment processor (268 not included), standard remote control, completely cracked the original machine module, double shielding consistent with the original machine Transformer, 4700uf Mondofore fever capacitor is used. Strictly follow the original machine testing and production links. Components are strictly aging, tested, and paired; each group of modules is paired before installation, and all working points refer to the original machine; before leaving the factory, it will be burned for 100 hours; each unit is independently numbered, and the module parameters are archived for future maintenance. The sound field is wide, the details are rich, the sound is loose and natural, and full of charm. 6 groups of balanced input, 1 group of balanced output, 1 group of recording input and output, 1 phono amplifier power supply output. Adjustable left and right channel balance and phase reversal.

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Note: Because the pre-stage gain is high, you must wait until the warm-up is completed and the indicator light is always on before adjusting the volume.
On the front panel of 268C, the indicator light of the preheating stage will be flashing after starting up, and it will be on after the preheating is completed.
Power switch, power indicator, volume knob (remote control), left and right channel balance potentiometer
6 groups of input switch buttons, 4 function buttons (recording monitoring, monaural monitoring, phase inversion, attenuation 20dB), linear EQ knob
268C backplane: 6 groups of balanced inputs, 1 group of balanced outputs, 1 group of recording input and output, 1 phono amplifier power output; ARC acoustic environment processor (not included in 268)
268C internal structure: the upper green PCB is a linearized EQ circuit, and the core pre-amplification circuit is in the lower layer (see 266 pre-stage)
The same double shielded transformer as the original machine, and Mondolfo 4700uf capacitor
Professional test equipment: AP SYS-22, Kikusui signal generator, 3012b Tektronix oscilloscope

Product introduction:
     After in-depth understanding of the FM268 pre-amplifier circuit, Ledi made a 1:1 replica. The input amplifying circuit uses the latest hr input module to achieve high impedance input and low impedance output, with a variety of different signal sources. The input module THD+N is as high as 100dB or more, and it has excellent anti-interference ability. hr is high-precision adjustment, including the output amplifier module is all precision adjustments to correct the hot and cold end waveforms and output swing consistency.
       FM268 has a linearized EQ function, which can adjust the important frequency range of music. The frequency band is not arbitrarily determined like general equipment, but is set to a frequency at which human hearing has been proven to include the basic elements of music reproduction. Set the linearization circuit control frequency band at 50HZ, 200HZ, 800HZ, 3.3KHZ, and 12.8KHZ into five frequency bands. For this module, we use bridges for precision pairing and AP for frequency adjustment, so that the real indicators are consistent with the original factory. EQ adjustment is plus or minus 6dB and 12dB. This linear EQ is different from ordinary EQ. The linearization circuit is not a filter but is placed in parallel instead of series in the signal path to control the amplitude characteristics of each frequency band. Without phase interference, high-performance frequency control can be performed for the first time in the analog domain without affecting the quality of the signal system. The music can be restored and optimized according to the entire system, software, and environment.

Parallel linearized EQ
     The filter capacitor adopts 4700uf Mondofore fever capacitor, and the decoupling and coupling use are the same as the original Nikon PW and ELECTEL film capacitors. The transformer uses the same transformer as the original manufacturer, which is a double-shielded transformer.
     Unique ARC（Ambient Acoustic Processor）The circuit improves listening pleasure and realism by eliminating or reducing room standing wave patterns and other resonances. For each machine, we will refer to the original factory test diagram, compare the re-engraving machine test and send it to the customer. Ensure the reliability of equipment reproduction.
     The bandwidth of the input module is as high as 1M. The transistors used in the input and output modules have all undergone precision aging and matching tests. The amplifier module ensures that the positive and negative output swings are consistent with the square wave, that is, the accuracy of the amplification is adjusted. This adjustment is also a relatively difficult adjustment for the amplification module. It requires the same positive and negative square wave and the same output swing. It is a relatively difficult core technology to adjust. The positioning level transparency in the playback will be very large.
      “FM268”Can reduce（Or eliminate）The unpleasant sound of CD, LP and tape, etc., and can also emphasize the weak part of the music signal. All of this is done in the analog domain, completely retaining the characteristics and transparency of the original signal. Linearizer improvements range from subtle nuances to incredible areas.
     have a look“FM268”The linearization controller on the front panel looks like an equalizer, but“FM268”The working principle of the line level linearizer is completely different from that of the equalizer. Equipped with all-aluminum alloy remote control, you can switch volume, mute, and linearize EQ.
       The company will send a video to the orderer to ensure that the test indicators reach the original factory value.
 

268 original machine EQ and Ledi 268EQ measured curve comparison (the black and white picture is the original machine, the color AP picture is the Ledi)
The THD+N is only 0.00232% when the 3V output of the Ledi 268 front stage is measured
Ledi 268 pre-stage measured signal-to-noise ratio 107dB

Measured frequency response curve of Ledi 268 pre-stage

Technical parameters:
Gain: 20dB 
Maximum input level: 7.75 V 
Maximum output level: 18.5 V
Input impedance: 100kΩ
Output impedance: 20ΩOr lower
THD+N: 0.003% or more
Signal to noise ratio: 95dB or above
Input terminal: balanced（XLR）x 6
Output terminal: balanced（XLR）x 1
Recording input and output terminals: balanced（XLR）
Power supply: 230V, 115V AC, 50 / 60Hz