FM ACOUSTICS FM245
1,650,000 (Released October 2002)
¥ 1,780,000 (around 2005)
¥ 2,047,500 (around 2006)
¥ 2,600,000 (around 2007)
Commentary
A preamplifier with an original circuit design.
The enhanced Class A circuit developed by FM Acoustics provides excellent stability and high-purity signal processing. This circuit does not use any overall feedback / feed-forward.
With a specially designed bias circuit, it reaches operating temperature very quickly, eliminating the need for long warm-ups and avoiding changes in strain characteristics before and after warm-ups.
Four unbalanced high-level stereo inputs, each with a high input headroom of + 21 dBv and linear input impedance over the entire frequency band.
Input 1/2 can be attenuated to -6dB or -10dB by setting the internal DIP switch.
It is equipped with a buffered type high-precision unbalanced tape monitor loop.
Fully balanced output by pure symmetrical output circuit is mounted.
Even with unbalanced connections, the output impedance and output level are the same as those of balanced connections. The output circuit can be driven with excellent reproducibility and stability under any load, including a high capacity load equivalent to a 1000m cable.
The output is fully short-circuit protected.
The phase inversion switch on the front panel accurately inverts the phase of the main output by 180 ° without using any additional circuitry and the signal does not enter the 180 ° phase inversion stage.
No wiring material for signal transmission is used inside the body to eliminate variations in performance due to differences in wire routing.
Low noise characteristics and low distortion factor are realized in the power supply section by high efficiency toroidal transformer with reinforced shield and low impedance high precision power supply circuit.
The chassis has a mechanically damped design that protects the electronic components from inductive resonance.
Chassis side panels, covers, bottom and transformer mounting are supported by special suspensions.
The continuously variable output level control and the high-resolution spread balance control are isolated by a unique enhanced Class A buffer circuit to minimize variations in characteristics when changing the volume or balance.
A delay type switch-on function is adopted. When the switch is turned on, the signal on the output is shown in a flow chart. Self-diagnosis is performed, and after each part is completed, the control circuit starts the output. It takes approximately 10 seconds to complete the operation.
Equipped with a protective circuit against voltage drop and overvoltage.
The FM245 also has an independent sensor that protects the FM245 and connected devices from overvoltages of 140%, transient failures and excessive voltage drops that can cause DC instability.
Model Rating
| Type | Stereo preamplifier |
| Circuit | Input imbalance and output balance Unique discrete enhanced class A circuit using ultrahigh-speed hand-select semiconductors Circuits are individually analyzed and selected, and carefully selected through listening tests. The whole unit consists of an enhanced class A module by hand calibration made by FM Accor Stix. |
| Input | Four stereo and unbalanced systems |
| Tape loop | One stereo input / output system |
| Input impedance | 50k Ω (linear for the whole regeneration band) |
| Input headroom | +21dBv(9VRMS) |
| Input sensitivity | 100 mV per 100 mV tape output |
| Maximum gain | 0 dB at tape output for all inputs 20 dB at main output for all inputs |
| Frequency characteristic | 20 Hz to 20 kHz ± 0.03 dB |
| Playback bandwidth | 1 Hz ~ 2 MHz (without RF filter) 1 Hz ~ 100 kHz (When Using Built-in RF Filter) * The actual frequency characteristics of the preamplifier is intentionally attenuated to 100 kHz or higher by the linear phase anti-RF circuit. It can be bypassed depending on the purpose. |
| Phase accuracy | -0 ゜ / + 1 ゜ (without RF filter, 20 Hz to 20 kHz) |
| Rise time | 300 nanoseconds = 0.3 μ sec (electronics capability, measured without RF filter) |
| Fall time | 300 nanoseconds = 0.3 μ sec (electronics capability, measured without RF filter) |
| Hum and noise | 0 dBv or Less = -95dBV or Less, -120dB or More (20 Hz to 20 kHz Full Output) |
| Output | Balance Stereo 1 System (3rd Hot) |
| Maximum output level | + 28 dBV (19.5 Vrms vs. 4.7k Ω load) |
| Recommended load impedance | 600 Ω or more |
| Stereo separation | 85 dB or more |
| Channel separation | 95 dB or more |
| Harmonic distortion factor | 0.003% or More (3 v Output, Full Regeneration Band) |
| Front panel | Hand polish after brushing 4 mm laser cut aluminum 9000. No wear as the lettering has been oxidized and anodized. High-precision output level, balance control is hand select, dust-proof treatment. Switches are high-performance self-cleaning and long-life specifications. Power switch and power-on indicator. |
| Rear panel | Hand polished aluminum 9000. No wear as the lettering has been oxidized and anodized. High-precision RCA and XLR connectors for input and output terminals, electrical ground is lifted from the chassis to avoid ground loops, and star ground may be used depending on the connected equipment |
| Operating temperature | -20 ° C to + 40 ° C |
| Operating humidity | Long-term : 0 to 85% Short-term : 0 to 95% Long periods of high humidity shorten the life of some parts |
| Shipping burn-in time | Temperature test 1000 cycles (minimum 200 hours) |
| Vibration test at time of shipment | Vibration test 50,000 cycles (minimum 60 minutes) |
| Power supply voltage | 115 V (95 V ~ 135 V), 50Hz/60Hz |
| Power consumption | Continuous 15W |
| External dimensions | Width 446x Height 62x Depth 280 mm |
| Weight | 6kg |