DIATONE DA-F550
¥ 35,000 (released in 1973)
¥ 38,000 (around 1974)
Commentary
FM/AM tuner with high sensitivity and high selectivity by refining the circuit structure.
The FM IF stage uses a phase-linear ceramic filter, monolithic IC with excellent limiter effect, and a discri transformer with peak separation of 1 MHz, thereby improving various characteristics such as effective selectivity and distortion factor characteristics.
Equipped with FM / MPX noise filter, noise can be removed when receiving FM stereo.
The FM multi-circuit employs a double-balanced differential circuit using iC, which improves the distortion characteristics compared with conventional circuits using diodes.
The FM / MPX transformer uses a mold type with excellent environmental characteristics of temperature and humidity. This improves the separation which is especially susceptible to temperature and humidity.
A muting circuit with low pop noise is used. In this circuit, the bias condition of the transistor is always constant regardless of whether the muting operation is ON or OFF, so that the pop noise is kept low.
The muting level is 20 dB.
It is equipped with a carrier leak filter. In this circuit, the filter by LC is tuned to 19 khz and 38 khz to suppress carrier leak.
The IF stage of the AM circuit uses a triple tune IFT with three tuning circuits to improve sound quality and selectivity.
On the back panel, a FM DET OUT terminal is mounted so that the FM detection output can be extracted. This terminal is compatible with FM4ch broadcasting.
It is designed as a pair with DA-U550. In addition, the same wood case with DA-U550 was sold as an option separately.
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Model Rating
| Type | FM/AM Tuner |
| FM Tuner Section | |
| Antenna | 300 Ω balanced, 75 Ω unbalanced |
| Practical sensitivity | 1.8 μ V (IHF) |
| Effective selectivity | 60dB(IHF) |
| Capture ratio | 1.5dB(IHF) |
| Image interference ratio | 60dB |
| IF interference ratio | 70dB |
| 1/2 IF interference ratio | 60dB |
| S/N | 70dB |
| AM suppression ratio | 50dB |
| Harmonic distortion factor (100% modulation) | mono:0.2% stereo:0.5% |
| Separation | 40dB(1kHz) 30dB(10kHz) |
| Muting | ON/OFF enabled |
| MPX Noise Filter | ON/OFF enabled |
| <AM Tuner Section> | |
| Antenna | Ferrite bar antenna |
| Practical sensitivity (S/N 30 dB, bar antenna) | 55dB |
| Selectivity | 35 dB (± 10 kHz) |
| Image interference ratio | 40dB |
| S/N | 50dB |
| <General> | |
| Output | Fixed:150mV Variable : 0 to 700 mV |
| Power consumption | 15W |
| External dimensions | Width 380x Height 133x Depth 301 mm |
| Weight | 6.8kg |
| Separately Sold : Wood Case CA-550 (¥ 6,500) for 550 Series | |
| External dimensions | Width 445x Height 165x Depth 297 mm |
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