Fera / RFT (Fernseh-Radio) HiFi 50 Quadro-effekt, 1974, made in Germany

The amplifier 50 HiFi Quadro effect of PGH TV-Radio Berlin is the successor of the famous HiFi 50. He is the first hi-DDR-home amplifier having the connection for two additional speakers to pseudoquadrofonen playback. This process should not be a substitute for real quadraphony, but is intended as an improvement of the stereo reproduction that significantly improve the three-dimensional sound image despite the low technological effort. The electrical and mechanical properties would otherwise remain virtually unchanged compared to the HiFi 50, so the description largely done with the text. ifatwww.et.uni-magdeburg

The amplifier has on the rear side of the tape 5 inputs, phono, tuner, micro and specialty, the latter is mainly intended for the connection of electronic musical instruments that can be selected via a push-button set. The signals of the five inputs, which have a total of 3 different sensitivities are input, coupled to the base of the three-stage input amplifier via various passive RC networks. This is equipped with low noise Miniplast transistors, thermally very stable and due to strong negative feedback relatively insensitive to transistor manufacturing tolerances. An equalizer amplifier for magnetic sensing systems for the phono input is not provided in HiFi Quadro 50 effect.

The preamplifier is in two stages and also equipped with low-noise transistors. It allows dual potentiometer on the control for bass, treble, balance and volume, the latter is affected aurally. A rumble filter and the Mono button is still available, the existing the old model noise filter has been replaced by the contour button, which should provide at low volume for a more brilliant sound.

The power amplifier, a four-stage electrically coupled network is set up discretely, fully equipped with silicon transistors and operates as a quasi-complementary output stage in Darlington circuit. It is powered by unbalanced supply voltage and thus requires Auskoppelelkos. In a speaker protection circuit, and a delay was waived. Only an overdrive protection circuitry has been provided which abtennen briefly about each one relay the speakers at excessive level peaks.

The HiFi 50 provides connections for 2 speakers and a stereo headphone, said the non-switchable socket is located on the rear panel. He also has a red lamp as network control, and red clip indicators for both channels, in addition a green stereo display is now available.

The optical design of the HiFi 50 is simple and technically in a modern, slim case made of wood. The front panel is made of black painted aluminum and is labeled with a white screen printing in German. The round keys are made of black plastic with chrome cap, the knobs are made of chromed plastic.

Another variant has a two-part front with black frame and silver aluminum front panel. The keys are square and made of black plastic, as well as the knobs.

The HiFi 50 Quadro effect was presented at the Leipzig Autumn Fair 1974, the first time the public.

Усилитель был взят за основу для построения Fera V150 в 1982 году. radiomuseum | rft-hifigeraete

собран на:
4 x Tungsram 2n3055 (Hungary) Silicon PNP Power Transistor

Technical specifications: radiomuseum
Country: Germany
Manufacturer / Brand: Fernseh-Radio Berlin (FERA), PGH; (Ostd)
Year: 1974 Type: Audio Amplifier or -mixer
Semiconductors (the count is only for transistors) 24:
Principle Audio-Amplification
Wave bands - without
Power type and voltage Alternating Current supply (AC) / 220 Volt
Loudspeaker - This model requires external speaker(s).
Power out 50 W (undistorted)
from Radiomuseum.org Model: HIFI 50 Quadro-Effekt - Fernseh-Radio Berlin FERA, PGH
Material Wooden case
Shape Book-shelf unit.
Notes: stereo audio amplifier with 2 x 25 watts RMS output power into 4 ohms, 5 inputs, level meter, additional Quadro Effect speaker outputs. The design of the front panel has been changed during the production period several times.
Operating voltage: 220V, 50Hz

Power consumption at rated power: 155 W
Sine Output Power: 2 x 25 W with k = 0.5%
THD at f = 1000 Hz; 25 W: 0.5%
Frequency response: 20 - 20000 Hz
Signal to noise ratio at 25 W:> 50 dB
Crosstalk at 1 kHz> 40 dB
Input voltage range: 0.05 ... 2 V
Setting "Bass" at f = 40 Hz: +/- 15 dB
Setting "Treble" at f = 16 kHz +/- 15 dB
Setting "Balance": +8 dB / -13 dB
Dimensions W x H x D: 430 x 100 x 250 mm
Weight: 6.8 kg
Price: 980, - M

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