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Qualiton APR 204 Stereo Röhren-Vorverstärker

The launching of the vacuum tube stereo power amp Qualiton APX 200 entailed the demand for developing a thoroughly classic vacuum tube preamp. The vacuum tube preamp Qualiton APR 204 is meant to meet this demand by not wanting to seem to be more than it is: it is in fact one indispensable element of the sound chain which was developed based on clear guiding principles and is able to evoke the classics of tube electronics.

At the same time, three audio sources with line level output signals as well as one signal source with MM phono output signal level can be connected to the RCA connectors at the rear panel. With the help of the audio source selector switch at the front panel, the user can determine, out of these four audio sources, which one of the relay-switched, volume-controlled signal should reach the output RCA connectors.

If the input selector unit is in ‘P’, i.e. PHONO position, the signal to be processed gets on the grid of the first voltage-amplifying vacuum tube through RCA connectors marked PHONO - thus, through the shortest possible signal paths. From here, in the before-mentioned classic way, the signal component gets on the grid of the second voltage-amplifying stage through a passive correction network between stages according to RIAA standard, realised exclusively with passive elements. We use both in the first and in the second voltage-amplifying stage double triodes ECC83/12AX7. Through an appropriate tuning circuit and volume control potentiometer, the output of the PHONO stage is connected to LINE stage, consisting of double triodes E88CC/6922.


Nominal output level - Line                        2 V

Input sensitivity - Line                                 500 mV, to nominal output level

Input sensitivity - Phono                             5 mV, to nominal output level

Number of input ports                                3 unbalanced input per channel,

                                                                        1 MM-level input per channel

Number of output ports                             1 unbalanced line level output per channel,

                                                                        1 headphone output per channel

Max. input signal - Line                               7 V

Max. input signal - Phono                           200 mV

Gain - Line                                                     +12 dB

Gain - Phono                                                 +52 dB, (f = 1 kHz)

Total harmonic distortion - Line                 < 0.05%, (f = 1 kHz, input level: 500 mV)

Total harmonic distortion - Phono             < 0.5%, (f = 1 kHz, input level: 5 mV)

Frequency response - Line                          4 Hz - 300 kHz, (-1 dB)

Frequency response - Phono                     20 Hz - 20 kHz, (-0.3 dB)

Input impedance - Line                               100 kOhm

Input impedance - Phono                           47 kOhm

Signal-to-noise ratio - Line                          > 100 dB

Signal-to-noise ratio - Phono                      > 70 dB

Tubes required                                               4 x ECC83/12AX7; 2 x E88CC/6922

Weight                                                            8.4 kg

Dimensions                                                    43 x 10 x 32 cm