Vintronics Classic 25 User Manual

VINTRONICS

TM

CLASSIC 25 POWER AMPLIFIER

The Classic 25 Power Amplifier has been designed and Hand-Built in the UK.
It combines the sound proven electronic circuitry together with fine build quality and
components.
The Amplifier is constructed from the finest brushed stainless steel chassis, which
has been laser cut for precision finish. This is complemented by teak wooden side
panels varnished in a satin finish. The front and rear panels are hand engraved 1mm
thick Perspex panels finished in a dark blue ink. Brushed aluminium control knobs
compliment the finish. No question, this amplifier is of the highest design and build
standard. Heavy rubber feet act as sound absorbers to protect against microphony of
the valves. Local companies have been used to provide the parts for this amplifier.

The power amplifier is based around two pairs of EL34 (6CA7) tetrode output valves
operating in a pure Class-A push-pull output configuration.
The output transformers have been specially designed and wound to our
specifications. They have been de-rated so as to avoid core saturation at Low
frequencies. Hence this provides full frequency response right down to 20 Hertz.
Similarly, the power supply transformer has been de-rated to stop voltage sags at
peak current demands from the output amplifier stage.
This then combines to make a rugged amplifier virtually flat across the whole audio
frequency spectrum, even under complex load conditions.

The input stage has a high frequency roll-off at 30KHz so as to limit the wasted
energy in the following stages.
The input amplifier stage adopts the Double Triode ECC83 high gain valve in a
Totem pole configuration. This enables a high input impedance together with fine
linearity in frequency response. The output of this stage then feeds into a Phase
inverter stage, another ECC83 valve being used for this. Its output then feeds into the
output driver stage with an ECC82 valve being used for the purpose.
Signals from this stage are then fed into the EL34 push-pull output stage. Full power
supply voltage is applied to these valves to maximise output power.
Conversion of the high voltage signal is then done in the output transformers. They
convert the high impedance high voltage into low impedance high current drive to the
loudspeakers.
The input, phase splitter and driver valves are separately heated from the output
valves which dramatically improves the stability and noise performance.

Best quality components have been used in this amplifier.
We have utilised high tolerance quality wirewound and carbon resistors, polyester
and silver mica signal capacitors, porcelain valve bases and matched output valves.

SPECIFICATIONS

Power Output 25 Watts RMS per channel

THD at 1KHz 0.05% at 5 Watts

0.45% at 22 Watts
THD at 100Hz 0.22% at 5 Watts

0.57% at 22 Watts
Noise Better than -66dB

Crosstalk Better than -80dB

------------------------------------------------------------------------------------------------------­Frequency Response 25 Hz to 25 KHz (-0.9dB/-0.8dB)

Power consumption 180 Watts

Loudspeaker Loads 4 Ohm, 8 Ohm

Valves 2 x ECC82

3 x ECC83
4 x EL34 (6CA7)

Input Sensitivity 0.7V RMS

Connections Inputs 4 x RCA Phono
Outputs 2 x 4mm Terminal Posts
Power IEC Mains inlet

Weight 10.3 Kilos

Dimensions 420 x 290 x 150 mm High

* TYPICAL VALUES MEASURED WITH LINDOS LA101/2 TEST SET.