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TUBE-TECH PA 6
STEREO HEADPHONE AMPLIFIER
General information
Sound quality in headphone monitoring has usually been the end of the line as far as studio
engineering is concerned. This is primarily due to the fact that amplification for this type of
monitoring is nearly always done with amplifiers that have been exclusively designed for
powering loudspeakers.
The
TUBE-TECH PA 6
providing the listener with maximum fidelity.
PRECAUTIONS:
THIS AMPLIFIER CAN PRODUCE VERY HIGH SOUND LEVELS.
CARE SHOULD BE TAKEN WHEN LISTENING TO HEADPHONES, AS YOUR HEARING
MAY BE DAMAGED WHEN EXPOSED TO HIGH SOUND LEVELS.
Design information
The output stage is designed around a dual power triode working in push-pull class A with a
adjustable bias and balancing circuit.
The input and driver circuit also uses dual triodes making the whole amplifier symmetrical from
the single ended input to the output.
All the voltages (except heater voltage for output and driver tubes) are fully stabilised.
has been designed especially to be used with headphones and
Operating information
Several ways of operation are possible:
The
TUBE-TECH PA 6
the same way as the various loudspeaker systems are used.
The
TUBE-TECH PA 6
Here the
systems.
In either case the objective of using the
quality of sound in the headphones, thereby giving the listener a superior sonic experience.
TUBE-TECH PA 6
is used in the control room for high quality listening on headphones in
is used as the power amplification to drive the cue system in the studio.
replaces the customary power amplifiers used with most studio cue
TUBE-TECH PA 6
LYDKRAFT ApS
Ved Damhussøen 38,DK 2720 Vanløse
Denmark
is to substantially improve the
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ADJUSTMENT PROCEDURE:
INITIAL ADJUSTMENT:
POWER SUPPLY:
The power supply PCB is located on the rear panel.
1. Adjust the voltage for the output stage to 155V with P1.
AMPLIFIER OUTPUT STAGE:
IMPORTANT:
After replacement of output tubes, it is important that the "initial bias adjustment"
is carried out.
If this step is neglected, the output tubes may be permanently damaged, due
to the possibility of high cathode current.
INITIAL BIAS ADJUSTMENT:
1. Turn off Volume.
2. Place a voltmeter between TP3 for the left channel (TP6 for the right
channel) and 0V.
3. Turn on power.
4. Observe that the voltage does not exceed 10 V after a few minutes,
otherwise adjust with the multiturn trimpot marked "BIAS".
BIAS AND BALANCE ADJUSTMENT:
1. 10-15 minutes after power turn on, the current in the output tubes has
stabilized and the bias and balance can be adjusted with a voltmeter.
2. Place the voltmeter between
50mV
(< +/-2mV) with the multiturn trimpot marked
TP1
and
and adjust the voltage to
TP3
BIAS
.
3. Place the voltmeter between
(< +/-1mV) with the multiturn trimpot marked
0V
4. Repeat step 2-4 until correct.
LYDKRAFT ApS
Ved Damhussøen 38,DK 2720 Vanløse
Denmark
TP1
and
and adjust the voltage to
TP2
BALANCE
cont.
.
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5. Place the voltmeter between
50mV
(< +/-2mV) with the multiturn trimpot marked
TP4
and
and adjust the voltage to
TP6
BIAS
.
6. Place the voltmeter between
(< +/-1 mV) with the multiturn trimpot marked
0V
7. Repeat step 5-7 until correct.
The adjustment is more quickly made with 2 voltmeters, one hooked up as
in step 2 (step 5) and the other hooked up as in step 3 (step 6)
With correct adjusted bias and balance, the voltage measured between
and 0V, and
TP3
CHANGE OF OUTPUT IMPEDANCE
1. Remove the bottom cover
2. Beneath the output transformer is the impedance strapping located.
The following scheme shows how the strapping can be altered:
TP6
and
TP4
and 0V, will now be between +13,6V - +16,5V
and adjust the voltage to
TP5
BALANCE
.
120
(factory setting)
30
7,5
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LYDKRAFT ApS
Ved Damhussøen 38,DK 2720 Vanløse
Denmark
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Technical information:
Output power (40Hz 1% THD): 5W (in minimum load)
Minimum output voltage (RL=600): 30V (strap for 120)
Minimum Load (strapable): 120/30/7,5
Frequency response (-3dB): 5Hz - 80KHz
Input impedance: >10K
Input sensitivity: 0 dBU for max output
Noise (22-22kHz): -70 dBU (strap for 120)
Power requirement: 115/230V
Power consumption: 90W
Dimensions (W/H/D): 225x170x250 mm
Weight: 7 kg
Loading of the output can be lower than the recommended minimum impedance, without
damage to the output stage.
(unbalanced)
The output can withstand shortcuts, but a shortening of the life of the output tubes must be
expected if exposed to continuously shortcuts
LYDKRAFT ApS
Ved Damhussøen 38,DK 2720 Vanløse
Denmark
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