Lautstärke regeln

Hi ho,

kleine Frage an die Profis:
Wie Regelt man am billigsten die Lautstärke?

Bauteile:
-Class T China-Endstufe. 2x160W (Eingangsspannung bis 50V)
-Netzteil 50V

An nen Stereopoti hab ich schon gedacht aber ich denk der ist für die 
Leistung nicht ideal.

Wie wird das Richtig gemacht? (z.B im Autoradio)


Herstellerangaben :

Class T Digital Amplifier Board Stereo 2x160W HIFI AMP with Fan for 
Audio DIY Better than TDA7498E TK2050 TDA8950 TPA3116

Features:
- Class T amplifier board
- 4 pieces high frequency capacitor filter onboard
- Input adopts 2.2UF/ 63V capacitor
- CBB capacitor
- With heat sink and high speed fan

Actual power test:
- Power supply 50V,load 6Ohm,THD+N is 10%, output voltage is 31.6V, 
output power is P=31.6x31.6/6=166w
- Power supply 50V,load 6Ohm,THD+N is 10%, output voltage is 35.5V, 
output power is P= 35.5x 35.5/6=210w
- Power supply 50V,load 8Ohm,THD+N is 0.86%, output voltage is 31.8V, 
output power is P=31.8x31.8/8=126w
- Power supply 50V,load 8Ohm,THD+N is 10%, output voltage is 37.1V, 
output power is P=37.1x37.1/8=172w

Parameters:
- Power supply voltage: DC 30V-50V(recommended 8Ohm and 6Ohm horn with 
50V power supply; if you want to to be with 4Ohm one, please do not 
exceed 32V.
- Maximum output power: 2X170W
- Efficiency: >=90% (different power, voltage, horn are not the same)
- Signal to noise ratio: 100dB
- Total harmonic distortion per channel: (172W/1KHz/50V/8Ohm -10%) 
(126W/1KHz/50V/8Ohm-1% () () (210W/1KHz/50V/6Ohm-10%) 
(166W/1KHz/50V/6Ohm-1%)
- Frequency range: 20Hz-20KHz.
- Input impedance: 30K
- Speaker: 4-8
- Input signal sensitivity: 0.7VRMS
- Voltage amplification factor: 53 times
- Power amplifier board size:LxWxH=90x60x38mm
- Weight: 120 g