Vermes
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It is a construction of AmpliSilence Dual Mono 40W/8ohm RMS amplifier.
Assumptions:
- simple and modern look
- DualMono construction
- analog indicators
- input signal attenuation control
- power switch on the front
- RCA input
- supply of two columns in each channel
- output for active subwoofer
Parameters:
- rated power: 40W/8ohm – 60W/4ohm RMS
- input impedance: 75kohm
- sensitivity: 0,775V
- frequency: 3Hz-135kHz (1dB)
- power frequency: 10Hz-20kHz (0,5dB)
- signal/noise > 110dB
- crosstalk between channels > 110dB
- nonlinear distortion (THD): 0,005%
- distortion (TIM): 0,003%
- slew rate > 100V
- dimensions (WxHxD): 435x160x280mm
- weight: 4,1kg
How it was made:
Chassis was made of double-sided copper laminate (2mm thick). Plates of laminate are linked together by point soldering on both sides. In addition, chassis was stiffened with four aluminum profiles, which were screwed to its sides. Front and rear walls were placed in 2mm milled groove. Chassis was painted with the car wheel spray. This chassis is lightweight, well-shielding and paramagnetic.
Power supply:
Power supply consists of two independent toroidal audio transformers, 120VA each, 2x24V with 9V winding (for the system of delayed turn on, supply of LEDs and VU system). Filtering 2x10000uF/63V per channel.
System of delayed turn on the columns:
It was inspired by system designed on www.amplifiers.com.pl. When constant voltage appears at the output, system immediately turns off the speakers and does not turn them on until there is no DC. System also turns off the speakers when fully drive and power of the amplifier while fed f<15Hz at the input. Delay can be adjusted from 2 to 8 seconds.
System of signal level measurement at the input and power measurement at the output:
Power/drive indicators operate with a small VU switch under the knob on the faceplate.
Power measurement at the output is implemented by a simple system based on two germanium diodes operating in system of duplicating the voltage. Scaling for 1000Hz/40W/8ohm. Measurement of reference input signal level is performed using LM358 and scaled to 0,775V/1kHz RMS (0dB).
Implementation:
The whole is built as two mono blocks in a common housing prepared so that each channel was mounted in a separate shielding place, on both sides of the chassis. Signal or magnetic, only RCA sockets and potentiometer ALPS RK27, 2x47kA are common. That potentiometer is on VU board, mounted in a special way, so that length of link between the RCA and „input” leg of ALPS is as short as possible (10mm). Output of the potentiometer is connected with the input of the power amplifier by a microphone cable of a small capacitance (56pF/m) and 13cm long.
RCA socket ground is the only point galvanically connected to the chassis. Other systems are galvanically separated from the chassis.
Output to the Sub consists of sum of L and R output signals given by resistors 220k bypassed to the ground.
Supply cables R and 0 from the power socket to mains switch are special 2,5mm2 shielded cables.
Backlight of indicators and gaps in faceplate is implemented using short LED strips.
Housing is made of black acryllic plexiglass (3mm). It was made in AutoCad.
1kHz sine, 0,775mV, 40W/8ohm
10kHz rectangle, full power/8ohm
1kHz rectangle, full power/8ohm
100kHz rectangle, full power/8ohm
And other pictures:
Link to original thread - Wzmacniacz AmpliSilence Dual Mono 40W/8ohm RMS