A simple quasilogarithmic amplifier detector was developed for the JLH amplifier.
Designed to work with arrow VU meters
Simple and cheap components are applied.
Scheme:
Amplitude characteristics
The circuit has a boost circuit
Appearance of the front and rear together with a VU meter SO-53
Can be used with almost any VU meter and any amplifier.
Designed to work with arrow VU meters
Simple and cheap components are applied.
Scheme:
Amplitude characteristics
The circuit has a boost circuit
Appearance of the front and rear together with a VU meter SO-53
Can be used with almost any VU meter and any amplifier.
I dont see why you are using a log amplifier ... the Arsonval is linear but the scale scale printed on the faceplate is a log scale ....
You should test the meter with a dc power supply and a resistor .....
maximun current for full scale +3 dB
70 % of maximum for 0 dB
50 % of maximum for -3 dB
10 % of maximum for -7 dB
otherwise
Nominal current fo 0 dB
141% of nominal for +3 dB
71 % of nominal for -3dB
50 % of nominal for -6 dB
10 % of nominal for - 10 dB
As far as I know you dont need a log amp to drive the meter .....
You should test the meter with a dc power supply and a resistor .....
maximun current for full scale +3 dB
70 % of maximum for 0 dB
50 % of maximum for -3 dB
10 % of maximum for -7 dB
otherwise
Nominal current fo 0 dB
141% of nominal for +3 dB
71 % of nominal for -3dB
50 % of nominal for -6 dB
10 % of nominal for - 10 dB
As far as I know you dont need a log amp to drive the meter .....
I dont see why you are using a log amplifier ... the Arsonval is linear but the scale scale printed on the faceplate is a log scale ....
You should test the meter with a dc power supply and a resistor .....
maximun current for full scale +3 dB
70 % of maximum for 0 dB
50 % of maximum for -3 dB
10 % of maximum for -7 dB
otherwise
Nominal current fo 0 dB
141% of nominal for +3 dB
71 % of nominal for -3dB
50 % of nominal for -6 dB
10 % of nominal for - 10 dB
As far as I know you dont need a log amp to drive the meter .....
I can understand that. I used the VU meter I had.
The scale of this meter can be easily replaced by a homemade. I made a quasilogarithmic amplifier for another reason.
At a comfortable volume the usual linear VU meter shows almost nothing the Arrow lies at the beginning of the scale and almost does not move.
So I applied dynamic range compression to visualize the performance of the amplifier.
I understand your situation but then all you have is a moving needle ....
With a régular set up ( no log amplifier ) you can know how much power the amp is driving.
If you calibrate for 0 dB - 6.3 volts RMS you have 5 watts in 8 ohm
then
+3 dB - 8.9 volts RMS you have 10 watts in 8 ohm
-3 dB - 4.5 volts RMS you have 2.5 watts in 8 ohm
-7 dB - 2.8 volts RMS you have 1 watts in 8 ohm
-10 dB - 2.0 volts RMS you have 0.5 watts in 8 ohm
-20 dB - 0.63 volts RMS you have 0.05 watts in 8 ohm
With a régular set up ( no log amplifier ) you can know how much power the amp is driving.
If you calibrate for 0 dB - 6.3 volts RMS you have 5 watts in 8 ohm
then
+3 dB - 8.9 volts RMS you have 10 watts in 8 ohm
-3 dB - 4.5 volts RMS you have 2.5 watts in 8 ohm
-7 dB - 2.8 volts RMS you have 1 watts in 8 ohm
-10 dB - 2.0 volts RMS you have 0.5 watts in 8 ohm
-20 dB - 0.63 volts RMS you have 0.05 watts in 8 ohm
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