While checking the output voltages, I got the following values:
5V range: 2.86 Vrms (4.04 Vp)
1.5 V range: 0.97 Vrms (1.37 Vp)
0.5 V range: 0.30 Vrms (424 mVp)
0.15 V range: 93 mVrms (131 mVp)
Bob Cordell probably meant with 5V range a 5Vrms range, meaning 7.1 Vp (14.2 Vpp). I couldn't understand why the voltage levels in this range before and after R38 (620 Ohms) changed from 13 Vpp to 8.4 Vpp. Turns out that, since I measure this output-voltage on PCB4 with a full-bridge rectifier with an input-impedance of 1 K (R10 on PCB4), the output-voltage is 0.6 times the E11 voltage. If I remove the flatcable to PCB4, I get the 13 Vpp value again, which proves my observation.
Bob probably didn't mean this, since he doesn't measure the output-voltage of the signal-generator, as far as I can see.
So what do we want here? I might be inclined to use the output-levels as a peak voltage, so 5V range means that the maximum peak-voltage is 5 V (10 Vpp, 3.54 Vrms). This seems more than enough for testing power-amplifiers (my opinion). Or do we need more and should we stick to Bob's original design? In that case we have to increase the input-impedance of the FWB rectifier on PCB4 (e.g. change R10, R11 and R14 all from 1K to 10K).
ADC1 voltage: IC5 on PCB4 amplifies too much and gets stuck to the rail-voltage (13 V for this opamp, no rail-to-rail). So a max output voltage of 5 V (peak) should be within this range. If we lower R12 from 150K to 68K, the max. voltage at IC5 output (pin 6) is now 10.7 V. Ideally, with R192 set half-way, the ADC1 voltage should then be 4.5 V, so it is always lower than the max. allowed voltage (5V). If R8 is increased from 2k7 to 4k7, the ADC1 voltage is now adjustable between 3.4 V and 5.3 V. The software should now use a full-scale value of 4.5 V instead of 5.0 V now. If we go for Bob's original design the max. output voltage is 5 Vrms and R12 should be lowered to 47K.
While checking the output voltages, I got the following values: 5V range: 2.86 Vrms (4.04 Vp) 1.5 V range: 0.97 Vrms (1.37 Vp) 0.5 V range: 0.30 Vrms (424 mVp) 0.15 V range: 93 mVrms (131 mVp)
Bob Cordell probably meant with 5V range a 5Vrms range, meaning 7.1 Vp (14.2 Vpp). I couldn't understand why the voltage levels in this range before and after R38 (620 Ohms) changed from 13 Vpp to 8.4 Vpp. Turns out that, since I measure this output-voltage on PCB4 with a full-bridge rectifier with an input-impedance of 1 K (R10 on PCB4), the output-voltage is 0.6 times the E11 voltage. If I remove the flatcable to PCB4, I get the 13 Vpp value again, which proves my observation.
Bob probably didn't mean this, since he doesn't measure the output-voltage of the signal-generator, as far as I can see.
So what do we want here? I might be inclined to use the output-levels as a peak voltage, so 5V range means that the maximum peak-voltage is 5 V (10 Vpp, 3.54 Vrms). This seems more than enough for testing power-amplifiers (my opinion). Or do we need more and should we stick to Bob's original design? In that case we have to increase the input-impedance of the FWB rectifier on PCB4 (e.g. change R10, R11 and R14 all from 1K to 10K).
ADC1 voltage: IC5 on PCB4 amplifies too much and gets stuck to the rail-voltage (13 V for this opamp, no rail-to-rail). So a max output voltage of 5 V (peak) should be within this range. If we lower R12 from 150K to 68K, the max. voltage at IC5 output (pin 6) is now 10.7 V. Ideally, with R192 set half-way, the ADC1 voltage should then be 4.5 V, so it is always lower than the max. allowed voltage (5V). If R8 is increased from 2k7 to 4k7, the ADC1 voltage is now adjustable between 3.4 V and 5.3 V. The software should now use a full-scale value of 4.5 V instead of 5.0 V now. If we go for Bob's original design the max. output voltage is 5 Vrms and R12 should be lowered to 47K.