If the incoming signal is between 100Hz - 20 kHz, and based on the illustration above, the gain control results obtained are as follows:
- Middle Potentio Position: AV = Rt/R.in =(R1+1/2 P)/R1 =(5+25)/5 = 6x reduction
- Right Potentiometer Position: AV = Rt/R.in =(R1+P)/R1 =(50+5)/5 = 11x reduction
- Left Potentiometer Position: AV = Rt/R.in =R1/R1 =5/5 = 1x reduction
Pre Amp Mixer
Pre Amp Performance Analysis
Low Noise Tone Control Circuit
1. Measuring the Output of IC NE 4558 (Tone Control)
| Test | BASS | TREBLE | VOLUME | POSISI | VO (Vp-p) |
|------|------|--------|--------|--------|-----------|
| 1 | v | v | Max | Max | 1.8 |
| 2 | v | v | Max | Min | 2 |
| 3 | v | v | Max | Mid | 1.9 |
| 4 | v | - | Max | Max | 2 |
| 5 | - | v | Max | Min | 1.8 |2. Measuring Amplifier Voltage Gain
| Test | Frekuensi (Hz) | Vo (Vp-p) | Test | Frekuensi (Hz) | VO (Vp-p) |
|------|----------------|-----------|------|----------------|-----------|
| 1 | 50 | 13.6 | 17 | 50k | 11.6 |
| 2 | 100 | 12.8 | 18 | 60k | 11.4 |
| 3 | 200 | 11.8 | 19 | 70k | 11.2 |
| 4 | 500 | 11.8 | 20 | 80k | 11 |
| 5 | 1k | 11.8 | 21 | 90k | 10.8 |
| 6 | 2k | 11.8 | 22 | 100k | 10.4 |
| 7 | 3k | 11.8 | 23 | 200k | 6.4 |
| 8 | 5k | 11.8 | 24 | 300k | 4.4 |
| 9 | 6k | 11.8 | 25 | 400k | 3.3 |
| 10 | 7k | 11.8 | 26 | 500k | 2.6 |
| 11 | 10k | 11.8 | 27 | 600k | 2 |
| 12 | 15k | 11.8 | 28 | 700k | 1.8 |
| 13 | 20k | 11.8 | 29 | 800k | 1.6 |
| 14 | 25k | 11.8 | 30 | 900k | 1.4 |
| 15 | 30k | 11.8 | 31 | 1Mk | 1.2 |
| 16 | 40k | 11.8 | - | - | - |Conclusion:
- Vin = 0.24 Vp-p
- Average Vo: 258/22 = 11.8 Vp-p (Band width)
3. Tone Control Amplifier Analysis
| Test | Frequensi (Hz) | Bass (Max) & Treble (Max) | Bass (Max) & Treble (Min) | Bass (Min) & Treble (Max) |
|------|----------------|---------------------------|---------------------------|---------------------------|
| 1 | 50 | 10.8 | 11.0 | 0.5 |
| 2 | 100 | 8.2 | 8.2 | 0.6 |
| 3 | 200 | 4.9 | 5.1 | 0.9 |
| 4 | 500 | 2.7 | 2.8 | 1.6 |
| 5 | 1k | 2.0 | 2.3 | 2.1 |
| 6 | 2k | 2.5 | 1.8 | 2.6 |
| 7 | 3k | 2.2 | 1.4 | 3.3 |
| 8 | 5k | 4.8 | 1 | 4.8 |
| 9 | 6k | 5.6 | 0.8 | 5.6 |
| 10 | 7k | 6.3 | 0.8 | 6.3 |
| 11 | 10k | 8.4 | 0.5 | 8.2 |
| 12 | 15k | 10.4 | 0.6 | 10.4 |
| 13 | 20k | 12.0 | 0.4 | 12 |
| 14 | 25k | 12.6 | 0.4 | 12.8 |
| 15 | 30k | 13.2 | 0.35 | 13.2 |
| 16 | 40k | 13.4 | 0.35 | 13.4 |
| 17 | 50k | 12.2 | 0.35 | 13.2 |
| 18 | 60k | 10.4 | 0.35 | 10.4 |
| 19 | 70k | 9.0 | 0.35 | 9.0 |
| 20 | 80k | 7.8 | 0.3 | 7.8 |
| 21 | 90k | 6.8 | 0.3 | 6.8 |
| 22 | 100k | 6.2 | 0.3 | 6.1 |Conclusion:
When Bass & Treble are at Maximum, while the frequency is between 30Hz - 30kHz, it has a waveform like the one below:
Meanwhile, when the frequency is between 40kHz - 100kHz, the waveform is as follows:
When Bass is Maximum and Treble is Minimum, while the frequency is between 50Hz - 100kHz, it has a waveform like the following:
When Bass is Minimum and Treble is Maximum, while the frequency is between 50Hz - 30kHz, it has a waveform like below:
Meanwhile, when the frequency is between 40kHz - 100kHz, it has a waveform like the following:
4. Mixer Analysis Results
- Gain: Min
- Volume: Med
| Test | Frequensi (Hz) | Bass (Max) & Treble (Min) | Bass (Min) & Treble (Max) | Bass (Max) & Treble (Max) |
|------|----------------|---------------------------|---------------------------|---------------------------|
| 1 | 20 | 2.5 | 0.25 | 2.5 |
| 2 | 50 | 2.2 | 0.3 | 2.2 |
| 3 | 100 | 1.8 | 0.36 | 1.8 |
| 4 | 200 | 1.2 | 0.4 | 1.2 |
| 5 | 500 | 0.8 | 0.5 | 0.8 |
| 6 | 1k | 0.65 | 0.6 | 0.6 |
| 7 | 2k | 0.6 | 0.8 | 0.8 |
| 8 | 3k | 0.5 | 0.9 | 0.8 |
| 9 | 4k | 0.4 | 0.95 | 0.9 |
| 10 | 5k | 0.4 | 1.2 | 1.2 |
| 11 | 6k | 0.4 | 1.4 | 1.4 |
| 12 | 7k | 0.35 | 1.5 | 1.5 |
| 13 | 8k | 0.3 | 1.6 | 1.6 |
| 14 | 9k | 0.3 | 1.7 | 1.7 |
| 15 | 10k | 0.3 | 1.9 | 1.9 |
| 16 | 12k | 0.3 | 2.2 | 2.2 |
| 17 | 14k | 0.3 | 2.3 | 2.3 |
| 18 | 16k | 0.25 | 2.4 | 2.4 |
| 19 | 18k | 0.25 | 2.4 | 2.4 |
| 20 | 20k | 0.25 | 2.4 | 2.4 |- Gain: Max
- Volume: Med
| Test | Frequensi (Hz) | Bass (Max) & Treble (Max) | Bass (Max) & Treble (Min) |
|------|----------------|---------------------------|---------------------------|
| 1 | 20 | 11 | 11 |
| 2 | 50 | 9 | 9 |
| 3 | 100 | 8.5 | 8.3 |
| 4 | 200 | 8 | 8 |
| 5 | 500 | 6.5 | 7 |
| 6 | 1k | 4.9 | 5.4 |
| 7 | 2k | 5.9 | 4.3 |
| 8 | 3k | 6.8 | 3.6 |
| 9 | 4k | 6.8 | 2.8 |
| 10 | 5k | 6.8 | 2.6 |
| 11 | 6k | 6.8 | 2.2 |
| 12 | 7k | 6.8 | 1.8 |
| 13 | 8k | 6.8 | 1.6 |
| 14 | 9k | 6.8 | 1.4 |
| 15 | 10k | 6.8 | 1.4 |
| 16 | 12k | 6.8 | 1.2 |
| 17 | 14k | 6.8 | 1 |
| 18 | 16k | 6.8 | 0.8 |
| 19 | 18k | 6.8 | 0.8 |
| 20 | 20k | 6.2 | 0.8 |Variation:
- When the AFG (Audio Function Generator) signal becomes the amplifier input, and when Bass and Treble are at max, Volume Med and Gain min, the output which was initially large suddenly becomes small and then increases again.
- When Bass is max, Treble min, Volume Med, and Gain min, the output will decrease as the frequency increases.
- When Bass Min, Treble Max, Volume Med and Gain Min, the output will increase as the frequency increases.
- The maximum SCR voltage gain in the Gain, Bass, Treble and Volume sections can be influenced by Effect.
Conclusion:
- When the bass is max and the treble is min, the higher the frequency, the smaller the V.out.
- When the bass is min and the treble is max, the higher the frequency, the higher the V.out.
- When the bass is maxed and the treble is maxed, the V.out which was initially bigger, gets bigger again.
- when the gain is min, then V.out is small.
- when the gain is max, then V.out is large.