The Circuit
Note that no output short circuit, so when the speakers will be shorted, while the amplifier is working (with signal amplifier), there is a real danger that the transistors destroyed. Since this amp was built commercially, the savings were worth the risk – most of these amplifiers were installed in the speaker box, so short selling is unlikely (unless you short the speaker’s voice coil as) a few times. Because the cost of the equipment used (minimum), it is a cheap amp to solve, even if you are blowing air.
Basic Specifications
The following shows the basic measurement results …
| Gain | 27dB |
| Input Impedance | 24k |
| Input Sensitivity | 1.22V for 100W (8 ohms) |
| Frequency response 1 | 10Hz to 30kHz (-1dB) typical |
| Distortion (THD) | 0.04% typical at 1W to 80W |
| Power (42V supplies, 8 ohm load) 2 | 90W |
| Power (35V supplies, 8 ohm load) 3 | 60W |
| Power (35V supplies, 4 ohm load) | 100W |
| Hum and Noise 4 | -73 dBV unweighted |
| DC Offset | < 100mV |
60W audio power amplifier circuit
Reduced the value of the Class A-based resistance to 560 ohms **
Increased the value of the bootstrap capacitor 100uF
Decreased Stabilization 100pF caps on (she was formerly 220pF)
Added the output inductance and damping resistance (see News)
** It is conceivable that with a few transistors, the value of 560 ohms is not correct. If this is detected, you should “optimize” this resistance to at least maintain DC offset. If you really wanted, you could even with a 2k trimpot (), and set it for at least DC offset. It is best to wait until the first temperature stable, but it will not change much anyway.
Apart from these changes, the amplifier is loaded with highly original and provide a + /-35V (voltage), as indicated at 70W into 8 ohms give completely satisfied. In his life, many of the above mods have done, because I never had the schedule when I needed him to find, as often as it went, like me! It is an evidence of the fair amplifier that can handle all types of resistor and capacitor replacements are made, and it still works well.
The noise and distortion figures are a bit pessimistic – there is so little distortion at 1V (20V or for that matter) that my major problems for the disruption, has a readable measurement. The oscilloscope output shows that most of what I see is noise – the integration of the production (my scope is that it is not) to eliminate the noise shows very little at all.
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