 |
|
|
|
AUDIO CIRCUITS I have design some power amplifier and many more base on my own basic electronic knowledge. The aim for this circuit is to give DIY fan a chances in making own power amplifier. The circuit originally design by myself therefore some of the result may not satisfied the specifications of HiFi lovers. I use for very cheap material in building the circuit. Please BE CAUTION some of the circuit using our main 230V/110v, please get and advice from an authorize electrician. M60B-60W POWER AMPLIFIER New Upgrade from M45A power Amplifier A circuit base from M45A now been upgrade from 45W RMS to 60W RMS. The power transistor TIP142/147 is a Darlington build-in package is very useful in increasing the power output. Using a pair of TIP142 and TIP147 will get the total power output to 60W RMS. Now when in a stereo mode the total power transistor used is 8 pieces. The case of the power transistor will not bring you problem it is easy mounted on the heat sink unit. The Circuit The full schematic are shown below, there not many changes, only an extra power transistor TIP142 and TIP147 (Q6, Q7) and higher the supply rails to 40V. This extra power transistor will provided a total of heat 2 times from original heat. I suggest use a bigger heat sink when run it at higher current. Totally the damping factor now increased, the bass now more deeply and tighter then ever. If you want to get more powerful output using a 6 pair of power transistor just a way to powering the output. There will no penalty noise when using a pair of the power transistor. A total of 4 pair is enough for normal use of power. Now the power section is increased well follow the power of the power amplifier. A total of 150VA from 24V center tap transformer is enough. A 200VA to 300VA is very good to minimize the transient effect at a high power handling. I used a 150VA transformer because the cost of the transformer very high then the power transistor. A total of 150VA will cost me a RM50.00. A 300VA will be RM100. Still the unit will drive as lowest to 4 Ohm. I do not recommended to drive lower then this or the power transistor will push it limit and get burn. The 5.6K preset is to set the current for the power transistor. Using a THD meter and a multi turn pot is recommended for best result. I even now not have the distortion analyzer, the best for overall performance I just set to 80mA to 100mA for the current.
M60B power amplifier full schematic (click to enlarge) Test Result A good tight bass now been heard. I using only a pair of each power transistor the result very change so much. The noise now decreased and the bass deeper then before. At high power handling the sound of treble very details and the bass not over handling the amp hold the bass well. That why many high end power amplifier use many power transistor at the end of the system is to hold the bass sound. The overall unit now became neat in a bass and low noise. I use only a conventional switch power transistor (TIP142/7) not the Audio but the linearity is the best form the audio and the respond to high frequency very well. Now the Celine Dion - Prayer have a big bass ever then better just after the M45A. A Mary Jane Blage - Family Affairs deep bass in action cover all the small room demanding. The bass outrages then ever well the damping factor now better then a single pair power transistor. The voice of the vocal not really clear and seem to lack maybe because the CMRR of the circuit it self still low. I will try to using a better circuit in the long input pair unit. The using of a mirror current at the LTP sure make the circuit lower noise than now. Anything better then a DC servo circuit. Sooner or later Equipment The test is only a benchmark to demanding the sound of my system. All the same unit again:
All system is under low noise there no pricey loudspeaker nor the pre amplifier in my home. That thing surely a lot of money. nanhifi October 2002
|
|
