Hello to all you amplifier design guru's,
In case I would want to double the number of output transistors in the output stage of a power amplifier (in order to beef up its current capabilities for driving 3-4 Ohms loads), need the output transistors then be matched?
If so, what matching should I shoot for then?
In case I would want to double the number of output transistors in the output stage of a power amplifier (in order to beef up its current capabilities for driving 3-4 Ohms loads), need the output transistors then be matched?
If so, what matching should I shoot for then?
Sometimes paralleling output transistors needs compensation or paralleling more faster ( lower COB) driver transistors depending on the output trz capacitance.
Not all schematics are automatically stable when adding more parallel power devices.The BE junction capacitance is double thus the driver needs to slew double the current into it.That can cause problems if the driver trz is not good enough.
Not all schematics are automatically stable when adding more parallel power devices.The BE junction capacitance is double thus the driver needs to slew double the current into it.That can cause problems if the driver trz is not good enough.
The amp, an Elektuur/Elektor 1983 elegant design, is discussed here, including the beefing up of the output stage by member Spookydd. There is - to my best of knowledge- no discussion about any selection and/or matching of the power-transistors. https://www.diyaudio.com/community/threads/amplifier-based-on-2n3055.10337/page-2
So the questions still stands.
The amp is already built many years ago, and will serve only subwoofer duties to 100 Hz, so any discussion about faster output transistors is moot. 2N3055 is the output device. The power supply is beefy enough to provide some + and - 35 Volts at 5 amps per channel.
So the questions still stands.
The amp is already built many years ago, and will serve only subwoofer duties to 100 Hz, so any discussion about faster output transistors is moot. 2N3055 is the output device. The power supply is beefy enough to provide some + and - 35 Volts at 5 amps per channel.
Replace the 2N3055 with stronger TO3 transistors. It is also the simplest mechanically, and it will sound better. Proposal MJ15003G-ON. With +-35VDC supply it works at 4 ohms without any problems (if the heatsinks are big enough and the power supply can achieve this). Otherwise, 2N3055 should not be used over +-30VDC. I don't think pairing is necessary in this case.
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