Here is my latest project a class AB 500 watts peak into 4 ohms amplifier in a PC case.
It has an LTP with CM and CCS, a VAS stage with CCS, a Vbe Multiplier.
It has a driver stage then 2 pairs of bi-polar output transistors.
Sound is very clean with plenty of low end.
Underneath the PC case is my amplifier test bed. It uses a 2 amp transformer in case of shorts, this stops output transistors blowing if a fault occurs.
If I power up an amp and the transformer grumbles I know there is fault.
In the background there is a 1980 Maplin 50 watt amplifier pcb.
It has an LTP with CM and CCS, a VAS stage with CCS, a Vbe Multiplier.
It has a driver stage then 2 pairs of bi-polar output transistors.
Sound is very clean with plenty of low end.
An externally hosted image should be here but it was not working when we last tested it.
Underneath the PC case is my amplifier test bed. It uses a 2 amp transformer in case of shorts, this stops output transistors blowing if a fault occurs.
If I power up an amp and the transformer grumbles I know there is fault.
In the background there is a 1980 Maplin 50 watt amplifier pcb.
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Its a brand new pc case I got it for £20 with power supply on ebay.
The new case has the blanking plates on the front for mounting in/out jack sockets and a volume control.
I strip out the power supply except for the mains socket.
I also use the fan to keep the heat-sink cool.
The new case has the blanking plates on the front for mounting in/out jack sockets and a volume control.
I strip out the power supply except for the mains socket.
I also use the fan to keep the heat-sink cool.
What about adding emitter degeneration to both the LTP and the TIS?
BTW, even expanded I cannot read any detail.
BTW, even expanded I cannot read any detail.
Emitter degeneration might help make the DC offset adjust a bit less touchy.
Without going into 4 pages of pictures it is difficult to show the circuit diagram.
Built up another pcb with heat-sink tonight and it sounds good too.
Got caught with some swarf behind a transistor which shorted it to the heatsink.
A quick clean with a rag got rid of it.
I always check for shorts between the transistors and the heat-sink before powering up.
Its also wise to deburr the mounting holes.
Got caught with some swarf behind a transistor which shorted it to the heatsink.
A quick clean with a rag got rid of it.
I always check for shorts between the transistors and the heat-sink before powering up.
Its also wise to deburr the mounting holes.
Adding resistors to the signal path can add noise and it also reduces loop gain.
There seems to be a split in opinion as to whether emitter degeneration should be used.
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