Good day everyone
I am currently working on a stereo 3-Way active crossover system. This means that I will need six power amplifiers.
I have taken a design published in ETI October 1993 for a 50W 8 Ohm amplifier and slightly changed the design. I have a few questions with regards to the design (see attached schematic).
1. The article calls for MKM capacitors, may I use any film type capacitors for those?
2. Some of the capacitors are shown as electrolytic in the schematic, but the BOM calls for ceramic capacitors, like C5 & C6.
3. The schematic calls for 220uF capacitors for C3 & C8, but the BOM calls for 2200uF. Which will be the correct value.
4. Q3 calls for BF245A, which seems to be obsolete, what would be a good replacement part?
5. The original design used BDT64/BDT65 darlington units for output transistors. I replaced them with a compound arrangement (in the blue border) using the (almost) same resistor values as in the BDT64/65 datasheet. Will this work or am I missing something? Would it be better to only use TIP142/TIP147's? Rod Elliot is convinced that the compound arrangement causes lower distortion than the darlington arrangement. NAD also uses the compound arrangement in their designs.
I used two output transistors in parallel, this will sort out any possible dissipation problems with the high current required for a 4 Ohm load.
Any advice and inputs will be appreciated!
I am currently working on a stereo 3-Way active crossover system. This means that I will need six power amplifiers.
I have taken a design published in ETI October 1993 for a 50W 8 Ohm amplifier and slightly changed the design. I have a few questions with regards to the design (see attached schematic).
1. The article calls for MKM capacitors, may I use any film type capacitors for those?
2. Some of the capacitors are shown as electrolytic in the schematic, but the BOM calls for ceramic capacitors, like C5 & C6.
3. The schematic calls for 220uF capacitors for C3 & C8, but the BOM calls for 2200uF. Which will be the correct value.
4. Q3 calls for BF245A, which seems to be obsolete, what would be a good replacement part?
5. The original design used BDT64/BDT65 darlington units for output transistors. I replaced them with a compound arrangement (in the blue border) using the (almost) same resistor values as in the BDT64/65 datasheet. Will this work or am I missing something? Would it be better to only use TIP142/TIP147's? Rod Elliot is convinced that the compound arrangement causes lower distortion than the darlington arrangement. NAD also uses the compound arrangement in their designs.
I used two output transistors in parallel, this will sort out any possible dissipation problems with the high current required for a 4 Ohm load.
Any advice and inputs will be appreciated!
Attachments
Last edited: