leesonic
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I am thinking about designing and producing a drop in power amp board for the Kenwood KA-8300 and 9100 amplifiers that use the TA-100W darlington pack, instead using discrete output transistors. When I say designing and producing, I am fortunate in my new job to be working with a bunch of talented individuals, one of whom said he would do the PCB design. As for the circuit, I would be borrowing the circuit from one of their other amps, like the KA-7100 or 8100.
The idea is to make a board exactly the same size (if possible) as the boards in these amps, with the connections for power, input, output etc. in the same physical locations. The output transistors would be two plastic power devices that could bolt to the heatsink using the existing screw holes left behind by the TA-100 modules. The board would be shipped fully populated, with the bias and offset already adjusted.
There are certain questions that arise in producing such a board :
1) The 7100 and 8100 power amps run on 47V and 50V respectively. The 8300 and 9100 power amps run on 51V and 57V respectively. What would be the implications of running, say, the 7100 circuit on the power supply of the 9100 which is 10V higher?
2) Both the 7100 and 8100 circuits use pretty straightforward components that are easy to find modern substitutes for. The output transistors for example would be MJL21193/94, the TO-264 versions of the MJ21113/94. What might be difficult to source would be the dual FET uPA63H that is used at the input. Also, the 5TP-41L thermistor TH1 and TH2 that sit on the same heatsink as the outputs.
3) Would the "Kenwood sound" of the 8300 and 9100 be compromised by using the circuitry of the 7100 or 8100? I have had several 7100s, and was always pleased with their sound. This amp also received rave reviews in the HiFi press back in the day.
My biggest problem would be finding a suitable KA-8300 and/or KA-9100 to try this project on. Both these amps seem to sell for around $200 upwards for parts units, which I am reluctant to spend on what would be a test bed for this new power amp board.
I have attached screen grabs of the schematics of the four amps mentioned.
Lee.
The idea is to make a board exactly the same size (if possible) as the boards in these amps, with the connections for power, input, output etc. in the same physical locations. The output transistors would be two plastic power devices that could bolt to the heatsink using the existing screw holes left behind by the TA-100 modules. The board would be shipped fully populated, with the bias and offset already adjusted.
There are certain questions that arise in producing such a board :
1) The 7100 and 8100 power amps run on 47V and 50V respectively. The 8300 and 9100 power amps run on 51V and 57V respectively. What would be the implications of running, say, the 7100 circuit on the power supply of the 9100 which is 10V higher?
2) Both the 7100 and 8100 circuits use pretty straightforward components that are easy to find modern substitutes for. The output transistors for example would be MJL21193/94, the TO-264 versions of the MJ21113/94. What might be difficult to source would be the dual FET uPA63H that is used at the input. Also, the 5TP-41L thermistor TH1 and TH2 that sit on the same heatsink as the outputs.
3) Would the "Kenwood sound" of the 8300 and 9100 be compromised by using the circuitry of the 7100 or 8100? I have had several 7100s, and was always pleased with their sound. This amp also received rave reviews in the HiFi press back in the day.
My biggest problem would be finding a suitable KA-8300 and/or KA-9100 to try this project on. Both these amps seem to sell for around $200 upwards for parts units, which I am reluctant to spend on what would be a test bed for this new power amp board.
I have attached screen grabs of the schematics of the four amps mentioned.
Lee.
