I've already modified the salvaged 7 channel amplifier as it was very modular and easy to understand into a 4 channel (to use in a stereo Bi-amped setup) and using the remaining output transistor's in parallel for driving high current into a low impedance subwoofer and got it all working as expected (using a total of 14 pair's of 2sa1962 / 2sc5242 
So moved on to finish the power supply modification's but unfortunately i was wrong about the Onkyo transformer it appears to have 3 secondary winding's providing 3 different voltages to the amplifier stage all split rail out, +/-24Vac Gray Wires, +/-33Vac Yellow wires and finally +/-48Vac and a common black wire centre tapped rail coming from the transformer and the +/-24Vac is hard wired straight to it's own rectifier then to the B+/B- of the amplifier,s reservoir capacitors, then the +/-33Vac is controlled by 2 relay's again going through it's own rectifier before connecting to the same B+/B- of the amplifier,s reservoir capacitors and the same is repeated for the +/-48Vac with it's own pair of relay's and rectifier before connected to the B+/B- of the amplifier,s reservoir capacitors,
would this be used when you set the speaker's ohm's rating's or required power power output and how do i stand having all 3 supply's connected at once for extra current as that's what's thrown me all being different voltages and the lower +/-24Vac supply is constantly connected and the other two are relay controlled ?
Scrap's my idea of using the different winding's to power different channel's for left and right as i wrongly presumed they was all the same adding up to more current output capability however what's peoples ideas on using this setup with 2 higher controllable voltages to power 4 channel's aimed at Bi-amping a stereo pair of speaker's and i'll just add to the already 18'000uf reservoir capacitors and drive the remaining modified channel's run in parallel from the separate +/-65Vdc power supply
would this be of any use in my application ?
i may just use a 3 way switch on the rear of the enclosure once i've found one for power output rating of Low, Medium and High output wattage because that's the only thing i can think of doing with it ?
Any ideas please ??
So moved on to finish the power supply modification's but unfortunately i was wrong about the Onkyo transformer it appears to have 3 secondary winding's providing 3 different voltages to the amplifier stage all split rail out, +/-24Vac Gray Wires, +/-33Vac Yellow wires and finally +/-48Vac and a common black wire centre tapped rail coming from the transformer and the +/-24Vac is hard wired straight to it's own rectifier then to the B+/B- of the amplifier,s reservoir capacitors, then the +/-33Vac is controlled by 2 relay's again going through it's own rectifier before connecting to the same B+/B- of the amplifier,s reservoir capacitors and the same is repeated for the +/-48Vac with it's own pair of relay's and rectifier before connected to the B+/B- of the amplifier,s reservoir capacitors,
would this be used when you set the speaker's ohm's rating's or required power power output and how do i stand having all 3 supply's connected at once for extra current as that's what's thrown me all being different voltages and the lower +/-24Vac supply is constantly connected and the other two are relay controlled ?
Scrap's my idea of using the different winding's to power different channel's for left and right as i wrongly presumed they was all the same adding up to more current output capability however what's peoples ideas on using this setup with 2 higher controllable voltages to power 4 channel's aimed at Bi-amping a stereo pair of speaker's and i'll just add to the already 18'000uf reservoir capacitors and drive the remaining modified channel's run in parallel from the separate +/-65Vdc power supply
would this be of any use in my application ?
i may just use a 3 way switch on the rear of the enclosure once i've found one for power output rating of Low, Medium and High output wattage because that's the only thing i can think of doing with it ?
Any ideas please ??
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in fact with more deeper investigation with a test meter it appear's to be different tap's of the same secondary winding providing different voltages controlled by relay's,
any idea's why ? benefit's of doing this please as it's the first time i've come across it in a project where i need a basic understanding of why and how best to use it if at all ?
would it serve at providing different wattage output's into different load's ? 4-8-16 ohms
cheer's
any idea's why ? benefit's of doing this please as it's the first time i've come across it in a project where i need a basic understanding of why and how best to use it if at all ?
would it serve at providing different wattage output's into different load's ? 4-8-16 ohms
cheer's
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I think it's Class AB, here's a link to the service manual that show's the individual channel driver boards then the next couple of pages after that show the main output transistors then the power supply coming from the transformer,
Onkyo TX-SR875 Service Manual (Page 15 of 166)
Onkyo TX-SR875 Service Manual (Page 15 of 166)
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