I bought a new Quad 99 as a local shop here is selling for less then 500 USD.
I hv solder a direct wire from the RCA input to the amplifier board, and eliminated the messy Quad link circuitry that killed the sound.
I hv also adjust the bias of the driver much higher, with the voltage across the driver BE-EB junction near 1.25 voltage but didn't measure the current yet. In any case the drivers and pre drivers are hot now, especially the pre driver. But the higher bias really bring out the sound.
Now the right channel is giving me an intermittent problem with a muted sound from time to time. I think it must be due to the protection circuit.
Does any body have the Quad 99 power amp diagram?
I am also thinking of removing the LM 317 and 337 regulator to supply power to the Quad link. They are there just to pollute the power supply...
Tks
William
I hv solder a direct wire from the RCA input to the amplifier board, and eliminated the messy Quad link circuitry that killed the sound.
I hv also adjust the bias of the driver much higher, with the voltage across the driver BE-EB junction near 1.25 voltage but didn't measure the current yet. In any case the drivers and pre drivers are hot now, especially the pre driver. But the higher bias really bring out the sound.
Now the right channel is giving me an intermittent problem with a muted sound from time to time. I think it must be due to the protection circuit.
Does any body have the Quad 99 power amp diagram?
I am also thinking of removing the LM 317 and 337 regulator to supply power to the Quad link. They are there just to pollute the power supply...
Tks
William
A few more adjustments here and there will really bring out the sound from there, it will sound like this: Kaboom!! Quad amps are especially not the ones where you can start to rip off things from here and there, and readjust parts values, unless you know very well what you are doing. I am not questioning your expertise, but what you've written down here does......
Quad 99 pwr amp
Haha... very bad habit of me since young, but Quad 99 is not more complicated then most other amps in terms of construction.
The sound is just much better with higher bias and better capacitor, it actually sounded quite similar to the modified Mac 2600.
hope I can find the diagram og quad link, as I tried to seperate the quad link input circiit from the mute and on/off logic curcuit. After that I might be able to remove ghe LM 317/337 regulator. I have cut out the power supply pins of most op amps, logic switches, and the comparators at the Quadlink input stage, just 3 more ic to go...
Haha... very bad habit of me since young, but Quad 99 is not more complicated then most other amps in terms of construction.
The sound is just much better with higher bias and better capacitor, it actually sounded quite similar to the modified Mac 2600.
hope I can find the diagram og quad link, as I tried to seperate the quad link input circiit from the mute and on/off logic curcuit. After that I might be able to remove ghe LM 317/337 regulator. I have cut out the power supply pins of most op amps, logic switches, and the comparators at the Quadlink input stage, just 3 more ic to go...
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