Are the amps intended to be in the same location so it would be easy, short ICs, to use the same sources for both amps. If so why use any switches? Just turn on the amp or amps you want playing. A remote volume control in the preamp would be nice. But if separate balance of each system is wanted why not add a remote volume control in each amp? I don't understand the need for a somewhat complicated switch.
Now there's an idea! 🙂
I agree.
It's funny how framing works. I was so focused on implementing a switch that I forgot to take a step back and look at what was actually needed in the application. You're right, Henry. No need to make it any more complicated.
Tom
Typical equipment from the "good old days" has the speakers in series when the switch is set to A+B. I've repaired, reverse engineered, and gutted quite a few units and this is what I almost always see.
My Pioneer that I'm using right now (early 90s) is rated 35 watts/channel into 8 ohms. This would suggest a split 60-70 volt supply (+/- 30-35 volts) but in fact it is a split 110 volt supply. Why? So it can deliver full power into 16ohms (2x8 ohm in series). So if you run 4-8 ohm speakers you can expect around 15 watts RMS per speaker to be available, which is reasonable.
What consequences does this present? Well the amplifier runs a lot hotter driving 8 ohms. The power supply sags too. But on the plus side, higher voltage means higher linearity, and a little headroom too. In fact, 2-3 dB headroom is available for tone bursts.
The design is a compromise, but it works as intended and works quite well too. Of course I hacked it (wired around the stupid graphic equalizer and put a sound processor and bass/treble controls in its place) but the point is that the power amplifier is a superb little unit with low distortion and nice headroom.
You can only run a 3886 on around 70 volts, so this approach is limited. You can calculate how far you can push this concept. You also have the option of using a lower voltage for parallel driving, which reduces power available to an 8 ohm load.
I hope this helps you understand your limitations and options.
My Pioneer that I'm using right now (early 90s) is rated 35 watts/channel into 8 ohms. This would suggest a split 60-70 volt supply (+/- 30-35 volts) but in fact it is a split 110 volt supply. Why? So it can deliver full power into 16ohms (2x8 ohm in series). So if you run 4-8 ohm speakers you can expect around 15 watts RMS per speaker to be available, which is reasonable.
What consequences does this present? Well the amplifier runs a lot hotter driving 8 ohms. The power supply sags too. But on the plus side, higher voltage means higher linearity, and a little headroom too. In fact, 2-3 dB headroom is available for tone bursts.
The design is a compromise, but it works as intended and works quite well too. Of course I hacked it (wired around the stupid graphic equalizer and put a sound processor and bass/treble controls in its place) but the point is that the power amplifier is a superb little unit with low distortion and nice headroom.
You can only run a 3886 on around 70 volts, so this approach is limited. You can calculate how far you can push this concept. You also have the option of using a lower voltage for parallel driving, which reduces power available to an 8 ohm load.
I hope this helps you understand your limitations and options.
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