I checked the forum, and most of the hits were in the chip-amp forum and was dedicated to the "how to" of wiring existing chip-amps. That's nice, bit it doesn't help me understand how to set up the design parameters to get the desired output power from the partially designed mono-blocks. If this specific issue HAS been addressed and I missed it, a pointer to the thread would be greatly appreciated.
The situation :
I will have two mono-blocks per channel in an amp I'm working on (in simulation and a single rough prototype). They will be driving an 8 ohm speaker/crossover. I'm looking to get about 50W/ch, and rough math says I should have about half that power in each mono-block, but I'm getting confused with the math, and could use some help.
Rough math says to get 25w into an 8 ohm speaker, each mono-block will have to put in about 1.75A driven by 14Vrms, or roughly 40Vpp.
What I think the solution space looks like :
If I understand Bridged Mode correctly, while we get twice the voltage swing, each amp sees half the resistance, so we're now trying to drive 25w into 4 ohms, which results 2.5A at 10Vrms or roughly 28Vpp. Each mono-block provides that much voltage, at the same current, so that's 20v (total) swing at 2.5A, for 50w of power to the speaker.
If I understand Parallel Mode correctly, it is the opposite, each mono-block sees twice the resistance, but contributes to the total current, so you get twice the current you'd expect for the (doubled) resistance. In this case, 25w into 16 ohms results in 1.25A at 20Vrms, or roughly 56Vpp. But each mono-block provides that much current at the same voltage, so it's 20v at 2.5A (total), for 50w of power to the speaker.
The BIG question:
Is my math correct, and did I get the two circuit topologies right?
If so, bridged looks to be the way to go, from ease of setting up the power supply and modifying the circuit. Getting a clean 56Vpp signal sounds like a bit of a pain...
Next up will be to get to the output voltage of 10Vrms... from line level input. That will take a total of 30dB in gain (31x gain from 0.32v, consumer line-in levels, to the final output voltage of 10v).
Presently, the amp design gives about 12dB of gain, and I hope to get a fair bit more out of it, but I doubt I'll get all the way to 30dB gain out of such a simple amp design.
So, if I understand this part of the problem correctly, I'm looking at a pre-amp that can punch it up part way. The preamp will have to add (30dB-PowerAmpdB) worth of gain to get from consumer line-out level to 10v, and achieve 50w/ch, correct?
The situation :
I will have two mono-blocks per channel in an amp I'm working on (in simulation and a single rough prototype). They will be driving an 8 ohm speaker/crossover. I'm looking to get about 50W/ch, and rough math says I should have about half that power in each mono-block, but I'm getting confused with the math, and could use some help.
Rough math says to get 25w into an 8 ohm speaker, each mono-block will have to put in about 1.75A driven by 14Vrms, or roughly 40Vpp.
What I think the solution space looks like :
If I understand Bridged Mode correctly, while we get twice the voltage swing, each amp sees half the resistance, so we're now trying to drive 25w into 4 ohms, which results 2.5A at 10Vrms or roughly 28Vpp. Each mono-block provides that much voltage, at the same current, so that's 20v (total) swing at 2.5A, for 50w of power to the speaker.
If I understand Parallel Mode correctly, it is the opposite, each mono-block sees twice the resistance, but contributes to the total current, so you get twice the current you'd expect for the (doubled) resistance. In this case, 25w into 16 ohms results in 1.25A at 20Vrms, or roughly 56Vpp. But each mono-block provides that much current at the same voltage, so it's 20v at 2.5A (total), for 50w of power to the speaker.
The BIG question:
Is my math correct, and did I get the two circuit topologies right?
If so, bridged looks to be the way to go, from ease of setting up the power supply and modifying the circuit. Getting a clean 56Vpp signal sounds like a bit of a pain...
Next up will be to get to the output voltage of 10Vrms... from line level input. That will take a total of 30dB in gain (31x gain from 0.32v, consumer line-in levels, to the final output voltage of 10v).
Presently, the amp design gives about 12dB of gain, and I hope to get a fair bit more out of it, but I doubt I'll get all the way to 30dB gain out of such a simple amp design.
So, if I understand this part of the problem correctly, I'm looking at a pre-amp that can punch it up part way. The preamp will have to add (30dB-PowerAmpdB) worth of gain to get from consumer line-out level to 10v, and achieve 50w/ch, correct?