Looks like a project that would be a good fit in this mighty chassis?
https://www.diyaudio.com/forums/swa...100w-class-amplifier-modules.html#post6575665
https://www.diyaudio.com/forums/swa...100w-class-amplifier-modules.html#post6575665
How many AB or Normal watts capacity/size does a heatsink need to dissipate the 100 Class A Watts?, dumb question but I'd love to understand the difference.
Here Papa explains it:
Pass LabsLeaving Class A - Pass Labs
100 Watts into 8 Ohm is 3,5 Ampere RMS in sum for the P and N devices.
You need 28 Volts RMS for 3,5 Amps RMS. So you need 40 Volts DC rails. 3,5 Amps RMS is 5 Amps DC bias which gives 200 Watts heat.
But do not trust me as I am a bloody beginner and have zilch knowledge of amplifier design. My BA-3 clipped at 100 Watts and 290 Watts heat, so the theoretical calculation above can somehow not generally be right.
If you would want to do it single ended with only N devices you have only positive rail of now 80 Volts makes 400 Watts of heat.
Cheerio
Pass LabsLeaving Class A - Pass Labs
100 Watts into 8 Ohm is 3,5 Ampere RMS in sum for the P and N devices.
You need 28 Volts RMS for 3,5 Amps RMS. So you need 40 Volts DC rails. 3,5 Amps RMS is 5 Amps DC bias which gives 200 Watts heat.
But do not trust me as I am a bloody beginner and have zilch knowledge of amplifier design. My BA-3 clipped at 100 Watts and 290 Watts heat, so the theoretical calculation above can somehow not generally be right.
If you would want to do it single ended with only N devices you have only positive rail of now 80 Volts makes 400 Watts of heat.
Cheerio
I like Ozorfis explanation very much. As a fellow beginner, this is also how I might think of it. Hope it's OK to expand on their thoughts a bit. As always... I'd love to know if I have it completely mucked up.
A few examples below:
Amp 1 - 100W "Pure Class A" into 8ohms - Dissipation might be 200W.
Amp 2 - 200W with 100W in Class A into 8 ohms - Dissipation is ~200W*
Amp 3 - 200W with 50W in Class A into 8ohms - Dissipation is ~100W*
* - yes, dissipation will go up a bit when the Class B power is "accessed".
If the intent of the question was around what people might use for heatsinks in relative terms for those amps, then it might look something like.
Amp 1 - Heatsink 1 - chosen for 200W dissipation at a targeted device and heatsink temperature above ambient.
Amp 2 - Still use heatsink 1 - Same general dissipation. In general, the extra 100W available in Class B will only be used for very brief musical peaks in the real world. If amp #1 is not not
, then using the same sinks will likely be just fine.
Amp 3 - Smaller than heatsink 1, but likely not "1/2" the size. Chosen for around the ~100W dissipation. The extra 150W available in Class B will still only be for very brief peaks (if ever), so why pay for bigger sinks?
Overall, if an amp is designed for class A/B, some of the likely goals were: smaller sinks / smaller size, lower cost, lower average heat, lower average power consumption, higher efficiency. All of those benefits with peak power still available on an as-needed basis usually for brief periods of time.
That is completely separate from designing around an operating point for particular devices to achieve their "best" sound. Assume in all the above examples that we're using the "best" devices at the "best" operating points between amps, and that they'd all sound equally awesome even when the A/B amps "klunk". 😀
That's oversimplified, but I hope it helps.
A few examples below:
Amp 1 - 100W "Pure Class A" into 8ohms - Dissipation might be 200W.
Amp 2 - 200W with 100W in Class A into 8 ohms - Dissipation is ~200W*
Amp 3 - 200W with 50W in Class A into 8ohms - Dissipation is ~100W*
* - yes, dissipation will go up a bit when the Class B power is "accessed".
If the intent of the question was around what people might use for heatsinks in relative terms for those amps, then it might look something like.
Amp 1 - Heatsink 1 - chosen for 200W dissipation at a targeted device and heatsink temperature above ambient.
Amp 2 - Still use heatsink 1 - Same general dissipation. In general, the extra 100W available in Class B will only be used for very brief musical peaks in the real world. If amp #1 is not not
, then using the same sinks will likely be just fine.Amp 3 - Smaller than heatsink 1, but likely not "1/2" the size. Chosen for around the ~100W dissipation. The extra 150W available in Class B will still only be for very brief peaks (if ever), so why pay for bigger sinks?
Overall, if an amp is designed for class A/B, some of the likely goals were: smaller sinks / smaller size, lower cost, lower average heat, lower average power consumption, higher efficiency. All of those benefits with peak power still available on an as-needed basis usually for brief periods of time.
That is completely separate from designing around an operating point for particular devices to achieve their "best" sound. Assume in all the above examples that we're using the "best" devices at the "best" operating points between amps, and that they'd all sound equally awesome even when the A/B amps "klunk". 😀
That's oversimplified, but I hope it helps.
