I just looked in the F6 text:
"As a push-pull Class A amplifier we traditionally expect it to operate in Class A to peaks of
twice the value of the bias current. With degeneration a circuit designed to operate at 30
watts rms into 8 ohms in Class A, would by definition leave Class A at 60 watt peaks. Here,
the actual bias of 1.55 amps would be expected to give 3.1 amps peak output, a 76 watt peak
into 8 ohms (with adequate supply voltage), and half of that (38 watt peak) into 4 ohms.
This calculation of the bias and the “Class A-ness” of the circuit depends on the output
devices having significant Source resistance, which is generally the case. Fets and Tubes
have what is known as a “square-law” characteristic, which means that as you raise the input
voltage to the Gate, the Drain-to-Source current increases disproportionately. In a singleended
design this produces the familiar second harmonic. Using degeneration resistance
tends to remove this effect by adding a linear component to this characteristic."
"As a push-pull Class A amplifier we traditionally expect it to operate in Class A to peaks of
twice the value of the bias current. With degeneration a circuit designed to operate at 30
watts rms into 8 ohms in Class A, would by definition leave Class A at 60 watt peaks. Here,
the actual bias of 1.55 amps would be expected to give 3.1 amps peak output, a 76 watt peak
into 8 ohms (with adequate supply voltage), and half of that (38 watt peak) into 4 ohms.
This calculation of the bias and the “Class A-ness” of the circuit depends on the output
devices having significant Source resistance, which is generally the case. Fets and Tubes
have what is known as a “square-law” characteristic, which means that as you raise the input
voltage to the Gate, the Drain-to-Source current increases disproportionately. In a singleended
design this produces the familiar second harmonic. Using degeneration resistance
tends to remove this effect by adding a linear component to this characteristic."
In the Burning amp 2016 part 2 video Nelson tells why he uses higher voltages on the Ixys hockey pucks. It's at about 13:50 in the video.
https://www.youtube.com/watch?v=pNVO3JN1KF0
https://www.youtube.com/watch?v=pNVO3JN1KF0
Where are you getting that from?
I read:
25W Class A into 8 Ohms
50W Class A into 4 Ohms
100W Class AB into 2 Ohms
Always pays to read Papa's articles a million times (all of them).
It's so easy just to cave man this, ie 30V rails, 2A bias and heatsinks capable of dissipating 120W, job is done. We don't need to put artificial limitations on ourself here
No need to have a brain melt down, plus or minus 10% on either side of those values would also work based on Brother Lynn's measurements.
For me personally I'm more interested in the 1Watt region and below.
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Yeah fair enough.
I personally think you already know most of it, you just don't realize what else there is to know.
It's hard to know what you don't know, if you don't know it, which could also mean maybe you do already know.
Genius is 1% inspiration, 99% perspiration.
In my case it would be: Dumbness is 1% toilet time, 99% perspiration.
Hahahaha
Either way, great work Lynn.
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For me personally I'm more interested in the 1Watt region and below.
Then you can try +/-15v supply and 5A bias
I think you've already discovered this.
1) Papa's distortion measurements suggest he is no where near voltage clipping at 25W. This suggests that most likely 28V rails or greater are used.
2) You can then apply appropriate amounts of bias to stay in the power dissipation window to check whether performance into 4 Ohms is maintained.
Then just keep adjusting to satisfy both criteria.
No rocket science, just work.
I'm quite happy using the transformers I have on hand, as I know I will never exceed 4W peaks anyway.
I think it will be ok.
I'll wait and see, if there is a problem.
Heatsinks are good for around 140W per side (lazy calculation, possibly a little higher) but total dissipation of amp channel will be 100W. There will be 2 cases. Serious amount of over engineering on the heatsinks. Hopefully last cases I build.
If it needs more then I will add Zen Mod Is Genius for more flow.
Bottom plate will have sigificantly more ventilation than top plate.
Just to add some extra info holes are 9mm in diameter x 32 per side.
I'll wait and see, if there is a problem.
Heatsinks are good for around 140W per side (lazy calculation, possibly a little higher) but total dissipation of amp channel will be 100W. There will be 2 cases. Serious amount of over engineering on the heatsinks. Hopefully last cases I build.
If it needs more then I will add Zen Mod Is Genius for more flow.
Bottom plate will have sigificantly more ventilation than top plate.
Just to add some extra info holes are 9mm in diameter x 32 per side.
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This genius seems to have many holes......
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Images include use of smilies, the BB code