Near field (in phase), less than 2m but 3.9 Ohms of minimum impedance. My modded KEF Q100 5.25" coaxial loudspeakers is like 5 Ohms. Better 4 Ohms to estimate the max power.
The calculations were made with 8 Ohms speakers -> I need about double, 25 watts.
I would need Alpha Nirvana 25 watts at 4 Ohms. Heat, aka watts dissipated?
Advantage: KEF little coaxials have very great soundstage -> SPL in near field (in phase) is almost the same that in random phase at the same distance, in a not big room.
The calculations were made with 8 Ohms speakers -> I need about double, 25 watts.
I would need Alpha Nirvana 25 watts at 4 Ohms. Heat, aka watts dissipated?
Advantage: KEF little coaxials have very great soundstage -> SPL in near field (in phase) is almost the same that in random phase at the same distance, in a not big room.
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These are rough estimates, but I think you can do it with about 100w dissipation per channel.
Assuming 17v rails and 3A bias, that is 34v x 3A = 102W or 51W per MOSFET. 17vx2=34v and subtract 6v for headroom we have 28vpp. 28v/2.83=10vrms. 10Vrms^2/4ohm=25w.
Assuming 17v rails and 3A bias, that is 34v x 3A = 102W or 51W per MOSFET. 17vx2=34v and subtract 6v for headroom we have 28vpp. 28v/2.83=10vrms. 10Vrms^2/4ohm=25w.
So Maty,
Will you get an Alpha Nirvana and join the Class A crowd finally? 100W dissipation in a 4U x 400 mm is very doable.
I am thinking about it. But before you commented 100 watts by channel -> 200 watts in total, until a small stove in summer.
Then the efficiency is not 43% in the AN at 25 watts 4 Ohms! Or your previous comment was wrong.
Then the efficiency is not 43% in the AN at 25 watts 4 Ohms! Or your previous comment was wrong.
My quick sim shows about +/17.0v rails, 1.86A bias current, and 62W dissipation per channel for 28.3Vpp or 25W into 4ohms or about 40% efficiency. More tweaking needs to be done by Hugh though to optimize harmonic profile.
Hi Maty Tinman,
Hugh just completed a sim for 25W I to 4ohms. Unfortunately, it will dissipate more heat than the 8ohm version and not be as efficient. Hugh designed it to be able to handle 3ohm loads in case speaker dips down. It will be about 3A bias current at +/-20v rails. 58W dissipation per MOSFET. Are you still interested?
Hugh just completed a sim for 25W I to 4ohms. Unfortunately, it will dissipate more heat than the 8ohm version and not be as efficient. Hugh designed it to be able to handle 3ohm loads in case speaker dips down. It will be about 3A bias current at +/-20v rails. 58W dissipation per MOSFET. Are you still interested?
Hummm... 2 MOSFET by channel
About 120 watts by channel -> 240 watts in stereo in a small room (about 23 m3). I think it is too much in July + August (heat + hummid) in the Mediterranean coast, at least in Tarragona.
The answer, to my regret, is NO.
About 120 watts by channel -> 240 watts in stereo in a small room (about 23 m3). I think it is too much in July + August (heat + hummid) in the Mediterranean coast, at least in Tarragona.
The answer, to my regret, is NO.
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Thanks to the mods for reinstating this thread in the SS forum, appreciated from all of us involved here.
Maty, how would be a 20V rail AN with 2.5A quiescent, giving 50W for each mosfet, 200W the total. You can blow the hot air through a little hole under the amplifier in the floor, to the basement of your home? Or even through a home 'heating' ventilation to the outside. I have done this with an early Zen in 328 years ago in my early experimental period, worked very well.
Hugh
Maty, how would be a 20V rail AN with 2.5A quiescent, giving 50W for each mosfet, 200W the total. You can blow the hot air through a little hole under the amplifier in the floor, to the basement of your home? Or even through a home 'heating' ventilation to the outside. I have done this with an early Zen in 328 years ago in my early experimental period, worked very well.
Hugh
My initial idea was 25 watts at 4 Ohms -> 50 watts at 8 Ohms. With an efficiency a little lower than 43% after the modifications, about 40% -> 125 watts. Maybe up to 150 watts.
In the main room, where I have the Big speakers, 3-ways, 91 dB (with very strange configuration of speakers, crossover and... kidnapped), I could with 240 watts and more but in that small room it is still excessive if it is working more than an hour.
In the main room, where I have the Big speakers, 3-ways, 91 dB (with very strange configuration of speakers, crossover and... kidnapped), I could with 240 watts and more but in that small room it is still excessive if it is working more than an hour.
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Not only the problem i the heat, but also the distance at which the amplifier is from where I am sitting. I can easily change the volume manually without using the remote. So those watts matter more than if the amplifier were farther from me!
Have you considered liquid cooling and transporting the heat outside like an air conditioner? Just a few tubes and a small fan. Use the pc gaming overclocker stuff. Available everywhere.
I have air conditioner (and heat bump) but the modded AVR Marantz SR4500 is too close. 200 watts of heat so near... In addition they are several hours running continuously. I do not see it.
That would give 12.5 watt class A @ 4 ohm, probably max 32 watt A/B; class A efficiency of 12.5 % 🙄
Besides, a single pair of IRFP's would blow up more sooner than later.
Nelson Pass used double pairs of the same mosfets with the same quiescent for a reason in his Aleph J (which correctly specifies 25 watt class A @ 8-16 ohm using the same quiescent current....).
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That's why I suggest piping the heat out with liquid cooling. It is very compact and the temp is very cool. Like this (but longer tubes):
Use FQA MOSFETs like suggested and the heat load is no problem. You like to quote famous EE's whenever it supports your position. It was Pass who invented the Aleph CCS which permits SE Class A efficiencies exceeding 25%, but you choose to ignore Pass in that context. You quote Rod Elliot when his general observations of SE Class A max power suits your thinking. When are you going to quote Cordell or Self? I am waiting...
Why are you here again? With the same old same old broken record. Ok, we heard your opinion and your position. You obviously don't understand electronics or how to read schematics, so stop pretending like you do. Designing amplifiers and understanding them is a lot more than just quoting notable soundbytes from famous EE's. There is context, and there is topology. You need to go back and roll your eyes in your own thread like the mods suggested.
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1. Pass provided the DIY community with a CCS Aleph; he did not "invent" CCS of output stages (done long before);
2. Efficiency of the Aleph J is ~21% (output fets dissipating 30 watt each for 25 watt of output power).
Yes, I quote when it makes sense (by the way try to spell names correctly...).
In the meantime I also read (and learned) a bit about bootstrapping (Yes Douglas Self!).
Bootstrapping is a clever way of maximizing the swing of the output stage (making the input impedance of the output stage higher by positive feedback).
Bootstrapping does not alter the quiescent current, so it has nothing to do with class A / class A/B (the normal rules to calculate class A output power also apply to the Nirvana).
In the Nirvana amp bootstrapping is applied to maximize output swing, because when using vertical mosfets (IRFP240/9240) it is impossible to reach output swing approaching the power rails when the input stage runs on the same rails. With lateral mosfets that would be a bit less of a problem.
That's also why it was suggested by one of my "mentors" to give the input/power stage higher voltage rails, or a better bootstrapping technique (transistors).
Would you stop me here from being, as long as I don't break any forum rules?
I am learning each day 🙂.
Own Thread? I did not open a thread myself; it was done by moderation.
Moderation will tell me when I am not allowed here, not you!
Another good read :
The JLH Class-A Output Stage. Single-ended or push-pull? | ldsound.ru
But I will be out of here X (unless you force me...), because we are not likely to agree.
I am not to derail your thread (or spoiling your business).
When I have useful comment, I will use my "own" thread....OK?
Correction post #379: That's also why it was suggested by one of my "mentors" to give the input/power stage higher voltage rails, or a better bootstrapping technique (transistors). should be .....input stage........
I am not to derail your thread (or spoiling your business).
When I have useful comment, I will use my "own" thread....OK?
Correction post #379: That's also why it was suggested by one of my "mentors" to give the input/power stage higher voltage rails, or a better bootstrapping technique (transistors). should be .....input stage........
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