Since I'm crazy for Mosfet SE sound signature rather than PP Class A I've built , Anyone pls tell me what type of Mosfet device that could deliver 40-60Watt Power out in 8 Ohm load with only single device per ch ....
Just finished Pavel Macura SE Amp 17Watt, love the sound but need more power for my Heavy Speaker.
Years ago I also already built some SS's Class A PP like Bebe T,JLH,Hiraga,Firstwatt F4,F5,Tumos etc
Just finished Pavel Macura SE Amp 17Watt, love the sound but need more power for my Heavy Speaker.
Years ago I also already built some SS's Class A PP like Bebe T,JLH,Hiraga,Firstwatt F4,F5,Tumos etc
Nelson Pss Schade Feedback MOSFET 60W
Hi,
check out thie talk from BAF 2015 festival, where Nelson Pass presents SE mosfet ampifier 60W into 8 Ohms.
http://www.diyaudio.com/forums/pass-labs/280950-baf-2015-coverage.html
Hi,
check out thie talk from BAF 2015 festival, where Nelson Pass presents SE mosfet ampifier 60W into 8 Ohms.
http://www.diyaudio.com/forums/pass-labs/280950-baf-2015-coverage.html
Hi Kacernator,
Thanks for the link, since the Device (2SK77b) hard to find,but its give me idea to look for the max SOA of all my Stock devices for bigest SE Pout capabilities ....
Rgds
Ado
Thanks for the link, since the Device (2SK77b) hard to find,but its give me idea to look for the max SOA of all my Stock devices for bigest SE Pout capabilities ....
Rgds
Ado
Maybe one of the big motor drive modules made by Semikron and the like?
Something like this: http://au.mouser.com/ProductDetail/...Td1kCS88WpVTAMNytliguh4T4wZ9SaAfifiZtQYWK2A==
Something like this: http://au.mouser.com/ProductDetail/...Td1kCS88WpVTAMNytliguh4T4wZ9SaAfifiZtQYWK2A==
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Hi Kacernator,
Thanks for the link, since the Device (2SK77b) hard to find,but its give me idea to look for the max SOA of all my Stock devices for bigest SE Pout capabilities ....
Rgds
Ado
In that thread and in the Nelson Pass talk, he presents alternative with IXFN140N20P mosfet in schade feedback configuration. Check it out.
Here is the link to slides:
BAF Slides Nelson Pass | Audiohobby.com
Attachments
Andrea has been designing single ended follower for what seems like decades.
the Power Folllower
One variation even has constant current ClassA while delivering power to the load.
the Power Folllower
One variation even has constant current ClassA while delivering power to the load.
And what about to use some common MOSFET as source follower, and provide bootstrapped drain voltage to it, to reduce the dissipation?
Sajti
Sajti
I need at least SE 50W/ch to free the load Spk choices due to their sesitivities, the Mosfet device candidates available out there. The problem how to reduce heatshink size , maybe the CCS usage : the Lamp,Big Resistor(do they still need the heatshink ?) or a heater element instead of a Giant Inductor...
Any suggestion wellcome.
Ado
Any suggestion wellcome.
Ado
how to reduce heatshink size
Any suggestion wellcome.
Ado
Use fan. This will reduce the size, with about 50-70%, depending by the size, and speed of the fan.
Sajti
50W into 8ohms requires an output of 28.28Vpk and 3.536Apk into a non reactive test load.
You cannot get 50W into 8ohms by any other combinations of volts and amps.
A single ended amplifier that has a fixed maximum output determined by the bias setting of the output device must be set up to achieve that 3.536A into the test load.
That determines the heat and the sink requirement.
Attach a reactive 8ohms speaker that will demand more current than a dummy load will force the SE amplifier into current clipping on fast changing transients.
That will sound terrible.
To avoid current clipping one should set up the amplifier to pass transient currents far in excess of what a resistive dummy load will demand.
You cannot get 50W into 8ohms by any other combinations of volts and amps.
A single ended amplifier that has a fixed maximum output determined by the bias setting of the output device must be set up to achieve that 3.536A into the test load.
That determines the heat and the sink requirement.
Attach a reactive 8ohms speaker that will demand more current than a dummy load will force the SE amplifier into current clipping on fast changing transients.
That will sound terrible.
To avoid current clipping one should set up the amplifier to pass transient currents far in excess of what a resistive dummy load will demand.
Yes Sajti,the nowday CPU cooler & also the fan is one of the choice but the risk when it failed will blowup the devices beside the fan annoying noise ...
Ado
Ado
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I think you overestimate the type of fan required.
Also, the risk of critical failure due to overheating can simply be mitigated with a ~100 degree thermo fuse mated with the device to kill the power.
Also, the risk of critical failure due to overheating can simply be mitigated with a ~100 degree thermo fuse mated with the device to kill the power.
I need at least SE 50W/ch ................
?and another thermal switch so he can listen on low volume without fan noise
How do you get a low dissipation amplifier that is also SE?
Yes Sajti,the nowday CPU cooler & also the fan is one of the choice but the risk when it failed will blowup the devices beside the fan annoying noise ...
Ado
It's very easy to use some thermal switch to turn OFF the amplifier if overheating.
Another idea to use variable speed fan, to reduce the noise to the absolute minimum.
Sajti
?
How do you get a low dissipation amplifier that is also SE?
i do not think that way, simply put lm317 with ptc 1k and 240r r1 ,on 12v pc fan. if there is amplifier of little changing dissipation/output power(dclass) ,i put thermistor on transformer, what is wrong with this i dont know but for me it works well in lots of different amplifiers.
To avoid current clipping one should set up the amplifier to pass transient currents far in excess of what a resistive dummy load will demand.
Yes, I've seen measurements showing peak currents of 3-5 times that for resistive loads. into a reactive loudspeaker load.
Yes, I'm late to the party.
I'd say "sure, go for it" … and then be disappointed by what happens when the accumulated wear-and-tear on the MOSFET eventually causes it to melt down. I've done it, it happens. Especially when little whisker shorts somehow happen on the way from amplifier to speaker setup.
Myself, these days, I like to add active circuitry - and FAST circuitry! - to clamp current spikes on the output. Seriously. Whether you're using 1 or 10 MOSFETs (or bipolars) in parallel, you might as well include cathode / source / emitter side current-sense resistors of low value. Remember … its been 50 years since the invention of the OPAMP, and they are finally being recognized as pretty fast, pretty low-voltage, pretty stable devices. Especially for current-sense current-clamp circuits.
Just saying.
Make the beautiful design. PROTECT it from unexpected operating conditions. Sit back and enjoy the music until another wild hare enters your mind, and you need to 'do' another amplifier. REPEAT.
GoatGuy
I'd say "sure, go for it" … and then be disappointed by what happens when the accumulated wear-and-tear on the MOSFET eventually causes it to melt down. I've done it, it happens. Especially when little whisker shorts somehow happen on the way from amplifier to speaker setup.
Myself, these days, I like to add active circuitry - and FAST circuitry! - to clamp current spikes on the output. Seriously. Whether you're using 1 or 10 MOSFETs (or bipolars) in parallel, you might as well include cathode / source / emitter side current-sense resistors of low value. Remember … its been 50 years since the invention of the OPAMP, and they are finally being recognized as pretty fast, pretty low-voltage, pretty stable devices. Especially for current-sense current-clamp circuits.
Just saying.
Make the beautiful design. PROTECT it from unexpected operating conditions. Sit back and enjoy the music until another wild hare enters your mind, and you need to 'do' another amplifier. REPEAT.
GoatGuy
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