Hi!
Trying to build an amplifier around 70W@8 ohm, and 520W@1 ohm, with as many output MOSFET as the Aleph 1.2, or more if I have to, so that it can cope with speakers with low impedance. My current speakers are 6 ohm nominal and drop to less than 1.5 Ohm. I am an old man in a small apartment and do not usually listen to music at moderate level.
The rail voltage will be +-38V, transformers are 2500VA for each channel, may be overkilled but I like to be able to reuse it should I decide to build a larger amplifier.
It will have the usual thermistor to limit inrush current etc.
For Fuse 1, I will use a 10A slow blown fuse, pretty straight forward.
For Fuse 2 and 3,
At 1.5 Ohm, the speakers will draw max. 25A, but being the low efficiency SE Class A, the amplifier may draw 4-5 times as much so perhaps 100~125A.
Q1) should the fuses be located between the capacitors and the amplifier? Or between the transformer and rectifier? Each capacitor has a ripple current of 70A.
Q2) what value should they be? For rail voltage of +-38V, should it be
a) 2500VA/38dc=68A; or
b) 2500VA/28ac=88A; or
c) 2500VA/(38+38)=34A; or
d) 2500VA/(28+28)=44A
Q3) should they be fast blown or slow blown fuses?
Thank you.
Trying to build an amplifier around 70W@8 ohm, and 520W@1 ohm, with as many output MOSFET as the Aleph 1.2, or more if I have to, so that it can cope with speakers with low impedance. My current speakers are 6 ohm nominal and drop to less than 1.5 Ohm. I am an old man in a small apartment and do not usually listen to music at moderate level.
The rail voltage will be +-38V, transformers are 2500VA for each channel, may be overkilled but I like to be able to reuse it should I decide to build a larger amplifier.
It will have the usual thermistor to limit inrush current etc.
For Fuse 1, I will use a 10A slow blown fuse, pretty straight forward.
For Fuse 2 and 3,
At 1.5 Ohm, the speakers will draw max. 25A, but being the low efficiency SE Class A, the amplifier may draw 4-5 times as much so perhaps 100~125A.
Q1) should the fuses be located between the capacitors and the amplifier? Or between the transformer and rectifier? Each capacitor has a ripple current of 70A.
Q2) what value should they be? For rail voltage of +-38V, should it be
a) 2500VA/38dc=68A; or
b) 2500VA/28ac=88A; or
c) 2500VA/(38+38)=34A; or
d) 2500VA/(28+28)=44A
Q3) should they be fast blown or slow blown fuses?
Thank you.
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Looks ok as shown. Choose the F2 and F3 as small as possible, but so they don't blow much during normal use.
It's best to size them by trial and error, so buy a bunch of them. Maybe start at 5A fast blow and go from there.
Bear in mind that if a fuse blows, you could have full rail DC voltage on the speaker.
It's best to size them by trial and error, so buy a bunch of them. Maybe start at 5A fast blow and go from there.
Bear in mind that if a fuse blows, you could have full rail DC voltage on the speaker.
