Stock Aleph J is biased to 2A per channel (4A total)
Are you saying you have biased each output mosfet to 0.85A?
Are you saying you have biased each output mosfet to 0.85A?
I was certain the stock Aleph J was biased at 2A.
6L6 may have suggested reducing the bias because of heatsink limitations.
I haven't read this thread so I can't say for sure why he suggested that bias point.
I could be mistaken though, my memory is from when I first built it back when Peter Daniel did PCBs many years ago.
6L6 may have suggested reducing the bias because of heatsink limitations.
I haven't read this thread so I can't say for sure why he suggested that bias point.
I could be mistaken though, my memory is from when I first built it back when Peter Daniel did PCBs many years ago.
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He also wrote:
"As this amp is built in a 5U chassis, I will crank the bias to the hottest I want to take it (where the Mosfets are just under 160F / 70C) This is slightly above the 65C recommended for good longevity. The heatsinks are about 130F/55C. I suspect that if I were to use the Keratherm red silpads or thin mica&grease I would have slightly cooler devices and warmer sinks. 500mV bias = 1.06A = 22.55W/device. This is hot. You could not do this if you build your amp in the 4U chassis without a fan somewhere. "
So it's the matter of temperature and heatsinks size.
I think that I can put 2A to simulations and I'll be on the safe side 🙂
Regards,
Maciek
"As this amp is built in a 5U chassis, I will crank the bias to the hottest I want to take it (where the Mosfets are just under 160F / 70C) This is slightly above the 65C recommended for good longevity. The heatsinks are about 130F/55C. I suspect that if I were to use the Keratherm red silpads or thin mica&grease I would have slightly cooler devices and warmer sinks. 500mV bias = 1.06A = 22.55W/device. This is hot. You could not do this if you build your amp in the 4U chassis without a fan somewhere. "
So it's the matter of temperature and heatsinks size.
I think that I can put 2A to simulations and I'll be on the safe side 🙂
Regards,
Maciek
in that case , having 2 x 0A75 per channel , means you're having 4 x 0A75 for 2 channels
CCS for sim needs to be 3A
regarding Iq ...... it's pretty arbitrary , depends of heatsink capacity mostly
you can count on figures 6L6 gave in his thread as pretty good ones
and , I really never read that Pa said that Aleph J is biased to 2A per channel
I'm pretty sure that value of 2A goes from our estimation, taken from claimed dissipation (juice from wall) numbers .......... and Pa is sometimes slightly misleading with those 🙂
CCS for sim needs to be 3A
regarding Iq ...... it's pretty arbitrary , depends of heatsink capacity mostly
you can count on figures 6L6 gave in his thread as pretty good ones
and , I really never read that Pa said that Aleph J is biased to 2A per channel
I'm pretty sure that value of 2A goes from our estimation, taken from claimed dissipation (juice from wall) numbers .......... and Pa is sometimes slightly misleading with those 🙂
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so , take CCS with value of 4A , then count that everything will be as simmed , or even better
point to exact schematic you are using and describe if you changed any value
for power on and off behavior , few RC constants at pcb are important , especially one in LTP CCS
for power on and off behavior , few RC constants at pcb are important , especially one in LTP CCS
decrease c4 to 1u
situation will also improve somewhat later , when you shorten all those wires between PSU And channels
situation will also improve somewhat later , when you shorten all those wires between PSU And channels
