Recently built one of two AJ mono-blocks and have a question for Mr. Pass or anybody about max temperature on the fets. I can hold my hand on the HS's indefinitely, but more concerned about temp of fets. What range in C should i be looking for? Much thanks to Bill who help me do something i could not have done by myself without either blowing something up or buying multiples of new parts.
Offset side to side is 30mV and offset at terminals is 2mV. Both after about an hour. Bias is a little over 1A. HS's can take more, but am more concerned with mosfets,
Offset side to side is 30mV and offset at terminals is 2mV. Both after about an hour. Bias is a little over 1A. HS's can take more, but am more concerned with mosfets,
The device is rated at 150 watts at a 25 deg C case temperature,
derate at 1.2 W per deg C.
I like to run them around 25 watts, and I have run them as
high as 50 watts without excessive failure rates, but this is
heat sink dependent.
I am running my fets @ 25W but the case temp is 40C. Heatsinks can be touched indefinitely. Measures at exposed metal cutout on side, fets are hotter than 50C.
De-rating them according to above figures drops max dissipation to 130W.
Am i getting poor heat transfer if HS's are at slightly different temp than fet case
Worried about turn off thump(push out). More severe than turn on. My driver is FR and has max x-max of 8mm which only 6mm should be used for peaks in response. Turn off looks to be 1/4" of travel. Any suggestions? Tried searching but no answers. Perhaps my wording is wrong. I will probably get speaker protection circuit, but while waiting, would like solution if possible.
everything counts
give us proper schematics of amp an PSU , along with pictures
it's hard to use crystal balls , these winter days
Using Brian GT boards. Thump is not unusual, from what I have read, and has to do with uneven DC drain, I think. Amp is functioning great otherwise. Plus, you have been around the block enough to draw the schematic in your head
I have built two pairs of Aleph Js with standard schematic and standard PS. Turn off thump exists for Aleph J, due to uneven drain at power off. When connected to speakers it lasts for a very short while but the excursion is big at turn off. I have had no problems. My fostex fe206s have no problem dealing with the turn off.
same old drek
replace 220uF on neg leg input with shortie , re-set bias and offset and inform us ;
but - be aware that's almost carbon copy of commercial Aleph amps ; be sure that Papa is releasing just foolproof and idiotproof stuff .
so - even Lowther is surviving
I don't mind being an idiot, just don't want to hurt drivers. What is to be accomplished by removing Cap on -input? A bird whispered in my ear that it could be problematic.
turn off thump dealt with. Built second monoblock, everything checks out good with light bulb tester. Pull light bulb, lower variac voltage to set bias safely. Increase voltage to 80VAC, entire negative side has Vdrop across source resistors of about .500+/-. The positive side(Aleph CS) has two source resistors showing .380V and the third .680 and climbing. Checked Vdrop across fet and first two are 4.2V. Remaining fet D-S Vdrop is slowly dropping apparently in sequence with source resistor drop going up. Does this mean my fet is bad, having no internal resistance.
Seems like there's a lot going on at the top, but the feet are groovy.
Definitely won't take the prize for neatness. More pics to come of a prettier version, giant feet included.
turn off thump dealt with. Built second monoblock, everything checks out good with light bulb tester. Pull light bulb, lower variac voltage to set bias safely. Increase voltage to 80VAC, entire negative side has Vdrop across source resistors of about .500+/-. The positive side(Aleph CS) has two source resistors showing .380V and the third .680 and climbing. Checked Vdrop across fet and first two are 4.2V. Remaining fet D-S Vdrop is slowly dropping apparently in sequence with source resistor drop going up. Does this mean my fet is bad, having no internal resistance.
I have the same "turn off thump" issue that is pretty bad. How did you solve it?
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