hey now,
i'm attempting to build the SOZ amplifier as a test project using parts i have lying around, before actually building the real deal with massive heatsinks. the aim of this project is to get ~2W from a pair of monoblocks into 2 altec 755a's mounted in an open baffle (so efficiency is not a consideration, but NOT blowing up the speakers IS!)
here's the 2 questions, i apologize in advance for their complete stupidity, if applicable
1- i set up the circuit to match my MOSFETS's - IRF540 as described in the PASSDIY.com how-to section. Used a 24VDC power supply and a 50ohm 10W resistor. the problem i have is that after plugging in the MOSFETS's the Vgs starts out as ~3.9V, but falls down to ~3.7V, presumably as the transistor heats up, in approximately 1 minute. what am i doing wrong? or how am i supposed to match these?
2- i plan to use 4 regulated power supplies (lab retirees from the university) that each source 24VDC-8A, (running +/- 24VDC rails for the 2 monoblocks). but unfortunately, found that they hum! i.e. mechanically vibrate (electrically rock stable - measured AC is < 0.1mV). is this just because these have old transformers with shaky laminations? is there something i can do to fix them up, i would hard pressed to build something like these on my own! my backup plan was to use 4 12-volt car batteries and setup a relay to put them on trickle charging when amp is switched off. is this a feasible idea?
i'm attempting to build the SOZ amplifier as a test project using parts i have lying around, before actually building the real deal with massive heatsinks. the aim of this project is to get ~2W from a pair of monoblocks into 2 altec 755a's mounted in an open baffle (so efficiency is not a consideration, but NOT blowing up the speakers IS!)
here's the 2 questions, i apologize in advance for their complete stupidity, if applicable
1- i set up the circuit to match my MOSFETS's - IRF540 as described in the PASSDIY.com how-to section. Used a 24VDC power supply and a 50ohm 10W resistor. the problem i have is that after plugging in the MOSFETS's the Vgs starts out as ~3.9V, but falls down to ~3.7V, presumably as the transistor heats up, in approximately 1 minute. what am i doing wrong? or how am i supposed to match these?
2- i plan to use 4 regulated power supplies (lab retirees from the university) that each source 24VDC-8A, (running +/- 24VDC rails for the 2 monoblocks). but unfortunately, found that they hum! i.e. mechanically vibrate (electrically rock stable - measured AC is < 0.1mV). is this just because these have old transformers with shaky laminations? is there something i can do to fix them up, i would hard pressed to build something like these on my own! my backup plan was to use 4 12-volt car batteries and setup a relay to put them on trickle charging when amp is switched off. is this a feasible idea?