Hello all, I'm looking at an amp kit on eBay based on a single pair of IRFP240, IRFP9240 MOSFETS.
Class AB MOSFET L7 Audio power amplifier boards KIT DUAL-CHANNEL 300-350W
Are these wattage claims reasonable at the supply voltage specified rails?
Output power of 150W 8R DC + - 56V
300W 4R DC + - 56V
350W 2R DC +-45V
Here's another reference thread. The design is by LJM who seems to have many designs floating around here.
Thanks for any input.
Class AB MOSFET L7 Audio power amplifier boards KIT DUAL-CHANNEL 300-350W
Are these wattage claims reasonable at the supply voltage specified rails?
Output power of 150W 8R DC + - 56V
300W 4R DC + - 56V
350W 2R DC +-45V
Here's another reference thread. The design is by LJM who seems to have many designs floating around here.
Thanks for any input.
300W into 4 ohms... on one pair of mosfets, yeah right... maybe for a very short time before their SOAR is exceeded and they explode.
2 ohms, forget it.
2 ohms, forget it.
Yeah, exactly what I thought.
hmm.. Now to find something in that power range that is fairly simple with a MOSFET output stage.
I'd prefer to find a nice kit of some sort, but a bare PCB would suffice.
hmm.. Now to find something in that power range that is fairly simple with a MOSFET output stage.
I'd prefer to find a nice kit of some sort, but a bare PCB would suffice.
the voltage is good for the claimed power. but one pair of transistors can no way take that abuse.
I made an amp with 6 off this L 7 It sounded very good. I sold it to a friend . He woulkd use it for a 3 unit system and digital filters. For a while he used only one amp in each channel and some very good old speakers ( 4 ohm ) He has used a lot off amps on the system with no problems. He used the L 7 for some months and suddenly the L7 burnt itself and one off the speakers. Voltage was just 47 Vdc. Now I have to take the amp back and pay him the 5500 dk.kr. back as well.
Take care !
It would probably make a nice 50W amp with lower supply voltages. Not bad for the price, IMHO - $40 for 2.
find the datasheet for the output device/s
calculate the total dissipation capacity of the whole output stage.
maximum output power ~ = 25% for mosfets and ~ = 17% to 20% for BJTs if your heatsink can keep Tc< 75°C
eg a two pair output stage using mj21193/4 can deliver ~ 170 to 200W for Tc~85°C (increased from 75 due to Tcmax = 200°C).
If you keep them cooler for your duty, then you can get (a lot) more power output.
calculate the total dissipation capacity of the whole output stage.
maximum output power ~ = 25% for mosfets and ~ = 17% to 20% for BJTs if your heatsink can keep Tc< 75°C
eg a two pair output stage using mj21193/4 can deliver ~ 170 to 200W for Tc~85°C (increased from 75 due to Tcmax = 200°C).
If you keep them cooler for your duty, then you can get (a lot) more power output.
Well, it's a LIE, pure ans simple.
As of "having many designs floating around", I beg to disagree.😡
All I found was schematic less commercial posts, where the best (still absolutely useless) was a screen capture from some simulation program (not a PCB design one) with no parts values and many actually covered by the audio voltmeter image, a bad joke.
He also does not send schematics with kits 😱 , uses non standard pinout parts on purpose and even brags about
😡
Indeed?
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