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Registered Member #509
Joined: Sat Feb 10 2007, 07:02AM
Location:
Posts: 329
One relatively slow day at work, I was snooping though some cabinets and found a plastic box with this in it, and I played around with it for a bit.
Pretty small boardfor 500w, even if the heatsink could deal with growing a bit.
I nosied though the datasheet and was shocked by how simple the schematic was. I dont know what I was expecting but it sure was more.
Anyway, after playing with it and hooking it up to a subwoofer, and starting to hit the current limit on my puny 1A supplies, I examine the schematic, and find it pretty similar to the SSTC schematics Ive seen around here. If you were to take off the output LC filter and put in a TC primary, with an impedance of 4 ohms (to keep from overloading the amp) @ 400khz, would it be that easy to make a audio modulated SSTC?
Considering a 4 ohms seems like a lot for just a few turns of copper, I was turned off at first. But I did a bit of math, and came up with only 1.6 uH needed
Now granted that particular kit is $700+ if I remember right, I'm not suggesting using that particular one, but class D amps on the cheap arent that hard to find.
Does this seem reasonable or did I miss something and I'm barking up the wrong tree?
Registered Member #1024
Joined: Sun Sept 23 2007, 10:56AM
Location: Northern NSW, Australia
Posts: 95
I'm convinced, sounds reasonable. I strongly reccommend you try it and let us all know how you go. Then we will all know I'm sure there is a long list of reasons not to try it, but I'm happy to ignore them if you are .
Registered Member #146
Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055
It seems much cheaper to build your own, and it would likely be better suited for the task.
But if indeed you need an "off the shelf" solution, its pretty close to being right. I wouldnt try to audio modulate it right off the bat, i dont know if it would like the DC offset on the primary of the SSTC. Have a good DC blocking cap on the primary at least! The thing is, as an audio amp, you adjust the PW from 50% to modulate the average "DC" output, and you rely on the low frequency impedance of the speaker to still be about 4 ohms. With your 1.6uH primary, the impedance may be 4 ohms at 400khz, but at like 100hz (audio modulation) its like a small fraction of an ohm. Really, the modulation scheme is wrong for playing music through a SSTC.
Registered Member #509
Joined: Sat Feb 10 2007, 07:02AM
Location:
Posts: 329
Steve Ward wrote ...
It seems much cheaper to build your own, and it would likely be better suited for the task.
But if indeed you need an "off the shelf" solution, its pretty close to being right. I wouldnt try to audio modulate it right off the bat, i dont know if it would like the DC offset on the primary of the SSTC. Have a good DC blocking cap on the primary at least! The thing is, as an audio amp, you adjust the PW from 50% to modulate the average "DC" output, and you rely on the low frequency impedance of the speaker to still be about 4 ohms. With your 1.6uH primary, the impedance may be 4 ohms at 400khz, but at like 100hz (audio modulation) its like a small fraction of an ohm. Really, the modulation scheme is wrong for playing music through a SSTC.
ok, makes sense, I was just wondering if this should be a project I could keep in mind if I ever came across and old junked amp, I.E. cost of the amp doesnt really factor in too much. I wasnt suggesting buying a new 500W+ amp and hacking it up :p
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Off the shelf SSTC driver?
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