tarandfeathers
Member
Hi, first post!
I recently built an 8 channel mic pre in which I'm using a 48v supply for phantom power and to power a relay for phase reverse on each channel, plus LED indicators for each function. The total draw with everything turned on should be 440mA. At the moment the 48V supply is sagging to around 20-25V with everything switched on. It's based on a pair of 7824s stacked up, run off an 18-0-18 transformer with the secondaries in series which gives me 56V rectified/unregulated (I tried a 24-0-24 but it came out at 84V, the regulators couldn't take it). I'm guessing this probably isn't a great design, although it's worked in the past at much lower currents with no problems.
Everything still works but I want it rock solid so at some point over the next month I'm going to replace the PSU board completely with a new design. Does anyone have any suggestions for a layout that will handle that kind of current with no sag? The 317 is obviously a popular choice but I'm interested in the TL783 since that won't involve floating the reference... Any suggestions are welcome! Also any advice regarding heatsinking and so forth.
I found this thread which seems to be a similar problem, yet that was solved by using a meatier transformer, and I'm pretty sure mine should be ok.
Thanks!
Daniel.
I recently built an 8 channel mic pre in which I'm using a 48v supply for phantom power and to power a relay for phase reverse on each channel, plus LED indicators for each function. The total draw with everything turned on should be 440mA. At the moment the 48V supply is sagging to around 20-25V with everything switched on. It's based on a pair of 7824s stacked up, run off an 18-0-18 transformer with the secondaries in series which gives me 56V rectified/unregulated (I tried a 24-0-24 but it came out at 84V, the regulators couldn't take it). I'm guessing this probably isn't a great design, although it's worked in the past at much lower currents with no problems.
Everything still works but I want it rock solid so at some point over the next month I'm going to replace the PSU board completely with a new design. Does anyone have any suggestions for a layout that will handle that kind of current with no sag? The 317 is obviously a popular choice but I'm interested in the TL783 since that won't involve floating the reference... Any suggestions are welcome! Also any advice regarding heatsinking and so forth.
I found this thread which seems to be a similar problem, yet that was solved by using a meatier transformer, and I'm pretty sure mine should be ok.
Thanks!
Daniel.