Actually the need for a soft-start is not dictated by anything on the secondary side of the transformer, but by the inrush current due to core saturation on applying voltage. So add as much capacitance as you like 🙂
" So add as much capacitance as you like "
You going to buy everyone a new bridge rectifier when it blows?
I thought not.
With a large VA transformer and large filter caps the diodes in a bridge will blow when you go over about 30,000µF and the transformer is over 500Va or so.
Been there, done that.
You going to buy everyone a new bridge rectifier when it blows?
I thought not.
With a large VA transformer and large filter caps the diodes in a bridge will blow when you go over about 30,000µF and the transformer is over 500Va or so.
Been there, done that.
You make a valid point, but it does depend on the bridge rectifier used. For the kind of conditions you suggest I would recommend a big meaty square one or big TO-247 diodes, at least 20A continuous rated.
The practical limits on how much capacitance can be added to these amps may be limited to how much you can fit on the *board*. It's not an ordinary power supply, the caps are in the signal path providing double-duty as supply reserviors and AC coupling of the output signal (inside the feedback). Go putting in great big soup cans with running wires all over inside and you may or may not end up with a stable amplifier.
Crown and Crest use more conventional amplifier topologies and these are more amenable to these type of 'upgrades' then the QSCs or their clones.
Crown and Crest use more conventional amplifier topologies and these are more amenable to these type of 'upgrades' then the QSCs or their clones.
cheers for the continued input guys, (no pun intended). It's a shame the rail voltages are so high as I have many large high quality 63v philips caps and 100v caps aren't so common to come across.
You can see the rectifiers are KBPC250w's but I can't find any datasheet on them as they appear to be make by some chinese company, they do look pretty heavy duty though.
I can't go crazy with caps anyway as there isn't physically the room in the case, I'm already going to have to use low gauge cables going between the caps to other areas of the case, not ideal.
Assuming the rectifiers are able to take the current, will 30000uf per rail, per channel still be ok?
Also I'm set to put a 1r 20w resistor and 500nf in series as the zobel network
You can see the rectifiers are KBPC250w's but I can't find any datasheet on them as they appear to be make by some chinese company, they do look pretty heavy duty though.
I can't go crazy with caps anyway as there isn't physically the room in the case, I'm already going to have to use low gauge cables going between the caps to other areas of the case, not ideal.
Assuming the rectifiers are able to take the current, will 30000uf per rail, per channel still be ok?
Also I'm set to put a 1r 20w resistor and 500nf in series as the zobel network
The bridge is rated at 10A, the W may be another number - 2,4,6,8 maybe - which denotes the voltage.
Another factor saying this amp is no way rated to 700W. A 400W into 4 ohms class-d amp (which is a lot more efficient than a class-ab like the Behringer) pulls around 12 amps.
Also taking djk's advice, this bridge may well pop if loaded with more capacitance.
Another factor saying this amp is no way rated to 700W. A 400W into 4 ohms class-d amp (which is a lot more efficient than a class-ab like the Behringer) pulls around 12 amps.
Also taking djk's advice, this bridge may well pop if loaded with more capacitance.
richie00boy said:
If you're gonna do this at all, replace the freakin bridge. 50 amp bridges cost a whopping five bucks!
AC draw ratings are NOT at full power. They're at 1/8 power. Put a sine wave into this thing and it will draw about 18A off the wall, and get blistering hot, and blow breakers. And it won't quite put out 700W/ch, either.
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