Yep, here is one of those powerful PS that can be used if bridging is required:
SMPS3KA700 - Switching Power Supply Hypex 85V 3000W — Power Supply | Axiomedia
It has to do with the way these are bridged. As most know, an amplifiers maximum output is set by its maximum current and voltage. The higher the load impedance the more that the rail will set the limit. The lower the impedance the more that current will set the output limit.
with a BTL or bridge tied load, you double the voltage differential because the amplifier is run in differential mode. This doubles the power as each half of the amplifier is also now seeing half the impedance. Assuming sufficient current, an 8 ohm load would see double the output. But many then can’t handle 4 ohm loads because each half of the amp sees a 2 ohm load.
This amplifier is already a BTL design. So the voltage differential is as high as it can get. So they do a Parallel BTL version in which the amps sit on top of each other. This means the voltage differential doesn’t increase. You simply doubled the available current. It also means each amp is actually seeing a higher impedance, not lower. So suddenly the amp can do much more power into low impedance loads.
this amp was not current limited in the slightest at 8 ohms, was slightly current limited at 4 ohms, and obviously was very current limited at 2 ohms. By paralleling the amps in a PBTL arrangement you get the higher output into 2 ohms.
Hello Matthew, I would like to suggest that we avoid the kind of confusing or misleading explanation such as the seemingly popular/often reference to "...in BTL connection each half of the amp (or just the bridged amp) seeing half the impedance. In fact in BTL, the two "half" of the 2 channel amp still seems the same impedance. The simple fact is, in such connection the output voltage at the speaker terminals is doubled, vs the same amp but not bridged. I know you didn't start such misnomer lol.., but would like you to join me in trying to right the wrong, not a big deal but would be nice to do as it helps turn the tide in may be 50 years.
In reality such connection for bridging a 2 channel stereo amp could produce
4 times the output power if the amp is not current limited. That is actually more intuitively understandable because the bridged amp gets 2X the voltage so 4X the power. It would typically and more practically to be rated 2 times the power because of current limitation of most power amps that are not truly rated for 2 ohm (or even 4 ohm, in some cases) loads.
So power amps that are truly rated for 4 ohm load should be able to deliver close to 4X the power into an 8 ohm load. And again, in any case, we both know that the bridge amp still sees the same 8 ohm load, you get more power output because of the higher available voltage at the speaker terminal. It should be easy for even non technical people to understand when you put two 1.5 V battery in series you get 3 V. Too bad, in the audio world people seemed to want to find some seemingly smart way to explain things when it really doesn't.
The term RMS power, or 100 W RMS is another example, that started as something very wrong technically but as more people doing the same, hearsay etc., it ended being accepted as the norm, another misnomer.
I can create a 2 ohm load with my resisters but I need to wire them into a voltage divider because the QA devices I use can’t handle the voltage it would get from a 2 ohm load at that power output level. Since I only have 8 ohm resistors it’s not possible to do that. So I need to buy some 2 ohm resistors as well to create the 2 ohm load (parallel series wired). I didn’t see a reason to test it though. It had already been tested and I trusted who tested it.
Agreed, that's too much work for little gain, not worth it. Personally I wouldn't bridge such amps unless I have the schematics to see what kind of output devices are used, and also the power supply specs.
I would definitely feel safe and good to bridge amps such as the 100 W rated class AB Benchmark AHB2 that uses a form of switching power supply, yet it could be bridge to output 380 W 8 ohms and 480 W 6 ohms.
