# Need Clarification About Bridge Tied Load x2 Amps and Power Supply Amperage

#### DWD1961

##### Gawd
When using bridge tied load, will your power supply need to have double the amperage in order to get the benefit from using BTL?

ex:

Power Supply 24V @ 5A
Amp Chips: Both amps need 24V @ 5A to meet their single maximum power rating.

So, if you use x2 of those amps, will yuor power supply amperage need to double in order to supply the addition power?

#### Zepher

##### [H]ipster Replacement
What do you think?

#### DWD1961

##### Gawd
Ok just checking if I understood it right or not. So BTL just allows for more voltage from teh same PSU, becasue of sine inversion, so the power supply voltage stays the same, but, again, something has to increase, which is amperage? If so, got it.

#### B00nie

##### [H]F Junkie
Ok just checking if I understood it right or not. So BTL just allows for more voltage from teh same PSU, becasue of sine inversion, so the power supply voltage stays the same, but, again, something has to increase, which is amperage? If so, got it.
Bridging effectively halves your impedance -> more current is required. Remember also that if you use a 4 ohm speaker in a bridged amp, the amp must be stable to 2 ohm load.

#### DWD1961

##### Gawd
Bridging effectively halves your impedance -> more current is required. Remember also that if you use a 4 ohm speaker in a bridged amp, the amp must be stable to 2 ohm load.
Yes, remember the ohms thing. My main question was that is you are using BTL you don;t get extra power from thin air. You effectively need to double amperage to get the benefit from bridging.

While were at it, what about the benefits and requirements when running 2 amps in parallel?

#### B00nie

##### [H]F Junkie
Yes, remember the ohms thing. My main question was that is you are using BTL you don;t get extra power from thin air. You effectively need to double amperage to get the benefit from bridging.

While were at it, what about the benefits and requirements when running 2 amps in parallel?
The benefits are obvious, with a single amp of, say, 10 volts max voltage, you can create a sine wave of 10 volts. When you couple it with another amp of 10 volts with an inverse signal, you can have +- 10 volts i.e. 20 volts overall output, doubling the power output. People who are familiar with car amps most likely know this effect, practically all modern car radios use a bridged amp to create a usable power from the low 12V line. A non bridged car amp (without a switching power supply) can provide only 7,2 watts of power and a bridged one provides 14,4 watts. Most likely the player will boast a 2x50 watts or even 2x100 watts With the exception of rare cases a car radio will have only 2x14,4watts of power.

With a switching power supply it's possible to get thousands of watts out of the 12V battery, but the current requirements increase to hundreds of amps also (you can actually weld metal with the best of the amps). Some car amps are stable to 0,25 ohms of loads. But when impedance drops, the damping factor of the amplifier drops also so the increase in power is at the cost of speaker control. If you run low impedance systems it's necessary to keep your speaker enclosures well damped if you want good quality sound since the amp is pretty much powerless in damping factor.

Damping factor, however, is not such a big deal as advertised because even the slightest impedance in the speaker cables will drop the theoretical damping factor from, say 200-300 to closer to 1-1,5. So instead of focusing on your amplifiers damping factor, get a low, LOW gauge speaker cables to keep your resistance/impedance/inductance down. It's what dictates damping and high frequency drop.