why are bridged gainclones less popular than parallel ones - diyAudio
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Old 16th November 2007, 03:37 PM   #1
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Default why are bridged gainclones less popular than parallel ones

Looking for schematics and ideas for my new bpa-200 (seriously tweaked from the application note) it's quite surprising to found that there are much more parallel designs than bridged ones.

I know that heat generation when bridging is a serious issue, but that's about sound quality.

There are three points at where the bridged topology is brilliant:

Speaker return is not connected to ground and current flows from V+ to V- keeping the reference voltage much more stable and thus improoving stability and sound quality.

They double the slew rate!

They run from lower voltages, this sometimes may be an advantage.

Another interesting thing is the addition of intended offset in the parallel design to allow for a flow of 1A (+0.1 -0.1) between the ballast resistors and making the amplifier capable of giving up to 8 watts while operating in class A and keeping the ability to get more than 100W into class B assuming the amplifier is also bridged (here low voltage is a very important point since it reduces the dissipation coming from the 1A class A bias).

I guess i'm missing something
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Old 16th November 2007, 05:30 PM   #2
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Most power op amps have reasonable output current ratings but they are still not that great considering the voltages that the chips operate at and the loads they are often used to drive. Low impedance loads need more current not more voltage, hence the popularity of paralleling chips to get higher current capability.

As for biasing the chips into class a, there really isn't much point to doing that since they not intended to operate in that manner. You'd be better off building a different class a amp.

You also brought up an interesting point about using lower voltage supplies with a bridged design. There may be some slight sonic advantages to this approach but it will be at the expense of more parts and will require a higher impedance load.
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Old 16th November 2007, 05:36 PM   #3
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If we are discussing GC's the bridged design has somewhat lower THD but is less tolerant of high rail voltages (as the effective impedance is halved).
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Old 16th November 2007, 06:00 PM   #4
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Seems it was alluded too already, bridge design often requires better thermal design since the impedance is lower as seen by each chip/channel. Not sure why one is more popular, the BTL design gives better audio performance in numbers and sound. Common mode noise is not audible while in parallel noise is higher.

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Old 16th November 2007, 07:32 PM   #5
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The problem of current handling can be usually solved using a bridged-parallel design, anyway, it isn't easy to understand why people using auricaps and black gates go for a sonically inferior design to save on heatsinks.

I guess there are more causes regarding low popularity of bridged designs
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