Hello there all,
It came to my attention years ago that 'common mode' noise could be reduced [in a cancellation way] by running amplifiers in Bridge Mode configuration.
More recently I read that depending on 'pre-stage' phase orientation, third harmonic distortion can actually be changed to predominantly second order.
Could someone please elaborate regarding this + the general Pros & Cons of Bridge Mode 🙂
It came to my attention years ago that 'common mode' noise could be reduced [in a cancellation way] by running amplifiers in Bridge Mode configuration.
More recently I read that depending on 'pre-stage' phase orientation, third harmonic distortion can actually be changed to predominantly second order.
Could someone please elaborate regarding this + the general Pros & Cons of Bridge Mode 🙂
Do you have references to the mentioned ancient and more recent information about this topic?
What do you mean with " 'pre-stage' phase orientation" - position of musicians on stage, or otherwise?
I'm trying to wrap my mind around this phasing of flutes and violins when post-processed them through a bridge mode...
Would that reduce third harmonics (even if the composer intended this in the first place!) and promote even harmonics?
Imho, in general is bridging favourable because of the better power control of the loudspeaker, but this requests a double set of hardware.
What do you mean with " 'pre-stage' phase orientation" - position of musicians on stage, or otherwise?
I'm trying to wrap my mind around this phasing of flutes and violins when post-processed them through a bridge mode...
Would that reduce third harmonics (even if the composer intended this in the first place!) and promote even harmonics?
Imho, in general is bridging favourable because of the better power control of the loudspeaker, but this requests a double set of hardware.
Bridging basically allows half the supply voltage, and naturally supports differential inputs (hence common-mode noise rejection). Distortion tends to be increased as the load impedance seen by each amp is halved, so an 8 ohm loads looks like 4 ohms, etc.
Don't know about this, sounds dodgy to me. I'd predict both increasing due to the heavier load, all else being equal. However even-order distortion can be addressed by better symmetry, and in bridge mode both polarities of output voltage are driven by both NPN and PNP output devices, which is more symmetrical than single ended, so 2nd harmonics might reduce a bit due to this, but higher orders are likely dominated by loading effects (cross-over distortion is sensitive to loading), and odd-orders cannot benefit from even symmetry at all.
Besides half-wave symmetry, there could be a reduction in even harmonics due to cancellation between the two legs. For example, the fundamental phase on one of the legs is 180* with respect to the other (BTL) and its second harmonic would therefore have a phase turning of 360* which is the same as that of the other leg. Estimating the phases for the higher order even harmonics in a similar manner should be fairly easy.
Anyone looking to encourage even harmonics shouldn't be looking at bridging at all.
Anyone looking to encourage even harmonics shouldn't be looking at bridging at all.
Is this meant to be more of a question of what are the similarities between bridging and balancing?
To clarify,
I started the Thread to discuss the Pros & Cons of amplifiers in bridge mode > IE. amplifiers where no speaker connection is ground.
I wasn't referring to 'Balanced Audio' connection > IE. 3 pin XLR situations.
I'm even hoping that some dedicated Bridge Mode amp. schematics might be posted > even bridge mode Chip Amps.
I'm just interested in the whole 'general topic' 🙂
https://www.google.com/search?q=fam...SBw4wLjQuMTYuMi4xLjctMaAH6sAB&sclient=gws-wiz
I started the Thread to discuss the Pros & Cons of amplifiers in bridge mode > IE. amplifiers where no speaker connection is ground.
I wasn't referring to 'Balanced Audio' connection > IE. 3 pin XLR situations.
I'm even hoping that some dedicated Bridge Mode amp. schematics might be posted > even bridge mode Chip Amps.
I'm just interested in the whole 'general topic' 🙂
https://www.google.com/search?q=fam...SBw4wLjQuMTYuMi4xLjctMaAH6sAB&sclient=gws-wiz
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This post may be of interest:
https://www.diyaudio.com/community/threads/topping-b100.417717/page-17#post-7881065
https://www.diyaudio.com/community/threads/topping-b100.417717/page-17#post-7881065
Bridge or floating load is just that, a floating load.
Any whoopsie Doo to Ground or short.
Has the pleasure of destroying 2 amplifiers instead of One.
You do get more voltage swing past the voltage limit of the amplifier.
But the load is floating. Each amplifier will see only half the load.
So for a little more voltage swing you drink up 2x more current.
The load is half for each amp now, so distortion goes up and it gets hotter.
Distortion goes up. No benefit.
Except for add copy claiming more power.
And musicians get to " imagine" there is more power, reality overheating the amps.
When the speaker load will reach distortion with less power than the non bridge amplifier.
Car stereo guys get lost in the concept too. Might as well pull more current
from a low voltage source that is already current limited.
And again the speaker usually reaches distortion with less power than the non bridge power
anyways. Again "imaginary" power and hot amps.
The added benefit is killing 2 amps, the amps power supply and your alternator too....yay
Any whoopsie Doo to Ground or short.
Has the pleasure of destroying 2 amplifiers instead of One.
You do get more voltage swing past the voltage limit of the amplifier.
But the load is floating. Each amplifier will see only half the load.
So for a little more voltage swing you drink up 2x more current.
The load is half for each amp now, so distortion goes up and it gets hotter.
Distortion goes up. No benefit.
Except for add copy claiming more power.
And musicians get to " imagine" there is more power, reality overheating the amps.
When the speaker load will reach distortion with less power than the non bridge amplifier.
Car stereo guys get lost in the concept too. Might as well pull more current
from a low voltage source that is already current limited.
And again the speaker usually reaches distortion with less power than the non bridge power
anyways. Again "imaginary" power and hot amps.
The added benefit is killing 2 amps, the amps power supply and your alternator too....yay
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The expectation is that if you use bridge tied amps they are already adequately rated for half the load resistance... Using higher voltage single ended amp to get the power also has drawbacks, such as it being harder to get adequate safe operating area with higher voltage, and the output voltage itself may fall under different regulatory framework (i.e. those for mains voltage).
For class D amps bridge-tied is the normal way as it has lower EMI.
And if you actually think about it for a bridge tied setup shorting either speaker wire to ground only affects one of the amplifiers, not both.
Some commercial PA amplifiers take advantage of the BTL arrangement to provide redundancy - if one amp fails its output can be bypassed to ground - so you still have output, albeit 6dB less - far preferrable to nothing!
For class D amps bridge-tied is the normal way as it has lower EMI.
And if you actually think about it for a bridge tied setup shorting either speaker wire to ground only affects one of the amplifiers, not both.
Some commercial PA amplifiers take advantage of the BTL arrangement to provide redundancy - if one amp fails its output can be bypassed to ground - so you still have output, albeit 6dB less - far preferrable to nothing!
There are a number of benefits from using a BTL format for an amp. Starting with the basic common mode noise rejection if you have a balanced source to getting more power from a given voltage supply etc. Another is that the load current does not pass through the ground circuits of the amp, something that can be pretty significant. The load current goes from supply to supply. Filter caps tied from supply to supply will be substantially more capable that caps in series tied to ground. Also since less swing on the amp is needed you get a doubling of slew rate.