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Class D PBTL use case - woofer/subwoofer ?

jmf11

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I see in class D amps datasheets some advertising about the PBTL config providing 1 channel with twice the power. However, this only seems effective with low impedance drivers (2-3R).

Looking at datasheets, I don't see 5", 6", 8" drivers with "low impedance": 4-8R seems the norm. Is this correct? In those cases, the PBTL does not looks much relevant.

There seems to be better use cases for subwoofers, by combining dual coils for ex. So PBTL configuration would be relevant only (almost) for subwoofer?

Can PBTL help for woofers ?

Best regards,

JMF
 

fpitas

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.I'm not sure what amps those are, or what PBTL is. Bridging stereo amps to mono, maybe? In any event car stuff uses real low impedance because of the low voltages involved, and the desire for high power. Common domestic drivers are 4 or 8 ohm.
 
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jmf11

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I think of TI TPA/TAS chips (TAS3251, TPA3255...) or Infineon Merus MA12070, MA2304...

PBTL is a design configuration where you "paralel" 2 channels for more current (with same Voltage).
 

fpitas

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I think of TI TPA/TAS chips (TAS3251, TPA3255...) or Infineon Merus MA12070, MA2304...

PBTL is a design configuration where you "paralel" 2 channels for more current (with same Voltage).
Ahhh. Gotcha. Yes, definitely sounds like stuff for cars.
 

fpitas

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Probably for every one of the class D amps we review here, there are 100s intended for cars.
 

voodooless

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I think those schemes are mainly designed to be able to put some large Wattages on the sticker ;). In general though, it’s indeed practical for subwoofers:

 

alex-z

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Most drivers labelled as 4 Ohm are actually around 3 Ohm minimum, and many 8 Ohm drivers are 6 minimum. PBTL is therefore quite useful for driving low efficiency 4 Ohm bookshelf speakers, or MTM designs with parallel 8 Ohm woofers.
 

voodooless

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Most drivers labelled as 4 Ohm are actually around 3 Ohm minimum, and many 8 Ohm drivers are 6 minimum. PBTL is therefore quite useful for driving low efficiency 4 Ohm bookshelf speakers, or MTM designs with parallel 8 Ohm woofers.
The point is that many of these amps already work optimally at 4R. Paralleling them makes them work better for 2R loads.
 
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