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Class D Switching Power Amplifiers and Power D/A conversion

TI TPA3255EVM
TI TPA3255EVM
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Old 6th October 2017, 08:56 PM   #21
DPH is offline DPH  United States
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How many modules are you powering, Variac, and what speaker impedances? For me, 2 modules on 8 ohm drivers doesn't make sense to go above 600 W. But it's certainly a nice psu!
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Old 6th October 2017, 09:12 PM   #22
doctormord is offline doctormord  Germany
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LRS-350-48
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Old 6th October 2017, 11:07 PM   #23
bk856er is offline bk856er  United States
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TI TPA3255EVM
Arrow has good prices on meanwell units. I picked up a 36V LRS 350 for my Wiener PRO and just today took delivery of a Cresnet 600W 48V for the EVM.

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Old 7th October 2017, 09:02 AM   #24
Kay Pirinha is offline Kay Pirinha  Germany
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I've found this one at a German vendor, which is adjustable from 43 to 55 VDC: https://www.reichelt.de/Schaltnetzte...35455003828724. Seems to fit optimally!

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Old 9th October 2017, 05:52 PM   #25
Kay Pirinha is offline Kay Pirinha  Germany
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A little basic question to these chips, especially the TPA3255: To achieve more tham 300 watts from a single +53.5V rail, bridging two power amplifier sections is a demand. And yes, the evaluation board can also be configured as four separate amps. But how does it work to get monophonic 600 watts from this chip, as the specs state?

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Old 9th October 2017, 05:56 PM   #26
DPH is offline DPH  United States
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Bridged paralleled into a very low load. (2 ohm?) I.e. using all 4 channels together.
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Old 9th October 2017, 06:43 PM   #27
Tubelab_com is offline Tubelab_com  United States
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There are some graphs on the TPA3255 datasheet that reveals the power, supply voltage, load impedance and configuration required to get a particular power output.

There are graphs at 1% THD and 10% THD. AT 1% with a 2 ohm load and a 53 volt supply the most you will get is 550 watts, but that's at +75C. You might get a few more watts at a lower temp. Max power at 10% distortion is over 600 watts.
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Old 9th October 2017, 09:31 PM   #28
doctormord is offline doctormord  Germany
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How would you get more watts at lower temp? Even 50W more
is way less than 1dB, beside the fact keeping the casetemp below 75degC. Even the EVM isn't doing that much power with the heatsink supplied. (These performance specs are tested with modified heatsink and massive forced cooling)
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Old 10th October 2017, 02:25 AM   #29
Tubelab_com is offline Tubelab_com  United States
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Figure 24 on page 13 gives output power VS case temperature for 3 different load impedances. For the 2 ohm case, about 670 watts are obtained at 0C but only about 595 watts are available at 100C. 75C provides about 620,,and 50C about 640, while 25C gets you about 655 watts.
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Old 10th October 2017, 05:54 AM   #30
Variac is offline Variac  Costa Rica
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So i’m Planning to use TPA 3255 to power my Linkwitz LX 521 woofers, which are multi-amped.

Each of 2 channels has two of these 4ohm subwoofers because they are open baffle so need some mojo. I’ve watched the speakers in action and the cones move a Lot.

Seas L26RO4Y 10" Subwoofer - 4 Layer VC - (D1004-04)

So I have a choice of putting the woofs in parallel for 2ohms, in series for 8ohms.
Looks like 2 ohms is Ok?

So my ultimate plan is one tpa3255 for each channel. I ordered a second 3255. Paid the $150 for this one, hope they let me get it. 10% distortion doesn’t work for me, even occasionally, so I want plenty of headroom.

Its occurred to me that a better approach might be to split each 3255 into 2ch and use one channel into each 4ohm driver per side.

I suspect I’m just a bit jumpy about a 2ohm load, but do these amps handle that fine? Which the best option?
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Last edited by Variac; 10th October 2017 at 08:48 PM.
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