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Class D Switching Power Amplifiers and Power D/A conversion

420W TDA8954TH Overkill? Lithium powered project
420W TDA8954TH Overkill? Lithium powered project
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Old 22nd March 2019, 10:17 PM   #1
eshamp is offline eshamp  United Kingdom
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Default 420W TDA8954TH Overkill? Lithium powered project

I bought a 420W TDA8954TH chipped amp for a passive PA conversion to be powered by LifePo4 batteries.

I have bought a Wharfedale Titan Pro 8, rated at 150w RMS and 500w peak. Is the amp overkill?

I was planning to run at 23.1v, should I reduce the voltage? I understand sounds quality should at least be decent with an underutilised amp. Will reducing the voltage reduce the efficiency and if so would I be better off just buying a smaller capacity amp? Being battery powered, efficiency is key.

Set-up:

Amp: New 420W TDA8954TH Large Power Digital Audio Amplifier Board A+D Class Amp AC24V | eBay

Low pass filter as pre-amp (though looking for a standard bluetooth pre-amp): Low-pass Filter NE5532 Bass Tone Subwoofer Pre-Amplifier Preamp Board 12-24V UK 958748772515 | eBay

Speaker: Impedence 8Ω Titan 8 | Wharfedale Pro - Sound Reinforcement and Live Sound Equipment

Batteries: 23.1v LiFePo4 at 23,800 mAh (potentially 47,600 mAh further down the line for hopefully over 24 hours of battery life)
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Old 23rd March 2019, 12:23 AM   #2
voltwide is offline voltwide  Ireland
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The datasheet of TDA8954 shows that this chip operates with a split supply voltage upto +/- 41Vdc. It is not designed for single supply voltage such as any batteries or accus.
Considering something close to 20V I recommend TPA3116 or TPA3118 in full bridge configuration
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Old 23rd March 2019, 08:31 AM   #3
eshamp is offline eshamp  United Kingdom
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Quote:
Originally Posted by voltwide View Post
The datasheet of TDA8954 shows that this chip operates with a split supply voltage upto +/- 41Vdc. It is not designed for single supply voltage such as any batteries or accus.
Considering something close to 20V I recommend TPA3116 or TPA3118 in full bridge configuration
Thanks but they seem underpowered for my speaker. It seems from tests TPA3116D2 will only deliver 28.1W at 24v and 8ohm. YouTube

Do you know of any amplifiers that can be powered from 24v batteries that can supply the full capacity of my speaker? Wharfedale Titan Pro 8, 150w RMS and 500w peak, 8 ohm.
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Old 23rd March 2019, 12:27 PM   #4
eshamp is offline eshamp  United Kingdom
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I'm not actually tied to 24v, I can go up to 53v. The speakers I have being 150w RMS at 8ohm, I'd like to get the most out of them.
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Old 23rd March 2019, 06:23 PM   #5
Khron is offline Khron  Finland
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I don't suppose you could swap that speaker for a 4 ohm version of the same (assuming there is one available), can you?

It's just that, in most cases, class-D amps (especially chip-amps) aren't rated for very high voltages but are easily capable of large(r) currents, so lower-impedance drivers are kinda better suited.

Sure, there are chips like the TDA898xx series, but they need split supplies, as mentioned above.

For 150W into 8 ohms, according to page 33 of the datasheet, you'd need a +/-27V supply or thereabouts. Although for subwoofer use, i've got a hunch your SPL will be rather limited by the maximum excursion of the woofer at low frequencies (especially in a vented enclosure), rather than available power.
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Old 23rd March 2019, 06:42 PM   #6
Nenola is offline Nenola  Finland
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I wonder if it is possible to connect two of those batteries in series and create a split power supply by taking the 0-line between them?
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Old 23rd March 2019, 08:07 PM   #7
strongbow60 is offline strongbow60  Sweden
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Yes, it is possible to have a center tap with a battery pack.


@eshamp:

Have a look at the page for the TDA8954TH amp. It says it is to be powered by 24V AC transformer and by the sketch (in one of the pictures) is a centertap 24V AC transformer, giving about +- 33 V DC to the TDA.
Also +- 4V tolerance gives minimum +- 28V DC to the amp. The preamp stage can use max 24V. It's going to get fiddly.

It might be a BTL configuration, but with a +- 33V supply you only going to have 120-140 watt out to the speakers. But even that should be an impressive sound volume.
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Old 23rd March 2019, 08:43 PM   #8
DUG is offline DUG  Canada
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Take a look at TPA3255.

Run two 24V for 48V...no need to split supply.

TPA3255 will run 18V to 50+V
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File Type: jpg TPA3255-PWR.JPG (133.2 KB, 220 views)
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Old 24th March 2019, 09:52 AM   #9
eshamp is offline eshamp  United Kingdom
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Thanks for all the replies. For simplicity I could try this DC IRS2092S ?

At 48v I should get about 125W?

I am looking to make a standalone speaker so have been looking for mono amps.
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Old 24th March 2019, 03:48 PM   #10
eshamp is offline eshamp  United Kingdom
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If volts x current = watts, why is it so hard to find high wattage/low voltage class D amps?
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