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Audiophile help please - Ohms and power

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magic:
This is surely the best answer, but if I were to guess just from the marketing numbers alone, I would assume that saturation voltage (how close the output can get to the rails) depends only on peak load current. Then calculate saturation voltage and peak current for the three examples they give and use them as a very coarse guideline.

Siwastaja:
Being class D with MOSFET output stage, and claimed 90% efficiency, the voltage over the MOSFETs is not much, and also does not vary much (relatively to the full output swing). If it would, the MOSFETs would dissipate significant amount of the total power, and cooling those tiny integrated parts would be difficult, so it's easier just to minimize the voltage drop by using large enough MOSFETs (with small enough Rds(on)).

Some limitation to the analog output voltage swing is likely due to the modulation algorithm, i.e., they do not necessarily let the MOSFETs run at 100% or 0% duty.

DW1961:

--- Quote from: Siwastaja on August 02, 2020, 06:25:32 am ---
--- Quote from: DW1961 on August 01, 2020, 11:05:46 pm ---I'm talking speicficallya bout teh amp chip I posted above:

    2 × 50 W Into a 4-Ω BTL Load at 21 V (TPA3116D2)
    2 × 30 W Into a 8-Ω BTL Load at 24 V (TPA3118D2) Diff chip
    2 × 15 W Into a 8-Ω BTL Load at 15 V (TPA3130D2) Diff chip

No other variables. How would I calculate power for 19V?

--- End quote ---

Opening up the datasheet, Figure 13 on page 10 shows the output power at any input voltage. Yes I know; no calculation involved, you were given the answer directly.

They calculated, simulated or measured it, because no one else can know all the internal details of the chip that affect the exact value. Do still note this is just a single figure for a single part, there will always be unit-to-unit variation so even when this graphs says 22W at 19V at 1% THD to 8 ohm load, if you measure that on your system, it might be 21W or 23W. Also your external filter network components affect the power, for example, if you have more resistance than TI did in their test system, you are losing part of the power there.

--- End quote ---

Dude! Thanks. I was close, but the chart looks like abut 21 watts at 19V. I was about 19.6. But, more importantly, there is no way to know without them telling you, and thanks for that.

However, one thing: In the power chart, it looks like at 1% THD, the amp puts out actually 34 watts. I'm also assuming the chart is "per channel?"

Also, another problem: The specs are not for the same amp chip! I just noticed that. They are all different chips, so what does that do for the table?
2 × 50 W Into a 4-Ω BTL Load at 21 V (TPA3116D2)
2 × 30 W Into a 8-Ω BTL Load at 24 V (TPA3118D2)
2 × 15 W Into a 8-Ω BTL Load at 15 V (TPA3130D2)

If the table is for any of the three chips, then the table tells the story.

 It's more like 34 (x2) watts at THD of 1% at 8 Ohms @ 24V. At 21V it's 25 watts x2. At 19V it's 21 watts x2. Am I reading it correctly?

Here is the link to the PDF:
https://www.ti.com/lit/ds/symlink/tpa3116d2.pdf?ts=1596389304658&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FTPA3116D2

emece67:
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