Author Topic: Driving a speaker with CODEC analog output  (Read 606 times)

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Offline zphazeTopic starter

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Driving a speaker with CODEC analog output
« on: June 17, 2020, 05:41:11 pm »
Hi,

I'm using a SOM (System on module using NXP iMX8M) that has an option to use a WM8904 codec.
The thing is that, on the SOM, I can't access LINEOUT, only HPLOUT and HPROUT (output amp).

I want to drive a speaker with an OK quality mono signal, so I will use a summing opamp and then output the signal inside a LM4862.

Speaker I'd like to use : https://www.digikey.ca/en/products/detail/cui-devices/CDS-15158-SMT-TR/5355550

Now, according to the datasheet, the WM8904 has a built-in "Wolfson class W headphone amplifier". The datasheet is confusing.
Never heard of a class W amp. What I'd like to know is what kind of output should I expect from this amplifier?
The WM8904 seems to be powered by a 1.8V smps. But I wonder if it's DC-biased or not? The datasheet seems to
say the headphone output is ground referenced, does that mean it goes from something like 1.8V to -1.8V?

I wonder if anyone more familiar with this kind of IC could help out! Thanks! It's only really to power a small speaker.
 

Offline TheMG

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Re: Driving a speaker with CODEC analog output
« Reply #1 on: June 17, 2020, 06:36:14 pm »
Class W is a meaningless marketing term, not an actual amplifier class.

From their description of it, sounds like it's a class G or H, essentially a traditional class AB output but with dynamically variable supply voltages to limit power dissipation.
 

Offline zphazeTopic starter

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Re: Driving a speaker with CODEC analog output
« Reply #2 on: June 17, 2020, 06:54:57 pm »
I see. Marketing huh.

Still, if it's class AB that would mean there is no actual DC offset?
 

Offline Marco

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Re: Driving a speaker with CODEC analog output
« Reply #3 on: June 17, 2020, 08:31:14 pm »
The block diagram shows the signal outs and ground directly connected to a jack, so yeah presumably it needs no dc blocking capacitors.

PS. oh the datasheet explicitly says it doesn't need capacitors.
« Last Edit: June 17, 2020, 08:33:13 pm by Marco »
 


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