0
\$\begingroup\$

Here a schematics of my project:

enter image description here

  • There is only one speaker (the sound is mono)

  • The DAC I will use is a mono DAC, its reference is ES8311 and its datasheet is here: URL. It has two ouputs: OUTP and OUTN.

  • Because of component shortage, I have to use the following audio amplifier: PAM8019 (datasheet : URL). It is a stereo amplifier, it has two inputs (L_IN and R_IN) and four outputs (L_OUT_P + L_OUT_N and R_OUT_P + R_OUT_N).

I have two questions:

  • Is it possible to use this stereo amplifier with the audio DAC?
  • If so, how should I connect OUTP and OUTN to the inputs of the audio amplifier? Mono amplifiers generally have two inputs (IN+ and IN-) so the connections are clear, but in such a case it is a bit unclear

Thanks.

\$\endgroup\$
5
  • 2
    \$\begingroup\$ Is your question really "how do I convert a balanced signal (P/N) into single-ended?" \$\endgroup\$
    – TypeIA
    May 30, 2022 at 10:25
  • 2
    \$\begingroup\$ You have one output channel and amp has two channels. Ignore the second amp channel. \$\endgroup\$
    – Justme
    May 30, 2022 at 10:49
  • \$\begingroup\$ @Justme - That's not the question. The question is how to go from differential outputs to single-ended inputs. \$\endgroup\$
    – WhatRoughBeast
    May 30, 2022 at 11:13
  • \$\begingroup\$ JackOfHearts, by the way, mono amplifiers do not generally have differential inputs. Just like stereo amplifiers, some do, others have single-ended inputs. You're really just combining DAC and amplifiers ICs that differ in their most fundamental characteristics (differential out/input and numbers of channels) , so I'll argue that you'd probably, chip availability crisis being what it is, still are putting yourself in unnecessarily hard places by combining exactly these two ICs. \$\endgroup\$
    – Marcus Müller
    May 30, 2022 at 11:32
  • 1
    \$\begingroup\$ @WhatRoughBeast Well there are two questions, can it be used (yes), and if yes, how. I did not see the second question (multiple questions in one) and for the first part I commented. \$\endgroup\$
    – Justme
    May 30, 2022 at 11:41

1 Answer 1

Reset to default
2
\$\begingroup\$

The problem is not on the input, but on the output side!

The block diagram of the PAM8019 suggest completely independently running PWM modulators for the left and right channel. (they don't necessarily actually are independently free-running. It's just that the datasheet doesn't make any statements that they'd be linked, or linkable, at all. )

That means you cannot in general directly connect the output bridges, because that might lead to shorts. (look at the diagram on page 2 of the datasheet. You'll notice the Push-pull stages. It's perfectly possible that if you connect two outputs together, one push-pull stage will connect the output to VDD, and the other to ground. Now you have a large current flowing from VDD to the first output pin, into the other output pin, into ground. That will make the chip very sad.)

So, if anything, you'd need to have an output filtering state for both channels, and then add them up. But that directly works against the filterless design. So,

Because of component shortage, I have to use the following audio amplifier : PAM8019

You will have to use two speakers, or a different amplifier IC. I'd tend towards the latter.

Alternatively, you can just ignore all outputs for the right channel, and just connect your DAC to the left channel.

But: the DAC you chose already contains, just like your amplifier, a differential output stage. That's annoying, because your amplifier has a non-differential input. The datasheet says the output has "differential output option", but doesn't say how to disable it, so it seems it's always differential.

So, honestly, wrong DAC for this amplifier, wrong amplifier for this kind of job.

\$\endgroup\$
5
  • \$\begingroup\$ @TypeIA true. I was just assuming they didn't want to only use half of the chips total power capacity. \$\endgroup\$
    – Marcus Müller
    May 30, 2022 at 10:21
  • \$\begingroup\$ @TypeIA addressed that. Trying to connect the differential DAC with an amplifier of its own to the single-ended input is just another obstacle. \$\endgroup\$
    – Marcus Müller
    May 30, 2022 at 10:27
  • \$\begingroup\$ Thank you. Does it mean that, if I have to keep on using these two ICs, I need to make sure that the mono DAC can be configured to outputs a single-ended signal, and if so connecting it only to one of the channels of the amplifier? \$\endgroup\$
    – JackOfHearts
    May 31, 2022 at 8:01
  • \$\begingroup\$ if you can do that, it would be easiest. Otherwise, you'd need to figure out how to make the output single-ended. In the easiest case, that can amount to just letting the inverted differential output float and using the non-inverted, but that depends on the architecture of the output stage of your DAC, whihc is completely underspecified. In the more complex case, you'd want to build a difference amplifier to convert differential to single-ended. Honestly. I've checked. Mono amplifier are not that hard to get right now. Spare yourself. \$\endgroup\$
    – Marcus Müller
    May 31, 2022 at 8:07
  • \$\begingroup\$ Thanks a lot, I think I will look for another amplifier. :) \$\endgroup\$
    – JackOfHearts
    May 31, 2022 at 8:44

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.