English Translation
I love coffee.
The TTS says コーヒーは instead of コーヒーが.
If it’s the same as what google translate produces, I’d say it’s a が.
They are generally pretty close, but が is a pretty soft “g”, and は would be a more pronounced “w” sound.
Try both in google translate to hear them side by side:
https://translate.google.com/?sl=ja&tl=en&text=コーヒーが好きです。
コーヒーは好きです。&op=translate
It’s not what GT produces. You can check by going to Collections, 500 most common, … button, Manage sentences, search for コーヒー, 3rd sentence down. There doesn’t seem to be a way to produce a link.
I have to agree, it sounds a lot like は. But still, I think it’s supposed to be a が because it does sound different from the は in other sentences.
It sounds more like “va”, while は does sound like a proper “wa”.
Try the sentence 私はコーヒーが好きじゃない。where you have both in the same sentence.
It may also be a special case for が after コーヒー with this TTS voice, because in other places it does sound like “nga”, for example in 彼が私に何て言ったと思う？
In any case, it definitely is a weird edge case of this TTS voice.