Pronouncing th in 'thanks' or 'thank you' as in 'that' (/ð/)

[She'lock Holmes]

Hello,
I noticed that a very small minority of Americans pronounce 'thank' with a voiced fricative /ð/ instead of the GenAm typical /θ/. Is it a known feature of any group in the USA?

 

[natkretep]

Can you say when you heard this pronunciation? I don't recall hearing this.

 

[She'lock Holmes]

Can you say when you heard this pronunciation? I don't recall hearing this.

I heard it from the voice acting of Matthew Charles and I think Dough Cockle too; apparently, both are Californians. I am sure I didn't mishear it as several threads on the internet discuss this phenomenon but are quite vague on who does it.

 

[dojibear]

I haven't heard it, so I don't think it is common.

I'm guessing (since I haven't heard it) that it may happen more often in certain situations. By that I mean with certain sounds before "thank".

 

[elroy]

Never heard this.