It is known that orthography has both positive and negative effects on second language acquisition. However, I can't really figure out when the effect is due to the L1, the L2 or both. For example, German obstruents are devoiced in syllable-final position; however, this rule is not represented in the orthography: /bʊnd/ is realized as [bʊnt] but is spelled bund rather than ∗bunt. Research shows that English speakers fail to devoice the final consonants the more they are exposed to orthographic input (Young-Scholten, 2000).
With this in mind, would you say such hindering effect occurs due to the orthography of the L2 (because is not transparent) or due to the L1 (because English has orthographic correlates for both voiced and unvoiced sounds)?