Aye, but in pronounciation, the f is not spoken (according to Dillon and Ó Cróinín in TYI), except maybe a h, so to ones ear, in the first conjugation, there is often little differences for a number of verbs:
thógainn vs thóg(h)ainn
d'ólainn vs d'ól(h)ainn
d'fhéachainn vs d'fhéach(h)ainn
Does one devoice the consonant to show the difference?
According to the Erris book, for monosyllabic stems, there is often just a /h/ difference, caillim:
Imperfect:
[xaL'iN']
[xaL'h@]
[xaL'@d s'e:]
[xaL'@d siN']
[xaL'@d siv']
[xaL'@d
si@d']
Conditional:
[xaL'hiN']
[xaL'h@]
[xaL'
h@d s'e:]
[xaL'
h@d siN']
[xaL'
h@d siv']
[xaL'
h@d si@d']
Some other paradigms have the forms having fallen together.
Verns with root ending in /x'/ , /j/, or /w/ might be able to use the voice/devoice tendency (that admitedly, seems weak) as 'léighim' (léim today) has /l'e:
j@d s'e:/ (Imp) vs /l'e:x'@d s'e:/
However, there is no exmaples of voiced/w/ vs devoiced /w/, as the Erris grammar is not very detailed.
I know it sounds a little anal, but if there is no sound difference, one needs to know them some other way