You need to create your text in CMYK, not RGB or use a conversion profile that gives you the black generation you want for the text, knowing that it will probably play havoc with the rest of your image.
If you are using small-to-medium size text, yes, you want just black. You just want 100% K. A minor press misregistration will give you some rather unpleasant color fringing.
In addition, if you are printing type against a white or very light background, your eye will perceive the type as black. In fact, very dark colors, which in color patches are quite distinct, if used as a text color against white will appear black or near black. It’s how your eye perceives them.
I just now had a pie chart in PS where there was a a couple lines of black text (not in the chart itself), and I converted to CMYK using Maximum Black Generation to ensure that the text was on the black plate only — Is my chart going to be hosed or will it be OK?
ps1 – you may not be hosed, but your image might print darker and with less saturation than you intended. If I were you, I would make two separation, one for the text and one for the rest of the image and combine them together to get the best of both. Of course, if it’s just a small illustration, it may not be worth the effort and no one may even care what it looks like.
