ilford delta is optimized for reletevly big enlargements (20x24'' or something around x17). there are some factors to be taken in order to make highh quality enlargement:
- critically good focused image
- very well exposed and developed negative. note, here the creatitivity and taste plays a very big part. so,some of the combinations u may like cannot be optimized for such a big enlargements. u have to try and experimante.
since u loose the contrast in greater magnification i will be forced to develop longer or to use harder paper. u have to find the correct balance for u. there is selenium toning for the negative which can help very much. note, it is not a magic but if u know to control the process it will add u very much ( more contrast and creaspy detail definition without increasing or changing the grain pattern.)
- the enlarging lense u use is of critical importance. popular nikons (which are very good) meoptas low price schniedrs and rodens are not for this job. most of them are optimized at around x10. even the componon-s is not the best choice but close with its roden competitor. there is rodenstok lense which is specially optimized for those cases but i dont use them - price!
hope it will help u for the next time