I'd rather stick with the well documented Fermaid and DAP. Where do you get yours?
So far, mail order from the US (actually there's an ebay seller I've got FermaidK and GoFerm from).
The Youngs yeast nutrient is di-ammonium phosphate and ammonium sulphate, so both sources of nitrogen - and considerably less hassle than finding pure di-ammonium phosphate. Likely providing the same 200 ppm per gramme per litre nitrogen.
You're reason for wanting to stick to the Fermaid is pretty much why I source it i.e. it's well documented with known provision. Actually that's why I stick mainly to Lallemand products, just that it can be hard work getting anything that's not packaged and aimed at the home brew market.
I'm thinking of contacting the Lallemand office in France, as they're the nearest to me. Your local contact is likely to be
LALLEMAND Specialties GesmbH. Triesterstraße 4a
2353 Guntramsdorf
Austria
Tel : 02236 506 299 - Fax : Fax : 02236 506 299 17
e-mail:
weintechnologie@lallemand.com
www.weintechnologie.at
Though whether they have a minimum quantity for selling or at least a local distribution company (last time I was looking at the France office, FermaidK came in 2.5kg packs and I understand that the minimum was 10kg - don't know for certain as I didn't ask, just what I could work out from the website)........