Maybe the Champagne yeast causes the sulphur smell??
Lets clarify some yeast stuff here. I think people are getting their yeast strains confused.
2 strains of "wine" yeast have been discussed in this thread. Montrachet and EC1118.
The manufacturer says this about Montrachet yeast.
"This strain is recommended for full bodied reds and whites. It is not recommended for grapes that have recently been dusted with sulfur, because of a tendency to produce hydrogen sulfide in the presence of higher concentrations of sulfur compounds."http://homebrewheaven.com/montrachet-wine-yeast.htm
They say this about EC1118:
"The EC-1118 strain was isolated, studied and selected from Champagne fermentations. Due to its competitive factor and ability to ferment equally well over a wide temperature range, the EC-1118 is one of the most widely used yeasts in the world.
OENOLOGICAL PROPERTIES AND APPLICATIONS
The fermentation characteristics of the EC-1118 - extremely low production of foam, volatile acid and H2S - make this strain an excellent choice. This strain ferments well over a very wide temperature range, from 7° to 35°C (45° to 95°F) and demonstrates high osmotic and alcohol tolerance. Good flocculation with compact lees and a relatively neutral flavor and aroma contribution are also properties of the EC-1118.
The EC-1118 strain is recommended for all types of wines, including sparkling, and late harvest wines and cider. It may also be used to restart stuck fermentations."http://consumer.lallemand.com/danstar-lalvin/ec1118.html
So there is a dichotomy when you say "Maybe the Champagne yeast causes the sulphur smell.", given that EC1118 is a champagne type yeast and it has not caused a sulfur smell for me and Montrachet is not a champagne yeast and it has caused a sulfur smell in some apfelweins. (I think I am the only one using EC1118, btw.)
So Montrachet yeast isn't a typical champagne yeast and thus probably shouldn't be referred to as a champagne yeast. And, as far as I can tell, the sulfur smells were coming from fermentations that used Montrachet.
EC1118 is a champagne type yeast. It is a very clean yeast and has never caused a sulfur smell for me and is not causing one in my apfelwein at this time.
I think a correct statement for you might have been "Maybe the Montrachet yeast causes the sulphur smell??