Ginger beer has sulphur smell

[MadMarble]

Had a crack at a ginger beer recipe I found on the forum (sorry can't remember who posted it), down sized to one gallon as a trial run in the hope of doing a full five gallon soon.
5 gallon recipe
1kg Fresh grated ginger
5tsp Dried ground ginger
1tsp Cream of tartar
2 lemons
2 limes
2.5kg Sugar
2tsp Yeast nutrient
1 sachet champagne yeast
I started everything off in a fermenting barrel after boiling for 30mins and dissolving the sugar. After about five days I racked into a demijohn. I kept checking the gravity and when it was stable I back sweetened for shmbo and bottled with priming sugar. After two weeks priming at 20 degrees I cooled and served after another week.
Now here is the problem -
When I back sweetened everything tasted fine. When I opened a bottle and decanted into a glass it was nicely carbonated (slightly chuffed first time bottling), but there was a sulphur smell to the brew. Any ideas on what caused it? Would it have gone away with longer maturation?
Although I was still pleased overall (6.5%) I would have liked more ginger flavour up front. Any ideas on how to achieve this. Heat was fine from the dried ginger just lacked that strong ginger flavour in the mouth.

[Mther]

I brewed a strawberry cider once using champagne yeast and I had that unpleasant aroma which you can also notice in a warm cheap champagne. Smells like fart or cooked cauliflower, but it is not too intense. If that's the case, I think it is because of the yeast, it's not DMS. If it is too intense then maybe your batch is infected.

[MadMarble]

Thanks Mther.

It wasn't too intense. Certainly noticeable. Flavour wasn't effected.

Anyway its all gone now. I just want to improve on it next time and hopefully avoid the sulphur smell.

Anyone else had this happen to a brew?

Anyone any thoughts on improving the ginger flavour?