I’m getting a frame with tapered headtube but wanting to run my straight steerer dt Swiss forks ,what headset do I need ?

More info needed….
Is it integrated – i.e. Do the bearings sit directly in the frame?
Or is it semi-integrated, where the bearings have a housing that goes in the frame.
Then you need to know what length bearings you need, and if they’re 45/45 or 45/36.
Headsets are a fun game these days!

If it’s an fully integrated 45/45 degree headset you need, then the Brand-X integrated one on CRC is decent quality and not too expensive. You’ll need to also buy a 1.5 to 1 1/8 crown race reducer/adaptor too.

Hope pick n mix headset cups will sort it

Hopes are nice, but be aware that with an integrated headset all you are basically getting is 2 bearings, a crown race and a top dust cover. So no nicely machined cups like headsets of old.
I can never quite work out how companies can justify charging £60+ for them considering the bearings themselves cost maybe £10-20 tops.
I’ve got integrated headsets on 2 bikes and when the bearings have gone I’ve just replaced with like for like bearings bought on eBay for about £5.

Personally I’d go with whatever tapered headset fits the frame and floats your boat and put a Hope HS136 adapter on your fork.

The frame is a mk3 cotic soul

Then this is what you need to read….

headset info from Cotic website

You’ll still need an adaptor to use straight steerer forks.
£70-80 for the Hope, but you can get cheaper!

I used to have that frame with a straight steerer revelation. I ran the hope pick n mix headset with a type 1 upper cup, type H lower and the adapter I mentioned above. A cheaper option would be the Nukeproof pick and mix, they do an external lower cup for a straight steerer, for that you’ll need a T1 top cup and B4 lower, however this means you won’t be able to swap forks in future without changing the lower cup.
Also, don’t be tempted to fit a zero-stack lower cup as this can cause clearance issues between the fork crown and downtube.