not sure if this is the right place to post this question but here we don't have a "tech" forum ...
 
what's a good way to impose a "vinyl" character on a sample i.e. make it sound like it came from a dusty, a bit scratched record that has been forgotten in the hot car ... you know a bit of crackling (but not this harsh digital stuff), a period click from a scratch that runs across and makes the needle jump, ...
 
I was wondering if there was some impulse response for this kind of FX. I would want to transfer a mix into something that sounds like it came from a record player in the back of the room.

Izotope has a free Vinyl VST that's very good and customizable. Should do everything you want and more. You can set it up in the track fx bin or even as clip fx. For "back of the room" I'd suggest an impulse based reverb (Perfect Space or ReMatrix should be available if you're on Platinum/Producer). And you could add a little EQ if you want to simulate small speakers. Roll off lots of lows and some highs 
 

+1 to Izotope Vinyl.

Another +1 for Izotope Vinyl.
All the best.

Hey thanks guys! This looks brilliant. I much appreciate that.
 
This shows once more that this forum is THE source for collective wisdom :-)

A side note for Vinyl... if that is used on a track/buss, it will insert noise even with the transport not running. Freaked me out first time I used it, but as long as you know this you are in good shape.

agreed with all above. there are others around but izotope's offering, especially in its new 64-bit anniversary version, is pretty much the cream of the crop, and free is a nice price...

mettelus
A side note for Vinyl... if that is used on a track/buss, it will insert noise even with the transport not running. Freaked me out first time I used it, but as long as you know this you are in good shape.

Just give it a quick try and think I will have to apply (parts of it) in parallel anyway i.e. the dust and needle jumps seem to be a bit hard to control when you insert the plug in the track to "vinylized" - so on my first go at Izotope Vinyl I applied 2 instances: EQ and warp on the track and dust/scratch on parallel track which had no audio clip ... need to play more with it, though

Ohh its free too. Run lola run!

If used for a discreet sample, you can put it in the Clip FX bin (not the track FX). I am not sure if "sample" in the OP meant a discreet clip or not.