my first a5 conv, not hapy w/ride
 

I just picked up this 2010 A5 cabrio, premium plus & it does not give me as nice a ride as the car I test drove @ the dealership.
the car I test drove, also a 2010, seemed as it was riding on a cloud. the car I bought, {private sale) just feels like any average 4 year old car, & certainly does not feel like a luxury ride.
the car has MM ,navigation, back up camera, B&O sound system but I do not see any option for ride control. am I missing something?

Only thing I could think of would be to have the suspension components checked out, you don't mention the mileage numbers but that could be what's making the ride stiffer. The struts/shocks could have worn out. Or the person who had it before you could have replaced the springs/lowered it some.

On my 2014 there are no ride options, but you'd need to check the options that were sold with it. The sport ride option was pretty rare to find in my area at the time so it'd have to be specifically ordered. It may be you don't have it. It should be under the 'car' button on mine at least.

Also my 2014 Coupe (non cabrio) isn't 'riding on a cloud' feeling, it's a little aggressive. It's not TT aggressive but it's not A8 smooth either.

Though one's cloud can be anthers aggressive so that's hard to say exactly.

Audi's, and German cars in general, do not provide "riding on a cloud" experiences. They provide great road feel and feedback.

What you are feeling could be worn tires. Many performance tires develop noise and transmit some harshness as they age.

I remember being a little upset many years ago as my Continental summer-only tires wore down on my A4. I mounted Bridgestone Potentza RE70AS (all seasons) and the ride improved and nosie was gone, even after many miles.

It could also be cold weather. All suspensions feel more rough in very cold weather.

If the car is equpped with the Audi Drive Select option then you can change the ride characteristics to "comfort" - so perhaps that's what you experienced with the car at the dealership. Does the car you purchased have that option? If so you can get it to ride like a Lexus if you want.

the car has 29K on it
the tires look ok, not too worn or uneven

There are a lot of factors. Tire size, Audi drive select, s-line. What are the specs of your car verses the one you test drove. You could have test drove a standard A5 with 18's and drive select and you car could be a S-line with 19's and no drive select.

both are a5 premium plus cars w/18's
not sure if the other car has drive select but apparently mine doesn't

29K on original tires are about the limit. When you replace your tires try a set of Continental DW or DWS depending if you need an all weather or just summer. These tires will give you a very nice ride. If you have Pirellis on your car you will get a harder ride even more so if the car sits for a few days (flat spots)
FYI
It will never ride like an Accord, it's a German car after all. Make sure you salute it before and after each ride. You will notice the difference. :)

I assumed he was on his second set of tire. 29K on one set? Expect lots of noise and harshness

The tires can make a difference. I just got an allroad and the Pirellis are pretty hard. I reduced tire pressure by 2 and it helped. I'm switching to Continental, once these tires wear off.

The Dunlop tires on my S5 are Ok, but it's useless in snow - so I'm going to change that to Continentals as well. The Continental Extreme DWS on my previous A6 was extremely quite and smooth. I miss those tires. Luxurious ride.