CD shops in Madrid Spain?

Im in Spain for the next couple of weeks. Primarily in Spain and Valencia. Looking for used CD (and vinyl although hard to pack) shops. Any help would be much appreciated!

 

Same question.

 

Found a couple... the names escape me but will post if I can find them.

edit:

Killer's Discos
Discos La Metralleta

one more but can't remember. I took a photo in front of the shop. I can't remember right now but it was close to Plaza Mayor...

 

one all the more yet can't recollect. I took a photograph before the shop. I can't recollect at this moment however it was near Plaza Mayor...

 

Thank you. I found plenty on Yelp.