I have a feeling that because of my Palomar 300a's preamp's failure I may need to purchase an external preamp. My antenna (a99) isn't top side. My receive is greatly improved by the preamps on my other amps (mostly used for skip). Unfortunately the preamp on the 300a isn't working. If I can't repair the preamp I will need to purchase an external preamp. If you have owned or used one of these please let me know which one work well. Thanks.