Hard to know for sure what's causing your problem, given that you only swapped out the speakers. However, you should check / eliminate the following possible causes of the problem:
1. check the tubes in your preamp -- one of them may need replacement;
2. check the cartridge's cantilever to see if it has gotten bent or damaged.
Hope others on the forum can offer some other suggestions.
1. check the tubes in your preamp -- one of them may need replacement;
2. check the cartridge's cantilever to see if it has gotten bent or damaged.
Hope others on the forum can offer some other suggestions.