Spl elector and Sugden SPA-4

Just hooked up my new preamp an SPL Elector to my Sugden SPA-4 power amp, for some reason I get a single level muffled output in my speakers regardless of where the volume on the SPL is? I’m using the XLR inputs from preamp to the Sugden and can’t figure out what’s going on. Any thoughts or insights would be appreciated. Btw it happens no matter the front end — Turntable, DAC or an older Arcam cd player I use. 
 

thanks in advance for any thoughts.