I have 2 swr sm400 amps .1 is a back up have u checked your preamp tube they do die slowly you know. I run mine to a goliath III 4x10 8 ohm run in series with a son of bertha 1x15 8 ohm bridged mono out of the banana clip. My amp slams. Im getting almost 400 watts and with my gain at 4 master...