Hi All,
I was recently gifted a TOA VM1120 100v and 70v line amp, it's one of their earlier models with a transformer output stage rather than direct coupling to the transistors. It's a 120w rated amp but I've been testing it with a 30w speaker, 16w speaker and 6w speaker (all set to 100v) but I've noticed what I'd class as an unreasonable amount of distortion to the sound, when bass notes hit they make a "pop" noise and the whole amp chassis judders, almost like an electromagnet is being energised. It seems to me like the output transformer core is being saturated, this happens above 25% volume (sound is crystal clear and rich below 25%) and is worse on the 100v tap than the 70v tap. I've noticed adding more speakers in parallel also reduces the problem but it's still there. Does anyone have any ideas what the cause might be, or whether this is what these amps are always like?
Thank you in advance.