BLUE Matamp on the bench made in UK by Radio Craft. These amps are pretty nice builds with their PCB turret board construction. Seems rugged, and you can tell there is time taken into making something special. This layout is very similar to the Blue Matamp I had in a post a while back if you would like to peruse for more in depth info.
Wrangling the line out which had been somehow manipulated (added?) at some point in the past. The output of the amp is in yellow and the line out is in blue. As you can see it is very distorted from the original signal, and only about 200mV RMS.
Original voltage divider ratio for line out was 6.8K:470K. Adjusting to 510R:10K worked much better.
Gotta love these custom Matamps. No schematic available so you just have to sort it out yourself.