I have a QM3 here. I even met the man who made these, Tom Repps.
The desk is discrete as far as the fader, and the busses. After that it uses opamps. 5534's generally. The PSU is +24V. The outputs clip around +20dB
Very low by todays standards, and won't drive modern converters fully.
The insert and I guess 'direct' outs are around -10dB. That's the way it is.
That series Quiet Mixer, is extremely quite. Great for ribbon mics. Beat many preamps in tests here, including a Neve 9098
Note the pad is after the first pre stage. If your gain pot is around 9-10 O Clock there is great danger of input overload.