These double diodes are in quite a few places in this amp, what's it doing here and would a suitable replacement be 2 x 1n4148 in series?
Do not replace what is not broken. They are refference voltage drop.
Those diodes were probably chosen for a good reason. They are unlikely to be stressed so I’d agree with adason here.
Prior thread on these slightly unusual diodes https://www.diyaudio.com/community/threads/varistor-diodes.190374/#post-2599541
Prior thread on these slightly unusual diodes https://www.diyaudio.com/community/threads/varistor-diodes.190374/#post-2599541