Naim Nait 5 Service Manual wanted

Hello all fellow members and friends, I am looking for a service manual or schematics for Naim Nait 5 (not "i" model) amplifier. The problem of this unit is that the signal levels on both channels are not equal. Investigating the signal path, I assumed digital volume control is not working with same way for both channels OR signal level is not equal before this. Unfortunately, it is too difficult to decrypt circuit without schematics.
Thanks anyone who will reply.
Regards,
John