When changing over from active pickups to passive pickups you will need to change all the pots, capacitors and jack socket because active pickups use different values that will not work with passive pickups.
For use with passive humbuckers you will need 550K volume and tone pots, 0.022mfd capacitor for the tone, a mono jack socket (all available from our shop) and also get a ground wire installed from the bridge through to the wiring cavity.
I would make sure he has followed all these procedures properly as the Black Dog just isn't a thin sounding pickup, see example -
https://www.youtube.com/watch?v=CaqEET376-IIf your tech confirms he has followed all of those steps correctly, the next step would be to send them into us to have a look at for you. If you do decide to send them in for us to check over, be sure to contact us on
sales@bareknucklepickups.co.uk so we can give you all the details on sending pickups back to us for repair.