[TenTec] Sidetone thump

[g p]

Recently acquired a Corsair, works well but the sidetone thump kind of bugs me a little, I did the sidetone mods as per Ten Tec wiki and it sounds better but there is still a thump that increases as the power out is increased. Now I can live with it but boy it would really make it much more enjoyable taking out the thump, this thump happens with either slow or fast QSK.
Input appreciated, thanks
 
Gil