is there absolutely no way to get these aluminium rings? i got in love when i see them today first time
Sorry for taking so long to reply, I have been away for a few days. The guy who made the rings, Mick Harris, made them as a "one off" for a few of the forum members and he definitely won't be making any more. He is now retired and has moved to Guatemala, he spends his days enjoying tequila and tacos and at night he plays the maracas with with his local band Musica Maya AJ
Hey, thanks for all the schematics and all the contributions for those mods. I can share my mod (of the mod :-)) for HD-681F It's based on HD681-F-IV-05-2013 schematics from Solderdude (DIY-Audio-Heaven, PDF currently available here: d.zaix.ru/9TaF.pdf ). The original mod has C3 and C4 set to 680nF which gives nice filtering around 10k but still leaves piercing and nasty frequencies around 12/13k. By changing C3 and C4 to 470nF (making them equal to C1 and C2) the frequency dip is shifted more towards 11k and filters nicely harshness of sound giving warmer signature. Additionally R3 and R4 have to be 62 Ohm instead of 56 making the frequency drop deeper. You might want to try 68 Ohm - it's a matter of taste really.