In a search to replace a modified SMSL headphone amp that I use at work, I decided to build a DOA SeNNator, a variant of the filtering headphone amp for the Sennheiser HD 650, published by Solderdude over at - diyaudioheaven along with measurements of the HD650's responses.

It's based on the "HD 650 SeNNator" and "SeNNator build tips" pdfs. In adapting the design, DOAs were used. An upgrade to the filtering caps from polyster to polypropylene. To the original circuit, circuits and design ideas from:

• Sam Groner - +/-30mv DC offset adjust and DC bypass cap.
• Layout idea lifted from Jeff Steiger's CAPI-2 Line Stage Amp, from Capi-gear.
• DC filter from Collective Cases, reducing the numerous different electrolytic caps and upgrading the linear regs. from LM217/337 to LT1963/3015.

Minimized mechanical assembly, using the default PWBs available in Kicad, each channel and the DC filter/regulator boards are in a Euro card form factor...