Replaced the 6N3 tubes in the Little Bear P-8 headphone amp with these. Also replaced the 6AS7-G tube with a CRC/JAN RCA tube. Interesting note, both the 5670 and 6AS7G tubes were considerable smaller in size. With a total investment of $200 I have an absolute killer amplifier. Shop smart. Shop S-Mart. The sound is detailed like sparks from mesquite chunk charcoal.