I'm hearing a difference between these two stock walnuts, one has purple caps the other has black, both are same spec elna silmic 2, but the black caps are bigger than the purple despite same capacitance, voltage, and temp rating. The purple caps sound more natural in vocals and instruments, warmer, more body, slightly more closed in. The purple caps win for jazz, pop, classic rock, 80's stuff. The black sound more transparent, open and cooler in tone, more separation and definition. The black caps win for fast electronic, metal, orchestra, classical. I really like both of them! I have three walnuts now, and I'm going to mod my first walnut as it has same caps as one of these. And I'm still the only person with limited edition red light walnut? Not a good thing, that blinking red light shows through my shirt pocket, I would be tackled to the ground in an airport! The yellow light is much more friendly lol. Disclaimer, these are new walnuts that need burn in so these impressions may not be forever.