Sennheiser HD 650 vs 6xx vs 660S

TA-26 is an OTL amp, it’s made for high impedance headphones only. Do some research and get new tubes for it, you will be surprised even more.

One thing of note is crin’s measurements show a significant treble dropoff for the HD 650 with worn pads while the HD 600 mostly keeps the balance even though they’re the same pads, may it be unit variation?

I just did this. Bought the 650 and heard how it opens up on a tube amp. So turned on the Feliks Audio Euforia… amazing! It is a real treat to the ears.

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Totally different headphone on tubes

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