Samson S-Amp: A Cheap Amplifier For The 600ohm Beyerdynamic DT880 - YouTube
Amazon.com: beyerdynamic DT 990 Edition 600 Ohm Over-Ear-Stereo Headphones. Open design, wired, high-end for use with headphone amplifiers : Electronics
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Amazon.com: FX-Audio Tube-02 Pro Tube Headphone Amplifier, Vacuum 5725 Tube Preamp, Mini Hi-Fi Integrated Stereo Class A amp Supports 32-600 ohms of Headphones, for Stereo Amplifier/Active Speaker : Electronics
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A Comparison of Beyerdynamic DT 880 32 ohm, DT 880 250 ohm, and DT 880 600 ohm Headphones Page 2 | Stereophile.com