Topping A90D Headphone Amp Review & Why The Disconnect Between Measurements & Performance?

Thanks to Apos Audio for the loan of A90D!

Buy from Apos (affiliate link): https://apos.audio/products/topping-a90-headphone-amp?_pos=1&_sid=5184daa97&_ss=r&sca_ref=1448954.julYPU81dF

Support me on...

Patreon: https://www.patreon.com/wavetheory1
Donate on Paypal: https://www.paypal.com/donate/?hosted_button_id=7N7Z8WRLWQ36E

My Reviews of Other Topping Gear:

DX7Pro+:
L30: https://forum.hifiguides.com/t/topping-l30/15085/89
A50s: https://forum.hifiguides.com/t/topping-a50s-headphone-amp/19204/5
A30Pro: https://youtu.be/tpfVxVkQU5I
A90: https://youtu.be/8Vz9VI-o9QE
E30: https://forum.hifiguides.com/t/topping-e30/10184/215
D50s: https://forum.hifiguides.com/t/topping-a50s-headphone-amp/19204/5
D30Pro: https://youtu.be/Op22DP2_PBI
D90SE: https://youtu.be/mavyGioiFhE

My Reviews of Other Mentioned Gear:

Lake People G111mk2: https://youtu.be/kSxg9OJWlXQ
Schiit Bifrost 2: https://youtu.be/gydqRIWgbrc
Singxer SU-2: https://youtu.be/0WNxN11QY8o

Beyerdynamic DT880 600 ohm: https://youtu.be/gwmP7r8ffA0
Focal Radiance: https://www.youtube.com/watch?v=o1DDTtN57VQ
JM Audio OCD Extreme: Stealth Edition (HiFiMan HE-R9 mod): https://youtu.be/PPlWEeebCPA
HiFiMan Ananda Stealth Magnet Edition: https://youtu.be/oU8SJW5-NH0
HiFiMan HE6sev2: https://youtu.be/NnwqHJlAjxk
HiFiMan HE1000se: https://youtu.be/Hf_0NqehvPg
HiFiMan Susvara: https://youtu.be/mZJ78eXWkt0
Sennheiser HD6XX: https://youtu.be/865BRrqBR3Y

For more about Waves and Wave Superposition, check out Part 2 of my Cables Matter Series: https://youtu.be/Cq12Uhh6VIU

Channel Intro: https://youtu.be/mAEiO10iF4A
My Hearing Quirks: https://youtu.be/lIKtrGJwit0

Timestamps..

00:00 Intro & Disclaimers
00:48 Shameless Self Promotion
01:16 Pricing, Specs, Build
12:02 Sound Preface
14:03 Test Gear
16:04 Sound
26:11 Comparison with OG A90
27:23 Comparisons with Competition
28:32 Wrapping Up A90D On its Own
30:37 Thoughts on Measurements vs Performance