I'm using the BeyerDynamic DT-880 headphones and the headphone output on my MOTU 828mkII is very quiet compared to most headphone outputs when using the DT880s, and I've also noticed that when I plug them into my computer speakers (Bose 2.1) headphone output, it's also relatively quiet. I rarely listen to music at high outputs (aside from short reference tests), but even at maximum headphone output, they are at a comfortable level for long-term listening. When I plug my Sennheiser HD280Pros into those same outputs, they are much louder.

I also have a Behringer HA4700 4-channel headphone amp that I use with two pairs of the HD280s for tracking - I don't use it for mixing because it has tone controls, etc. and it notably colors the sound, even at the 0-positions. But, when I use the DT880s with that amp, I have no problem getting them to an unbearable listening level.

So, I'm thinking that the issue is an impedance issue? Here are the impedance specs:

BeyerDynamic DT880 Impedance: 250 Ω

Sennheiser HD280Pro Impedance: 64 Ω

Behringer HA4700 Output:
- Maximum Output Power: +24dBm (load impedance 100 Ω )
- Minimum output load impedance: 8 Ω

MOTU 828mkII Headphone Output: can't find the specs anywhere

BTW, the DT880s are also available in 32 and 600 Ω versions, but I have the 250 Ω version. So, my questions (finally!) are:

1) does anybody know the output power/impedance for the MOTU 828mkII headphone output?

2) am I correct in thinking that the output impedance for the 828mkII is not a good match for the DT880s?

3) Would an impedance mismatch cause coloration of the sound? I know that my Focusrite ISA preamps have variable impedance for the mic inputs, which is used for coloring the input sound, so it seems that the same concept would apply to headphone outputs?

4) If I were to buy a dedicated headphone amp for the DT880s (for mixing), what should I be looking for in terms of output power/impedance? Any recommendations for a headphone amp for these cans (but, please don't just throw out your favorite headphone amp without considering this entire discussion!)

Oh, and before you ask, yes I have had my hearing tested numerous times over the past decade, don't listen to loud music regularly, always wore earplugs back in the day when I played/ran sound 5 nights/week, and most people are amazed that I can hear people whispering at the other end of my office, so it's not a hearing issue.

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