I have a pair of HE400s, which are great in all but bass. But when I try fixing it with an EQ, I notice that the music gets almost completely silent whenever there's a bass kick at higher volumes. The maximum volume is also rather low. I am using them with my Android phone. Can this be fixed with an external amplifier?
If the problem were power it wouldn't likely just suddenly lower the volume of everything else. Perceptively it can, ie auditory masking, just not only during peaks.
This might be an issue with the EQ software.
According to the specs of the audio chip in my device, it's supposed to be able to give 120mW at 32 ohms and 150mW at 16 (I may be looking at the wrong number here, I found it under "rx processing" and then "class h differential output"). I haven't really seen any portable amplifiers with a much higher output. Is the mW value the right thing to look for here?
Er...what device is that exactly?
That outputs kind of high. That's way above the limit of what some smaller DAPs are rated for, like the Quad DAC ESS9218 (ie similar tech as in the LG phones) in the Hidizs AP80 that produces 70mW per channel on Class G (albeit a very quiet one). That's more on par with older DAPs using a dedicated DAC chip, line output, and amplifier output stages using op-amps...on Class A/B mode. So one possible explanation might be that that chip really is designed to crank out more power, then they rated it at a higher power
and distortion+noise rating (ie in some cases even the same circuit or chip can actually produce more power than what it is rated for, but past that point the distortion and noise really start piling on). If you're into computers, think of it this way: you can have an RTX 3070 at 125w+25w dynamic boost (Asus) or 140w (Alienware) or 150w (best MSI), which is kind of like the DAP; and then you can have a desktop RTX 3070 running at 2250mhz core and +750mhz on the VRAM sucking over 300w, but it perpetually crashes due to core instability, which is kind of what might be happening on that Class H chip.
That said the problem you're having seems to be more of software bug.
That or the keyword there is "differential output," meaning you need to use a plug and cable that completely isolates L- and R- on two independent pins on the plug and on the cable all the way to the drivers to get that much output, more commonly known as "balanced drive." If that's the case it may only have half that. Check if your device takes a 4-pole jack that is
not just for the mic. If it does, then you might need to try out a cable for your headphone that has these specs (note: not just the plug, it has to be the whole cable). Using a regular SE cable into the normal jack will at minimum mean the actual power output might only be half what it's rated for.
Sadly reducing all other frequencies equally produces the same effect. I also tried it on my laptop with equalizer APO, same thing
How exactly did you try it on the laptop? You used EQ APO on the laptop with your earphones hooked up to the laptop's 3.5mm jack, or are you using BT to stream from the laptop to the phone?
If you're plugged into the laptop and playing music stored on or streamed from the internet by the laptop that's kind of weird that two apps would simultaneously have the same bug; if you're streaming music on your phone to the laptop (note: not the remote mode on Spotify or HiByLink for example) it could be that the Android EQ app is still running; if you're streaming from the laptop to the Android, then the audio chip on the phone might be causing it, or the Android EQ app is also running.
