For the adapter, I bought a new Sennheiser 1/4". John thought that might be why the mids were so recessed/low quality vs. unamped, but the new adapter didn't seem to change anything.
I never noticed adapters changing the sound other than outright failure like signal drop outs due to bad connections.
They will not meaningfully alter the sound unless you had one made of, say, pure silver vs another one made of pure copper, ie why it can matter for cables but not for adapters or even adapters with two plugs connected by a short cable.
I gather from your response that it's normal for IEMagni to have much less bass response than Atom? You believe that's just how they're built?
I haven't heard the Atom much less vs a Magni, so I did not mean that
specifically about this comparison. I'm just saying that
generally Schiit has half its product line being less warm than many other brands'. The other half - Asgard and Lyr - are not markedly leaner/brighter, and the Valhalla is only "lean" or "bright" in comparison to most other OTL amps let alone the Darkvoice.
I did consider that the potentiometer could be at fault for channel imbalance, but isn't that only an issue at low volumes? On Atom, at low gain, volume was almost up to halfway, and on IEMagni at low/mid gain (not lowest gain), it was probably up two thirds.
If you're well past 9:00 on the dial and you're still getting an imbalance the only way the pot is the problem would be if it's a very bad potentiometer design, or somehow you have two different brand amps both with broken pots. The latter is highly unlikely though.
Still, if you're not getting any imbalance not using an amplifier - for example hooking up the HE400i to a smartphone - then the problem isn't with the HE400i either.
What analogue interconnects are you using? Did you try flipping the connectors? If you only flip them on one side and the issue shifts then it could be the cable. If you're using the same source unit then it could be there too so try another one.
Maybe the low gain on each of these amps is not the same DB?
Amps having the exact same gain is only more common than two different car models having the exact same gear ratios even if the body type and engine displacement were the same. And in this case the reason why there is an IEMagni on top of there being a Magni is because it's a Magni with
very low gain.
It's kind of like Meier audio amplifiers from the 2000s that could be used with IEMs and Grados, even the most powerful ones, because they had a -10dB low gain and a +4dB high gain, basically constricting the output so much at low gain as to allow for the knob to move past the point where the potentiometer has uneven output even on a 120dB/1mW IEM like my Aurisonics ASG-1. Now the Jazz has +0dB low gain and +16dB low gain because it uses a digital volume control that doesn't have an imbalance so they can just give you higher gain for say a 90dB/1mW planar headphone.
I cannot seem to figure out why I would need more volume on the IEMagni when considering that it's a lot more powerful of an amp.
Because gain determines how fast things get loud, not just the power. Same way my Meier Cantate.2 can have about 1watt/channel IIRC but if you set it to -10dB low gain you can get to between 8:00 and 9:00 on the dial to get past imbalance and not blow out your eardrums, and yet my 500mW/ch Pangea HP101 can blow out my eardrums before it gets past imbalance if I put an IEM on it.
Look at it this way. It wouldn't matter if you have a Lamborghini - let alone an old one with the Reverse and 1st gear on the left - if you put the wrong transmission ratios on it. If the ratios are too high and you've barely moved off the line with the V12 just spinning the rear tyres and now you have to do a dog leg 1-2 shift while the Porsche with 35% horsepower and torque is already well into 2nd gear and flying down the drag strip. Too low gear ratios and you'll probably get off the line just fine, only for the Porsche to get to 3rd and about to shift into 4th near the finish line while you've just kind of hit the 7000rpm shift point in 2nd gear. (and this is just in a drag race; it gets even more complicated once you have to turn at various kinds of corners and patterns of corners)
If you don't drive, I hope you at least have a bicycle, because gear ratios work the same way there too but with a 1mp power source: you can't use the regular go pick something up at the store bike's gear ratios and expect to outrun somebody in a mountain bike going uphill (unless the 1mp power source varies enough, like, if he has emphysema or corona virus disease). If you have a camera, low gain is like having a neutral density filter.
Is it because of the existence of the lowest gain setting, even though I am not using that setting?
If you're not using that setting then it shouldn't matter, but if the gain setting on the Atom is not the same as the Magni's then you can still have a good variance in output that would not line up with what you think the output would have to be based on dial rotation because again dial rotation is like throttle angle (or how deep you step on the accelerator) while gain is like transmission gear ratios.
And again both amps having something screwed up is statistically unlikely vs having something else in the chain that is in both screwing up. If you use the same source then it could be the problem; if you use the same cable and source then it could also be the cable; if you're using the same cable for two different sources and get the same problem then it could be the cable, or ya know...the HE400i.
I agree that I tend to adore mid-focused headphones, and the HE400i is considered U-shaped, I guess?
It was really the only respected mid-fi headphone I could afford.
I don't like these descriptions to start with because it is easily misinterpreted. A "u" means the extremes are elevated. The HE400i doesn't have the extremes elevated, it has the midrange scalloped out. If it looks like a latter it looks like a cursive smaller case "v" by somebody with whatever an FBI profiler will associate with why the apex on the V isn't sufficiently pointy. And even "u-shaped" response graphs don't even look like a "u," some look like cursive W's with spikes all over and the ends rise but then nosedive into the extreme ends.
It was really the only respected mid-fi headphone I could afford.
Apart from it not matching your preferences, the HE400i is only respected for performance. Reliability and ease of serviceability vis a vis factory support...not so much. So given two amps have a problem with it that may not just be in terms of whether they're tuned to the sound you're used to and prefer, the possibility that there's something wrong with the headphone can't be discounted.
I mean if there was no imbalance and you really just think the sound is very weak then at least that's attributable to the possibility that your ears may have very weak response at the upper midrange as to perceive +5dB at 3500hz to be much better than -5dB at the same range.
For a similar example but on sensitivity than amp power: I have the Aurisonics ASG-1.3 which is 120dB/1mW at 1000hz, but everything above that is on average weaker by about -3dB, and a KZ ZSN which is 112dB/1mW at 1000hz and has a huge mountain range in the 2500hz to 8000hz range, and despite the 8dB/1mW difference in sensitivity I can crank up the Aurisonics more if I just go by "at what point do my ears tap out?" because at the same output level that 2500hz to 8000hz range would be roughly 11dB louder than on the Aurisonics.
