Cyan69:
You seem understandably frustrated.
You asked: Does the price-point on a headphone amplifier change how the sound quality will be effected?
A: Well yes, to some degree, but twice as much money doesn’t get you twice as much sound quality. Maybe 5-10% closer to perfection, and more features. There’s good gear available at reasonable prices.
I wasn’t aware that you had already tried some headphone amps. Sorry if you had already told us that, and I missed it.
But that new (to me) info does change things. With the gear you have tried … headphones, amps, and a DAC … you SHOULD have heard things that were reasonably high on the “sounds good, makes me happy” scale … and yet, that has not happened.
Hmmmm. [think think.]
In your shoes, I would try to set up the simplest possible path for testing purposes, with the goal of eliminating as many possible problems as possible, and once I’d gotten that working, try to transfer the magic into the more complex system. And the biggest complexity I see is the Denon AVR, mainly because it’s multi-channel. So for testing purposes, we don’t want that in the headphone system.
Can you reborrow the CMA 400i ???
If so …
(1) connect the OPPO 203D BluRay player to the CMA 400i, using the digital coax (preferrably) or optical if you don’t have a “digital” coax cable. (Note that a coax cable LOOKS like an RCA cable, but an RCA cable may not have the bandwidth to work perfectly. Order a new one if there’s any question about what you have … the Amazon Basics cable is good & cheap, and quick to get … https://www.amazon.com/AmazonBasics-Digital-Audio-Compatible-Coaxial/dp/B01D5H8TS4. Note also that optical cables are fairly fragile. Amazon Basics has those too.)
(2) plug in one of your sets of headphones
(3) play a CD, either something you know well and enjoy, or something that’s been described as being a notably good recording in terms of sound quality.
(4) Listen.
That SHOULD work. You SHOULD hear good stuff.
If it does, try playing 2-channel tunes off of your USB-stick. Some 16-44 and some higher resolution files. If all those work, you’ve eliminated the file formats and the source (player) as the cause of the troubles you’ve had.
Then listen to a BluRay or DVD with multi-channel sound. How does that sound? I would assume “probably not good” initially, as I don’t think the CMA 400i will handle a 5.1 format. So use the Oppo’s controls to set (approx) “downmix to 2-channel.” (That’s an option in the menus, under Speaker Setup.) Hopefully, that gets back to good sound.
Next, I’d like you to try to use the Oppo’s DAC (instead of the CMA 400i’s), but it appears that the CMA 400i has only digital inputs, so can’t do that.
2nd thought: did you borrow the CMA 400i from someone close enough to visit easily? If so, go to his place, and take some headphones, the Oppo, a couple of reference CDs, and some cables with you. Listen with his gear with your headphones … they work right? Then connect your Oppo to his CMA 400i, and listen to your headphones again. Does that work?
If so, I’m back to where I was with my previous post, that you need a headphone amp, and then get it connected up correctly with your AVR system in a way that doesn’t get your 2-channel music signal split into unlistenable 5.1 or mangled into faux-surround.
That’s the minimum. Alternatively, you could also get an external DAC, or an integrated DAC+Amp like the CMA 400i.
This doesn’t have to be expensive, which is part of the reason I recommended the Schiit Jot 2. The Robert Neve is reportedly good, and so is the Questyle CMA 400i. Any of those SHOULD be a very solid part of a starting headphone system. (The Klipsch Heritage Headphone Amp is a model I haven’t heard/read anything about.)
HTH. It’s not supposed to be so hard.