Long story short, headphone impedance for audio interface. Having trouble mixing for quite a while, never knew to check for those things until today. While researching, noticed people talk about impedance/audio quality singling out the dedicated headphone output. I happened to have an RCA (red and white) to 3.5mm adapter and a 3.5mm to 1/4" adapter. So now running my high quality studio cans through two adapters for the RCA outputs of audio interface instead of the front headphone panel.

I FEEL like I hear an improved quality difference, but I'm not sure if that's real or one of the many placebo effects we get in the mixing process.

So here's my question: what's the science behind doing it this way? Am I still losing any audio quality or something going through the back and these adapters, or is this an effective juryrig until I get a proper solution going for it?

 

No idea what audio interface you have but TYPICALLY, RCA (phono) jacks are setup to carry LINE LEVEL signals. Line level circuits (by themselves) are not made to drive any sort of speaker or headphone. They will generally require a power amplifier device to properly drive a set of speakers or a headphone. Not real sure how you could be getting any kind of quality out of that current setup. If your phones are too high an impedance for the actual headphone jack the safer and better sounding solution would be to connect a small headphone amplifier to that current set of RCA jacks (assuming they are an output) and plug your phones into the amplifier. Selection of the amplifier would depend on the impedance needs of your phones themselves. Or you could simply get a set of phones that are a better impedance match for the headphone out. Suggest looking at your audio interface manual/specs to determine what impedance is optimal for your headphone out jack.

 

Last edited: Dec 2, 2025

What kind of headphone amplifier would work there? Doesn't have to be RCA, I have 1/4" output jacks as well, I'm just not good at trying to shop for the "right" hardware solutions and researching/trying to figure this shit out on my own has proven exhausting and ineffective.

 

Most decent headphones amps have very low impedance so they will work with anything out of the box. If you want something cheaper, look for Fosi Audio. Something more expensive, FiiO or Topping. If you're living in the US, Schiit Audio is somewhat expensive but lasts very long. I'm still using my Schiit Magni 2 daily for over ten years, and this unit has enough juice for any headphones that currently exist (or existed in the past).

Most amps will be RCA because they're unbalanced, if you want 1/4" you're going to pay premium for it. And that's not always an improvement, there are many people who say balanced amps are actually noisier than unbalanced, which is quite a paradox in itself. You're also going to need to replace the headphones cable for a balanced cable, which also costs premium.

Edit: worth noting that you can connect a 1/4" output into a RCA input from an amp, if you don't want to lose the RCA output in the interface. Most interfaces will accept unbalanced 1/4" to RCA cables just fine even though the output is balanced. In this case, both RCA and 1/4" will perform the same since they're unbalanced.

 

Last edited: Dec 2, 2025

Unfortunately, you didn't mention which audio interface you're using!

The headphone output is specifically designed for headphones; some manufacturers offer excellent quality, while others don't.

Here's an example: The Audient ID14, for example, supports headphone outputs up to 600 ohms.

Headphone Outputs
LINEUP:18dBu = 0dBFS
THD+N @ -1dBFS:0.0009%
DYNAMIC RANGE:125.5dB A-Weighted
CROSSTALK:>116dB
FREQUENCY RESPONSE:±0.25dB 10Hz to 40kHz
MAXIMUM LEVEL @ 30R:2.59V Peak, 1.827V RMS, 223mW
MAXIMUM LEVEL @ 62R:4.18V Peak, 2.95V RMS, 280mW
MAXIMUM LEVEL @ 600R:7.72V Peak, 5.46V RMS, 100mW
1/4” TRS JACK:Tip (Left), Ring (Right) & Sleeve (Shield)

 

I would assume your headphones use a 1/4" phone plug for a connector. Your audio interface should typically (unless it's designed as a smaller overall size) use a 1/4 phone jack to deliver audio to headphones. If your headphones impedance is very high you'll need an amp that can drive HI-Z phones. If your interface headphone jack is not capable of driving your current phones there are inline amps (that plug between your interface 1/4" jack and your phones) that would amplify the signal coming from the headphone jack. These are generally a bit higher in background noise. There are also amps that will plugin between your RCA output and your headphones. Your phones then plug into a 1/4" jack on the amp. These (depending on the design of the amp) are generally lower in background noise. Regardless of the type of amp you get you will have to supply DC power to it via (wall wart), usb DC adapter, or a battery - just depends on the design of the amp device. The example below is ~35$ from amazon. This one is spec'd to drive impedances from 18Ω-600Ω which covers a very wide range of headphone models.

Here's a typical example of the latter type from amazon

 

Last edited: Dec 2, 2025

I had an earlier reply that an internet outage prevented from getting posted. Trying here again.

I bookmarked that Douk model and started looking around for the level above; I feel if I cheap out too much here, I'll just end up back where I started and $40 poorer. Now I'm looking in the $70-$100ish range.

What do you think of these models? Would these work for bridging the gap as well?
Atom Amp+ - Shop JDS Labs
TOPPING DX1 DAC/Amp
ZEN Air DAC - High-Performance DAC for Rich Musicality

There's also a Schiit Magni 3 that I've seen recommended and at a decent price on Ebay, but finding an official product page for that is difficult.

 

This product is available for purchase:
JDS LABS: https://jdslabs.com/product/atom-amp/ $99

JDS Atom Amp+ Review (Headphone Amplifier)
https://www.audiosciencereview.com/...ds-atom-amp-review-headphone-amplifier.24680/

JDS Labs targets 99% of the state of the art in headphone performance and delivers. It is a breath of fresh air to check my measurements against their specs and see them very closely match with no weasel words used to get better numbers. Company has impeccable reputation for excellent customer service which when combined with such a low cost, means a winner in my book.

Excellent Budget Headphone Amplifier | JDS Labs Atom and Atom+ Amp Review 2023

 

So this would be the solution for the Sennheiser 660HD, do I have that correct?

 

What headphones and interface do you have? I'd bet you changed something that altered your gain staging, and you probably don't even need an amp. You might get better fidelity using one, even if you don't need one.

If your audio interface has a headphones amp already built into it, it will not be sending a line level signal to the headphones out. Finding an interface without a headphones amp built into it is actually more difficult than you might think. It just might not be a powerful enough amp to drive headphones over 150ohms impedance (rough number there).

Sennheiser HD 660S = 150 Ω
Sennheiser HD 660S2 = 300 Ω

Which ones, and then which interface?

 

I highly recommend the Magni, it's a great amp that works with absolutely any headphones money can buy.

This is the official place: https://www.schiit.com/

The Magni is more than enough for your needs, just a plain simple amp that lasts a lifetime.

 

In this price range, it's the best product for your headphones!

Sennheiser 660HD = Impedanz 150 Ω

Yes, the JDS Labs Atom Amp, priced at $99, can easily drive the Sennheiser HD 660S (with an impedance of 150 Ω). The Atom Amp has enough power to drive even higher-impedance headphones like the HD 660S without distortion or loss of performance. The Sennheiser HD 660S has an impedance of 150 ohms, which means it requires more power to reach its full potential, but the Atom Amp delivers enough output power to drive these headphones clearly and with detail. Many users report that the Atom Amp performs very well with headphones in this impedance range.

 

Even if you get the Topping, the L30 II is the better option:

Output power: L30 II vs DX1

• The DX1 — even though it’s a DAC + headphone amp — delivers up to ~ 280 mW × 2 into 32 Ω, and only ~ 51 mW × 2 into 300 Ω. TOPPING Official Store+1
  
  
• The L30 II, in contrast, is a dedicated headphone amplifier using a more robust circuit (NFCA). It delivers far more power: up to ~ 3500 mW × 2 at 16 Ω, ~ 2000 mW × 2 at 64 Ω, and ~ 560 mW × 2 at 300 Ω. Headfonia+2TOPPING Official Store+2
  
  

Spoiler

✅ What “more powerful” actually means here
Because L30 II supplies much higher current and can deliver significantly more wattage — especially into lower- and mid-impedance headphones — it will:

• produce louder volume
  
  
• drive power-hungry headphones (low efficiency or high impedance) more easily
  
  
• have more “headroom,” meaning it won’t clip or struggle when driving demanding cans

In practice: which is more powerful — and when DX1 might suffice anyway

• For most headphones, including moderately demanding ones (e.g. mid-impedance, decent sensitivity), the DX1 is adequate and gets the job done, with the added convenience of being a compact DAC + amp.
  
  
• For harder-to-drive headphones (low sensitivity, high impedance or planar headphones) or if you want maximum volume, dynamic range, and headroom, the L30 II is clearly more powerful — it’s more than capable where the DX1 might run out of juice.
  

Same with the Magni 3, but the Schiit is closer to the L30 II than the DX1;

Output power comparison

• L30 II (NFCA headphone amp): up to ~ 3.5 W per channel at 16 Ω; ~ 560 mW per channel at 300 Ω. Apos+2Headfonia+2
  
  
• Magni 3: ~ 2 W per channel into 32 Ω; ~ 430 mW per channel into 300 Ω. The Absolute Sound+1

 

Excellent recommendations, guys. Thank you for helping me turn a complicated, headache-inducing problem into much simpler solutions. I'll be looking at all those. Thanks again!

 

If you know what the impedance spec of your phones is (in Ω) you can more accurately shop around for just what you need. If I were you I would at least gather that spec before buying anything unless you get from a source that allows returns. Most of the amps listed will drive loads up to 600Ω which is pretty much the highest practical impedance you'll find in a pro model headphone. Headphone models that are rated higher than 600Ω start getting impractical from an amplifier drive standpoint. Most headphone amp circuits included with audio gear these days are hard pressed to drive a 300Ω load and lose the ability to drive the phones to an appreciable listening level.

You'll find many amps that will qualify for your usage - just get the one that will work the best with your particular headphone model and that has the lowest residual noise spec.

 

Last edited: Dec 3, 2025