Question about output impedance measurements/recommendation for IEM dac/amp

[InternetSandman]

Hi there, first post here, I hope this is the right place to post this

I've been reading a fair amount of headphone amp and dac/amp reviews on this site, and I've noticed that the output impedance measurements on products I've looked at are usually well above what they're advertised as (Fiio K5 Pro having twice it's advertised impedance, Schiit Heresy having over 10x the advertised impedance). This is one of the only sites I've seen that measures the output impedance of these components, so it's made shopping much more difficult realizing I have to disregard whatever a manufacturer is advertising and try to find measurements (I know that sounds like common sense, but it's still disappointing lol). I was wondering though, is it just simple false advertising on the part of the manufacturers? Or is there some more specific reason that these boxes are measuring so wildly different from their claims?

The reason I ask this is because I've been shopping for an IEM to use both at home and on the go, and the top pick for my tastes right now is the Shure SE846 (with the 64 Audio u12t coming in a close second at twice the price and half the noise isolation). I've seen discussions over how the SE846's ridiculously low impedance in the mids/highs mean you need to hook it up to an amp with <0.5 ohms of output impedance in order to preserve the higher frequencies, and finding a desktop amp that suits that is a lot more challenging than I thought it would be, given the variance between advertised/measured specs.

Making it more challenging, ideally I want a combination desktop dac/amp with an optical input, because I want to connect it to my computer "monitor"/TV (LG CX48). The Fiio K5 Pro seemed to be the top pick, but because it apparently has 2.2 ohms output impedance, even pairing it with the u12t seems a bit sketchy. Everything from Schiit is either backordered and/or would take forever to ship (and I can't trust their stated OI claims anyway). Are there any products, preferably less than $400, that would suit what I'm looking for? I'm also not too keen on Topping though I know they'd probably be a top recommendation, because again shipping would take forever and I can't find a retailer or etailer that would ship faster to my place in BC, Canada

 

[twsecrest]

This is the first time I've heard about "false" claims on output impedance by the manufacturers.
Where are you reading this, I want to know more?
A Xduoo XD-05 is something I would recommend to you.

 

[InternetSandman]

This is the first time I've heard about "false" claims on output impedance by the manufacturers.
Where are you reading this, I want to know more?
A Xduoo XD-05 is something I would recommend to you.

On Schiit's website, they advertise both the Magni 3+ and the Heresy as having less than .25 ohms of output impedance, but in this review:
https://www.audiosciencereview.com/...gni-3-and-heresy-headphone-amp-reviews.10311/
they are measured at having 1.3 ohms of output impedance. Not the 10x I claimed, but I was remembering them as advertising .1 ohms, not .25

For the Fiio, it's advertised as having less than 1.2 ohms of OI, yet
https://www.audiosciencereview.com/.../review-and-measurements-of-fiio-k5-pro.9118/
it's measured as having 2.2 ohms of OI

The JDS Labs Atom is advertised at 0.1 ohms
https://www.audiosciencereview.com/...ents-of-new-jds-labs-atom-headphone-amp.5262/
and is measured at 0.7. Definitely still amazing, but not accurate to the claims

 

[NTK]

Many of Amir's older headphone amplifier reviews have measured output impedance bottomed out at around 1 ohm. This was due to the fixture he used. I think he has upgraded his fixture recently and can measure down to, I think, 1/2 ohm or less. (See post)

https://www.audiosciencereview.com/...hpa-1-headphone-amp-review.10416/#post-287210

 

[InternetSandman]

Many of Amir's older headphone amplifier reviews have measured output impedance bottomed out at around 1 ohm. This was due to the fixture he used. I think he has upgraded his fixture recently and can measure down to, I think, 1/2 ohm or less. (See post)

https://www.audiosciencereview.com/...hpa-1-headphone-amp-review.10416/#post-287210

that explains a lot, all the reviews I was looking at were from around then too. Odd that the Fiio still measured almost twice it's 1.2 ohm rating, but understandable.

 

[twsecrest]

On Schiit's website, they advertise both the Magni 3+ and the Heresy as having less than .25 ohms of output impedance, but in this review:
https://www.audiosciencereview.com/...gni-3-and-heresy-headphone-amp-reviews.10311/
they are measured at having 1.3 ohms of output impedance. Not the 10x I claimed, but I was remembering them as advertising .1 ohms, not .25

For the Fiio, it's advertised as having less than 1.2 ohms of OI, yet
https://www.audiosciencereview.com/.../review-and-measurements-of-fiio-k5-pro.9118/
it's measured as having 2.2 ohms of OI

The JDS Labs Atom is advertised at 0.1 ohms
https://www.audiosciencereview.com/...ents-of-new-jds-labs-atom-headphone-amp.5262/
and is measured at 0.7. Definitely still amazing, but not accurate to the claims

I'm not really seeing an "issue", you can easily plug an IEM that is only 10-Ohms, into a jack with an output impedance of 2.2-Ohms and chances are you will like the sound (maybe slight bass boost).

 

[InternetSandman]

I'm not really seeing an "issue", you can easily plug an IEM that is only 10-Ohms, into a jack with an output impedance of 2.2-Ohms and chances are you will like the sound (maybe slight bass boost).

You're right, in most cases even 2.2 ohms probably wouldn't be an issue, but the SE846 (from everything I've read) has an impedance curve that goes from 16 in the low end, down to 4 or 5 in the mids and highs. To the best of my understanding and from posts I've seen, that means that the treble will quickly get weakened with higher OI

The reason I want the SE846 in particular is for its isolation, comfort, and high quality bass response in an IEM. The u12t seems like it would be even better, much more source compatibility and more extension in the top end, but I'd definitely have to work up the courage to spend twice as much for that little bit extra (and then I'd still need to pair it with something better than the Dragonfly Red I'm using right now)

 

[twsecrest]

You're right, in most cases even 2.2 ohms probably wouldn't be an issue, but the SE846 (from everything I've read) has an impedance curve that goes from 16 in the low end, down to 4 or 5 in the mids and highs. To the best of my understanding and from posts I've seen, that means that the treble will quickly get weakened with higher OI

The reason I want the SE846 in particular is for its isolation, comfort, and high quality bass response in an IEM. The u12t seems like it would be even better, much more source compatibility and more extension in the top end, but I'd definitely have to work up the courage to spend twice as much for that little bit extra (and then I'd still need to pair it with something better than the Dragonfly Red I'm using right now)

Your SE846 is going to have the same "issues" your talking about with just about any modern headphone amplifier.
I'm sure the SE846 have been plugged into many smartphones and their headphone jack output impedance would be higher then 2.2-Ohms and I'm guessing the SE846 still sounded good.

 

[3125b]

I'd worry more about noise floor than outpit impedance. Finding an amp with 0.1Zo or less is not difficult, finding one with >90dB 50mV SNR much more so.
You could get an E30/L30 stack. The E30 has a TOSLINK input and volume control via remote, the L30 has a very low noise floor and a -9dB gain setting. If you buy them now you should get a fixed 210X version - don't buy an L30 off eBay though, many seem to be selling the old ones they should have destroyed.

 

[Bob-23]

Or is there some more specific reason that these boxes are measuring so wildly different from their claims?

Technically, determining output impedances is not that easy to do, in particular, if your dealing with such extremely low values. You can't simply directly measure it, as you'd measure voltages: you have to hook up a variable resistor at the output of the device - a resistor with about the same (here: extremely low) resistance range, and you have to take into account the resistance of the measuring device/the probes...

You're on the safe side, if you find a headphone with a flat (or almost flat) impedance curve - as the impedance of these headphones is practically a fixed resistance, voltage division between output resistance (better term) and headphone resistance remains constant, thus, there is no impact on the phones frequency response.

But you may have a general power loss, as part of the current gets burnt in the output resistor. If this is a problem, depends on the amp.

On that site, for instance, you an research for impedance graphs:
https://reference-audio-analyzer.pro/en/report/hp/shure-se846.php
Your shure is definitely not flat.