output impedance

Armaegis · Oct 31, 2018

This started off with me kinda sad at getting my first dislike, but then I felt like the conversation had enough stuff that it should be a thread (or maybe merge if something similar exists already?) as we mumble about output impedance all the time but never get too deep into it aside from FR variances.

Copied over unedited from PMs (except for removing irl names) with permission:

Armaegis said:

Hey man, what's with the random dislike on a post of mine from over a year ago? It's not like I'm saying anything infflamatory there.
https://www.superbestaudiofriends.o...r-yes-hafler-headphone-amps.4564/#post-162606
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Magnetostatic_Tubephile said:

Hi Armaegis,

just noticed that you've only got a single dislike so far - from me! That says something. In fact, you are among my favourite posters on SBAF, believe it or not.

Honestly, do not take the dislike personally. The dislike is not about "disliking" your post, rather showing others that someone (in this case me) not quite agree with its general message. When I browse through SBAF researching gear, I tend to give "likes" and "dislikes" a lot as I go through countless amount of threads and posts.

The thing is that I had multiple amps so far with varying output impedances (Stratus - 3 / 8 / 115 / 120 ohm, Kenzie - 8 / 32 / 600 ohm, Sunrise III - 1 / 32 / 69 ohm, Valhalla 2 - 3.5 / 14 ohm, Torpedo - 32 / 300 ohm?) and always found it to be an important factor.

Short of high impedance dynamics, lower impedance outputs have always given me clearer sound, with more apparent dynamics and deeper bass response. Anything above 10 ohms is pretty much a no-go for me especially with planar magnetics but in general with all audiophile-level low impedance headphones.
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Armaegis said:

Ah ok. I was just taking some strange pride in being one of the few (or perhaps only member) not having any dislikes yet, or at least figured if I got one it would be for something more magnificent that a year old post in a thread nobody will ever see again. I would have found it more useful to see a quote and rebuttal instead to be more informative. I don't think I've ever actually given any likes or dislikes on sbaf.

I'm not discounting what you've heard, but I would like to point out however that your examples are all tube amps. This is a very different ball game, as now you are potentially changing the loading characteristics on the tube. Those that are transformer coupled are yet another level of complexity on top, because now you're using a different tap on the transformer on top of a different loading characteristic. In the case of the Valhalla, it was a change in gain structure that changed the impedance. I guarantee you these broad stroke changes are having a larger effect on the sound than the output impedance, again not counting the FR variation due to load impedance curvature.
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Armaegis said:

do you mind if I post this conversation? I feel like the viewpoints are valuable enough to be shared rather than being hidden away in PM.
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Magnetostatic_Tubephile said:

I would have preferred to specify my reasons for disliking directly to the post like it was possible on HeadFi in the past. Not possible on SBAF unfortunately. At the same time, I didnt want to "necro-post" in an old thread dedicated to a particular product with my opinion that is unrelated to the product.

Anyway, no problem with posting the conversation if you see it somehow benefitial to the community.

You are right - I probably havent owned a proper solid state amp with variable output impedance. Cannot recall one at least. Owned few hybrids with SS output stage though (apart from those listed above, I now recall also Vali 2), with the same general results noted. Might be also partially connected to other aspects of the amps as you suggest with Val2 but the general impressions related to output impedance remain to my ears anyway.

Things are not always black and white though. In case of Sunrise, Ive got more (macro) dynamics, bass depth and clarity with low impedance. On the other hand, the amp seemed more "suited" for higher impedance since the sound got a bit more refined and composed (subtle details were a bit more apparent, the overall sound less "forced" and fluent) that way. Also, I can imagine that extremely low output impedances (like 0.1ohm) might also not be sonically ideal. Generally speaking, anything within 1-10 ohm range is OK for me. But thats just me.
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Armaegis · Oct 31, 2018

@Magnetostatic_Tubephile
Why do you feel that a low output impedance would not be ideal?

Cspirou · Apr 27, 2023

This link is good for this discussion:

https://www.innerfidelity.com/content/musings-headphone-amplifier-output-impedance (dead)
https://cdn.head-fi.org/a/11423297.pdf

and this

https://sound-au.com/project56.htm

I'm also not completely sold on low output impedance since reading the articles Nelson Pass had about the F1 and F2. For multi-driver stuff with a passive crossover it's absolutely necessary. For single drivers though I think there's some good arguments to be made

edit: fixed dead links

Armaegis · Oct 31, 2018

Cspirou said: ↑

This link is good for this discussion:

https://www.innerfidelity.com/content/musings-headphone-amplifier-output-impedance
Click to expand...

Also this one:
https://www.innerfidelity.com/conte...-dt-880-250-ohm-and-dt-880-600-ohm-headphones

output impedance

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