How about some feedback to decrease the output impedance?

[xcortes]

Time for someone to find a review of the Sony MDR-R10 and see how flat its impedance curve actually is. This thread is spending a lot of time lately trying to solve an intractable issue which may not be a problem in the first place. Most headphones are quite flat and resistive, so the impedance of the source is a non-issue. Most good headphones are compatible with the standard 120 ohm source impedance and have a flat impedance curve.

I found an impedance measurement so I decided to resurect the thread. Any comments will be appreciated!

There's a lot of measurements here:
https://5991968839426898461-a-headphonehobbylab-org-s-sites.googlegroups.com/a/headphonehobbylab.org/filehost/home/files/CanJam2010HeadphoneMeasurements.pdf?attachauth=ANoY7cpq_A-JQHQ18Q828Jv3hPQnIXXJ0jnEIOmmBkE_E8Sb06Vej5KNQS8RXqmQR0u4BYRoKaO2cYOy8A-IZp9sgXKoe4yFjZ5uXJy6Np4IFdtUooe97qMg43vXjcSEc4r3xS05DH_WCBKmYJa2auRY3c1e_btUiCYvAKAIZQRipparyJ6kwFvI2BXJEK-WxykYBWic7PPtvPMmpSJBaYNbKHchYco2bGKMEQ6673_H2mwSd9qUV9NR3NVx2dyRVdhIVc6NX9sp&attredirects=0

[ironbut]

I visited Tyll and his headphone measuring rig in Chicago (good single malt in there!). He measured a pair of Audio Technica AD2000's while I was there. It didn't do so well with a good sized bump in the "presence" area (around 4k IIRC). In the real world, compared with most speakers with their room interactions most headphones are super flat.
That said, I don't think anyone would deny that listening to a great speaker rig is a richer experience.
I think that's one of the things that set the R10's apart. It seems to convey some of that speaker sound in a much more controlled environment.

[Doc B.]

Well, it's between 35 and 45 ohms. So the Crack isn't going to be the best match. We're working on a design that - if we decide it sounds OK - will be optimized for this kind of headphone load. It's still in the handwaving phase, we don't know if it will be good, no promises, etc.

[Mark424]

My apologies if this is a dumb question, as it's been 25 years since I've talked to Messrs Thevenin & Norton, but could you give the amp a friendlier load by putting a series resistor on the headphone output?  Not sure what that would do to the back EMF and ultimate performance.  e.g. I have the Westone UM3x at 56 ohm input impedance.  But since they are 124 db/mW, I could afford to loose 3-6db gain, no?  

One other question, does the speedball have any effect on performance for lower impedance phones?

Thanks

Mark