The specs for the LD mkV doesn't show 'bandwidth', AFAIK. Here's what you get from the manufacturer: http://www.littledot.net/forum/viewtopic.php?f=3&t=142&start=0 According to his specs it should be flat to within .5 dB. But wouldn't that depend upon the headphone used?
Here's the e9 specs....nothing about bandwidth here either: http://www.fiio.com.cn/product/index.aspx?ID=19 Will the specs for either show how well they will pair with the phones in question, the Q701? The E9 has a fairly high output impedance according to navguy's review....he claims it's not ideal for low impedance headphones. The mkV manufacturer refused to answer when he was questioned about the output impedance of the MKV on the LD forum. I wonder why that is.
Yes, the bandwidth is the frequency response: 10 Hz to 100 kHz, -0.5 dB.
The frequency response quoted refers to the output voltage of the headphone amp.
You are correct, though.
If the output impedance is high relative to the headphone impedance and the headphone impedance varies with frequency then you will get a reaction between the amp and headphone which causes variations in the actual voltage applied to the headphone. Basically the signal actually applied to the headphone would no longer be within their quoted spec. It would depend on the headphone. So if you are worried about this, get an amp with low output impedance, less than 3 ohms should be good enough even for Grados.
Little Dot refuses to answer? Must be "Top Secret" and "Highly Classified" in the interests of National Security. LOL!
I asked Schiit, guess what? they answered my question!
And who says output impedance is a meaningless spec? LOL!