Question on Astell&Kern AK70

[msknight]

Well, I walked in to Richer Sounds in Tower Bridge today.... very dangerous thing to do.  Ended up walking out with a Astell & Kern AK70  - good job my bank manager is a computer in a data centre, so it can't easily pick up a shotgun and come for my ass. Anyway, I digress....
 
I can't easily find in the specs, what the maximum reasonable impedance headphones it supports. I can't immediately see a high gain option in the menu structure and currently have them on my Sen HD 480 70 ohm version (thought I brought my HD 600 - ah well)
 
Here's the potentially relevant sections of the specs, but I don't know enough to make any sense of these numbers. Can someone help please?
 
Product Name AK70
Model PPE12
Supported Audio WAV, FLAC, WMA, MP3, OGG, APE (Normal, High, Fast),
Formats AAC, ALAC, AIFF, DFF, DSF
Sampling Rate FLAC, WAV, ALAC, AIFF : 8kHz ~ 192kHz
(8/16/24bits per Sample)
DSD : DSD64, Stereo/ DSD128, Stereo
Output Level Unbalance 2.3 Vrms/ Balance 2.3 Vrms (Condition No Load)
DAC Cirrus Logic CS4398 x 1 (Single DAC)
Decoding Support up to 24bit / 192kHz Bit to Bit Decoding
Outputs Phones (3.5 mm) / Balanced Out (2.5 mm, only 4-pole supported)
 
Audio Specifications
Frequency Response
±0.075dB (Condition: 20Hz~20kHz) Unbalance /
±0.075dB (Condition: 20Hz~20kHz) Balance
±0.56dB (Condition: 10Hz~70kHz) Unbalance /
±0.55dB (Condition: 10Hz~70kHz) Balance
S/N 116dB @ 1kHz, Unbalance/ 116dB @ 1kHz, Balance
Crosstalk 130dB @ 1kHz, Unbalance/ 130dB @ 1kHz, Balance
THD+N 0.0008% @ 1 kHz, Unbalanced / 0.0007% @ 1 kHz, Balanced
SMPTE IMD 0.0007% 800 Hz 10 kHz (4:1) Unbalanced /
0.0006% 800 Hz 10 kHz (4:1) Balanced
Output Impedance Balanced Out 2.5 mm (1 ohm) / Phones 3.5 mm (2 ohm)

 

[msknight]

I got home and plugged my HD 600 phones in and it worked a treat... It wouldn't surprise me if the unit is detecting the impedance and adjusting accordingly, because I'm using the same volume setting as with the 70 ohm HD 480.

 

[musickid]

Apologies first of all this is my first post here and was told not to start a new thread. I'm also looking for some advice. I have a yulong u100 amp/dac linked to my imac and it should sample to 24bit / 96 khz but as reported by another mac user in a review it came down to 24/48. With windows pc this does not happen. on my imac it again reduces to 24/48. my akg550 are also knackered so i want to upgrade now after 3 years. first of all does a dac at 24bit/ 48khz have the ability to handle Tidal and other forms of hi res music in the manner intended?
 
HiFi: Tidal
Flac 1411 kbps - Lossless 
(16/44.1 khz)
 
if not which i feel is the case here can anyone recommend a good dac and amp with mac compatibilty the key here. my budget including new cans is £550.
 
many thanks to all members