Zens comes with iPower2 5V/2.5A, if driving low ohms headphones or iems Power shouldn’t be the problem (for the DAC at least). So when do you think power is an issue for the AMP?
First, the ZEN DAC runs the headphone amplifier on 5V and the amplifier Chip(s) make a negative 5V supply for +/-5V.
It is a Class AB design for portable gear with very low power consumption without signal (~ 5mA @ 5V for 2 channels - 25mW idle power consumption).
It is designed to drive 16 Ohm headphones at 3.3V Power supplies with > 100mW output. It is meant to drive a "standard" earbud (100dB/mW) with 16 Bit+ dynamic range performance. Output power is quite limited even at 5V.
The Zen CAN run's the headphone amplifier on +/- 12V, it is a "high bias" class AB design (often marketed as "Class A", it is Class A up to a point, Class AB after that), which consumes copious amounts of power even without signal (240mA @ +/- 12V for 4 Channels - balanced - 5760mW). The power supply is around 70% efficient so without signal the Zen can consumes ~ 8VA @ 5V, or ~1.6A.
Now if a power supply maxes out at 2.5A and 1.6A are used up to run the circuit without signal, there is not much left over to drive hard to drive Headphones.
To put it simple, an easy to drive headphone has moderate impedance and high sensitivity. IEM's for example have very low impedance, but their sensitivity is so high, they need very little power to go very loud (and so background noise from the Amp is high as well).
An example would be Campfire Andromeda, with a whopping 141dB/1V and 8.8 Ohm average impedance. So to get 115dB SPL (which is very loud) it needs 0.05V (50mV) and 5.6mA current (both RMS). A problem is that if the Amplifier has (say) -100dB/V noise which is not that bad really, the background hiss will be at around 40dB SPL (which is quite annoying) and to get the background absolutely quiet an impossible -140dB/V noise level is needed.
A hard to drive headphone is one with low sensitivity and either high impedance (here we need a lot of voltage) or low impedance (there we need a lot of current).
Two examples are the AKG K240 Studio 600Ohm which is 91dB/1mW which translates to 12.4V & 20mA for 115dB and the DCA Expanse with 87dB/1mW and rated 23 Ohm which translates into 3.8V & 165mA for 115dB.
When we talk about noise, what’s about using iPowerX 5V/3A with (by company info) improved noise reduction? And do you talk about the DAC or the AMP (or both).
Due to design, the ZEN DAC will be more sensitive to power supply noise, while for ZEN CAN peak current available is the key metric.
P.S. My iDSD Signature runs fine, like not to switch the Pentaconn from my headphone but must accept balance issues up to 11 o clock
When iFi had proper QA/QC, balance issues should have been not noticeable after ~ 8 maximally 9 O'Clock. I do not think 11 O'Clock is acceptable.
(maybe we should order some potis and use a soldering iron ourselves)
If you can something that fits and has better channel balance, by all means.
My understanding is that the combination of Stereo Pot and switch makes it hard to manufacture with correct tracking. This was already in place for the second or third batch of the silver iDSD micro. When proper QC was in place more than 50% of potentiomenters received from the factory were rejected as unacceptable. There is a long story how this developed from there and how the problem reappeared after being fixed, I wrote it somewhere already. End result, everything went back to as it was before, except the over 50% rejects ended up in customers products.
For the HIP DAC I had already designed out the switch on the Pot and replaced it with push-button, this was reverted back to pot with switch. The Pot & Switch were also retained for versions of the iDSD micro following my departure (Signature, Finale, Diablo) as well, despite better solutions being fully developed. Take the Zen CAN, it has no switch on the pot (and a push button power switch) and no balance issues I heard of.
Thor
