HI,
I apologise in advance that my understanding of the specs is limited. I would like to know the answers to the following:
1) Is the DAC on the iDAC2 better or worse than the iDSD micro? (1 chip vs 2 chips makes a difference?), what about iDAC2+iPurifier vs iDSD micro?
2) Does the iDAC2 have pre-amp out?
3) How powerful is the amp of the iDAC2 compared to iDSD micro? More or less? (also how many watts into 50, 32 and 16 ohms?)
4) It only runs via USB and does it make a difference to the power of the amp if it run from USB 2.0 or 3.0?
5) Where can I order the iDAC2 launch bundle?
Thank you.
Hi,
To answer your questions:
1) Ceteris paribus, there is little in it so try both in your system with your speakers and decide for yourself. If you do not go portable much, then the less expensive iDAC2 is the one for you.
2) Nope, only on the 3.5mm so you can get a 3.5m > RCA cable and use the headphone section to work as pre-amp. But try this first to see if you like it.
3) It is less powerful than the iDSD micro operated in Normal and Turbo mode. It is somewhat more powerful than the iDSD micro in Eco mode.
> also how many watts into 50, 32 and 16 ohms?
These would have to be calculated based on the maximum output voltage (3.2V into 300 Ohm ) and the maximum voltage derived from the 16 Ohm Power Rating (2.4V/16 Ohm or 350mW/16 Ohm).
Basically, headphones of 300 Ohm or more will all have 3.2V maximum available (THD < 0.1%) while 16 Ohm headphones will be limited to 2.4V (THD < 10%, for THD < 1% it is around 2.2V) and impedances between will follow a straight line function of voltage vs current up to around 100 Ohm load above which the the voltage limit dominates.
Equally, for loads below 16 Ohm the implied current limit dominates.
Normally considering the current limit of the 16 ohm maximum output (2.4 V / 16 Ohm or 2.2 V / 16 Ohm in our case) and the maximum voltage into high impedances (3.2V into 300 Ohm) allow one to make a pretty accurate determination of available power into any given load.
IF the 16 Ohm voltage divided by 16 and multiplied with the headphone impedance gives a number lower than the maximum output voltage use that voltage for calculation.
IF the voltage calculated in the first step is higher than the maximum voltage, use the maximum voltage. This gives usually pretty accurate results (as a few mW one way or the other has little impact).
Power is voltage squared, divided by headphone impedance. So for example 3.2V squared is 10.24, divided by (say) 50 Ohm is 204mW.
As an aside, for a subjective doubling of perceived loudness, power needs to be increased tenfold, meaning if (say) an amplifier delivering 100mW into your headphones is not sufficient for comfortable listening levels, it is likely that you will need to step up to one delivering 1000mW into your headphones.
How much power for a given headphone is complex and is determined by sensitivity and impedance. It is better to look at headphones SPL normalised as dB/V (as used by Sennheiser) or as V/90dB (as used by Tyll Hertens in his tests for Innerfidelity). Conversion between the two is easy.
As examples (based on manufacturer spec - note, 1V is about the maximum output from an iPod, iPhone or other brands of smartphone):
Shure SE530 - 119dB/1mW or 134dB/1V - power at 1V = 28mW or 0.0007V/90dB
Audeze LCD-2 - 101dB/1mW or 113dB/1V - power at 1V = 14mW or 0.0710V/90dB
Sennheiser HD-650 - 103dB/mW or 108dB/1V - power at 1V = 3.3mW or 0.1250V/90dB
AKG K240 Monitor - 88dB/mW or 90dB/1V - power at 1V = 1.6mW or 1.0000V/90dB
AKG K1000 - 74dB/1mW or 83dB/1V - power at 1V = 8.3mW or 2.2000V/90dB
As can be seen, the spread of SPL @ 1V is 83dB to 134dB while the spread in power at 1V is 1.6mW to 28mW. So we can see power is actually quite meaningless in this context.
So in order to understand what power a headphone needs it is best to look for xxxV/115dB figure (115dB peaks are VERY LOUD and make sure you have enough reserve).
If using the xxxV/90dB figure from Tyll's tests simply multiply the Voltage from his test by 20 (+26dB) to know what voltage is needed for 116dB undistorted peaks. Then simply make sure your headphone amp can deliver this voltage into the headphone impedance.
If there is a figure of xxxdB/V, simply take the difference between 115dB and the actual dB (so a 115dB/1V Headphone needs 1V) and remember 3dB = *1.4, 6dB = *2, 10dB = *3.16, 20dB = *10 - these add, so 23dB is X * 10 * 1.4 or X * 14.
There is no really simple other way and often manufacturers’ recommendations for Headphone amplifiers are not what we would recommend.
e.g. recommending a 4W Headphone Amp for a 115dB/1V/20mW Headphone, the resulting SPL of 138dB is how should we put it…..‘
QUITE LOUD’.
ps: Anyone wishing to have the iFi headphone calculator excel, can open a support ticket to request it.
4) Any iFi dealer around the globe should be fine as they all have their allocation. The first 500 units are out there in the wild!
Just lookup:
http://ifi-audio.com/sales/
If you are in the USA, contact Music Direct or Avatar Acoustics. Either will look after you well.
Cheers.