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I do have a DAC with 24bit sample rate, ATH AD700, Grado SR60i, Beyerdynamic DT770 250 Pro, Shure SE215, Etymotic HF5, and Klipsch S2. So half full size half IEM, however I only have one pair of High impedance cans would the gain of 5 work for me? Most likely not, but if I got 2 more high impedance headphones then the Magni would be right I think.
What is the output level of your DAC? Lets assume it is 2V full scale.
Using the
reference here for headphone sensitivity you can guesstimate how your different 'phones will play with the Magni. First off, I find that the volume knob gain vales at the end of that post are very representative of my Magni's response. Let's assume you are okay with using a volume setting between 9 and 3 o'clock. Also note that Magni's 5x gain = 14 dB. The key number in the table is the headphone's sensitivity. It tells you how loud the headphone gets for a given voltage. Using Magni's gain and a full scale line level signal, we will decided what signal input to Magni we need to reach a certain loudness.
The idea is that the very very very loudest peak in the music could reach 110 dB SPL.
this is dangerously high! and rms values of SPL for extended listening should stay at or below 85dB SPL. Consider the 110 dB peak to be head room for nominally lower listening levels. We will let 110 dB be full scale voltage swing with the volume knob set at 3 o'clock and find out whether this will allow for sensible settings for the other components when using your phones.
DT 770 @250 Ohms: According to the
chart, needs a gain of 6 dB to reach 110 dB SPL. We want 110dB to occur when the knob is set to 3 o'clock, therefore you want
Code:
(6 dB target gain) = (14 dB Magni gain) + (-4 dB volume gain at 3 o'clock) + (-4 dB gain from software)
Hence, set your software volume to -4dB and you're golden (or set volume to 0dB and use 2 o'clock on the volume knob for max volume)
-ATH AD700:
needs -9 dB gain, therefore set software volume to -19 dB
-Grado SR60i:
needs -7 dB gain, therefore set software volume to -17 dB
-Shure SE215:
needs -22 dB gain, therefore set software volume to -32 dB
-Etymotic HF5:
needs -21 dB gain, therefore set software volume to -31 dB
(target gain in dB = 20*log10((0.1 V@105dB)*10^( (5dB)/20)/ (2 V ref)))
-Klipsch S2:
needs -22 dB gain, therefore set software volume to -32 dB
(target gain in dB = 20*log10((0.1 V@106dB)*10^( (4dB)/20)/ (2 V ref)))
With these settings, you will get a maximum of 110 dB SPL peaks with the knob at 3 o'clock and a maximum of 80 dB SPL peaks with the knob at 9 o'clock. The average loudness will be below that, although it will depend on how compressed your music is. I think it's fair to guess average loudness will be -20dB (for very dynamic) to -6dB (for very compressed) below the peak volume.
For the sake of completeness, let us consider the worst case scenario with your most sensitive IEMs. With a 24bit DAC, all of these will be okay with Magni---in theory, even with -32dB attenuation, the output of 24 bits will still be about 18bits (which exceeds full CD quality!) although in practice, no DAC has true 24 bit resolution. In general, 24bit DACs have effectively 20 bits above noise, so you still have 14bits (84 dB of dynamic range!) remaining after -32dB attenuation (which is still sufficient to be effectively undetectable)
(See
this for calculating the effective number of bits and
this for a disucssion about bit depth)
According to Schiit, the noise floor of Magni is better than 100dB at 1 V rms input. That puts the amps noise floor at about -68dB when the software attenuation is at -32dB. This is pretty far down, but perhaps not optimal.
It isn't the impedance of the headphone that is important when comparing a headphone with an amp with certain voltage gain---it is the sensitivity (usually a number in dB of SPL at 1 V) of the headphone that matters!
The DT 770, AD700, and SR60i will make good pairings with the Magni. The others will work, but the combination may not be optimal. As a reference, I've used my Magni with AKG 240's (103dB sensitivity), Senn HD280pros (110dB), Senn HD202s (119dB), and ATH AD900(114dB) with good results
Hope this helps!
Cheers
