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Schiit Magni Headphone Amplifier

Discussion in 'Headphone Amps (full-size)' started by barry s, Dec 12, 2012.
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  1. ab initio
    Quote:

    I don't think you want to open up the Magni.... then you would be in deep Schiit? [​IMG]
     
  2. MPBateman
    Haha, if the Magni could have a lower gain switch it would be perfect for me.
     
  3. ab initio
    What headphones do you use? In just about all cases where 24bit soundcard output is available, using software volume will have no detrimental effect on sound quality. The Magni noise floor is quite low.
     
     
    http://www.head-fi.org/t/671220/effective-number-of-bits-or-why-you-have-to-keep-software-at-full-volume-is-nonsense#post_9591557
     
    Cheers!
     
  4. MPBateman
    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.
     
  5. ab initio
    Quote:

    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
     
    GLrunner13 likes this.
  6. MPBateman
    I can tell you put quite a bit of time into that post, which I appreciate. Also informative. DAC I currently have has an output power of 150mW so 0.15W so 0.15V (as you can see I need an amp), how would the Magni handle that? Or does the output of one unit affect the other?
     
  7. ab initio
    Are you sure about the 0.15 V dac? You need to know the impedance of the load it is driving to calculate the output power from the output voltage.
    What model DAC do you have? I would guess it outputs closer to 1 or 2 volts :)

    Cheers
     
  8. MPBateman
    I have a fiio e10, looking at the manual right now, outputs 32 ohms at 150mw.
     
  9. ab initio
    Your profile says you have a fiio e10. This has a line level output which should mean 2volts.

    Therefore, i think the numbers i provided above in my previous post should be a fairly good estimate :)

    Cheers!
     
  10. MPBateman
    Thanks again!
     
  11. Gabardine
    I really wish you guys would have a better way of compiling information.

    What are the downsides to the magni?
    I keep hearing it's designed to be flat and is omg so flat but then I look up other reviews and they list the cons as being bass heavy and too bright etc etc
    WHICH IS IT?
     
  12. Skolar311
    It also depends a lot on the source... being just an Amplifier, it should just "cleanly" amplify the source. The Magni does a great job of staying neutral and not coloring the audio in any way.
     
    So to answer your question, to me it is very neutral and that's the primary reason why I bought it. This does not mean that it slouches in any area. Bass is still very tight and present while the treble is smooth and not shrill.
     
    Your ears will have to do the deciding, because everyone's ears are different. You have to take everyone's opinion with a giant grain of salt.
     
     
  13. ab initio

    It's flat. Any difference between magni and perfectly neutral response is order(s) of magnitude less than your headphones. People complain with conflicting opinions because magni isn't providing the coloration that suits their personal taste.

    If you want imperfect amplification that distorts the audio, get a different amplifier (like a tube amp) or use DSP to achieve the coloration you want.

    The downside to magni is that it's 14dB gain might make it a bit on the loud side if you use sensitive IEMs, or it doest have adjustable gain, or that it doesn't have pre amp outs, or it doesn't make you coffee, or it doesn't cost $10k so you can brag to your friends, etc... :wink:

    Cheers!


    Cheers
     
  14. Gabardine

    Alright mate, think I understand the lay of the land now.
     
  15. PXSS
    Has somebody thought of putting attenuators in the rca going into Magni or on the trs output? How would that affect sound quality? Could be a good way of controling gain for IEM's
     
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