[mbgrace]

   
Thanks Michael.
 
So if I wanted to use the m9XX as a DAC, what volume level would I need to set it at to achieve an approx. 2V output level from the RCA output?
 
Thanks again.

Setting the volume at 90 will result in the DAC running at full scale (with the attenuator at 0) and a 2Vrms output for a 0dBFS signal. 
This is the top of the low gain range.  This would be the optimal setting for using the m9XX as a fixed DAC.

 

[mbgrace]

By the way, the attenuator step size is 0.5dB.  The display indicates the half-dB settings by illuminating the decimal point.

 

[NA Blur]

Love their m903 and would like to compare this to it. It looks like the new O2 design.

 

[canthearyou]

Love their m903 and would like to compare this to it. It looks like the new O2 design.

The Element

 

[b14cx0ut]

m9XX? The Element? Bifrost 4490? WHAT IS A PERSON TO DO?

 

[m8o]

I just checked-out the power specs on the drop's page.  That headphone amp's power ratings are very atypical of a solid state amp; power rises with increase of impedance (to a point) rather than rise to a decrease in impedance as most every other solid state amp does (again, to a point, the current limit point).  One could mistake it for a full-fledged current-drive / transconductance amp.  But the super low output impedance doesn't jive with that.  One could be tricked into thinking the power supply is current limited; but given the pedigree I strongly doubt that.
 
Headphone Output Power - Low Power Mode (2 channels driven):

1. 22 mW @ 4 Ω
2. 45 mW @ 8 Ω
3. 90 mW @ 16 Ω
4. 100 mW @ 20 Ω
5. 175 mW @ 32 Ω
6. 280 mW @ 50 Ω
7. 79 mW @ 300 Ω

Headphone Output Power - High Power Mode (2 channels driven):

1. 240 mW @ 4 Ω
2. 490 mW @ 8 Ω
3. 940 mW @ 16 Ω
4. 1030 mW @ 20 Ω
5. 950 mW @ 32 Ω
6. 650 mW @ 50 Ω
7. 85 mW @ 300 Ω

Impedances:             

1. Headphone Output: 0.08 Ω   
2. Line Output: 47.5 Ω

 

[kawaivpc1]

I want to buy this ASAP.
On your website, it says the "Drop has ended."
Is it coming soon or no?

 

[b14cx0ut]

I want to buy this ASAP.
On your website, it says the "Drop has ended."
Is it coming soon or no?

Drop doesn't start until monday.

 

[kawaivpc1]

I love to know how it compares with m920 in sound quality...
Does it come close? I understand it has similar features...

I heard that DAC1 isn't too different from Benchmark DAC2.
The reviewer says DAC2 is the only device that outperforms M9XX...while m9xx sounds better than DAC1.
I've heard DAC2 D. It indeed sounds very accurate...

 

[HiFiGuy528]

@mbgrace  90 or 90. for unity gain on the RCA out?

 

[canthearyou]

I can power 2 headphones at one time with this amp?

 

[WillBright]

I can power 2 headphones at one time with this amp?

 
Yes you can, but you'll be splitting the output power across two headphones instead of one. On the low power mode, you should still be able to get decent power to two IEMs to do A/Bs. 
 
In the high power mode, you'll be able to do effective A/Bs with whatever headphones you desire. 

 

[HiFiGuy528]

I can power 2 headphones at one time with this amp?

 
use the same model hp or one may be LOUDER than the other due to different efficiency.

 

[tgray]

I'd love to get this... but I just got my M920 from Massdrop on Monday.  Guess I don't really need it
 
Looks like it would be a great travel setup with a laptop.

 

[mbgrace]

Hi m8o,
The curve you see on the power output vs load impedance is created by the interaction of several factors.
1. m9XX power supply is current limited to .52A when in buss powered mode and 1.6A when in High Power mode.
2. The m9XX uses a linear output amplifier.  A theoretically perfect linear amplifier will have a maximum efficiency of 70.7% at the onset of clipping. (the m9XX amplifier will reach a maximum efficiency of about 54%)
The efficiency drops proportionally as the signal voltage drops. 
3. Very low impednace loads will cause the power supply to reach its maximum current draw at very low voltages where the output amplifier efficiency is at it's lowest.
 
This combination yields low power to the load at low impedances.  As the impedance rises the amplifier can deliver more voltage to the load which also allows for more efficient operation.  This relationship increases until the load impedance is high enough that the amplifier runs out of voltage and not current.  For the m9xx this is at about 50 Ohms in low power mode and 20 ohms in high power mode.   As the impedance increases from there the amplifier maximum output voltage determines the maximim power ouput.  This it the portion of the relationship that you are familiar with seeing in power amplifier specifications.
I hope this makes sense!  I can follow up with some basic calculations that illustrate the amplifier efficiency curve tomorrow.
Best,
Michael