Massdrop O2 + SDAC DAC/Amp Discussions | Drop

Sep 22, 2017

MadSupraFrosty's right, the HD800 is harder to drive compared to the HE500. O2 won't be able to do it, it's barely enough for the HD6XX after you factor in amplifier distortion and impedance curve. I have both and the HD800 sounds bloody awful with my ODAC+O2.

Sep 22, 2017

tessierpg

Sep 22, 2017

JackulaI have the O2 and it drives either of my pairs of HD600 and HD6xx very easily even using the lower gain setting (2.4x on the standard gain Massdrop O2version), and even with a 1v input from my sound source (which is the line out of my Onkyo stereo network receiver). So don’t believe those who say that the O2 can’t drive properly these 300 ohms Sennheisers. I can’t speak for the HD800 however, but I would be very surprized that the O2 wouldn’t be sufficient to correctly drive these also.

Sep 22, 2017

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Sep 22, 2017

tessierpgWell all I can say is ymmv, it couldn't drive my HD600 that well, just a bit short. If you do the maths, the O2 would be at peak output with either the HD600 or HD6XX plugged in. Which is not good considering the distortion output at peak. The difference is certainly there with a bigger amp, same DAC.

Sep 22, 2017

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Sep 22, 2017

JackulaInstead of subjective assertions I will present you with actual measurements:
HD800 from Inner fidelity: Volts RMS required to reach 90dB SPL: 0.242 Vrms Power Needed for 90d BSPL 0.16 mW
HE500 from Inner fidelity: Volts RMS required to reach 90dB SPL: 0.310 Vrms Power Needed for 90d BSPL 2.04 mW
(removed Vrms reference for DAC/AMP as it was DAC section... good catch hugazebra!)
Conclusion: The HE500 requires more wattage/voltage than the HD800, this is due to the technology employed and inherently the sensitivity of the drivers. The vast majority (if not all) dynamic driver designs will be easter to drive than double-sided planar magnetic designs. I would agree the HD800 is harder to find a good amp pairing than the 500 but that's due to it's clinical precision and treble presentation... not because it is harder to drive.

Sep 22, 2017

Sep 22, 2017

ElectronicVicesYou are half right there, your measurements are at 1kHz. If you consider the impedance curve, the HD800 has more than double the impedance in the mid-bass, while the he500 is flat as planars are. I didn't believe it at first either, but the newer planars are far more efficient than high impedance dynamics.
To reach the same reference headroom, you need:
HE500: 10 ^ ((115 - 87.5) / 10) = 562mW @ 38 ohms HD800: 10 ^ ((115 - 96.8) / 10) = 66mW @ 300 ohms, assuming mid-bass impedance of 640 ohms you'll need about 141mW @ 300 ohms if scaling is linear and you're not current capped.
Getting 141 mW at 300 ohms is much harder than 562 mW at 38 ohms.

Sep 22, 2017

Sep 22, 2017

JackulaBy newer planars I take it you mean the single sided designs they have employed with every iteration after the HE-500 (unsure about the Susvara). Power is a function of voltage and current, with the HD800 requiring greater voltage swings from an amplifer and the HE500 requiring more current. If you care to post the math for the peak impedance power requirements for 90db I will happily concede. South of that my inference from Tyll's measurements at 1kHz, personal experience with these headphones and recollection from other forum discussions will feed my assertion the HE500 is the harder to drive of the two. I wouldn't recommend this rig for either, and neither is "easy" to drive.

Sep 22, 2017

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Sep 22, 2017

ElectronicVicesI don't know the specific construction, just that the Hifiman headphones like the 400's and 500's are far more efficient than I remembered them to be in the past. I don't disagree with you that HE500 needs more current and HD800 needs more voltage swing. Neither headphone needs much power for 90dB, my calculation gives 1.5mW for HE500 and 0.4mW for HD800 (I couldn't get Tyll's figures, my guess is his figures were measured, mine are based on nominal specs).
I don't dislike the O2, in fact I think it's the best for the price point. But the OP's claim was whether the O2 was powerful enough for the HD800, my standpoint is that factoring in amplifier distortion and clipping headroom, I agree it is not enough for the HD800.

Sep 22, 2017

Sep 22, 2017

JackulaOff the top of your head do you know other headphones that will make the O2 struggle other than the HD800, can it handle the HD6xx, 600ohm Beyers?

Sep 22, 2017

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Sep 22, 2017

E111Not from the top of my head, but the O2 shouldn't have much issues with all the other headphones on Massdrop. Even some 600 ohm Beyers are efficient enough that they will run off the O2 no issues. The O2 isn't a weak amp, and it isn't particularly powerful either. If you need to check a specific headphone, let me know, I can always help you with the calculations (assuming I can find the specs that I need).

Sep 22, 2017

hugazebra

Sep 22, 2017

ElectronicVicesNote that it is the SDAC that is spec'd at 2.15Vrms. The O2 can do 7Vrms into lower impedance loads, but with 300ohm impedance, it can only pump 90mW before distorting. So a little underpowered for HD800. That said, I use the O2 with an HD650 (slightly lower impedance that HD800) and classical music (i.e. not bass-heavy which sucks a lot of power) and find the combination sufficient.

Sep 22, 2017

Sep 22, 2017

JackulaIs there an easy way to see which amp is more powerful than another? Seems the O2 and Schiit Magni 3 use different ways to test their power

Sep 22, 2017

Sep 22, 2017

E111The Magni is a lot more powerful than the O2, leaving my personal opinion of the Schiit sound aside, you have to also be careful with too much power. Although you can get peak distortion at peak output, the reverse is also true. If you have a pair of really efficient low impedance headphones, there would be distortion due to amp mismatch.
It's a tough one isn't it? :P

Sep 22, 2017

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Sep 22, 2017

JackulaSo using some cheapo IEMs or even 32ohm phones could sound worse with a powerful amp than no amp at all?

Sep 22, 2017

Sep 22, 2017

E111Amps are still good, just make sure they fall in the middle somewhere. Not lower than say, the 10th percentile.

Sep 22, 2017

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JTCPingas

Sep 22, 2017

FrostyPNo. O2 is technically powerful enough to drive an HD 800. Subjective preferences aside, they aren't that demanding of a headphone.

Sep 22, 2017

Sep 23, 2017

E111Didn't have an issue with the HD650 as far as power goes (sound sig pairing is a different story), the HE500 and T1 v1 were a bit under driven in my opinion with the O2. I use it at the office and primarily with iems or occasionally the Audeze Sine. I picked up an O2 to validate all the claims of "this is the only headphone amp you need" and can say that for most it will be quite sufficient. I've always ascribed to the philosophy that one should have roughly 1-2x the headphone cost in signal chain (Amp/Dac). I don't think you will get your money's worth spending $1500 on a headphone and $150 on a DAC/AMP. Everyone's ears are different so I always suggest to start small and work up... everyone's stopping point will vary. The Headphone Rabbit Hole is deep and expensive... not Hi-Fi expensive but not certainly not cheap.
Frame of reference: Preferred amp for these high impedance/current hungry headphones is with a Schiit Lyr + 1969 Phillips MiniWatt SQ's. The soundstage is incredible with those tubes... used to be fairly good deal but can't be found much under $300 a pair these days....

Sep 23, 2017

Sep 23, 2017

E111Gotta have a reference point to make amp decisions with any efficacy... 1) Find the sensitivity of reference point/s (headphone) 2)Find power curve or table for desired amp(s) 3) Make sure to keep your units of measure straight db/V or db/mW on sensitivity and voltage or wattage for the amps 4) Factor in the nominal/max impedance of the reference point (impedance curves reflect max/min) 5) Familiarize yourself with ohms law and its derivatives 6) Do the math or use an online calculator 7) Factor in your own listening habits 8) Avoid an impedance mismatch or the frequency response can be affected (N/A for most planars). The output impedance of the amp should be 4 to 8x lower than the nominal headphone impedance to ensure minimal issues.
TLDR... nope not super easy to compare as there are also things like slew rate, phase linearity, capacitance, etc...
Advice: Trust your ears and buy from people with a good return policy!

Sep 23, 2017

Sep 23, 2017

ElectronicVicesThanks, I guess I'll figure out what cans I want in the future, definitally not going for anything $1,000+ I'm pretty happy with my 250 ohm dt880, but will probably go for the HD6xx if it ever pops up again, kind of leaning towards the Magni 3 and then getting a DAC in the future or waiting to see if they do a Modi 3, or just get this O2/SDAC

Sep 23, 2017

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Sep 23, 2017

E111As an owner of the HD650 and a former owner of the DT880 250 ohm (replaced with T1)... I can say you're on the right track. The options you mentioned are a great place to start and will be more than most people may need. I prefer separates to all-in-one units mostly due to the fact I can replace/upgrade one without having to change the other. Combining both and powering them from the same transformer/power supply can also have an impact on each others performance depending on implementation.

Sep 23, 2017

Sep 23, 2017

ElectronicVicesThe Magni and Modi would have a negative inpact on each other because they use 1 transformer or do you mean an amp/DAC in one?

Sep 23, 2017

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Sep 23, 2017

E111Dac/amp combo... sharing a power supply/transformer COULD lead to noise from one affecting the other. Schiit's wallwarts are actually pretty solid, some of them are linear (maybe all now). Put them on a power strip/center with isolated banks/outlets and you will negate most if not all of the interference. Can't do that with a combo.

Sep 23, 2017

Sep 23, 2017

ElectronicVicesOh okay, do the quality of power strips and RCA cables matter when it comes to a decent $20-30 surge protection strip with only the DAC/amp on it and Monoprice RCA cables? or anything around the same price but would clearly be better?

Sep 23, 2017

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Sep 23, 2017

Sounds good then

Sep 23, 2017

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Sep 23, 2017

E111Yeah don't go crazy on cables/power accessories. I've rocked Monoprice cables for years and have downscaled to Triplite power strips (HT with isolated banks) with no issues. I have three and they maybe total to 150 between them all. The main benefit of investing a little more than $30 bucks in a power strip will be Joule rating and the isolated banks. Keep in mind that lightning hitting the transformer or your residence will get past pretty much all surge protection known to man...
Edit: If you use a projector, get yourself a power center with a battery backup or UPS designed for home theater. If a projector loses power while running at best you will lose some lamp life at worst you will straight up lose the lamp. One power outage while running and the power solution pays for itself (bulbs range from $200-$500)

Sep 23, 2017

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