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Schiit Magni Heresy Headphone Amp Teardown

amirm

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This is a tear down of the recently reviewed Schiit Magni Heresy Headphone Amplifier. This version of Magni is uses integrated circuits ("OpAmps") as opposed to discrete output stage which in my measurements, garnered it far lower distortion and won my strong recommendation.

The screws were a bit less tight than the Magni 3+ I disassembled:

Schiit Magni Heresy Teardown PCB.jpg

The architecture here could not be simpler. AC input is rectified, filtered with good quality capacitors (Nichicon) and regulated to + and - 17 volts. Input signal is amplified by the OP1662 opamp/buffer.

A cluster of four OPA1688 headphone amplifier/opamps are used per channel. OPA1688 has exceptionally low distortion+noise:

Schiit Magni Heresy Teardown OPA1688.png

As you see, SINAD is 118 dB using 128 ohms. In my dashboard I use 300 ohms which is even a less stringent load. My measurements showed the same 118 dB SINAD confirming Schiit's implementation to be as good as the lab spec. Using four of these in parallel allows much more drive than a single one.

OPA1688 rated to operate at max voltage of +- 18 volts. So at 17 volts, it is near its max capacity so heat dissipation is going to be on the high side. To see how much, I put a 32 ohm load on the Heresy and drove it to 9+ volts output (about 2.5 watts). After just 3 to 4 minutes, the OPA1688s were cooking:

Schiit Magni Heresy Teardown Thermal Image 2 and half watts PCB.jpg


The highest temp is 63 degrees. Paralleling opamps is a crap-shoot in that you can't guarantee they all carry the same load. So some were hotter than others.

There is no heatsinking here whatsoever. If you are going to do crazy things like driving speakers with them, I suggest sticking a heatsink across all of them. Thermal efficiency will be low due to plastic packaging but hopefully better than none.

The back of the PCB was cleaner than the Magni 3+:
Schiit Magni Heresy Teardown Back PCB.jpg


The LED is where the mess was in the other one but I see no issues there. There is however residual solder as indicated. Given the through-hole parts, this is likely gone through wave soldering with some residue remaining. I suspect that is where the board is being held so solder is sticking to it.

Conclusions
This is a very clean and simple headphone design. Which means it will get copied. Fortunately Schiit has priced this amplifier quite low so the business opportunity is not that good for the clones. Ultra low distortion comes in the form of purpose built audio opamp meant for lower power headphone drive. By using four in parallel, much higher output level is available. Thermal management is fine for headphone listening.

A bit of solder residue could lead to failures in the field and should be cleaned up post inspection.

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As always, questions, comments, corrections, etc. are welcome.

Images in these teardowns are much larger due to complexity of images. This means soon I have to pay for more server storage costs. And you know me, I hate paying for things out of my pocket. So I hope you do your civic duty by filling my bank account as much as you can using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 

Tks

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Hey bossman, what's wave soldering?

This is a very clean and simple headphone design. Which means it will get copied. Fortunately Schiit has priced this amplifier quite low so the business opportunity is not that good for the clones.

Also cloning this would fail either way, even if it had even performance, the price + Made in USA designation simply leaves cloners in the dirt.
 

restorer-john

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Definitely an award winning headphone amplifier in the 2019 ASR awards.

Most improved budget offering from an established brand goes to... Schiit Magni, Heresy edition! I'm happy to accept the award (a free Heresy) on behalf of Jason or Paul
 

pavuol

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"wave solder residue"
come on, be a little more forgiving at least on Christmas... Schiit.. ehm... solder happens ;)
 

Eirikur

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This is a tear down of the recently reviewed Schiit Magni Heresy Headphone Amplifier.

So, based on these pictures, am I right in thinking that the volume control could have been in the center of the unit without consequence for sound quality? Longer traces from the (line level) input, and a shorter path of the attenuated signal to the buffer, that evens out - right?
 

gikigill

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Definitely an award winning headphone amplifier in the 2019 ASR awards.

Most improved budget offering from an established brand goes to... Schiit Magni, Heresy edition! I'm happy to accept the award (a free Heresy) on behalf of Jason or Paul

DITTO!!

Free Heresy please, Us Ozzies get shafted when it comes to hi-fi pricing.

(This might be the first Schitt product I,ll buy)
 

solderdude

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Technically there are 8 opamps (4 dual op-amp devices) in parallel on the output increasing current capabilities to 0.6Apeak = 0.42Arms.
The differences between the opamp outputs is equalized by adding 1 Ohm per opamp = 0.13 Ohm output R.
The OPA1662 is not a buffer but the gain stage and the output op-amps are in voltage follower (buffer) config.
 
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mmicko

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Interesting to see, that the power supply part (with LMxxx regulators) is same in both models. Looks like lower hum in Heresy is result of Opamp's better resistance to bad (noisy) voltage ... But there would be perhaps no added value in better power supply part, because the amp is already on the lab spec of opamp.
 

solderdude

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It's not entirely the same power supply.
The differences are in the 3+ which has 1 Ohm added to the outputs (behind the caps after the regs) and a set of extra reservoir caps near the output devices.
Differences in hum could be caused by idle current differences and/or ground/wire routing differences as well as PSRR of the circuits itself.
 

solderdude

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yes, all used opamps are dual-opamps (so 2 devices in one plastic DIP)
 

Rusty Shackleford

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"A bit of solder residue could lead to failures in the field and should be cleaned up post inspection."

You must be joking.
 

Neddy

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Yah, I have to agree that's a bit over the top, esp at this price point.
My first wave solder work involved my boss using a beaten up & abused old used one that smoked so much that we thought it was steam powered, and took 4-5 batches (each run!) before he got it to stop submarining and/or warping boards beyond rescue....still brings me fits of giggles remembering those early days.
But still, those boards (that survived) lasted for decades in pro theater and rental use, with far less critical aesthetic quality standards - almost all failures were wiring harness/wiring connector related, or ground loop 422 driver board launches...and those things sold for many thousands of dollars.
A few sprinkles on a masked section of a $100 product? Looks pretty good to me.
;)
 

Labjr

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Like others, I think the headphone jack is in the wrong place and too close to the volume pot. Would also like to see a brand name headphone jack (Cliff would drop in).
 

Ratatoskr

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@Labjr margins are very tight on a $99 product. Expecting Schiit to make rolling hardware or major design changes on a product in production is not realistic. I am sure Schiit monitors these threads and customer feedback and may consider making changes in future products. However you can not please everyone. If you think the volume knob is too small or too close to the headphone jack the solution is easy. Just buy an Asgard at $199 instead or a competitive $99 amp.
 
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