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Hardware Teardown of Schiit Lyr Hybrid Tube Headphone Amplifier

amirm

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#1
This is a teardown follow up to my review of Schiit Lyr Hybrid Tube Headphone Amplifier. The unit is on kind loan from a forum member.

Taking apart the Schiit Lyr, like their heavier units is a bit of a challenge as it uses an odd metal box inside another metal box. After taking out the outer box, you are greeted with the internal exoskeleton:

Schiit Lyr Headphone Amplifier Teardown.jpg


I could take this enclosure apart but that would require unscrewing the output transistors but since this unit is on loan, I chose to not do that.

Typical of most headphone amplifiers, the architecture is rather simple. To the left, covered by the box are a couple of transformers connected to AC mains (protected by a fuse). The output is rectified by a bridge rectifier and then filtered (cleaned) by the black electrolytic capacitors that are visible. They are made by Panasonic (very good brand) and rated at 105 degree C (much prefered to cheaper 85 degree C).

The first stage of the amplifier is a dual-triode tube configuration. Unlike simple tube amplifiers however, this is a hybrid unit meaning the rest of the amplification and output to headphone jack occurs through a pair of MOSFET transistors. I did not try to reverse engineer the circuit to see if that is a class-A operation or class AB. Either way, the transistor stage provides the very low output impedance required without using of transformers, etc. Documentation says no feedback is used which would explain the rather high distortions I measured in my review.

You can get a better view of the output MOSFET transistors from this angle which are made by the respected company, International Rectifier ("IRF"):

Schiit Lyr Headphone Amplifier output stage Teardown.jpg


As you can kind of see, the metal portion of the transformer is "crusty" for the lack of a better term. Not sure if this is due to rust, use of second-rate transistors, or just the way they look. I am used to seeing them without this oxidation/coloration.

The case is used for heat sinking so best to make sure there is good airflow underneath the box in addition to above (needed for the hot running tubes anyway).

BTW, the dual enclosure design means that the drilled holes in the outer case are fake. They are blocked by the internal case so do not provide any extra cooling that way.

All of these heat generating components mean there is convection/air movement which will suck in dirt. And dirt is what we had in this unit:

Schiit Lyr Headphone Amplifier dust Teardown.jpg


This is a good reason to avoid hot running electronics if you can. Solid state version of this device could be built completely sealed, avoiding this problem.

There is an IC opamp from respected company, ST Micro but I did not try to figure out what it does.

I was impressed to see a lot of 1% rated resistors in there. Not very impressed (but I guess mandatory in tube amps at this price point) is a variable resistor per channel:

Schiit Lyr Headphone Amplifier bias Teardown.jpg


That is going to drift over time and change based on temperature of the unit which partly explains my variable results depending on how long the unit was warmed up.

A rather nice volume control was used in the unit but for some reason the label was torn up:

Schiit Lyr Headphone Amplifier pot Teardown.jpg


Not so nice is what I noted in my review: the volume control knob had come loose. This is caused by a round shaft and a set screw that is attach it to the knob:

Schiit Lyr Headphone Amplifier volume Teardown.jpg


If you are going to use a knob with a set screw, the knob needs to have a flat side on the shaft. Or some way of inserting into that slot that is visible. Without it, the set screw will lose its grip constantly forcing you keep tightening it.

A bigger miss is the way the rather large and heavy transformers are secured (or not in this case):

Schiit Lyr Headphone Amplifier transformer Teardown.jpg


As I have noted, the transformers have four round holes in the corners meant to fasten them to the chassis. Whoever designed the PC board made accomodation for this by putting those holes in there. But no screw or any mechanical fastener was used in either transformer. Instead, the mounting relies entirely on the soldered terminals.

To be fair, they are using rather thick PC board and I could not flex the PC board by hand. Still, it is just not good design practice to have such heavy components not have good, solid, mechanical fasteners to the chassis. They put the screw holes on them for that reason. Seems like someone down the line decided that saving 20 cents on screws and a minute to put them on was a worthwhile cost optimization.

FYI I saw the same practice in Schiit Yggdrasil DAC so this is not an exception but rather than the rule.

More concerning and a failure waiting to happen is the placement of these two electrolytic capacitors right next to the hot running tubes:

Schiit Lyr Headphone Amplifier capacitor heat Teardown.jpg


The heat will dry them up and cause them to fail over time. They have been put on their sides away from tubes or some other scheme of distancing them from the hot tubes/tube sockets right next to them. Users should keep an eye on these capacitors and change them at the first sign of bulging, something leaking out of them, or as a routine measure every so often.

Conclusions
When taking apart electronics, I always look for design/manufacturing features that either put a smile on my face or a frown. In this case, we have some of each. Precision resistors, brand name parts, beefy chassis are good to see. Alas those are far outweighed by other flaws which would have been very easy to avoid such as screwing in the transformers, distancing capacitors from heat sources, etc.

This is certainly NOT a product that I would be proud to own or be associated with as an engineer.
 

Sythrix

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#2
Well I’m officially paranoid about my Magni 2U now that I’ve seen some tear downs of their products. Hope it doesn’t burn down my house or something...
 

restorer-john

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#3
So, was the Alps RK27 secured to the front panel with a nut or did they save a few cents there too?

No transformer mounting hardware is inexcusable.

They seem to have removed these capacitors too:

liar.JPG
 

amirm

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#4
So, was the Alps RK27 secured to the front panel with a nut or did they save a few cents there too?
My memory is hazy but I want to say it did have a nut.
 

amirm

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#5
They seem to have removed these capacitors too:
They seem to be the same caps but in a different position. They pushed them closer to the sockets for some reason. In the picture you show they seem to be the same Panasonic brand but in the one I opened, the marking was different.
 
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#9
This is a teardown follow up to my review of Schiit Lyr Hybrid Tube Headphone Amplifier. The unit is on kind loan from a forum member.

A bigger miss is the way the rather large and heavy transformers are secured (or not in this case):

View attachment 11569

As I have noted, the transformers have four round holes in the corners meant to fasten them to the chassis. Whoever designed the PC board made accomodation for this by putting those holes in there. But no screw or any mechanical fastener was used in either transformer. Instead, the mounting relies entirely on the soldered terminals.

To be fair, they are using rather thick PC board and I could not flex the PC board by hand. Still, it is just not good design practice to have such heavy components not have good, solid, mechanical fasteners to the chassis. They put the screw holes on them for that reason. Seems like someone down the line decided that saving 20 cents on screws and a minute to put them on was a worthwhile cost optimization.

FYI I saw the same practice in Schiit Yggdrasil DAC so this is not an exception but rather than the rule.

Conclusions
When taking apart electronics, I always look for design/manufacturing features that either put a smile on my face or a frown. In this case, we have some of each. Precision resistors, brand name parts, beefy chassis are good to see. Alas those are far outweighed by other flaws which would have been very easy to avoid such as screwing in the transformers, distancing capacitors from heat sources, etc.

This is certainly NOT a product that I would be proud to own or be associated with as an engineer.
In this product it seems the transformers would be adequately captured by the chassis immediately above them should they work loose. These small transformers, secured by 8 sturdy mounting pins, are probably the least of worries.

What about the board to chassis clearance below? It looks to be mounted on 1/4" spacers. Unless there is a layer of fish paper beneath, they could easily be in violation of safety, especially if AC primary leads are not trimmed close to the board.
 

Jimster480

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#10
Doesn't look overall too bad.... but considering what they charge for it there are a few things that shouldn't have been overlooked as you mentioned.
And you are right there is no reason the caps should be so close to the tubes...
 

Dismayed

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#11
My Schiit Lyr, the very same unit measured by Amir, is on the auction block. I've received bids, so it will sell today. Don't miss a chance to have Schiit in your own life! As for me - I'm done with Schiit.
 
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