[rb2013]

that is not true. the wa7 is pure class A and can run low impedance headphones. my issue with your post is that you are implying that the lyr 2s class ab is somehow special or a more pure class a than class ab when a lot of class ab amps run purely class a when it is possible. that is how class ab works.

Again I disagree with your statement.  The Woo WA7 is tube output based (6C45) - you're comparing apples and oranges.  Almost every tube output amp is biased class A (push-pull - some SE).  That is not the case with solid state outputs.  You're confusing some headphone amp designs. 

 

The Woo Audio WA7 “Fireflies” Amp/DAC is a combination of high performance vacuum tube headphone amplifier with a built-in USB Digital-to-Analog Converter. It is a pure tube design, utilizing 6C45 tubes in a class-A, single-ended topology, with transformer coupled outputs.​

 
That is not how class A/B works and the Lyr is different.
http://en.wikipedia.org/wiki/Amplifier
 
"A Little Knowledge is a Dangerous Thing"
Alexander Pope

 

[money4me247]

  Again I disagree with your statement.  The Woo WA7 is tube output based (6C45) - you're are comparing apples and oranges.  Almost every tube output amp is biased class A (push-pull - some SE).  That is not the case with solid state outputs.  You're confusing some headphone amp designs. 
 
That is not how class A/B works and the Lyr is different.
http://en.wikipedia.org/wiki/Amplifier
 

 
You are right that there are many implementations of class A/B, but the lyr's implementation of class A/B with class A operation at lower output levels is not one-of-a-kind invented-by-schiit only featured in the lyr as you are implying. It is a common topology among modern class a/b amplifiers be able to act as solely class A at lower output levels. The fact is that the lyr is a class a/b amplifier since it does not do pure class A. definition of a pure class A amplifier means it does not go into class B.
 

 Class AB
This is the compromise of the bunch. Class AB operation has some of the best advantages of both Class A and Class B built-in. Its main benefits are sound quality comparable to that of Class A and efficiency similar to that of Class B. Most modern amp designs employ this topology. 

Its main characteristics are: 

• In fact, many Class AB amps operate in Class A at lower output levels, again giving the best of both worlds
• The output bias is set so that current flows in a specific output device for more than a half the signal cycle but less than the entire cycle.
• There is enough current flowing through each device to keep it operating so they respond instantly to input voltage demands.
• In the push-pull output stage, there is some overlap as each output device assists the other during the short transition, or crossover period from the positive to the negative half of the signal.

There are many implementations of the Class AB design. A benefit is that the inherent non-linearity of Class B designs is almost totally eliminated, while avoiding the heat-generating and wasteful inefficiencies of the Class A design. And as stated before, at some output levels, Class AB amps operate in Class A. It is this combination of good efficiency (around 50) with excellent linearity that makes class AB the most popular audio amplifier design. 

There are quite a few excellent Class AB amps available. This is the design I recommended for most general-use applications in home and car. Usually, parts choice rivals that of Class A amps, and dollar for dollar these are some of the best values in stereo amplification. There can be some variation in design principle, but generally these are well-designed amps since their function is very well-understood by audio designers. 

http://www.hifivision.com/amplifiers/174-types-amplifiers-class-class-b-class-ab-class-d.html
 
also, judging amplifiers solely based on class would be a mistake. there can be well-implemented class A and well-implemented class a/b amplifiers & poorly-implemented class A or class a/b. The lyr 2 is a well-designed class a/b amplifier that operates as class A at some output levels, but that doesn't mean that all Class A is inherently superior or that its operation while in Class A is superior than its Class A/B operation.

 

[rb2013]

   
You are right that there are many implementations of class A/B, but the lyr's implementation of class A/B with class A operation at lower output levels is not one-of-a-kind invented-by-schiit only featured in the lyr as you are implying.
 

Never implied such a thing - in fact I own two integrated that use a similar biasing topology.  As did a few other innovative amp designers.  Now how Schiit implemented the adaptive biasing could be unique.  You would have to have them explain it to you - doubt they would as it's most likely proprietary information. I can not think of another head phone amp that uses this kind of dynamic biasing - but there surely are a few.
 
Can you name another one?
 
My point is class A/B is not the same as class A adaptive biasing.

 

[rb2013]

   
You are right that there are many implementations of class A/B, but the lyr's implementation of class A/B with class A operation at lower output levels is not one-of-a-kind invented-by-schiit only featured in the lyr as you are implying. It is a common topology among modern class a/b amplifiers be able to act as solely class A at lower output levels. The fact is that the lyr is a class a/b amplifier since it does not do pure class A. definition of a pure class A amplifier means it does not go into class B.
 
http://www.hifivision.com/amplifiers/174-types-amplifiers-class-class-b-class-ab-class-d.html
 
also, judging amplifiers solely based on class would be a mistake. there can be well-implemented class A and well-implemented class a/b amplifiers & poorly-implemented class A or class a/b. The lyr 2 is a well-designed class a/b amplifier that operates as class A at some output levels, but that doesn't mean that all Class A is inherently superior or that its operation while in Class A is superior than its Class A/B operation.

Again you are confusing amp designs - Class A/B means exactly that a compromise between Class A and Class B.  We are not talking about Class B amps.
 
What makes the Lyr unique is that is operates solely in Class A most of the time (depending on volume), then switches over to A/B when needed.  What also makes the Lyr unique is that the biasing for Class A to Class A/B is not static - but dynamic.  In real time.  The 'adaptive bias' is the special sauce, and what makes it different, what allows it to remain in class A for most of the time without sacrificing dynamics.  What also makes it stand out in it's price class is the implementation of MOSFET outputs vs other designs.  It is very rare to see a MOSFET solid state amp that runs as single ended class A.  But again they are not unique.
http://www.firstwatt.com/pdf/art_zen_amp.pdf
 
PS Added for clarification:
Difference in operation from Class A push-pull and Class B push-pull:
http://www.audioholics.com/audio-amplifier/amplifier-classes
Class A

...The defining principle of Class A operation is that all of an amplifier’s output devices must be conducting through the full 360 degree cycle of a waveform. Class A can also be broken down into single ended and push/pull amplifiers. Push/pull diverges from the basic explanation above by utilizing output devices in pairs. While both devices are conducting through the full 360 degree cycle, one device will shoulder more of the load during the positive portion of the cycle, while the other handles more of the negative cycle; the primary advantage of this arrangement is reduced distortion relative to single ended designs, as even order harmonics are cancelled out. 

Class A/B:

...The solution is actually fairly simple in concept: where Class B utilizes a push/pull arrangement with each half of the output stage conducting for 180 degrees, Class A/B amplifiers bump that up to ~181-200 degrees...

So for each individual waveform the Class A devices handle the whole 360 degrees of each, in Class A/B the 180 degree (half way point) of Class B is pushed to say 200 degrees.  There is still a device switching going on During each waveform.  The switching point or crossover point is just moved higher into the waveform.  There still is crossover distortion.  So A/B is a move from B purely at 180 degrees closer to A's 360 degrees.  But not Class A's purity - that is each device handling the whole waveform.
 
Edit: correction in a typo Class B should have read Class A/B - corrected.  Added further explanation for clarification

 

[money4me247]

  Never implied such a thing - in fact I own two integrated that use a similar biasing topology.  As did a few other innovative amp designers.  Now how Schiit implemented the adaptive biasing could be unique.  You would have to have them explain it to you - doubt they would as it's most likely proprietary information. I can not think of another head phone amp that uses this kind of dynamic biasing - but there surely are a few.
 
Can you name another one?
 
My point is class A/B is not the same as class A adaptive biasing.

I am not interested in getting in a pissing match and I agree with your last point. I never claimed that it to be the same thing. A quick google search would reveal the information if you are interested in alternative products.
 
All I was saying is that it would be a mistake to categorize an amplifier with class a/b operation as a pure class A amplifier as the original poster did. also, the class A operation in a class a/b amplifier is not uncommon. I don't see how those two points are controversial or worth arguing over. the dynamic biasing and how specifically the lyr switches between class A and B is not something I ever mentioned.
 
In summary, I think the information you provided is quite helpful for those interested in the subject and not sure why or what you are arguing for. I think you may be misunderstanding my posts. 

 

[rb2013]

  I am not interested in getting in a pissing match and I agree with your last point. I never claimed that it to be the same thing. A quick google search would reveal the information if you are interested in alternative products.
 
All I was saying is that it would be a mistake to call an amplifier with class a/b as a pure class A amplifier as the original poster did. also, the class A operation in a class a/b amplifier is not uncommon. I don't see how those two points are controversial or worth arguing over.
 
In summary, I think the information you provided is quite helpful for those interested in the subject and not sure why or what you are arguing for. I think you may be misunderstanding my posts.

I did a google search didn't find any.
 
But here is one I'm getting in line for - HiFiMan EF1000.  Should be $3k - $5K. 
 
The word pure is a misnomer and should not be used in describing the Lyr - nor should it be called a 'pure' class A/B amp as some have implied. 

It should be called what it is 'adaptive' class A.
 
Cheers!

 

 

[Boogirl]

 
Glad to help - the review is really good and goes into a lot of depth.  It's the reason I bought my Lyr, it had me curious, at the time I had a Woo WA6SE.  With the right tubes the Lyr was better for me and I sold the Woo.  The tubes you use in the Lyr will make a big difference.
 
Here is the tube review thread I recently posted.
http://www.head-fi.org/t/761078/6922-tube-review-17-top-6922-6n23p-e88cc-cca-7308-e188cc-tubes

Cheers!

 

I read on various forums, including in the 6moons review that the tubes in the Lyr are really difficult to change. Someone has even claimed to have once broken a tube whist trying to replace it. This does not sound very good, but I am wondering how much kudos I should really be giving this concern. Are people exaggerating how difficult it is to change the tube.
I was wondering what peoples experience is of changing the tubes here?

 

[Tuco1965]

I find it easy to change tubes in my Lyr by gripping the top with the soft foam packing some of my tubes come with.  This is just my experience with my hands.  YMMV

 

[rb2013]

  I read on various forums, including in the 6moons review that the tubes in the Lyr are really difficult to change. Someone has even claimed to have once broken a tube whist trying to replace it. This does not sound very good, but I am wondering how much kudos I should really be giving this concern. Are people exaggerating how difficult it is to change the tube.
I was wondering what peoples experience is of changing the tubes here?

They are snuggled in there pretty good, but most of us tube rollers use these risers.  That makes it really easy, and it looks really cool too.  They're sometimes referred to as 'socket savers' These are the ones I use, but there are cheaper on Ebay.
 
Over on the Lyr tube roller thread there have been some inventive methods to remove the tubes, using little foam tubes, etc...
I have never heard of anyone breaking a tube by removing it.
 
http://www.tubemonger.com/NOVIB_Socket_Saver_1960s_NOS_British_McMurdo_B9A_p/novib-mcmurdo.htm

 

[Rem0o]

  Again you are confusing amp designs - Class A/B means exactly that Class A and Class B.  We are not talking about Class B amps.
 
What makes the Lyr unique is that is operates solely in Class A most of the time (depending on volume), then switches over to A/B when needed.  What also makes the Lyr unique is that the biasing for Class A to Class B is not static - but dynamic.  In real time.  The 'adaptive bias' is the special sauce, and what makes it different, what allows it to remain in class A for most of the time without sacrificing dynamics.  What also makes it stand out in it's price class is the implementation of MOSFET outputs vs other designs.  It is very rare to see a MOSFET solid state amp that runs as single ended class A.  But again they are not unique.
http://www.firstwatt.com/pdf/art_zen_amp.pdf

It seems there is confusion about amp class design all arround these posts. Instead of spreading wrong or partially wrong information and arguing over it, I suggest the following website if you want to learn about the definition of each amp class design. Some electronic knowledge is required though.
 
http://www.electronics-tutorials.ws/amplifier/amplifier-classes.html

 

[rb2013]

  It seems there is confusion about amp class design all arround these posts. Instead of spreading wrong or partially wrong information and arguing over it, I suggest the following website if you want to learn about the definition of each amp class design. Some electronic knowledge is required though.
 
http://www.electronics-tutorials.ws/amplifier/amplifier-classes.html

There is nothing that I have said or posted that is incorrect about amplifier design or operation.  That link fails to explain the difference between push pull and single ended.  Also the differences for tube versus solid state in practical audio applications.
 
But you some might find these helpful
http://www.theaudioarchive.com/TAA_Resources_Tubes_versus_Solid_State.htm
http://electronicdesign.com/analog/tubes-versus-solid-state-audio-amps-last-word-or-house-fire-part-2
http://www.audioholics.com/audio-amplifier/amplifier-classes
 
I wish folks would just go to the Schiit website - it just takes two minutes:

 It’s a current-sensing adaptive output topology which allows the amplifier to dynamically adjust to the headphone load. The primary benefits are essentially single-ended Class-A operation for high-impedance headphones, moving seamlessly to push-pull Class A and finally into Class AB as current needs increase. This provides much higher overall efficiency.

 

[Guidostrunk]

Lol. Some great posts, Bob.

 

[rb2013]

Lol. Some great posts, Bob.

I hate getting picky/cranky in the morning.  LOL!    Apologies to everyone - it's all good...

 

[crixnet]

 

Lol. Some great posts, Bob.

I hate getting picky/cranky in the morning.  LOL!    Apologies to everyone - it's all good...

No worries, Bob.
 
"It is better to light a single candle than to curse the darkness." 

 

[rb2013]

 
No worries, Bob.
 
"It is better to light a single candle than to curse the darkness." 

I did typo one very important error - I corrected and added a further explanation.
Thanks OP!  I see what you were saying.