# So, the Objective2 headphone amp - designed entirely around the measurements? (PLEASE READ RULES BEFORE POSTING)



## Willakan

_Jude has kindly agreed to lift the ban on discussion of the works of banned members to allow discussion of the O2 headphone amp. However, please pay attention to the following before posting, otherwise this thread is likely to get locked:_
   
_1.This thread is about the amplifier, not NwAvGuy._
*2. No links to NwAvGuy's website, or resources maintained directly by him.*
*3. No links to sites where NwAvGuy is in direct and regular communication with people on such a site.*
*4. No discussion of the above rules or indeed moderation, as usual.*
_(The schematics and bill of materials I am mirroring (in compliance with CC license) in order that they may be linked to)_
   
   
  So, down to business. The O2 is a headphone amp designed purely around objective measurements and released under a non-commercial license (Creative Commons). It is cheap to build (PCB+parts run to 30 dollars) and also generally goes against much of what can be considered audiophile design philosophies; there are capacitors in the signal path, plenty of  50-cent ICs and it uses an AC wall transformer as part of the power supply.
   
  It also has an incredibly low noise floor and vanishingly low distortion, as well as easily enough power to drive popular dynamic headphones (K701, HD650, DT880) - even enough for high-end orthos if you don't listen excessively loud. Other notable features include current limiting and the ability to run off two 9V (8.4 volt in reality) batteries (power management kicking in to shut down the amp when the batteries are getting too low). Finally, it also fits perfectly into a cheap ($10) enclosure and has no SMD parts.
   
  Amp schematics and BoM (mirrored on my Google Docs): https://docs.google.com/viewer?a=v&pid=explorer&chrome=true&srcid=1WGBCwFbHXt-q82Ujih8IVu2vXsgMtlNpe6oHLLg_Klrf2LFxv5e9F1zloEZK&hl=en_US (WARNING: OUTDATED. See designer's site for latest)
   
  So, are you planning to build one? Any other thoughts?
   
  EDIT: Added Measurements Summary


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## Head Injury

I definitely want to build one. If I succeed (or if prebuilt ones are available this month 
	

	
	
		
		

		
			





) I'll grab an Asus card or something for a DAC and return my DAC1.
   
  That parts list is very intimidating for someone who's never touched an opamp or soldering iron.
   
  Also: Finally, an official thread which isn't going to be closed (I hope).


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## b0ck3n

This will be my first, and likely last as it neatly covers all bases, foray into the DIY world. I'm still hoping for a pre-assembled PCB to hit the market early on though.


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## Citan

Version with a dac and pre amp please!


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## Steve Eddy

Well, let's put it this way. The B22 was also an objective, simulation/measurement based design. I don't recall anyone complaining about that. So I don't see why the O2 should be impugned for taking the same approach.
   
  se


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## rroseperry

I'm interested, but having never soldered together anything, I'd have to wait for a kit or something to get one.


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## Satya

If it's any good, and that cheap, I'm hoping that populated PCB boards will be sold, and all one has to do is put it in a case and hook up some power, which is about the extent of my technical skills.  I'm sure there will be quite a few DIYers building them in the coming weeks, so I guess we'll see how well it performs and whether it it deemed worthy of partially assembled versions.


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## Head Injury

Quote: 





citan said:


> Version with a dac and pre amp please!


 

 A DAC with the same design goals would be great. Quality DACs are more affordable than quality amps in this market, it seems. Maybe because audiophiles respect neutral DACs but like colored amps.

 Quote: 





satya said:


> If it's any good, and that cheap, I'm hoping that populated PCB boards will be sold, and all one has to do is put it in a case and hook up some power, which is about the extent of my technical skills.  I'm sure there will be quite a few DIYers building them in the coming weeks, so I guess we'll see how well it performs and whether it it deemed worthy of partially assembled versions.


 

 There's very respectable measurements of the prototype online, but we can't post a link to them. It would be nice to see third-party measurements once some are built.


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## Currawong

The litmus test, IMO, will be its performance with complex music with a variety of headphones. That is something measurements don't show.  I might build one, for fun. I need a good transportable amp for testing headphones in-store that has consistent performance.


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## Steve Eddy

Quote: 





currawong said:


> The litmus test, IMO, will be its performance with complex music with a variety of headphones. That is something measurements don't show.


 

 Only if no one makes the measurements.
   
  se


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## SpaceTimeMorph

Are you going to sell some of these Steve Eddy?


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## deadlylover

Who's going to be the first? Or is everyone waiting for the boards?
   
  I'll probably have it done by next weekend, so long as Fedex doesn't balls it up (or I fall asleep and miss the delivery).
   
  I don't have any dynamics to use though, all I can borrow is the AD900 and LCD-2, and those are both very easy to drive.


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## SpaceTimeMorph

Quote: 





deadlylover said:


> Who's going to be the first? Or is everyone waiting for the boards?
> 
> I'll probably have it done by next weekend, so long as Fedex doesn't balls it up (or I fall asleep and miss the delivery).
> 
> I don't have any dynamics to use though, all I can borrow is the AD900 and LCD-2, and those are both very easy to drive.


 

 I put two orders into mouser for the parts, and am working on gathering some of the other stuff... but should be pretty quick once the boards are done.  I just want to error check as much as possible... it is a pretty solid design by the looks of it.  And all I have are Pro 900's, e3c's, ... yep nothing hard in this camp either.


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## Anaxilus

Somebody build one for Tyll.  Go!  Till someone with his pedigree hears it I'll remain skeptical.


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## Steve Eddy

Quote: 





spacetimemorph said:


> Are you going to sell some of these Steve Eddy?


 

 No. Why?
   
  se


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## deadlylover

Quote: 





spacetimemorph said:


> I put two orders into mouser for the parts, and am working on gathering some of the other stuff... but should be pretty quick once the boards are done.  I just want to error check as much as possible... it is a pretty solid design by the looks of it.  And all I have are Pro 900's, e3c's, ... yep nothing hard in this camp either.


 

 Boards? 
	

	
	
		
		

		
			





 Is there already a boards run underway or something?
   
  I'll be doing it point to point, dead bug style over here.
   
  Man, if Tyll weren't on the other side of the world, I'd give it to him. The shipping would be more than the parts cost though, and I don't think he will particularly fancy some robot vomit in a wooden box.


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## SpaceTimeMorph

Quote: 





deadlylover said:


> Boards?
> 
> 
> 
> ...


 
   
  Naw, I just mean whenever he gets the new layout done; I want to follow through with his PCB layout rather than point to point.  From what I can gather, that point (no pun intended) is still a couple of weeks out.  Even better for me, though.  End of August time frame is promising to be less busy at work than the craptastic pile of poo that I am dealing with right now...


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## khaos974

Shouldn't this be in the DIY sub forum?


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## Willakan

The DIY subforum gets a lot less traffic - besides, the reason I put it in Sound Science is because I thought that some people would want to bring up whether the measurements taken are the whole story, as Currawong already has, which is more of a Sound Science thing IMO.
   
  Also, deadlylover, doing it point to point would not achieve anything like advertised performance. Layout and grounding has to be extremely carefully optimised for the amplifier to measure well (NwAvGuy makes a point of it in his second article on his amp)
   
  Finally @Currawong, NwAvGuy mentions that his testing involved " playing real music into assorted worst case loads"


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## Currawong

That's good to hear.  It should really be in DIY, as that would include any measurement discussion.


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## deadlylover

Quote: 





willakan said:


> Also, deadlylover, doing it point to point would not achieve anything like advertised performance. Layout and grounding has to be extremely carefully optimised for the amplifier to measure well (NwAvGuy makes a point of it in his second article on his amp)


 
   
  I seriously doubt I will COMPLETELY balls up the amp by doing it point to point. Since I mess around with amps that can kill me so often, I like to pretend that I half know what I'm doing when it comes to DIY.
  
  Doing it point to point with everything star grounded with the shortest possible signal path should still be 'on nodding terms' with the PC board layout. I would hate to think the design is so sensitive and unstable that it will perhaps oscillate itself to death if I don't use the PC board.
   
  Come on, what's the worst that could happen? A slightly higher noise floor? Let's be real here, it's a bloody simple amp.
   
  I'm not going to go all 'nwavguy' on the O2 when I make it, I just thought that it would be nice to have some honest listening impressions compared to a well known amp like my balanced b22. I'm not setting out to bag on the O2 or anything, I absolutely hate dynamic headphones anyway, I really couldn't care less on how it compares to my b22. If it sounds just as good, then that's what I'll say, there's nothing to it.
   
  I'm not even going to bother anymore.


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## Willakan

I'm sorry, I'm just passing on what NwAvGuy said about his own design:
  " Moving a single track can change the distortion from 0.005% (-86 dB) to 0.1% (a lousy –60 dB). Really!"
  I don't think that is particularly novel as far as any high-performance design goes. Routing is not done well simply to lower the noise floor or just to get the shortest signal path. Whilst it would be possible to achieve high performance with a point-to-point approach, it would be very far from trivial.
  Why all the rage?


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## Steve Eddy

Quote: 





willakan said:


> I'm sorry, I'm just passing on what NwAvGuy said about his own design:
> " Moving a single track can change the distortion from 0.005% (-86 dB) to 0.1% (a lousy –60 dB). Really!"


 

 I find that a little hard to swallow.
   
  se


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## khaos974

It must be an extreme case, moving a track from its optimal position to the less desirable position possible, otherwise, I agree it's hard to believe.


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## deadlylover

Quote: 





willakan said:


> I'm sorry, I'm just passing on what NwAvGuy said about his own design:
> " Moving a single track can change the distortion from 0.005% (-86 dB) to 0.1% (a lousy –60 dB). Really!"
> I don't think that is particularly novel as far as any high-performance design goes. Routing is not done well simply to lower the noise floor or just to get the shortest signal path. Whilst it would be possible to achieve high performance with a point-to-point approach, it would be very far from trivial.
> Why all the rage?


 
   
  Yeah I'm sorry man, my bad. I just thought I was taking one for the team by cooking up another prototype, so I got a little bit offended when an armchair guru with no hands on experience pretends to know what he's talking about when it comes to DIY.
   
  I completely agree that proper board layout matters, but one does not simply compare it to point to point wiring, they're really different as one usually does not have to make the same 'compromises' as when routing a PC board. Sure, you won't get the modern niceties of a ground plane and susy, but I'm not going to go into that.
   
  I don't know if it's just my pathetic DIY experience kicking in, but the O2 is an _extremely _simple amp (that's not a criticism), it would be REALLY difficult to completely balls it up when doing it point to point.


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## Head Injury

Quote: 





deadlylover said:


> Yeah I'm sorry man, my bad. I just thought I was taking one for the team by cooking up another prototype, so I got a little bit offended when an armchair guru with no hands on experience pretends to know what he's talking about when it comes to DIY.
> 
> I completely agree that proper board layout matters, but one does not simply compare it to point to point wiring, they're really different as one usually does not have to make the same 'compromises' as when routing a PC board. Sure, you won't get the modern niceties of a ground plane and susy, but I'm not going to go into that.
> 
> I don't know if it's just my pathetic DIY experience kicking in, but the O2 is an _extremely _simple amp (that's not a criticism), it would be REALLY difficult to completely balls it up when doing it point to point.


 

 The parts are cheap enough. Do us a favor and make it point to point, then measure it


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## upstateguy

Quote: 





steve eddy said:


> No. Why?
> 
> se


 


  Thought you could do a run of populated boards like you did for the jack plug.
   
  No reason why you couldn't make something on it.  If it turns out to sound as good as nwavguy says it will, it's going to be a big seller...  even for finished products.
   
  I'm going to build one, but they're so inexpensive I'd also buy a populated board to see if there's any difference.


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## Willakan

I'm familiar with the disadvantages/advantages of point-to-point wiring vs PCBs. As I say, by all means have at it, but even simple point-to-point audio circuits require some degree of planning - and you have doubtless read the various articles on it where people complain how two point-to-point wired identical products sound different due to wiring variations (admittedly guitar amplifiers, which are not exactly comparable).
  Whilst a point to point circuit hugely simplifies things in some ways, there are still various concerns to deal with (parasitic capacitance ect) but it is a relatively simple design and you seem to know exactly what you're doing.
  You have to measure it after you're done though


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## Steve Eddy

Quote: 





> Originally Posted by *upstateguy* /img/forum/go_quote.gif
> 
> Thought you could do a run of populated boards like you did for the jack plug.


 

 Well, I had 100 of those jack plugs made and I still have about 90 of them left. 
	

	
	
		
		

		
		
	


	



   
  Quote: 





> No reason why you couldn't make something on it.  If it turns out to sound as good as nwavguy says it will, it's going to be a big seller...  even for finished products.


 
   
  I prefer to say away from other peoples' toys.
   
  I'm sure someone will pick up the ball and run with it though.
   
  se


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## sidel

I stumbled upon the O2 schematics the other day and actually do intend on building one.  This should be interesting,  no matter what the result is.


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## deadlylover

Quote: 





willakan said:


> Whilst a point to point circuit hugely simplifies things in some ways, there are still various concerns to deal with (*parasitic capacitance ect*) but it is a relatively simple design and you seem to know exactly what you're doing.
> You have to measure it after you're done though


 

 Somewhat critical in a direct coupled amp, but not so much in the O2 with it's caps left right and center. 
	

	
	
		
		

		
		
	


	



   
  Ahahah I don't have any fancy measurement gear, but I'll be sure to do what I can when it's done.


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## Focal1

I think it sounds like a pretty tempting design, and for a similar price as a CMOY design, or some of the Fiio amps that have been pretty well reviewed I'll probably plan to make one once the boards are available.


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## caracara08

i also will get one of these built since i have no experience with DIY.  i was looking for an amp that i can just turn on and go with.  warming up tubes and how hot it gets in my room is not something i want all the time... just almost all the time.


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## Anonanimal

I will definitely be building one of these.


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## dfkt

Funny that this thread is in "sound science". It's where unwanted things go to die here usually, no? I thought a regular amp with inputs, outputs, and volume control would go in a less shunned section of the forums.
   
  Either way, I'm looking forward to building my own.


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## sidel

Quote: 





dfkt said:


> Funny that this thread is in "sound science". It's where unwanted things go to die here usually, no? I thought a regular amp with inputs, outputs, and volume control would go in a less shunned section of the forums.


 
   
  The designer is apparently not very welcomed here.  /not saying more
  --
   
  It got moved!


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## Currawong

*It was posted by the OP in Sound Science originally.* It's a DIY amp so I moved it to DIY.  You guys need to try harder with your conspiracy theories.


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## madtone11

No conspiracy theories there. Pure (objective!) facts.


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## Willakan

The DIY forum is where I should have probably posted this initially. Let's not go over the top.
  Anyways, PCB and front-panel files should be released this week (Weds). Anyone planning on getting their own board made?


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## FallenAngel

Interesting design... are there really 2 channels of an opamp running in parallel for each of the 3 channels in the design, including ground?! That's a first. 
   
  Cool regulated power supply design.


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## nikongod

Quote: 





fallenangel said:


> Interesting design... are there really 2 channels of an opamp running in parallel for each of the 3 channels in the design, including ground?! That's a first.


 

 There is no ground channel. 
   
  Jan meier did the paralleled opamp thing a long time ago with his 50W all opamp amp. the CHA-47 is also kind of similar. 
http://gilmore2.chem.northwestern.edu/projects/showfile.php?file=meier3_prj.htm
   
  I dont really see how this amp measures significantly better than a pimetaV2, so why do we need new? if the point of a measurements first amplifier is measurements first... shouldn't they come first?


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## c61746961

They came first.


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## Satellite_6

Can you build those for 30 bucks tho?


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## nikongod

Quote: 





satellite_6 said:


> Can you build those for 30 bucks tho?


 

 Excluding the cost of the enclosure and not populating the ground channel? probably.


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## Satellite_6

I should really get into DIY then!


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## nikongod

Quote: 





satellite_6 said:


> I should really get into DIY then!


 

 Dont forget the case, and anything else that wasnt included in the $30. And tools to make the thing. 
   
  Its extremely easy to make an amp for $30. You just stop counting when you hit $75 and lie about the other $45.


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## Shike

Quote: 





nikongod said:


> I dont really see how this amp measures significantly better than a pimetaV2


 


  Where are the measurements for the PimetaV2?  Non-RMAA please.


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## kwkarth

Quote: 





nikongod said:


> Dont forget the case, and anything else that wasnt included in the $30. And tools to make the thing.
> 
> *Its extremely easy to make an amp for $30. You just stop counting when you hit $75 and lie about the other $45. *


 

 LOL!   Well said!


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## Citan

Yes, with exactly no facts included to back it up!  I think its fairly clear you both have an ax to grind.


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## The Monkey

Huh?


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## Avro_Arrow

Good one!
  
  Quote: 





nikongod said:


> Dont forget the case, and anything else that wasnt included in the $30. And tools to make the thing.
> 
> Its extremely easy to make an amp for $30. You just stop counting when you hit $75 and lie about the other $45.


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## Satellite_6

Quote: 





citan said:


> Yes, with exactly no facts included to back it up!  I think its fairly clear you both have an ax to grind.


 

 Do you mean no measurements? 
   
  [Measurements Removed]
   
  Go look at them elsewhere, they're impressive!


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## Citan

^^^
  The measurements are indeed impressive, I have no idea why some are claiming that the designer is misquoting the price by ~100% or that other amps in the same price range measure as well without a source.


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## deadlylover

Quote: 





nikongod said:


> Dont forget the case, and anything else that wasnt included in the $30. And tools to make the thing.
> 
> Its extremely easy to make an amp for $30. You just stop counting when you hit $75 and lie about the other $45.


 

 Aahahahah nice one!
   
  This 30$ amp is going to cost me about $85, and I like to pretend I'm a very good cheapskate.


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## elliot42

This looks like an interesting build, I'll put it on my "things to make next" list, which I might get around to sometime


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## Achmedisdead




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## b0ck3n

It's clearly stated that $30 will buy you the essentials only. Anyone should be able to get a kit that a kid could put together for under $100, which, considering the performance, seems like a bargain to me. I haven't seen anything that can compete with that, DIY or otherwise.


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## Ikelmonster

Quote:


achmedisdead said:


>


 

 x2


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## Soaa-

I'd be interesting in buying one of these off someone at some point.


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## redwarrior191

Quote: 





soaa- said:


> I'd be interesting in buying one of these off someone at some point.


 


  me too.. i don't DIY at all, but I'm really interested in the amp..


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## Soaa-

Quote: 





redwarrior191 said:


> me too.. i don't DIY at all, but I'm really interested in the amp..


 

 I can DIY, but I lack the time these days...


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## Anonanimal

Quote: 





shike said:


> Where are the measurements for the PimetaV2?  Non-RMAA please.


 

 I'm also interested to see this.  Did some quick searching (here and Google) and couldn't really dig anything up.


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## nikongod

I found RMAA pimeta-V2 measurements. 
   
  Its not loading right today, This is the cached version:
http://webcache.googleusercontent.com/search?q=cache:3CP6rv8c4woJ:tangentsoft.net/audio/pimeta2/bench/rmaa.html+pimeta+V2+rmaa&cd=1&hl=en&ct=clnk&gl=us&source=www.google.com
   
  What sucks here is that 1 person (who has a vested interest in the success of the amp in this thread) has measured his amp on equipment that is basically unobtainable to the casual user.
   
  An additional level of suck comes from the fact that there is no generally followed standard of testing headphone amps. One guy does one thing, the other guys do another.


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## Achmedisdead

Quote: 





nikongod said:


> What sucks here is that 1 person (who has a vested interest in the success of the amp in this thread) has measured his amp on equipment that is basically unobtainable to the casual user.


 

 A quote from that one person.....
   


Spoiler



And just to be clear, I'm not selling anything myself, and I don't get a penny of revenue from this design. It's open source hardware licensed under a Creative Commons License.


   
  So where is this "vested interest" ?


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## b0ck3n

Quote: 





> Originally Posted by *nikongod* /img/forum/go_quote.gif
> 
> What sucks here is that 1 person (who has a vested interest in the success of the amp in this thread) has measured his amp on equipment that is basically unobtainable to the casual user.
> 
> An additional level of suck comes from the fact that there is no generally followed standard of testing headphone amps. One guy does one thing, the other guys do another.


 

 The measurements will be verified by people who own that same equipment once all the details are released and the amps can be finished.
   


> An additional level of suck comes from the fact that there is no generally followed standard of testing headphone amps. One guy does one thing, the other guys do another.


 
   
  I think the measurements taken are pretty exhaustive. Which measurements are missing?


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## nikongod

Quote: 





achmedisdead said:


> So where is this "vested interest" ?


 

 It is the nature of all people to promote what they are passionate about. The fact that someone does not profit financially from something does not mean that he does not profit in other ways. 
   
  Many articles have been written promoting open source (software generally, but it extends equally well to other things) clearly illustrating that you cant pay someone enough to do quality work, but they will do quality work basically for free if they get some personal/emotional reward for it. Its interesting that people often do BETTER work without monetary compensation then they do at their "real" jobs. Anyways, this reward is why people do this, and open source designers often have a stronger interest in their designs then people who are only in it for the money.


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## khaos974

nikongod said:


> I found RMAA pimeta-V2 measurements.
> 
> Its not loading right today, This is the cached version:
> http://webcache.googleusercontent.com/search?q=cache:3CP6rv8c4woJ:tangentsoft.net/audio/pimeta2/bench/rmaa.html+pimeta+V2+rmaa&cd=1&hl=en&ct=clnk&gl=us&source=www.google.com
> ...




Considering that the schematics have been out for a single week, is it surprising that only 1 person has measured this amp?



achmedisdead said:


> A quote from that one person.....
> 
> 
> 
> ...




Could be a purely altruistic desire to design an affordable (even at $75) DIY design, could also be for his ego, celebrity on the net... Could be all of those, who knows?

What important is that the design is released and if you could prove his measurements false, then it was much ado for nothing. If his measurements (even using less rigorous methods), we have a DIY design that "certifiably" measures well into 99% of the loads that it can encounter.

Let's go back to the design and not its designer..


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## nikongod

Quote: 





b0ck3n said:


> The measurements will be verified by people who own that same equipment once all the details are released and the amps can be finished.


 
   
  I actually agree with this doublespeak, but let me translate it to English for the rest of the class.
   
  "The 3 people who are interested in DIY amplifiers that own the same expensive test equipment as the designer can test it."
   
  Its a good tactic really, limiting who can test an amplifier to a VERY narrow group.


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## khaos974

Anyone who can built it will be able to measure it, no one will be able to prevent those measures neither will anyone be able to prevent posting those measures for everyone to see.


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## samsquanch

Quote: 





nikongod said:


> I actually agree with this doublespeak, but let me translate it to English for the rest of the class.
> 
> "The 3 people who are interested in DIY amplifiers that own the same expensive test equipment as the designer can test it."
> 
> Its a good tactic really, limiting who can test an amplifier to a VERY narrow group.


 
   
   
  Maybe I missed it, but what equipment was used to test, and what tests were done?  I've got a grip of test equipment at work, maybe I'll build one and test it.


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## i_djoel2000

can't go wrong with 30 bucks.. if anyone running a pcb group buy, i'm in for one


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## khaos974

samsquanch said:


> Maybe I missed it, but what equipment was used to test, and what tests were done?  I've got a grip of test equipment at work, maybe I'll build one and test it.




The amp was originally measured on a Prism dScope III.



i_djoel2000 said:


> can't go wrong with 30 bucks.. if anyone running a pcb group buy, i'm in for one




$75 would be more accurate if you want accessories such as an enclosure.


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## b0ck3n

nikongod said:


> I actually agree with this doublespeak, but let me translate it to English for the rest of the class.
> 
> "The 3 people who are interested in DIY amplifiers that own the same expensive test equipment as the designer can test it."
> 
> Its a good tactic really, limiting who can test an amplifier to a VERY narrow group.




And others are free to do RMAA testing aswell. I don't see the problem.


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## Beftus

Interesting development, this amp. However I feel that in trying to prove the Mini³ is an underperfoming piece he has cheated IMO. What he has created is considerably larger than the Mini³. The O2 doesn't score points for pocketability... I would like to see his design for a single 9 volt battery amp that outperforms the Mini³ and still fits the Hammond 1455c801 enclosure.


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## mikeaj

The $30 figure taken out of context is pretty misleading, but in the original wording it was quite clearly stated that it was just the approximate cost of the PCB + components.  If you take a look at the BoM it should be quite clear what the costs are.  Comparing to other products, including shipping and all the other components, something a bit under $100 is more realistic.  However, you can get a full functioning amp for just the PCB + components + AC wall transformer ($5.55), so if you forgo the enclosure and batteries, it should be in the range of $50 which is hardly onerous.  One of the points was just that it doesn't use lots of $10+ op amps.
   
  PCB is relatively simple and apparently (we'll see) supposed to be around $10.  Group buys are great, but given that cost, the incentive is maybe not that high.
   
  In the comments to one of the articles, Tyll popped in and offered to test one, if that means anything.  Not sure if that's going anywhere.
   
  I'd always take testing by the designer with a grain of salt, but I'm not sure why it's offensive that it was done on gear that's not available to the average user?  You'd rather have it measured with less accurate equipment and with RMAA?  It's not like the noise measurements, THD measurements, and so on, are soooo bizarre.  You don't need to replicate the exact same tests to figure out if the performance is similar (or not) to what is being claimed.
   
  edit: I kind of agree about the size.  It is definitely on the fringe of "portable" for me.  It's not exactly gargantuan, but likewise I wonder how a single battery design (maybe with DC-DC conversion for the other rail) would do.  How large might a version be that does not use all through-hole components?


----------



## Shike

Quote: 





nikongod said:


> I found RMAA pimeta-V2 measurements.
> 
> Its not loading right today, This is the cached version:
> http://webcache.googleusercontent.com/search?q=cache:3CP6rv8c4woJ:tangentsoft.net/audio/pimeta2/bench/rmaa.html+pimeta+V2+rmaa&cd=1&hl=en&ct=clnk&gl=us&source=www.google.com
> ...


 

 Then do an RMAA with both amps to compare?  Fail to see what the problem is yet again - and there's already people with similar gear to his that have mentioned reaffirming the measurements are factual.  I fail to see how another design, especially if it performs as the measurements show, is a bad thing.
   
  As for RMAA measurements, I'm not too enthusiastic.  They work, but just for the minimal amount.  I will say though that when I fixed my dummy load and tested the mini^3 RMAA did report the correct crosstalk . . . around -40dB.


----------



## SpaceTimeMorph

He is not cheating with the Mini^3, he is trying to create a different amp altogether.  Fact is, to the best of my knowledge, there really isn't an amp that directly compares to this one; the mini^3 really isn't very close anyway and I don't personally agree with comparing.  This amp is also designed to compete as a desktop amp as well and is designed to drive just about any non-electrostatic, non AKG-1000 style headphone.
   
  Dropping to a single 9-V won't work because then you will have the virtual ground issues that crop up; which would violate the engineering premise behind the build.  You could utilize a small dual lion design or a multi-cell lion, however, that would violate the design premise of being an accessible amp for new DIY'ers.
   
  Isn't a manufacturer/designer that has made exhaustive measurements (not these, mind you) way better than a sales pitch with little to no factual bearing?  Simply put, there is enough information on his website to reliably recreate the tests he has made to check for accuracy (I really want to see those as well).  Furthermore, he has been actively engaged in promoting independent tests of this product to further reinforce the objective measurements.
   
  Does the designer have a stake in this?... yes, all designers do (for better or for worse).  Did he use a relatively inaccessible piece of equipment to measure the amp?... yes (what was he supposed to use, RMAA?).  Is this amp really $30... no, it is stated very clearly the entire amp can be had for just under $100 with shipping costs.
   
  Finally, in blind listening tests, this amp has been indistinguishable from the Benchmark DAC1 Pre.  Couple this with the fact that there are manufacturers (don't know who yet) in waiting willing to sell a finished PCB so that a person only needs an enclosure and a screwdriver to finish the amp, and I fail to see the problem with the amp.  All it needs is good, reliable peer review on the amp and all is well in the world, so to speak.


----------



## Willakan

The closest direct alternative to the Mini3, if you're hung up on size, that he's measured, is a CMOY off ebay. That still beat the mini3 by his numbers (admittedly it did require modification to change the default gain of 0
	

	
	
		
		

		
			





)
   
  As to NwAvGuy's measurements, they are comprehensive, they don't cheat to make his design appear falsely wonderful but are pretty impressive regardless and reliable people like Tyll Hertsens are interested in verifying their accuracy. What's not to like? He's giving away his design - many more people designing amps who would rather not let anyone get hold of their PCB files don't get their motivations questioned from the off, so why should he?


----------



## mikeaj

Well, as mentioned, you could do DC-DC conversion off of a single battery or something else.  These are all compromises though, both in performance and battery life (potentially cost too?) vs. size.
   
  Anyway, the battery/power protections in the current design look pretty interesting and functional.


----------



## i_djoel2000

Quote: 





khaos974 said:


> The amp was originally measured on a Prism dScope III.
> 
> 
> 
> $75 would be more accurate if you want accessories such as an enclosure.


 

 still worth nothing if it really competes with benchmark DAC1's amp section 
	

	
	
		
		

		
		
	


	



   
  i'm sure someone is already ordering pcb to a website, i just hope he sees my post and take me within his order


----------



## Mong0

I think it is pretty funny how some people are trying to turn all the work and documentation around by posting a reply of 10 lines against his book on the website. It is pretty clear who is the more credible, he has accounted for ALOT of stuff with theories which has consensus in the electrical engineering business(just not the audio business), but anyway.
   
  The point of using the dScope is not to block itself against other amps, but just to provide detailed and thrustworthy measurements. If anyone wants to disapprove the O2 all they would have to do is get him an amp and im sure he will be more than happy to measure it for comparing.
   
  Besides, i thought this thread was about discussing the amps design and not trying to set a house on fire which havent been built yet.


----------



## Anaxilus

I think everyone is interested in this project including myself.  I'd order a PCB myself to hear this thing.  Once again there is nothing wrong w/ data or people asking questions.  What is wrong is level of sensitivity some people seem to have.  It's really amazing.  Let's just stick to the amp and getting the thing built, tested and listened to.


----------



## qusp

Quote: 





fallenangel said:


> Interesting design... are there really 2 channels of an opamp running in parallel for each of the 3 channels in the design, including ground?! That's a first.
> 
> *Cool regulated power supply design.*


 

 exactly the first thing i said too. i probably wont build one unless its as a pressie for a friend or something, but i might steal that psu at some stage haha
   
  also, for the record, i have already registered my reservations on the ethics, or rather tactics and motivation behind the design and his previous agendas, so i'm not going to repeat them here, but the design itself is an interesting one, not so much interesting to me personally, but interesting all the same


----------



## Currawong

Quote: 





achmedisdead said:


> So where is this "vested interest" ?


 

 Do you know who he is? You know what? Nobody does. Not only that, he has gone to extensive effort to hide his identity. Maybe you should wonder why. 
   
  Quote: 





shike said:


> Then do an RMAA with both amps to compare?


 

 RMAA isn't the be-all and end-all of measurements and wont tell you everything about how an amp behaves when playing music. If only it were that simple. Personally, I'd like to see some square wave output off a scope at least, under different loads, but I'm sure we'll get to that at some stage anyway.
   
  Quote: 





mong0 said:


> Besides, i thought this thread was about discussing the amps design and not trying to set a house on fire which havent been built yet.


 

 Indeed. Ironically this is one of those times where I think subjective impressions of building and listening would be more interesting. This thread will inevitably go the way of threads such as the HD-800 and T1 threads where there was much noise before anyone gets an amp going.
   
  Again, if anyone missed it, I want to build one as a transportable amp to take into the local stores to try headphones with if it performs with as much linearity as claimed.


----------



## Soaa-

Quote: 





currawong said:


> Do you know who he is? You know what? Nobody does. Not only that, he has gone to extensive effort to hide his identity. Maybe you should wonder why.


 

 Fallacy: ad hominem.
  Claim: dubious amplifier design.
  Argument: designer's identity unknown.


----------



## nikongod

Quote: 





soaa- said:


> Fallacy: ad hominem.
> Claim: dubious amplifier design.
> Argument: designer's identity unknown.


 
   
  Cura was quoting a section regarding the designer's possible motives, and knowing his identity could be important in that. 
   
  Id jokingly say I wonder if its Why the lucky stiff, but why could actually write things people read.


----------



## Satellite_6

What's wrong with wanting to remain anonymous on the internet? What's wrong with an agenda based on solid evidence?


----------



## kwkarth

Quote: 





mong0 said:


> I think it is pretty funny how some people are trying to turn all the work and documentation around by posting a reply of 10 lines against his book on the website. It is pretty clear who is the more credible, he has accounted for ALOT of stuff with theories which has consensus in the electrical engineering business(just not the audio business), but anyway.
> 
> The point of using the dScope is not to block itself against other amps, but just to provide detailed and thrustworthy measurements. If anyone wants to disapprove the O2 all they would have to do is get him an amp and im sure he will be more than happy to measure it for comparing.
> 
> Besides, i thought this thread was about discussing the amps design and not trying to set a house on fire which havent been built yet.


 

 I think your post is pretty good.  I was thinking something similar myself.  Rather than reading about other's opinion about reading about reading about the amp design, I would like to start reading about how the amp sounds...


----------



## Citan

The amp shouldn't "sound" like anything.


----------



## Soaa-

Quote: 





citan said:


> The amp shouldn't "sound" like anything.


 

 Words of wisdom! A perfect amp does not draw attention to itself.


----------



## kwkarth

Quote: 





citan said:


> The amp shouldn't "sound" like anything.


 

 Please, let us not quibble over farkles 'n' fairy dust.


----------



## The Monkey

Everyone relax and just build the gotdam thing.  Children.


----------



## c61746961

currawong said:


> Maybe you should wonder why.


You know what?, I question your motives and attacks more than his*, and *you* should wonder why, since you have a social responsibility here, and he doesn't.

* You keep openly judging people and locking threads whenever someone questions the forum's policies, you also pass your opinions as facts as much as anyone else, I know this is a big place, it's free, and there's lots of work to do, but power comes with responsibility, and a forum is nothing without its audience.

Back on topic, I don't know how can some people still be weary about this, there is already a product, there's absolutely no point in speculating anymore.


----------



## BobSaysHi

subscribed. I'll wait for others to get this amp and give it a once over before I buy anything though.


----------



## qusp

Quote: 





soaa- said:


> Words of wisdom! A perfect amp does not draw attention to itself.


 

  
  you didnt seriously just open up a can of wisdom on his ass did you? it really isnt the time or place for portable audiophile hiaku


----------



## nikongod

Serious thoughts:
   
  In the schematics posted on the first page:
  u2b (one of the op amps used as a voltage source in the PS) does not have a 270Kohm resistor on it like U2a. These resistors and the0.22uf caps block anything but DC from reaching the mosfets. 
   
  Why arent the mosfets Q1/Q2 in the feedback loops of the opamps? It would reduce the output impedance of the power supply which would probably drop the crosstalk of the amp. 60db is "good" not "excellent" if we are talking about measurements without reference of audibility. 
   
  R25 could be exchanged for a JFET CCS or a CRD. CCS's are pimp. 
   
  The bandwidth limiting resistors and caps before the opamps is a nice addition. I hope this catches on in other amps. 
   
  Im 50/50 on the idea of the "opamp before the volume control" thing. Its not conventional, but has been done before. It solves the problem of noise from the opamp elegantly, BUT the gain stage is prone to overloading with excessive input voltage. This is noted on the schematic - its worth noting if you hook up to pro-level outputs. The fist kid who figures out how to set the gain to 10 (because 10 is more and more is better :facepalm: ) is going to have a wild ride. 
   
  The selected gains of 3 and 7 are pretty tasteful. Id lean towards just one. 3 or 4 covers you for 99% of all headphones, people just like switches.
   
  I think the 0.8db channel matching quoted in the test data may be misleading. Channel matching is primarily a function of the channel matching of the volume control, which is not generally great in those little pots. Maybe they all line up nicely at maximum volume, but at real levels Id bet on worse. Not really a fault of the designer just saying...
   
  Coupling caps, UGGGGGGH. UGGGh, uggggh. Thats the kind of stuff you'd expect to see in the kind of tube amp a guy like nikongod would design. Why not DC couple it? Ugggggh. At the very least put them in front of the pot where the signal is larger. Uggh, really? And just no. I guess they will save the headphones (sort of, but no) if the gain opamp goes all funky with excessive input signal. 
   
  I like the option of an output resistor outside of the feedback loop for the output op amps even though nobody will use it. I wonder if this admits the importance of subjective quality in spite of "knowing" how to do it right. heh. Id put a switch across this one so the user can switch on the fly like on the XIN amps. Its a good spot for ferrites or hand wound inductors should the need arise in actual use.


----------



## c61746961

That's interesting. You should question those design decisions in one of the places he can get into, though. The diy audio thread would be a great place.


----------



## nikongod

Quote: 





qusp said:


> it really isnt the time or place for portable audiophile hiaku


 

 you called?
   
  wow this amp is great
  it fits nicely in my hand
  but it sounds like trash
   
  Not directed at any amp in specific.


----------



## maverickronin

Quote: 





nikongod said:


> I like the option of an output resistor outside of the feedback loop for the output op amps even though nobody will use it. I wonder if this admits the importance of subjective quality in spite of "knowing" how to do it right. heh. Id put a switch across this one so the user can switch on the fly like on the XIN amps. Its a good spot for ferrites or hand wound inductors should the need arise in actual use.


 

 Well a few headphones here and there are supposedly designed for non-zero output impedance.


----------



## nikongod

Quote: 





maverickronin said:


> Well a few headphones here and there are supposedly designed for non-zero output impedance.


 

 I know, Im all about it (listening to HD800 from an amp with 450ohm Zo and loving it) jsut that its a monor thing that I like. Im mostly bummed so few people try it.


----------



## ujamerstand

Quote: 





nikongod said:


> you called?
> 
> wow this amp is great
> it fits nicely in my hand
> ...


 
   
 
   
  now that's signature worthy material.


----------



## maverickronin

Quote: 





nikongod said:


> I know, Im all about it (listening to HD800 from an amp with 450ohm Zo and loving it) jsut that its a monor thing that I like. Im mostly bummed so few people try it.


 


 Did Senn specifically design them for that or did you just play around with different resistors until you found something you liked?


----------



## digger945

Quote: 





nikongod said:


> I know, Im all about it (listening to HD800 from an amp with 450ohm Zo and loving it) jsut that its a monor thing that I like. Im mostly bummed so few people try it.


 

 I'm gonna try it.
   


  Quote: 





nikongod said:


> I guess they will save the headphones (sort of, but no) if the gain opamp goes all funky with excessive input signal.


 
  heh, or a cold or forgot-to-solder feedback resistor. Rail slam + parallel buffer = magic smoke.


----------



## nikongod

Quote: 





maverickronin said:


> Did Senn specifically design them for that or did you just play around with different resistors until you found something you liked?


 

 There is an optional standard for 120 ohms that it "feels" like they follow. 
   
  The amp has this output impedance by chance. I got the HD800, plugged them in, and was like whoa! 
   
  I know a few people who own 800s and B22's who dont like the amp. Maybe its what Im used to, but I like how it calms down the highs just a touch.


----------



## DingoSmuggler

Quote: 





> heh, or a cold or forgot-to-solder feedback resistor. Rail slam + parallel buffer = magic smoke


 
   
  Ha ha - but with $0.70 opamps, the magic smoke has a less pleasing aroma than most magic smoke.


----------



## khaos974

Sennheiser demo'ed their HD 800 with a Lehmann BCL which output impedance is 5 ohm though, and I seem to remember that a head-fier emailed them (or was it Beyer?) and Seenheiser recommended a near 0 output impedance.


----------



## mikeaj

Quote: 





> Originally Posted by *nikongod* /img/forum/go_quote.gif
> 
> Why arent the mosfets Q1/Q2 in the feedback loops of the opamps? It would reduce the output impedance of the power supply which would probably drop the crosstalk of the amp. 60db is "good" not "excellent" if we are talking about measurements without reference of audibility.
> 
> ...


 


 I'm pretty sure there are comments about most (but not all) of the points you bring up, in the docs...if one were to actually read them all.  Indeed there's a comment about the output resistor option, and coupling caps, and so on.  I'm not going to do all the work for you, but I remembered a few details.
   
  About the channel balance, that's easy to look up so I just did.  Yeah, that's pretty dependent on the pot you get.  But for reference the quoted value of 0.8 dB matching error is for -45 dB on the volume control, at least for the sample benched.  It's better than 0.8 dB above that level and still under 1.0 dB error at -55 dB, so these are pretty realistic levels.
   
  I'm not sure where you're getting the crosstalk figure, but the first article lists -65 dB crosstalk into 15 ohms, -72 dB into 33 ohms, -91 dB into 150 ohms, and -95 dB into 600 ohms (but a few dB worse at half volume, above 1kHz).


----------



## b0ck3n

In response to Currawong, RMAA was only suggested to nikongod as he argued that dScope measurements were somehow irrelevant, seeing as only a select few (and, he implied, likely biased) people could verify them.

I don't quite see the point in arguing something that's 60 dB below the music, especially a non-issue such as crosstalk. Again, assuming that the measurements provided are in fact correct, the design has no audible weakness. As far as subjective listening reviews go, they're completely irrelevant as they'll only adress the sound of the headphones used, or possibly the source. 

I don't mind constructive criticism - input on how to implement features, reducing costs or size etc, without compromising transparancy would be appreciated, undoubtebly by the designer as well. The goal is to put as good a product as possible, at a price as reasonable as possible, in as many hands as possible, and we're offered a chance to chime in and make suggestions for the amp to suit our specific needs. Afaik, it's unprecedented. So, whether the designer rubs you the wrong way or not, let's all give the design a fair shake and let it speak for itself.


----------



## Armaegis

Anyone taking bets on how long it'll be before a Chinese manufacturer swipes the design and starts selling?


----------



## khaos974

If they do it properly, I'd buy one to see how it sounds.


----------



## Maxvla

How much output power is this design capable of?


----------



## c61746961

> Max Output 15 Ohms 353 mW
> Max Output 33 Ohms 641 mW
> Max Output 150 Ohms 355 mW



Plenty.


----------



## Willakan

Nikongod, I actually contacted NwAvGuy regarding channel imbalance (he has since then updated his article to make it clearer)
  Firstly, the channel imbalance in the specs is 0.6, not 0.8db and is very much worse case. 
  Regarding DC coupling caps, that's just standard audiophile BS (OMG CAPS IN THE SIGNAL PATH! THEYLL DEGRADE MY BASSES). He addresses this at length in his articles.
  As for crosstalk, the 65db figure is into into 15 ohms; that's a pretty punishing load. Into 150 ohms it's 91db. Both figures are very respectable into their respective loads.
   
  And @Currawong, after your annoyance at fledgling Sound Science-related conspiracies, it's a bit rich to try to start a conspiracy theory of your own about NwAvGuy ("Do you know who he is? You know what? Nobody does. Not only that, he has gone to extensive effort to hide his identity. Maybe you should wonder why.")
   
  On a slightly more civil note, regarding your requests for square wave measurements, NwAvGuy has done several and they're in the original amp article, near the bottom. Square wave performance, performance into capacitive loads, slew rate and square wave rise time are all discussed.


----------



## qusp

Quote: 





kwkarth said:


> I think your post is pretty good.  I was thinking something similar myself.  Rather than reading about other's opinion about reading about reading about the amp design, I would like to start reading about how the amp sounds...


 

 my head hurts


----------



## Shike

Quote: 





currawong said:


> RMAA isn't the be-all and end-all of measurements and wont tell you everything about how an amp behaves when playing music. If only it were that simple. Personally, I'd like to see some square wave output off a scope at least, under different loads, but I'm sure we'll get to that at some stage anyway.


 

 But that would require hardware that many casual builders don't own!
   
  See: Nikongod's post for context of what I was saying.
   
   
  As for his identity: maybe he works at a larger audio company that would create issues if people knew?  There's plenty of reasons not to give your identity out online, and he certainly isn't obligated to especially when the design should speak for itself.  I can think of people who's identity we know of that are much less trustworthy.


----------



## nikongod

Quote: 





mikeaj said:


> I'm pretty sure there are comments about most (but not all) of the points you bring up, in the docs...if one were to actually read them all.  Indeed there's a comment about the output resistor option, and coupling caps, and so on.  I'm not going to do all the work for you, but I remembered a few details.


 

 I stop reading books after the 450'th page, and articles on DIY amps after the 12'th. 
   
  Quote: 





b0ck3n said:


> In response to Currawong, RMAA was only suggested to nikongod as he argued that dScope measurements were somehow irrelevant, seeing as only a select few (and, he implied, likely biased) people could verify them.


 

 Actually a proponent of the amplifier implied that RMAA measurements were somehow irrelevant by excluding them. 
   
  Quote: 





shike said:


> Where are the measurements for the PimetaV2?  Non-RMAA please.


----------



## nikongod

Quote: 





willakan said:


> Regarding DC coupling caps, that's just standard audiophile BS (OMG CAPS IN THE SIGNAL PATH! THEYLL DEGRADE MY BASSES). He addresses this at length in his articles.


 

 I'm not really concerned with the bass - the caps look to be appropriately sized for good bass response. I'm really concerned with the fact that they are there and what their sonic signature will do to the amp. Ewww. 
   
  With very few exceptions, every amp I have removed coupling caps from has sounded better to my ear. The one exception was adding a coupling cap to facilitate grid biasing a tube instead of cathode bias, but thats quite an apples to oranges comparison - it simply shows that cathode biasing a tube is worse than a coupling cap in that case.


----------



## svyr

willakan said:


> _Jude has kindly agreed to lift the ban on discussion of the works of banned members to allow discussion of the O2 headphone amp. However, please pay attention to the following before posting, otherwise this thread is likely to get locked:_
> 
> _1.This thread is about the amplifier, not NwAvGuy._
> _2. No links to NwAvGuy's website, or resources maintained directly by him._
> ...




where'd be those measurements  ? especially at different loads  ? (and power output levels  )... Though I guess the first one is not necessarily necessary, since you could go off the output impedance


----------



## khaos974

svyr said:


> where'd be those measurements  ? especially at different loads  ? (and power output levels  )... Though I guess the first one is not necessarily necessary, since you could go off the output impedance




There are a total of 3 articles on the amp in question, the first detailing the design criteria and whether the final design satisfied them with extensive measurements of the finished product, the second explaining the design choices and the final one about details in the circuit design and construction, with links to the BOM, the PCB schematics...


----------



## Satellite_6

Quote: 





svyr said:


> where'd be those measurements
> 
> 
> 
> ...


 
   


 [size=x-small]THD 1 Khz 150 Ohms[/size] [size=x-small]0.0017% Excellent[/size]       [size=x-small]THD 1 Khz 15 Ohms[/size] [size=x-small]0.0046% Excellent[/size]


----------



## Shike

Quote: 





nikongod said:


> Actually a proponent of the amplifier implied that RMAA measurements were somehow irrelevant by excluding them.


 

 I don't like RMAA because the accuracy varies based on input device (and the intelligence of the person using it).  This doesn't change the fact that, you know, you can still do them yourself if you really want.  I fail to see how you can hold measurements against the designer because you don't have the equipment to do it.
   
   
  Quote: 





> I'm not really concerned with the bass - the caps look to be appropriately sized for good bass response. I'm really concerned with the fact that they are there and what their sonic signature will do to the amp. Ewww.
> With very few exceptions, every amp I have removed coupling caps from has sounded better to my ear. The one exception was adding a coupling cap to facilitate grid biasing a tube instead of cathode bias, but thats quite an apples to oranges comparison - it simply shows that cathode biasing a tube is worse than a coupling cap in that case.


 
   
  Ah, the fabled better than physics golden ear.


----------



## kwkarth

Quote: 





shike said:


> I don't like RMAA because the accuracy varies based on input device (and the intelligence of the person using it).  This doesn't change the fact that, you know, you can still do them yourself if you really want.  I fail to see how you can hold measurements against the designer because you don't have the equipment to do it.


 
  ALL measurements regardless of the T&M equipment employed are completely subject to the intelligence and integrity of the person performing the measurements.


----------



## nikongod

Quote:


shike said:


> Ah, the fabled better than physics golden ear.


 

 You could always AB them.


----------



## Shike

Quote: 





kwkarth said:


> ALL measurements regardless of the T&M equipment employed are completely subject to the intelligence and integrity of the person performing the measurements.


 


  True, but I think you'll find the amount of people that use RMAA wrong disproportionately higher than those using dScope Series III analyzers at $10K.
   
  Quote: 





nikongod said:


> You could always AB them.


 
   
  You act as if I haven't.  The problem is this doesn't prove what you say is true. I can't hear a difference but that leaves me open for unfair criticism about my hearing, my gear, etc.  If these differences are so large, it's up to those making the claim to prove it.


----------



## kwkarth

Quote: 





shike said:


> True, but I think you'll find the amount of people that use RMAA wrong disproportionately higher than those using dScope Series III analyzers at $10K.
> 
> You act as if I haven't.  The problem is this doesn't prove what you say is true. I can't hear a difference but that leaves me open for unfair criticism about my hearing, my gear, etc.  If these differences are so large, it's up to those making the claim to prove it.


 
  You're probably right.  So too, is it true that comments in this and other threads contain a disproportionately large amount of hot air to actual fact.  Present company excepted.  
   
  I make no judgement upon your ability to hear, discriminate, or measure.  This is the internet.


----------



## Soaa-

So who's in for PCB group buy?


----------



## i_djoel2000

Quote: 





soaa- said:


> So who's in for PCB group buy?


 


  i'm in for one pcb if you're planning to run it


----------



## Soaa-

I don't have experience with such things sadly. I'm in to join a group buy, but not run it. 
   
  Oh! In other news, nwavguy informed us that his v1.1 PCB should be in his hands today and he'll build the amp and do some testing.


----------



## Willakan

As we don't even have confirmed PCB sellers, I think a group buy might be jumping the gun a bit.
   
  EDIT: You are allowed to use NwAvGuy's name you know!


----------



## c61746961

soaa- said:


> So who's in for PCB group buy?




Me me me me me me me!


----------



## Avro_Arrow

I did not find the Gerbers yet (are they even available yet?) but if and when I do I
  might etch a board myself and try it.


----------



## Willakan

Have updated first post with *Measurement Summary*.


----------



## Soaa-

Quote: 





avro_arrow said:


> I did not find the Gerbers yet (are they even available yet?) but if and when I do I
> might etch a board myself and try it.


 

 The author said he's going to release the v1.1 board once he finishes testing his prototype. He expects it to perform as well, or even better than the v1.0 against which the current measurements were made.


----------



## Avro_Arrow

I keep my eyes open and check back at his site once in a while then.


----------



## nikongod

yaay! I got signature quoted!


----------



## Avro_Arrow

lol 
	

	
	
		
		

		
			




   
  Quote: 





nikongod said:


> yaay! I got signature quoted!


----------



## BobSaysHi

Quote: 





nikongod said:


> yaay! I got signature quoted!


 

 hmmmmm


----------



## b0ck3n

There have been quite a few attempts made at derailing the thread - I'd suggest anyone who seeks to question the design or designer first read the articles and measurements on the O2. If you can't be bothered doing that, don't bother posting.

Looks like the revised board is complete. Pending measurements, and once the performance of the new layout is verified it'll be available to everyone - here's hoping vendors will jump on it quickly and provide some O2-for-dummies kits soon.


----------



## pcourtney1

I will ask my friendly pcb company to quote for the board with the bom populated on Monday when most of them are back to work from their holidays, should be fun 

And I wonder what parts (if any) will be on long lead times at the 1000+ qty , will find out soon I guess, this would probably suit most UK and European buyers, as the factory is based in England, so cheaper shipping/postage costs and no custom duties to worry about.


----------



## zammykoo

Quote: 





i_djoel2000 said:


> i'm in for one pcb if you're planning to run it


 

 +1


----------



## Willakan

Bulk Mouser buys for the UK could be possible - with shipping at £12 several people lumping together their orders to get them over the £50 free-shipping mark would save a reasonable sum of money.


----------



## fishski13

Quote: 





b0ck3n said:


> There have been quite a few attempts made at derailing the thread - I'd suggest anyone who seeks to question the design or designer first read the articles and measurements on the O2. If you can't be bothered doing that, don't bother posting.
> 
> Looks like the revised board is complete. Pending measurements, and once the performance of the new layout is verified it'll be available to everyone - here's hoping vendors will jump on it quickly and provide some O2-for-dummies kits soon.


 


  this is the DIY forum, not the SS.  friendly banter and a sense of humor is the norm here.


----------



## Beefy

Quote: 





nikongod said:


> Im 50/50 on the idea of the "opamp before the volume control" thing. Its not conventional, but has been done before. It solves the problem of noise from the opamp elegantly, BUT the gain stage is prone to overloading with excessive input voltage. This is noted on the schematic - its worth noting if you hook up to pro-level outputs. The fist kid who figures out how to set the gain to 10 (because 10 is more and more is better :facepalm: ) is going to have a wild ride.


 

 And as you increase the gain, you are running more power through the pot. A worst case scenario of 2VRMS input at a gain of 7 through a 10k pot gives you 19.6mW. An Alps Blue rated at 50mW would be fine - but it is high for, say, a TKD 2CP which is rated at only 20mW.
   
  I doubt it will be a significant problem, but certainly an odd decision to my mind.


----------



## SpaceTimeMorph

Quote: 





beefy said:


> I doubt it will be a significant problem, but certainly an odd decision to my mind.


 

 Not so odd... the pot won't add Johnson noise pre-amplification (which would just be amplified as it is pulled through the VAS if the pot were on the I/P).  Additionally, any noise created upstream of the pot has a chance of being attenuated by the pot; both cases reducing SNR going forward.  It's how a lot of non-audio applications where high SNR is a requirement take on adjustable gain through an amp/pre-amp package.


----------



## JamesMcProgger

did I read group buy for a kit with all the parts?


----------



## maverickronin

Not yet.  The design isn't quite finalized yet.


----------



## sgrossklass

Quote: 





beefy said:


> And as you increase the gain, you are running more power through the pot. A worst case scenario of 2VRMS input at a gain of 7 through a 10k pot gives you 19.6mW. An Alps Blue rated at 50mW would be fine - but it is high for, say, a TKD 2CP which is rated at only 20mW.
> 
> I doubt it will be a significant problem, but certainly an odd decision to my mind.


 
  There's no way you'd be able to get 14 Vrms into a volume pot with an amp running off of a +/-12 V supply. Maximum unclipped sine level at this point would be 7 Vrms and change, so we'd be closer to 5 mW. That's why the choice of two gain settings is handy, you can choose low gain such that there will be no clipping even with a hot sauce^Wsource (a few rare examples output up to 2.5 Vrms fullscale, and 2.2 Vrms is quite common among modern-day CD players), while high gain will accomodate weaker sources like portable players.
  
  As mentioned, it does make sense to come reasonably close to volume pot power handling in worst-case conditions (let's say, up to 20% or so). SNR still is defined by the ratio of signal power and noise power. Noise power is fairly constant, if we assume it to be dominated by Johnson (thermal) noise (no clue what the excess noise properties of typical volume pots would be). Hence, you don't get around dumping a certain amount of power into the pot if maximum SNR is a priority. Choosing a 10k instead of a conventional 50k pot simply increases available signal power by a factor of 5, so worst-case SNR could be expected to be up to 7 dB better. (Doing the math with the following stage's voltage noise included, it would be more like 5 dB in practice.) And noisy this design definitely isn't, with an advantage over a single-stage architecture that grows with gain.
   
  In order to avoid the first-stage clipping problem, one would have to employ a two-stage volume control, adding a second pot or stepped attenuator at the input.


----------



## deadlylover

Time to go kidnap a dynamic and fire up the beta22, I'll be back later tonight with some impressions.
   
  Let's see if this thing is the giant killer it's made out to be.


----------



## Anaxilus

Quote: 





deadlylover said:


> Time to go kidnap a dynamic and fire up the beta22, I'll be back later tonight with some impressions.
> 
> Let's see if this thing is the giant killer it's made out to be.


 

 Hopefully something more resolving than a HD600/650.


----------



## amb

Quote: 





> Originally Posted by *nikongod* /img/forum/go_quote.gif
> 
> Im 50/50 on the idea of the "opamp before the volume control" thing. Its not conventional, but has been done before. It solves the problem of noise from the opamp elegantly, BUT the gain stage is prone to overloading with excessive input voltage. This is noted on the schematic - its worth noting if you hook up to pro-level outputs. The fist kid who figures out how to set the gain to 10 (because 10 is more and more is better :facepalm: ) is going to have a wild ride.
> 
> The selected gains of 3 and 7 are pretty tasteful. Id lean towards just one. 3 or 4 covers you for 99% of all headphones, people just like switches.


 
   
  This is a real problem in this design, particularly on battery power.  Dual 8.4V batteries are specified, let's say that batteries are charged and does not fall below the rated voltage, we have 16.8V total spread, minus the forward drop of the two 1N5818 schottky diodes (0.5V each), this reduces the available voltage down to 15.8V.  And let's assume no further voltage drops in the power supply -- in fact there is some drop across the MOSFETs, but probably small enough to ignore for this discussion.  The NJM2608 opamp is not rail-to-rail.  It could only swing to about 2V above the negative rail and about 1V below the positive rail.  The signal's negative peaks will therefore clip first and effectively we have a maximum output voltage swing of 11.8Vp-p.
   
  The volume pot is not at the input to attenuate the input signal, so the input opamp "sees" the full output voltage from the source.  Let's assume a standard Redbook audio CD player's output voltage at 0dBFS of 2Vrms, which is 5.7Vp-p.  Even at the lowest gain setting of 2x, the opamp output will be swinging 11.3Vp-p which is right at the verge of clipping.  If you switch the gain any higher, it will clip rather severely.
   
  The designer states on the schematic "Input 4V RMS max".  If that was true, we'd need to be able to swing 22.6Vp-p at the output of the opamp for a gain of 2x (and more for higher gains).  Neither a battery-powered nor a wall-powered version of this amp could do that without clipping.
   
  This is irrespective of the headphone sensitivity or volume pot position.  While similar concepts have been used in commercial gear, the input stage in them would be powered by much higher supply voltages in order to avoid clipping, but that is clearly not an option here due to the batteries.


----------



## SpaceTimeMorph

Quote: 





amb said:


> This is a real problem in this design, particularly on battery power.  Dual 8.4V batteries are specified, let's say that batteries are charged and does not fall below the rated voltage, we have 16.8V total spread, minus the forward drop of the two 1N5818 schottky diodes (0.5V each), this reduces the available voltage down to 15.8V.  And let's assume no further voltage drops in the power supply -- in fact there is some drop across the MOSFETs, but probably small enough to ignore for this discussion.  The NJM2608 opamp is not rail-to-rail.  It could only swing to about 2V above the negative rail and about 1V below the positive rail.  The signal's negative peaks will therefore clip first and effectively we have a maximum output voltage swing of 11.8Vp-p.
> 
> The volume pot is not at the input to attenuate the input signal, so the input opamp "sees" the full output voltage from the source.  Let's assume a standard Redbook audio CD player's output voltage at 0dBFS of 2Vrms, which is 5.7Vp-p.  Even at the lowest gain setting of 2x, the opamp output will be swinging 11.3Vp-p which is right at the verge of clipping.  If you switch the gain any higher, it will clip rather severely.
> 
> ...


 

 However, 2 Vrms is not the standard for portable line input voltages.  Most portable players are ~1 Vrms, some significantly lower at around .5 Vrms.  2 Vrms is more likely for home usage.  Speaking of home usage, the power supply while running off of AC line voltage is rated for 24 Vpp.  Even accounting for .5V drop across the Schottky's you are dealing with 23.5 Vpp, which is 8.3 Vrms.  With a gain of 2x through the opamp that leaves you with a 4.15 Vrms input.  These leaves you with about 4% headroom here, which is cutting it awefully close.  However, the specified 4 Vrms max input was a design rating for input voltage, not a typical value.  With a 2 Vrms input and 3.1x gain you are dealing with 6.2 Vrms, which leaves you with a 33.9% headroom here; more than enough.  So, in short, you cannot compare the max output level of this for portable usage with a home source.  This is actually all explained within his articles.  Correct me if I'm wrong, but are there *normal *sources out there that would put out 4 Vrms or higher?
   
  Here is a link to the datasheet for the NJM2068.  I'm not sure what the performance of the 2608 is, but since it isn't used in his design...
http://www.datasheetarchive.com/NJM2068%2A-datasheet.html#datasheets


----------



## The Monkey

Is this a portable or a desktop amp?


----------



## khaos974

Portable, but still able to output 0.5W on battery (33 ohm load, 1 kHz, inferior to 0.01% THD+N), on AC it has maybe 15% more power, it should be able to drive the HE-6 at 110 dB.

Still waiting for independent confirmation of the measures.


----------



## Steve Eddy

Quote: 





willakan said:


> *2. No links to NwAvGuy's website, or resources maintained directly by him.*


 

 This needs to be modified to include no links to threads on other forums *not* directly maintained by him but where he may address critiques of the design (a link I posted previously to such a thread was subsequently deleted).
   
  Allowing a thread for the discussion *and critiquing* of a particular individual's design without that individual being able to respond to any of it is eminently unfair in my opinion and to that end I think this thread should be removed.
   
  se


----------



## odigg

Quote: 





steve eddy said:


> This needs to be modified to include no links to threads on other forums *not* directly maintained by him but where he may address critiques of the design (a link I posted previously to such a thread was subsequently deleted).
> 
> Allowing a thread for the discussion *and critiquing* of a particular individual's design without that individual being able to respond to any of it is eminently unfair in my opinion and to that end I think this thread should be removed.


 

 While I do agree that it's unfair that NvAwGuy cannot post in this thread, I don't think deleting this thread is the answer as Head-Fi is a popular site.  Many people who have the engineering know-how to comprehensively review and critique the O2 are on Head-Fi, not on the other mainstream forums.  Average Joe types (like me) are not on audio engineering forums and don't care to be since we can't much all that much sense of what is said.  Head-Fi is probably one of the few sites (that I know of) where the average Joe can make some sense of stuff said in the DIY section.
   
  Maybe NvAwGuy should be allowed back onto Head-Fi with the restriction that he can only post in this thread?  That makes the most sense to me as I'd like to hear what he has to say about critiques of his amp design.
   
  Anyway, I know I'm not supposed to discuss bans and what not so I'll leave it at that.


----------



## Steve Eddy

Quote: 





odigg said:


> While I do agree that it's unfair that NvAwGuy cannot post in this thread, I don't think deleting this thread is the answer as Head-Fi is a popular site.


 
   
  So you agree that it's unfair, but that's ok because HeadFi is... popular? Really?
   
  Quote: 





> Many people who have the engineering know-how to comprehensively review and critique the O2 are on Head-Fi, not on the other mainstream forums.


 
   
  And it's also ok because some people here aren't on other forums? Really?
   
  Quote: 





> Maybe NvAwGuy should be allowed back onto Head-Fi with the restriction that he can only post in this thread?  That makes the most sense to me as I'd like to hear what he has to say about critiques of his amp design.


 
   
  How 'bout just sticking to the rules as posted?
   
  "No links to NwAvGuy's website, or resources maintained directly by him."
   
  The link I posted was not to his website or to any resources maintained directly by him.
   
  Edit: I posted the link in response to another post which was also deleted suggesting that the thread be moved to someplace where NwAvGuy could respond.
   
  se


----------



## khaos974

steve eddy said:


> "No links to NwAvGuy's website, or resources maintained directly by him."
> 
> The link I posted was not to his website or to any resources maintained directly by him.




Actually, it's no links *direct or indirect* to nwvaguy, so let's stick to the design.


----------



## fishski13

Steve,
  while i have plans to build this amp for someone, i have to agree.  he's been banned here and elsewhere.  he has his own blog and diyaudio.com where anyone is free to join in on the discussion.


----------



## kevin gilmore

Lets assume that the amp is running on AC power, the voltage drop across the diodes and fets is zero and the
  input amplifier is rail to rail. At least according to the schematic, the voltage gains are 3.1 and 7.17
  So  1.2 VRMS is the maximum input voltage at a gain of 7.17 where the input amp is already clipping.
  And 2.76 VRMS is the maximum input voltage at a gain of 3.1 where the input amp is already clipping.
   
  Run it off of fully charged batteries and you get
  .83 VRMS at a gain of 7.17  and
  1.93 VRMS t a gain of 3.1
   
  practically after the diode and pass fet and the fact that the opamp is not rail to rail take
  about 20% off of those numbers.
   
  Over the years many manufacturers put the pot in the middle after the gain stage.
  Lots easier on tube gear where the power supply rails are in the hundreds of volts.
  The benefit is slightly lower noise. While its unlikely that this amp is going to be
  used with a cd player with a tube output stage, those typically put out well in excess
  of 5 VRMS.
   
  The pass fets and comparators are not a power supply, they are a under voltage
  kickout circuit. The pass fets are either very hard ON, or very hard OFF.


----------



## Steve Eddy

Quote: 





khaos974 said:


> Actually, it's no links *direct or indirect* to nwvaguy...


 

 That's not what the posted rule states.
   
  Quote: 





> so let's stick to the design.


 
   
  You say "the design" almost as if it somehow materialized out of thin air. But it didn't. It was designed by someone. So I don't see how the design can be discussed without it having implications for the person who designed it.
   
  se


----------



## Steve Eddy

Quote: 





fishski13 said:


> Steve,
> while i have plans to build this amp for someone, i have to agree.  he's been banned here and elsewhere.  he has his own blog and diyaudio.com where anyone is free to join in on the discussion.


 

 Yes, but the point is, he's not free to join in on the discussion here. And as I said above, you can't really separate the design from its designer.
   
  se


----------



## Anaxilus

Quote: 





steve eddy said:


> And as I said above, you can't really separate the design from its designer.


 

 You must be kidding, it's done here all the time.  This is not unique.  If I had a dollar for everytime Spritzer went to town on Rudistor I'd have a 009 by now.  
	

	
	
		
		

		
			




   
  I'm also not sure I'd agree the designer isn't or can't be represented here.  I see quite the contrary tbh.  To ask the thread to be removed on your grounds is over the top and unprecedented IMHO.


----------



## fishski13

Quote: 





steve eddy said:


> Yes, but the point is, he's not free to join in on the discussion here. And as I said above, you can't really separate the design from its designer.
> 
> se


 

 i agree, but he made his bed with his petulant behavior and refusing to desist.  he has a blog where he is free to act in any way he feels like and discuss whatever he wants.  i am surprised HF allowed this thread in the first place.


----------



## Shike

Quote: 





fishski13 said:


> i agree, but he made his bed with his petulant behavior and refusing to desist.  he has a blog where he is free to act in any way he feels like and discuss whatever he wants.  i am surprised HF allowed this thread in the first place.


 

  
  Two sides to every story.
   
   
  Either way, you can say he's rude but it doesn't change the fact that his measurements and design are good for the community.


----------



## fishski13

Quote: 





shike said:


> Two sides to every story.
> 
> 
> Either way, you can say he's rude but it doesn't change the fact that his measurements and design are good for the community.


 
   
  good for the SS community, fine, but i would disagree wholeheartedly for the DIY community.


----------



## Steve Eddy

Quote: 





anaxilus said:


> You must be kidding, it's done here all the time.  This is not unique.  If I had a dollar for everytime Spritzer went to town on Rudistor I'd have a 009 by now.


 

 Yes, Sprtizer went to town on Rudistor. Not some "design" that materialized out of nowhere.
   
  Quote: 





> I'm also not sure I'd agree the designer isn't or can't be represented here.  I see quite the contrary tbh.


 
   
  I don't see any posts by NwAvGuy. Are you suggesting he's posting using a sockpuppet account?
   
  Quote: 





> To ask the thread to be removed on your grounds is over the top and unprecedented IMHO.


 
   
  Well, there's a first time for everything.
   
  Personally I think going beyond banning someone and taking it to the point that the person cannot be mentioned and even prohibiting links to threads on other forums where the banned individual posts is rather over the top. It's right out of Orwell's 1984 and the old Soviet Union (see "unperson" or "nonperson"). And I only suggested this thread be removed when I discovered it had been taken to such an absurd extreme.
   
  se


----------



## c61746961

... or out of kindergarten. Maybe this thread should go, but not until there's another one with actual measurements and impressions over the finished product. This amp deserves the spotlight because it bears a flag, let the community decide if it's worthy.


----------



## Satya

Quote:


fishski13 said:


> i agree, but he made his bed with his petulant behavior and refusing to desist.  he has a blog where he is free to act in any way he feels like and discuss whatever he wants.  i am surprised HF allowed this thread in the first place.


 
   
  Just to check: if a banned, petulant person who happens to be a headphone amp designer has an amp design that you, as a member of the trade, are planning to sell, and there was much anticipation and posting occurring that is potentially leading to a flurry of said amps being bought and sold, would that thread be OK? 
   
  For the earlier post that stated "(a)llowing a thread for the discussion *and critiquing* of a particular individual's design without that individual being able to respond to any of it is eminently unfair":  - do you mean to say that are you sticking up for the disadvantaged designer?  Just to check: say the amp was designed by a Chinese electronics wizard that does not speak English and therefore cannot participate effectively in this forum, but based on preliminary indications has a great amp that you, as a member of the trade, intend to sell - would you feel more comfortable with a thread in which the designer cannot participate and respond to critiques?
   
  I may end up buying a pre-made version of this amp because of how it performs, regardless of whether the designer is petulant or a saint.   I believe it is possible to separate the design from the designer.


----------



## Anaxilus

Quote: 





steve eddy said:


> Personally I think going beyond banning someone and taking it to the point that the person cannot be mentioned and even prohibiting links to threads on other forums where the banned individual posts is rather over the top. It's right out of Orwell's 1984 and the old Soviet Union (see "unperson" or "nonperson"). And I only suggested this thread be removed when I discovered it had been taken to such an absurd extreme.
> 
> se


 

 Well if that is the crux of your point I can't say I disagree.  We are however moving beyond the scope of the thread though to a completely separate issue but your argument is not without merit.


----------



## fishski13

Quote: 





satya said:


> Quote:
> 
> Just to check: if a banned, petulant person who happens to be a headphone amp designer has an amp design that you, as a member of the trade, are planning to sell, and there was much anticipation and posting occurring that is potentially leading to a flurry of said amps being bought and sold, would that thread be OK?
> 
> ...


 
   
  i build as a hobby - maybe 8 amps a year.  i have zero interest in being profit driven.  i am actually building the amp for free, parts cost only.


----------



## Shike

Quote: 





fishski13 said:


> good for the SS community, fine, but i would disagree wholeheartedly for the DIY community.


 

 How is it bad for the DIY community?  If the measurements are to be believed it's one of the best performing in-spite of cost amps out there.  Please explain how that's a bad thing.


----------



## upstateguy

Quote: 





steve eddy said:


> Yes, Sprtizer went to town on Rudistor. Not some "design" that materialized out of nowhere.
> 
> 
> I don't see any posts by NwAvGuy.* Are you suggesting he's posting using a sockpuppet account?*
> ...


----------



## Steve Eddy

Quote: 





> Originally Posted by *Satya* /img/forum/go_quote.gif
> 
> For the earlier post that stated "(a)llowing a thread for the discussion *and critiquing* of a particular individual's design without that individual being able to respond to any of it is eminently unfair":  - do you mean to say that are you sticking up for the disadvantaged designer?


 

 No, I'm not sticking up for a particular individual. I'm sticking up for the underlying principle of the matter.
   
  Quote: 





> Just to check: say the amp was designed by a Chinese electronics wizard that does not speak English and therefore cannot participate effectively in this forum, but based on preliminary indications has a great amp that you, as a member of the trade, intend to sell - would you feel more comfortable with a thread in which the designer cannot participate and respond to critiques?


 
   
  First, I don't know why you bring in this "intend to sell" bit. Speaking for myself, I've no intention of selling anything having to do with the O2.
   
  Second, I make a distinction between whether or not a particular person is able themself to participate and their specifically being prohibited from participating.
   
  Quote: 





> I may end up buying a pre-made version of this amp because of how it performs, regardless of whether the designer is petulant or a saint.   I believe it is possible to separate the design from the designer.


 
   
  Certainly it's possible to separate the design from the designer when it comes to a simple purchasing decision.
   
  But until designs start spontaneously materializing out of thin air, I don't see how it's possible to separate the design from the designer when it comes to discussing and critiquing the design itself.
   
  se


----------



## Satellite_6

I have to say I agree with se. . . 
   
  At the very least the rules do need to be changed because they are misleading/inaccurate.


----------



## amb

Quote: 





spacetimemorph said:


> However, 2 Vrms is not the standard for portable line input voltages.  Most portable players are ~1 Vrms, some significantly lower at around .5 Vrms.  2 Vrms is more likely for home usage.  Speaking of home usage, the power supply while running off of AC line voltage is rated for 24 Vpp.  Even accounting for .5V drop across the Schottky's you are dealing with 23.5 Vpp, which is 8.3 Vrms.


 
   
  So you're arguing that the amp is only designed for portable usage with weak sources, yet force the use of AC power (which in this design, gives about 7Vp-p more swing from one rail to another than on battery power)?




   
  You also forgot to account for one more 0.5V drop because there are two 1N5818 schottky diodes -- one on each rail.
   
  Quote: 





> With a gain of 2x through the opamp that leaves you with a 4.15 Vrms input.  These leaves you with about 4% headroom here, which is cutting it awefully close.


 
   
  No it's worse than that.  You fail to account for the fact that the opamp is not rail-to-rail so it will clip several volts before the signal peaks swing to the rails.  That will cut about 4Vp-p off the available swing.  And subtract the missing 0.5V schottky drop, you're now left with 19Vp-p swing before clipping, and with a gain of 2x, the input cannot be more than 9.5Vp-p which is 3.4Vrms.  If you give the amp a 4Vrms signal, it will clip even on AC power.  Set the gain any higher than 2x and it will clip worse.
   
  Quote: 





> However, the specified 4 Vrms max input was a design rating for input voltage, not a typical value.  With a 2 Vrms input and 3.1x gain you are dealing with 6.2 Vrms, which leaves you with a 33.9% headroom here; more than enough.


 
   
  I already demonstrated above that the amp cannot handle 4Vrms input on AC power, let alone battery power which gives 7Vp-p less swing.  With 2Vrms input and gain of 2x, indeed you have 6.2Vrms, which is 17.5Vp-p.  This is only 1.5V before the 19Vp-p maximum swing, which is only 0.7dB headroom.
   
  With battery power, in my original post I showed that the amp could only swing 11.8Vp-p, so the 2Vrms input and 3.1x gain will clip severely.
   
  Quote: 





> Here is a link to the datasheet for the NJM2068.  I'm not sure what the performance of the 2608 is, but since it isn't used in his design...
> http://www.datasheetarchive.com/NJM2068%2A-datasheet.html#datasheets


 
   
  The "NJM2608" in my original post was a typo.  I really meant NJM2068, which is the opamp the designer chose for the input.


----------



## Satya

Quote:


fishski13 said:


> i build as a hobby - maybe 8 amps a year.  i have zero interest in being profit driven.  i am actually building the amp for free, parts cost only.


 

 Thanks for the reply.  Where I am coming from is that, as someone who 'showcases' the AMB designs (per your 4/29 post regarding the M3), designs which were recently criticized by the designer of the O2, I have to keep that in mind as I read your posts.


----------



## Shike

I've asked nwavguy about the 4V - he states this is regarding DAMAGING the amplifier and not in regards to clipping.  Using the default gain 2.25V should be safe for low distortion, or a lower gain can be used.


----------



## Satya

Fair enough.  As this amp gets built and tested by DIYers, the designer will presumably be criticized or lauded for a variety of reasons, one of which will hopefully be how the amp sounds.
  
  Quote: 





steve eddy said:


> Certainly it's possible to separate the design from the designer when it comes to a simple purchasing decision.  But until designs start spontaneously materializing out of thin air, I don't see how it's possible to separate the design from the designer when it comes to discussing and critiquing the design itself.


----------



## amb

Quote: 





shike said:


> I've asked nwavguy about the 4V - he states this is regarding DAMAGING the amplifier and not in regards to clipping.  Using the default gain 2.25V should be safe for low distortion, or a lower gain can be used.


 

 I assume "default gain" is 2x.  A 2.25Vrms input will give 4.5Vrms output, which is 12.7Vp-p.  This is almost a volt beyond the 11.8Vp-p maximum swing of the amp running on batteries and therefore will clip.


----------



## Shike

Quote: 





amb said:


> I assume "default gain" is 2x.  A 2.25Vrms input will give 4.5Vrms output, which is 12.7Vp-p.  This is almost a volt beyond the 11.8Vp-p maximum swing of the amp running on batteries and therefore will clip.


 
   
  "When the O2 is running from battery it's much more likely a battery powered source is being used and none of those produce anything close to 2 V RMS of output.

 On AC power the O2 produces acceptably low distortion even with 2.25V RMS input at the default gain settings. If you don't like those gain settings, they can easily be lowered. I haven't even determined what the best default gain settings are yet (and have posed that question on diyAudio). At 2X or 2.5X gain there's zero chance the O2 will have any issues at all."
   
  From the horses mouth.  I'm sure you can find one of the many threads to discuss this directly with him if you're interested or shoot him an email.


----------



## amb

No, I am not interested in discussing this directly with the designer.  If he is the brilliant engineer that he makes himself out to be, then he _must_ know these limitations.  Must use a weak source, must use low gain, must use AC power... too many ifs, ands and buts.  None of the amps that he lists as "competition" have these problems.


----------



## upstateguy

Quote: 





shike said:


> <snip>
> 
> *I'm sure you can find one of the many threads to** discuss this directly with him *if you're interested or shoot him an email.


 
   
  +1


----------



## Pyriel0

Quote: 





amb said:


> No, I am not interested in discussing this directly with the designer.  If he is the brilliant engineer that he makes himself out to be, then he _must_ know these limitations.  Must use a weak source, must use low gain, must use AC power... too many ifs, ands and buts.  None of the amps that he lists as "competition" have these problems.


 

 For $30 I can deal with a couple restrictions.


----------



## upstateguy

Quote: 





amb said:


> *No, I am not interested in discussing this directly with the designer. * If he is the brilliant engineer that he makes himself out to be, then he _must_ know these limitations.  Must use a weak source, must use low gain, must use AC power... too many ifs, ands and buts.  None of the amps that he lists as "competition" have these problems.


 


 Hi
   
  I have 2 M^3s and have been recommending them to others for years, but I don't understand why you're making comments here and not where the designer can answer them?


----------



## b0ck3n

Any source likely paired with the O2 on batteries will put out ~1v, so it's unlikely an issue. Can you name one 2.5v output portable device, Ti?


----------



## Steve Eddy

Quote: 





amb said:


> No, I am not interested in discussing this directly with the designer.


 

 But you _are_ interested in discussing it on a forum where he can't respond to your criticisms.
   
  Rather bad form if you ask me.
   
  se


----------



## sgrossklass

One could argue that audiophiles are already used to taking care of all kinds of ifs and buts, so a few more for a good cause (namely, optimum noise and distortion performance) wouldn't matter all that much. Equip low gain resistors for a worst-case scenario and be done with it.
   
  Any way of addressing this issue would involve increased complexity, and the board already is packed as-is (the price for all through-hole parts on a half-Eurocard sized board that also accomodates the batteries). Besides, while DC/DC generated supplies would be handy (I'm not a big fan of 9V blocks personally), switch-mode converters are a classic can of worms by themselves in the DIY realm.


----------



## amb

Quote: 





> Originally Posted by *Pyriel0*
> 
> For $30 I can deal with a couple restrictions.


 
   
  The $30 figure is fallacious as has been mentioned in this thread.  It is also misleading for the designer to claim that a Mini³ is "more costly" than the O2, when the price figure for the Mini³ is a professionally-built unit with labor costs added.
   
  Quote: 





			
				upstateguy said:
			
		

> I have 2 M^3s and have been recommending them to others for years, but I don't understand why you're making comments here and not where the designer can answer them?
> 
> Originally Posted by *Steve Eddy*
> 
> ...


 

 Simple.  He had been abusive to me on my own forum and in several other forums, not to mention his blogs, repeatedly.  What makes you think it would be different now?  I don't see anything constructive in me engaging him directly.  His fanboys could do me the favor and spare me the grief.
   
  Steve, that's the nature of this thread isn't it?  He can't respond to _anyone's_ posts here.  Not just mine.  And when was it bad form to state the truth?  Do you not agree that my analysis about the O2's low input voltage overload margin is correct?  Kevin Gilmore also posted the same...
   
  Quote: 





> Originally Posted by *b0ck3n*
> 
> Any source likely paired with the O2 on batteries will put out ~1v, so it's unlikely an issue. Can you name one 2.5v output portable device, Ti?


 
   
  As an (already quoted) example, the γ1 DAC puts out 1.6Vrms @0dBFS.  It definitely qualifies as "portable" since it's less than half the size of the O2.  1.6Vrms (4.53Vp-p) into a battery-powered O2 set to a gain of anything higher than 2.6x will clip.


----------



## The Monkey

I love the suggestions that criticisms of the design are inappropriate here. Pretty delicious irony.


----------



## amb

Yup.  Anyway, I've made my point, and to avoid stirring the pot any more, I'll refrain from further posts here and let others chime in.


----------



## Beftus

Quote:


b0ck3n said:


> Can you name one 2.5v output portable device, Ti?


 

  A GrubDAC comes close: 2Vrms. My GrubDAC lives in a Hammond1455C801.


----------



## purrin

Quote: 





steve eddy said:


> But you _are_ interested in discussing it on a forum where he can't respond to your criticisms.
> 
> Rather bad form if you ask me.
> 
> se


 
   
  It seems you are taking this a little bit too personally. I don't think amb was trying to kick the designer while he was down or sucker punch him. What amb pointed out is completely fair and logical. If you've ever met the guy, _carefully studied_ his project pages, or built his stuff, you would realize the kind of thought he puts into engineering things.
   
  I however am quite astonished at the lack of understanding from some of you of basic engineering principles such as safety tolerances, especially for a project that is supposedly based on "objective" measurements. You can't design anything and assume "oh, people won't be doing that" or "that possibly won't happen" or "this is what people would typically do".
   
  When I started out in this hobby, I ran a Headroom portable amp out of my DCX2496 XLR outputs. Now guess what would happen if I ran this amp that way? Probably only 3 of out 25 people would probably ever do something wierd like that. But it happens. Why not just improve upon the design instead of putting warning stickers on it: "DO NOT RUN OUT OF DESKTOP DAC" or "LIABLE TO CLIP IF BATTERIES AREN'T FULLY CHARGED"
   
  Solving potential issues like this is what makes engineering fun, not putting your fingers in your ears and saying "la la la la la la la"
   
   
   Quote: 





upstateguy said:


> Hi
> 
> I have 2 M^3s and have been recommending them to others for years, but I don't understand why you're making comments here and not where the designer can answer them?


 
   
  Because he's addressing the general community here (and possibly the designer, who may be lurking around.) I know I certainly appreciate it. I've looked up the schematics to this amp and was intrigued by the design with the pot after the gain stage. I'm glad amb took the effort to look up the parts, analyze the design, and give us a "Danger, Will Robinson" warning. That's enough for me; I don't think amb should be expected nor responsible for finding the particular forums the designer hangs around or notifying him personally.


----------



## Anonanimal

Hold on a second here- I'm a bit confused at the overall tone from the vets here.  Bear with me, please.
   
  So the limitations of the input stage are being touted as a "major problem" for the DIY crowd because it requires some forethought and building the amp such that the gain is correct for your gear?  From what I can gather, as long as you're paying attention when you build the thing, 99% of all situations are _easily_ compensated for with some basic reasoning.  It's very clear in the design documentation that it was an intentional choice for performance reasons, with minimal tradeoffs as long as you know what you're doing (or read first).
   
  What about the fact that the Beta22 boards allow you to install the trimpots backward, thus blowing parts up when power is first applied?  Even seasoned vets can make this mistake- and make no mistake that this is a _design problem._
   
  That being said, I'm a big fan of the Beta22 design and all of AMB's efforts in general.  I own one that I built myself (and no I did not make the backward trimpot error, though many have).  Don't take it personally- it's just a bit ironic.
   
  I don't know about anyone else here, but I prefer to learn something from my DIY experiences and if that's the limitation I have to work around to produce performance results like I've seen this amp is capable of... well, okay then.
   
  Don't be afraid!


----------



## purrin

Quote: 





anonanimal said:


> It's very clear in the design documentation that it was an intentional choice for performance reasons, with minimal tradeoffs as long as you know what you're doing (or read first).
> 
> What about the fact that the Beta22 boards allow you to install the trimpots backward, thus blowing parts up when power is first applied?  Even seasoned vets can make this mistake- and make no mistake that this is a _design problem._


 

  User error and builder error are two very different things.
   
  In this case, it wouldn't even be user error unless there was a manual or warning sticker telling users to only use portable DACs with low output. Perhaps the manual should even provide a list of DACs that may possibly cause clipping, the Grub and the γ2 among them.
   
  This is so wierd because didn't the designer of this amp "expose" some other manufacturer's gizmo to be prematurely clipping.


----------



## Anonanimal

Quote: 





purrin said:


> User error and builder error are two very different things.


 


  Fair enough.  I don't want to come across like I'm overreacting, was just trying to provide a parallel and it's a bit half-baked.


----------



## kwkarth

Who cares what the O2 sounds like anyway as long as it measures well in the listed parameters.  I guess the other measurements left out or neglected don't matter in that case either.


----------



## Anonanimal

Quote: 





kwkarth said:


> Who cares what the O2 sounds like anyway as long as it measures well in the listed parameters.  I guess the other measurements left out or neglected don't matter in that case either.


 


  Huh?


----------



## amb

Sorry I have to break my promise to post any more, but Anonanimal, what you said is not the same thing.
   
  A DIYer could indeed make mistakes installing parts on a PCB, this is not just trimpots, nor is it restricted to the β22.  But one could only go so far to prevent something like that from happening.
   
  Now about the gain structure of the O2 amp and its low input overload margin, is a problem that cannot worked around in many circumstances, even if the builder/user has full knowledge of the limitations.  For example, I find that with a γ1 or γ2 DAC feeding an amp with a gain of 5x just about perfect for my Sennheiser PX100 headphones (which are portable).  If you were to build an O2 with a gain of 5x and use it with these DACs, it will clip badly (on battery power or AC power) regardless of where you turn the volume knob.  If I was to use the O2 amp for my Sennheiser HD600 or HD800, I would prefer a bit more gain, which would make matters worse.


----------



## purrin

Quote:


amb said:


> Now about the gain structure of the O2 amp and its low input overload margin, is a problem that cannot worked around in many circumstances, even if the builder/user has full knowledge of the limitations.


 

 And I was just assuming a gain of 2, forgetting that a higher gain may be necessary.
   

       Quote:


amb said:


> If I was to use the O2 amp for my Sennheiser HD600 or HD800, I would prefer a bit more gain, which would make matters worse.


 
   
  Didn't you hear? Users of the Objective2 are not expected to be using these types of headphones. 
	

	
	
		
		

		
			





 Now I'm just being plain nasty...​


----------



## kiteki

I do not understand this thread.
   
  Just give me a link to where to order this thing, for once I'm going to do an impulse buy without any researching ^^


----------



## odigg

Quote: 





amb said:


> For example, I find that with a γ1 or γ2 DAC feeding an amp with a gain of 5x just about perfect for my Sennheiser PX100 headphones (which are portable).  If you were to build an O2 with a gain of 5x and use it with these DACs, it will clip badly (on battery power or AC power) regardless of where you turn the volume knob.  If I was to use the O2 amp for my Sennheiser HD600 or HD800, I would prefer a bit more gain, which would make matters worse.


 

  
  I have a question.  Please note that I'm asking this question honestly - I'm not an engineer and don't know the answer.
   
  What is the difference between the O2 and some other amp (e.g. the Mini3) in the regard?  In a previous post you stated that the "γ1 DAC puts out 1.6Vrms @0dBFS"  I have a MisterX Mini3 with a gain of 5 (the recommended gain).  I know the specified on battery output voltage is "9Vp-p (3.2Vrms)" according to the Mini3 spec page.  I have changed the battery - if I remember correctly its a 8.3V, so the output is even lower than 9Vp-p.
   
  Wouldn't the Mini3 with a gain of 5, or even 2, also clip with the y1 at 0dbfs?


----------



## purrin

Quote: 





odigg said:


> I have a question.  Please note that I'm asking this question honestly - I'm not an engineer and don't know the answer.
> 
> What is the difference between the O2 and some other amp (e.g. the Mini3) in the regard?  In a previous post you stated that the "γ1 DAC puts out 1.6Vrms @0dBFS"  I have a MisterX Mini3 with a gain of 5 (the recommended gain).  I know the specified on battery output voltage is "9Vp-p (3.2Vrms)" according to the Mini3 spec page.  I have changed the battery - if I remember correctly its a 8.3V, so the output is even lower than 9Vp-p.
> 
> Wouldn't the Mini3 with a gain of 5, or even 2, also clip with the y1 at 0dbfs?


 

 No, because you have a pot (volume control) in front of the voltage gain stage on the Mini3. The OBJ2 has the pot _after _the voltage gain stage. That means the output of the DAC is running full juice into that first op-amp.


----------



## SpaceTimeMorph

Quote: 





amb said:


> Sorry I have to break my promise to post any more, but Anonanimal, what you said is not the same thing.
> 
> A DIYer could indeed make mistakes installing parts on a PCB, this is not just trimpots, nor is it restricted to the β22.  But one could only go so far to prevent something like that from happening.
> 
> Now about the gain structure of the O2 amp and its low input overload margin, is a problem that cannot worked around in many circumstances, even if the builder/user has full knowledge of the limitations.  For example, I find that with a γ1 or γ2 DAC feeding an amp with a gain of 5x just about perfect for my Sennheiser PX100 headphones (which are portable).  If you were to build an O2 with a gain of 5x and use it with these DACs, it will clip badly (on battery power or AC power) regardless of where you turn the volume knob.  If I was to use the O2 amp for my Sennheiser HD600 or HD800, I would prefer a bit more gain, which would make matters worse.


 

 Then if you used those DACs you could up the voltage of the power supply (the 2068 will handle 30Vpp) and substitute 30Vgs FETs for the ones listed to handle the clipping issues.  The point is, for normal sources, the clipping won't be an issue.  And for the 1% or so that fall outside of this, there are options to upgrade the power supply/adjust the gain structure at the build stage to accommodate the sources.  If you have source(s) with nominal output voltages, all it would take is a careful selection of the proper gains to prevent clipping at the user stage.  Again, he talks about this in his articles.  If you have better suggestions for how to handle the outlier situations, I for one, would love to hear them.
   
  I will say, one point of disagreement we are having here is based on what NwAvGuy measured for the maximum voltage swing out of a 2068 versus what you are claiming.  He measured something much closer to the power supply rails than what even the spec sheet I found listed.
  Lastly, to maybe try to steer this thread towards some measure of amiability... good call Amb on the two Schottky's vs one... I wasn't thinking there.  See, we can get along after all.


----------



## purrin

Quote: 





spacetimemorph said:


> The point is, for normal sources, the clipping won't be an issue...


 

 It also depends upon what one considers is a normal source. Also higher gain levels needed to power the more demanding headphones will throw a wrench in the works. Here's one way to fix it:
   
http://www.amazon.com/DEWALT-DC9360-36-Volt-Lithium-Ion-Battery/dp/B000FNQYM0
   
  Quote: 





spacetimemorph said:


> I will say, one point of disagreement we are having here is based on what NwAvGuy measured for the maximum voltage swing out of a 2068 versus what you are claiming.  He measured something much closer to the power supply rails than what even the spec sheet I found listed.


 

  Spec sheets are always conservative - they are for a reason - to allow margin for worst case scenarios, manufacturing variances, bad power, etc. These debates just come down to matter of philosophy regarding safety margin. Fortunately, it's concerning the design of an amp, not a car.


----------



## upstateguy

Quote: 





kwkarth said:


> I think your post is pretty good.  I was thinking something similar myself.  Rather than reading about other's opinion about reading about reading about the amp design,* I would like to start reading about how the amp sounds...*


 

   
  Quote: 





kwkarth said:


> *Who cares what the O2 sounds like *anyway as long as it measures well in the listed parameters.  I guess the other measurements left out or neglected don't matter in that case either.


 

 Kevin !


----------



## SpaceTimeMorph

Quote: 





> Originally Posted by *purrin* /img/forum/go_quote.gif
> 
> http://www.amazon.com/DEWALT-DC9360-36-Volt-Lithium-Ion-Battery/dp/B000FNQYM0
> 
> ...


----------



## odigg

Quote: 





purrin said:


> No, because you have a pot (volume control) in front of the voltage gain stage on the Mini3. The OBJ2 has the pot _after _the voltage gain stage. That means the output of the DAC is running full juice into that first op-amp.


 


  That makes sense.  Thanks.  I think most every portable device I use outputs less than 1Vrms, so I guess I don't have to worry too much.


----------



## jude

I'm cleaning up some of this thread.
   
  If you want to discuss the moderating, send me (and/or other moderators) a PM.  I can't promise you'll receive an answer (and, if you do, it may or may not be one you'll like).
   
  If you want to discuss the amp, okay.


----------



## Shike

Quote: 





amb said:


> No, I am not interested in discussing this directly with the designer.  If he is the brilliant engineer that he makes himself out to be, then he _must_ know these limitations.  Must use a weak source, must use low gain, must use AC power... too many ifs, ands and buts.  None of the amps that he lists as "competition" have these problems.


 

 I'm pretty sure I posted that he was clearly aware.  Here's a question for you though: how is the Mini^3 immune to clipping with a gain of 5, or even 3 with the same examples?  Math please.


----------



## JamesMcProgger

I was asking of anyone have a link to a case that would fit and if the board will come in that design only? its kind alike square, not very pocket friendly-


----------



## Beefy

Quote: 





shike said:


> Here's a question for you though: how is the Mini^3 immune to clipping with a gain of 5, or even 3 with the same examples?  Math please.


 

 Because the O2 will clip at the input stage regardless of volume setting. The Mini3 will only clip if the volume is turned way up.


----------



## JamesMcProgger

Quote: 





beefy said:


> Because the O2 will clip at the input stage regardless of volume setting. The Mini3 will only clip if the volume is turned way up.


 


  how can you tell if the final design isnt even finish? ... or without trying one?


----------



## n3rdling

It's only been explained like 6 times


----------



## kwkarth

Quote: 





upstateguy said:


> Kevin !


 

 Tongue tucked firmly in cheek, as they say....


----------



## JamesMcProgger

Quote: 





n3rdling said:


> It's only been explained like 6 times


 


  mmm maybe it was deleted with the other comments


----------



## Shike

Quote: 





n3rdling said:


> It's only been explained like 6 times


 
   
  Ah, the location of the pot at the end rather than before at the signal input.  Still, we're only seeing a couple sources at best pop-up with enough voltage to even begin causing an issue.


----------



## upstateguy

Quote: 





kwkarth said:


> Tongue tucked firmly in cheek, as they say....


 
   
  Yeah, me too...


----------



## kwkarth

Quote: 





upstateguy said:


> Yeah, me too...


 
  Ahh..


----------



## fishski13

Quote: 





shike said:


> Ah, the location of the pot at the end rather than before at the signal input.  Still, we're only seeing a couple sources at best pop-up with enough voltage to even begin causing an issue.


 
   
  your gain setting is limited though.  if using a bog standard 2Vrms source, you need to keep the gain at 3.1x or lower or risk clipping at the input.  as stated before, go above this gain, and the signal will be clipping at the input no matter where the pot is sitting.  if using a lower V source, you have more flexibility with the gain.  do you need a gain higher than 3.1x with a 2Vrms source for the K601 - probably not.


----------



## deadlylover

I wish I had read the last few pages of this thread before I wasted an hour of my life wondering if I ballsed up the Obj2. When it sees the full fury of my source, really nasty stuff starts happening, I'm running it from AC with a gain of 3(ish).
   
  Sorry for no impressions guys, I didn't want to balls up my friend's LCD-2 (I was using the ibuds for testing =P).
   
  All I can really add is that it's a pretty simple build, first timers should have no probs building this.


----------



## fishski13

Quote: 





deadlylover said:


> I wish I had read the last few pages of this thread before I wasted an hour of my life wondering if I ballsed up the Obj2. When it sees the full fury of my source, really nasty stuff starts happening, I'm running it from AC with a gain of 3(ish).
> 
> Sorry for no impressions guys, I didn't want to balls up my friend's LCD-2 (I was using the ibuds for testing =P).
> 
> All I can really add is that it's a pretty simple build, first timers should have no probs building this.


 
   
  what is your source?


----------



## deadlylover

Quote: 





fishski13 said:


> what is your source?


 
   
  Audio-gd DAC19, I have no idea what it outputs.


----------



## Shike

Quote: 





deadlylover said:


> I wish I had read the last few pages of this thread before I wasted an hour of my life wondering if I ballsed up the Obj2. When it sees the full fury of my source, really nasty stuff starts happening, I'm running it from AC with a gain of 3(ish).
> 
> Sorry for no impressions guys, I didn't want to balls up my friend's LCD-2 (I was using the ibuds for testing =P).
> 
> All I can really add is that it's a pretty simple build, first timers should have no probs building this.


 

 How did you build it exactly - I don't believe the PCB is available yet is it?  You could still have messed it up :\
   
  EDIT:
   
  Seems your DAC outputs 2.5V, lowering the gain to around 2-2.5x seems to be the best solution.


----------



## deadlylover

Quote: 





shike said:


> How did you build it exactly - I don't believe the PCB is available yet is it?  You could still have messed it up :\


 
   
  Point to point, I may or may not have ballsed it up.
   
  But considering it works just fine as long as my volume control on foobar is low, I really don't think I ballsed it up =/.
   
  Think I've got a dodgy 2068?


----------



## Shike

Quote: 





deadlylover said:


> Point to point, I may or may not have ballsed it up.
> 
> But considering it works just fine as long as my volume control on foobar is low, I really don't think I ballsed it up =/.
> 
> Think I've got a dodgy 2068?


 


  See edit, seems like you may have pushed the gain too hard (your Audio-GD outputs 2.5V).


----------



## odigg

Quote: 





deadlylover said:


> Audio-gd DAC19, I have no idea what it outputs.


 

 You could measure the output voltage.  All you need to do is play a 1khz tone file through Foobar at full volume and measure the output voltage of the DAC.  You also need to make sure it's not clipping - I'll let somebody else tell you how to do that as I don't want to give you the wrong information.


----------



## deadlylover

Quote: 





shike said:


> See edit, seems like you may have pushed the gain too hard (your Audio-GD outputs 2.5V).


 
   
  Pushing the gain too hard on the second lowest option? =P.
   
  I'll adjust it and report back later, I hate the **** thing now.
   
  Quote: 





odigg said:


> You could measure the output voltage.  All you need to do is play a 1khz tone file through Foobar at full volume and measure the output voltage of the DAC.  You also need to make sure it's not clipping - I'll let somebody else tell you how to do that as I don't want to give you the wrong information.


 
   
  Yeah I get something like 2.7v, thanks.
   
  I didn't think it would be a problem as the stupid schematic said input 4V max, that's mighty misleading isn't it?


----------



## Shike

Quote: 





deadlylover said:


> Pushing the gain too hard on the second lowest option? =P.
> 
> I'll adjust it and report back later, I hate the **** thing now.


 

 1) your source is hotter than almost any DAC out there in terms of voltage.
  2) the amp swings a lot of voltage, you're swinging the maximum amount 100% of the time.  Drop the gain down to 2x and it should be alright.
   
   
  Quote: 





> Yeah I get something like 2.7v, thanks.
> I didn't think it would be a problem as the stupid schematic said input 4V max, that's mighty misleading isn't it?


 
   
  Read the associated article with it - he stated at 2v that 3.1x gain would be the max roughly.  You're at 2.7v.  The 4v max is in relation to damaging the amp.


----------



## evanft

Quote: 





shike said:


> 1) your source is hotter than almost any DAC out there in terms of voltage.


 

 Really? My E-MU 0204 outputs 6.7 dBV, which is about 2.2 Vrms or 3.06 Vpeak.
   
  Calculator: http://designtools.analog.com/dt/dbconvert/dbconvert.html


----------



## Shike

Quote: 





evanft said:


> Really? My E-MU 0204 outputs 6.7 dBV, which is about 2.2 Vrms or 3.06 Vpeak.
> 
> Calculator: http://designtools.analog.com/dt/dbconvert/dbconvert.html


 

 That .3v-.5v is substantial.  NwAvGuy said that in the case of 2.25v, 3.1x gain was about max - anything more and you're pushing it.  If the gain was dropped to say 2.5 it would be about 6.75v max, currently it's demanding 7.75v minimum causing clipping (7v max AC).


----------



## b0ck3n

Anyone who's likely to use unusually hot DIY DACs with the O2 is hopefully knowledgable enough to read the design guidelines and adjust the gain accordingly. I don't necessarily think that the O2 has to play to the esoteric, freakish power output equipment crowd - the O2 is about real world performance in real world situations. Ti Kan's example of running the 114 dB/V, 32 Ohm PX100 headphones with 5x gain is anything but "real world".


----------



## Steve Eddy

Here's the way I look at it.
   
  If your design goal is primarily pure performance, you end up with this:
   

   
  Not this:
   

   
  se


----------



## upstateguy

Quote: 





fishski13 said:


> your gain setting is limited though.  if using a bog standard 2Vrms source, you need to keep the gain at 3.1x or lower or risk clipping at the input.  as stated before, go above this gain, and the signal will be clipping at the input no matter where the pot is sitting.  if using a lower V source, you have more flexibility with the gain.  *do you need a gain higher than 3.1x with a 2Vrms source for the K601 - probably not.*


 

 If you're using a standard AC dac source, do you need a higher gain than 3 to listen to T-1s, LCDs, or 800s at decent volume levels?


----------



## kwkarth

Quote: 





upstateguy said:


> If you're using a standard AC dac source, do you need a higher gain than 3 to listen to T-1s, LCDs, or 800s at decent volume levels?


 
  By spec, it doesn't have adequate output to properly drive those cans regardless of gain structure.


----------



## nikongod

Quote: 





b0ck3n said:


> Anyone who's likely to use unusually hot DIY DACs with the O2 is hopefully knowledgable enough to read the design guidelines and adjust the gain accordingly.


 
   
  Your key assumption that the amp will only be used by tech-savvy people is hopelessly invalid. 
  It is infinitely more reasonable to assume that this amp WILL be sold to non-techy people second hand when DIYers tire of its sound, and new by DIY-MOT builders. It is also reasonable to assume that many people who are building the amp will lack the knowledge to set the gain appropriately - the default gain is seldom "right" for any particular end user, yet you still see people building are amps with the same gain as on the schematics. Surely you will agree with me when you reflect on your previous experience following Cmoy, M3, B22, ckkiii threads.
   
  Quote: 





b0ck3n said:


> I don't necessarily think that the O2 has to play to the esoteric, freakish power output equipment crowd - the O2 is about real world performance in real world situations. Ti Kan's example of running the 114 dB/V, 32 Ohm PX100 headphones with 5x gain is anything but "real world".


 
   
  The O2 is not about real world performance, it is about catering to the esoteric "freakishly good measurements" crowd. 
   
  I think the mention of the PX100 was meant to illustrate a situation where something that has always worked well for AMB and countless other people will not work at all here. 
  On that note, how is using the PX100 with gain of 5 any different than using the HD600 (as shown on the designers webpage, sitting next to the amp and test gear) with gain of 5? It has been clearly illustrated, and puppet-admitted on behalf of the designer that using high gain with a high output source (lol, high output=2v in this case, lol) causes clipping in the gain stages. If people are given the opportunity to screw something up they will. All it takes is a flip of a switch and kabooooom. 
   
   
  Quote: 





upstateguy said:


> If you're using a standard AC dac source, do you need a higher gain than 3 to listen to T-1s, LCDs, or 800s at decent volume levels?


 

 Way to open the worm can....
   
  You need to define decent volume levels and standard DAC levels  
  Less than 100 db SPL and a 2v source: gain of 3 leaves more than ample volume-control headroom (for quiet recordings) for both Hd800 and T1. Just spin the volume knob way up high.
   
  The problem is that people dont like to use their gear like that. I think there is some deep-rooted psychological thing going on here. Between mom yelling when we were kids to "never pass half way up" on the TV/radio volume control, to the feeling of power from only just barely pressing the gas pedal in a powerful car and taking off like a rocketship or maybe something totally different we get conditioned to like to use controls a certain way. 
   
  Looking around at meets, and a quick survey on teh forums will show you that many people only use the section of the potentiometer just above mute (the -60 to -40db range). There is so much fail in this, but it is a case where it takes a deliberate and conscious effort to break the mold. What REALLY sucks is that when you do, people get visibly nervous about spinning the knob up past half way and then complain it lacks power despite not topping it out.
   
  There are 2 kinds of need going on here... What you need for functionality, and what you need to get most people to give your gear 2 listens.


----------



## khaos974

]





kwkarth said:


> By spec, it doesn't have adequate output to properly drive those cans regardless of gain structure.




At how many dB SPL do you consider a pair of headphones properly driven?


----------



## b0ck3n

My assumption was that people who use DIY DACs are likely more tech-savvy than the agerage user. The average user is more likely to use a 1v iPod. Besides that, the O2 isn't a commercial product and requires some interest and research to find out about it. For example it's far less likely to harm the end user than a Schiit amp is, the latter also being marketed to a much wider spectrum of consumers.

Edit: the O2 won't harm the end user ever, but if your preferred source is ridiculously hot then you might want to adjust the gain accordingly.


----------



## Maxvla

@ Nikongod

"Looking around at meets, and a quick survey on teh forums will show you that many people only use the section of the potentiometer just above mute (the -60 to -40db range). There is so much fail in this, but it is a case where it takes a deliberate and conscious effort to break the mold. What REALLY sucks is that when you do, people get visibly nervous about spinning the knob up past half way and then complain it lacks power despite not topping it out."

Absolutely true. I see this all the time. I for one don't subscribe to this and put the volume knob wherever the hell I please. If I need it past halfway that's where it goes.


----------



## kwkarth

Quote: 





khaos974 said:


> At how many dB SPL do you consider a pair of headphones properly driven?


 
  Well, I know this will bother many of you, but even though a couple of the cans will make noise, will the quality of that noise properly showcase what those cans are capable of?
   
  No.  It all depends upon one's level of experience and expectation, quality of source, quality of program material, etc.  SPL alone does not even come close to being the whole story.


----------



## khaos974

kwkarth said:


> Well, I know this will bother many of you, but even though a couple of the cans will make noise, will the quality of that noise properly showcase what those cans are capable of?
> 
> No.  It all depends upon one's level of experience and expectation, quality of source, quality of program material, etc.  SPL alone does not even come close to being the whole story.




I've run a few calculations using 
- Tyll's measurements, specifically the "Vrms needed to reach 90 dB SPL" figure, which is the reference voltage
- the 1% THD clipping limit voltage at 33 , 150 and 600 ohms (the figure at 150 and 600 ohm is the same at 7.3 V)

Since we are not taking into account any possible problem about gain structure, those figures are fine, with a possible 1-2 dB margin of error.

So 20 log (clipping voltage/ Vref) give:
- 24.5 dB gain for the T1
- 26 dB gain for the LCD-2
- 25 dB gain for the HD 800

Multiplied by a 0.9 factor, all tho voltages fall under the 0.01% THD+N range, which is still above 110 dB SPL for any on the concerned headphones.

EDIT: Of course that's only taking into account distortion and not audible factors that give the perception of headphone being well driven.


----------



## chinesekiwi

Quote: 





kiteki said:


> I do not understand this thread.
> 
> Just give me a link to where to order this thing, for once I'm going to do an impulse buy without any researching ^^


 

 Just look up Nwavguy's blog for everything you need. Funny how some people bagging it haven't even read the posts on his website. As direct linking is banned, I'm sure you can look it up.


----------



## b0ck3n

What audible factors, besides volume without distortion, do you suggest exists?


----------



## deadlylover

It's also funny how some people seem to know exactly how it sounds despite never having heard the amp before.


----------



## kwkarth

Quote: 





b0ck3n said:


> What audible factors, besides volume without distortion, do you suggest exists?


 
  If nothing else occurs to you, then this is not the place to discuss it.  You will probably have to discover this for yourself.  I certainly would not expect you to take my word for it.


----------



## Anaxilus

Quote:  
   
  Well put.  Reading the design intent definitely raised an eyebrow.  
	

	
	
		
		

		
			





  But hey, I'm willing to see if a jack of all trades actually can be a master some.  Rarely the case but I'm not an EE.
   
  Quote: 





maxvla said:


> @ Nikongod
> 
> "Looking around at meets, and a quick survey on teh forums will show you that many people only use the section of the potentiometer just above mute (the -60 to -40db range). There is so much fail in this, but it is a case where it takes a deliberate and conscious effort to break the mold. What REALLY sucks is that when you do, people get visibly nervous about spinning the knob up past half way and then complain it lacks power despite not topping it out."
> 
> Absolutely true. I see this all the time. I for one don't subscribe to this and put the volume knob wherever the hell I please. If I need it past halfway that's where it goes.


 

 x3.  I thought I was alone.  I figured everyone else had bat hearing even though my ears test fine.
   
  Quote: 





kwkarth said:


> Well, I know this will bother many of you, but even though a couple of the cans will make noise, will the quality of that noise properly showcase what those cans are capable of?
> 
> No.  It all depends upon one's level of experience and expectation, quality of source, quality of program material, etc.  SPL alone does not even come close to being the whole story.


 

 Agreed.  How many times do we run into, "my cans are loud, they don't need an amp."  Yeah, well they don't 'need' anything do they.


----------



## Beftus

Quote: 





> Ti Kan's example of running the 114 dB/V, 32 Ohm PX100 headphones with 5x gain is anything but "real world".


 


  That's exactly what I do: iPod Classic line out into a Mini³ (5x gain) into a pair of PX100's. Works like a charm. Could easily blow your eardrums, I think.


----------



## b0ck3n

Except Ti uses a higher voltage source than the Classic, talk about blowing your ear drums.


----------



## Beftus

GrubDAC output into Mini³ into PX100's gets really loud past 11 o'clock using recent source material. Go beyond that and your eardrums start clipping violently, but not the Mini³...


----------



## b0ck3n

Quote: 





kwkarth said:


> *By spec*, it doesn't have adequate output to properly drive those cans regardless of gain structure.


 

  
  khaos974 already provided the math that proves you wrong.


  Quote: 





kwkarth said:


> If nothing else occurs to you, then this is not the place to discuss it.  You will probably have to discover this for yourself.  I certainly would not expect you to take my word for it.


 


 I have discovered for myself that alot of people are influenced by placebo and expectation bias, and mistake the difference in human perception for a difference to the signal. The O2 is about busting myths, not perpetuating them - the designer has provided exhaustive measurements showing that the O2 can drive a variety of loads admirably, including loads that relate to the T1, HD800 and LCD2 (much louder than most portable amps including the Mini3 before clipping, mind you - granted that you've matched O2 gain to your source, and that source doesn't put out more than 7v). If you propose that there's something at work here which can't be measured then I'm not sure I'm up for discussing it anywhere.


----------



## amb

Quote: 





> Originally Posted by *b0ck3n*
> 
> Ti Kan's example of running the 114 dB/V, 32 Ohm PX100 headphones with 5x gain is anything but "real world".


 
   
  It's as real as it gets, my friend.
   
  The PX100's quoted "114dB" sensitivity is for 1Vrms (according to the PX100 manual and other web sources).  This is a little unusual.  The typical convention for headphone sensitivity specification is dB/mW, not dB/Vrms.  So the PX100's sensitivity figure is not directly comparable to most other headphone specs.  In fact on the same amp, at the same volume knob position, the PX100 is only a little louder than the HD600.
   
  For 1Vrms into 32 ohms, the power being delivered is a bit over 31mW.  To get 1mW into 32 ohms, you need only 0.18Vrms. Doing a conversion from one to the other. the PX100's sensitivity becomes 99dB/mW.  I mention all this to show that it's not the most efficient portable headphones compared to many others.  Yet it is an immensely popular model so it's appropriate to use as an example.
   
  How much gain is needed?  You must take into consideration the sensitivity of the headphones, the output level of the source, *and add enough headroom to account for recordings that are low in volume* so that you don't run out of volume pot travel.  Many recordings are almost constantly pegged near the 0dBFS line and dynamically compressed.  These recordings will sound very loud (and bad).  But there are also recordings that are recorded very low in level (some from the late 70s and 80s for example), maybe 10-15dB below 0dBFS.  Thus, it is prudent to select an amp gain level above and beyond what's needed to amplify a 0dBFS signal to compensate.
   
  Let's say we want to have 15dB of additional headroom.  And we assume we want to be able to have unclipped peaks of 114dB (just take Sennheiser's spec as an example because it's a reasonable number and happens to require a nice clean 1Vrms).  To add 15dB extra headroom we need to swing 5.6Vrms.  Note that we're not actually going to run 5.6Vrms into the headphones, we would set the volume control to whatever listening level we want.  Let's then assume a y2 DAC as the source with 1.4Vrms output @0dBFS.  The gain we want is then 5.6V/1.4V = 4x.  If we increase the peak dB SPL requirement to 120dB then we need a gain of 8x.
   
  This illustrates that a "Mini³ with gain of 5x driving the PX100" case I mentioned is not outside "real world" usage, and is in fact quite a nice setting.  On average recordings (not too loud, not too soft), my volume pot position is usually a little over half way, but on really soft recordings I can turn it up to satisfactory levels without running out of pot travel.


----------



## fishski13

Quote: 





b0ck3n said:


> khaos974 already provided the math that proves you wrong.
> 
> 
> 
> ...


 


  i would echo the above response from Ti and heed the concerns about having a very limited input source V and gain to drive multiple headphones.  having some headroom for differences in recording volume is not about placebo or expectation bias.  it's real.
   
  this amp at 2Vrms/3.1x gain would not be able to drive my AKG 88dB/600 with any of my older Steely Dan albums to an adequate volume - 80-85dB.  also, 2Vrms is not a hot source.


----------



## Shike

2v RMS is a "normal" source.
   
  2.5v RMS is a "hot" source
   
  2.25v RMS is roughly the limit when using a 3.1x gain.
   
   
  The Audio-GD is the hottest listed so far.
   
  DacMagic: 2.1
  EMU: 2.2
  HRT Streamer: 2.25
  Audio-GD Dac 19: 2.5 (2.7 measured)
   
  One of these isn't like the others no matter how you look at it.


----------



## agdr

Quote: 





deadlylover said:


> I'll adjust it and report back later,
> 
> 
> Yeah I get something like 2.7v, thanks.


 

 A gain of around 2.3x for the low setting would fix it.  That would be a max input of around 7/2.3 = 3.0v. The gain equations in his write-up look like they haven't been updated yet since he added the gain switch.  It should be:
   
  gain = 1 + R16 / R17   for one channel and gain = 1 + R22 / R21  for the other.  He states its is best to leave the feedback resistors R16 and R22 at 1.5k, so solving the equations gives:
   
  R17 = R21 = 1500R / (2.3 - 1) = 1153R.  Closest standard 1% value then would be 1.15k,  For 5% values 1.2k would be just fine, giving a gain of 2.36.  Best to actually measure the resistor first though - some can be way off.


----------



## kwkarth

Quote: 





b0ck3n said:


> khaos974 already provided the math that proves you wrong.
> 
> I have discovered for myself that alot of people are influenced by placebo and expectation bias, and mistake the difference in human perception for a difference to the signal. The O2 is about busting myths, not perpetuating them - the designer has provided exhaustive measurements showing that the O2 can drive a variety of loads admirably, including loads that relate to the T1, HD800 and LCD2 (much louder than most portable amps including the Mini3 before clipping, mind you - granted that you've matched O2 gain to your source, and that source doesn't put out more than 7v). If you propose that there's something at work here which can't be measured then I'm not sure I'm up for discussing it anywhere


 
   
   
   


> Sure, the math proves me wrong.  Happy listening!
> 
> I've been an audio professional since the early 1970's.  I'm sure you've got me pegged.  I must be influenced by placebo effect.


----------



## Anonanimal

Quote: 





upstateguy said:


> If you're using a standard AC dac source, do you need a higher gain than 3 to listen to T-1s, LCDs, or 800s at decent volume levels?


 


   


  Quote: 





kwkarth said:


> By spec, it doesn't have adequate output to properly drive those cans regardless of gain structure.


 


  Where is your data showing that the amp does not, by spec, have enough output to properly drive the quoted headphones?
   
  Actual power specs:
  6.25 volts RMS on AC power at < 1% THD into 150 ohms
  4.5 volts RMS on DC power at < 1% THD into 150 ohms
   
  Compare to this calculations chart using actual headphone specifications.  This is using a Gamma2 as the reference DAC.  YMMV but this should give you an idea.


----------



## Head Injury

Quote:  

 kwkarth, if you're not going to provide any objective concerns, I don't think this is the thread for you.
   
  Anonanimal, very handy table. Could you add LCD-2 rev.2 to the list for me? Audeze increased impedance to 60 ohms. Thanks 
	

	
	
		
		

		
			




  (I suppose I could just use the K701 and rev.1 as approximations)


----------



## Anonanimal

Quote: 





head injury said:


> Anonanimal, very handy table. Could you add LCD-2 rev.2 to the list for me? Audeze increased impedance to 60 ohms. Thanks
> 
> 
> 
> ...


 


  Sure.  I've upped the dB requirement to 115 for some additional headroom for quieter recordings.  In practice I've found this to be enough, but again YMMV.
   
  I'd attach the .xls file instead of posting screenshots but I seem to have been denied that ability.  Sorry!


----------



## kwkarth

Quote: 





anonanimal said:


> Where is your data showing that the amp does not, by spec, have enough output to properly drive the quoted headphones?
> 
> Actual power specs:
> 6.25 volts RMS on AC power at < 1% THD into 150 ohms
> ...


 

 Nice chart!  To answer your question, one word...  headroom.


----------



## limpidglitch

Quote: 





anonanimal said:


> I'd attach the .xls file instead of posting screenshots but I seem to have been denied that ability.  Sorry!


 


  Why not uploading the file to mediafire, Google Docs or similar, and post a link?


----------



## Anonanimal

Quote: 





limpidglitch said:


> Why not uploading the file to mediafire, Google Docs or similar, and post a link?


 


  I can do that if there's interest.  It's a series of pretty simple calculations but I've got them packed in a table for quick reference.


----------



## kwkarth

Quote: 





anonanimal said:


> I can do that if there's interest.  It's a series of pretty simple calculations but I've got them packed in a table for quick reference.


 

 I think it's potentially very useful!


----------



## digger945

Indeed, Google Docs integrates seemlessly for me and works great with Excel, whether uploading or downloading to or from Google Docs.


----------



## nikongod

Quote: 





anonanimal said:


> Sure.  I've upped the dB requirement to 115 for some additional headroom for quieter recordings.  In practice I've found this to be enough, but again YMMV.
> 
> I'd attach the .xls file instead of posting screenshots but I seem to have been denied that ability.  Sorry!


 


  Nice chart!
   
  Your numbers for Beyer and Sennhesier are off. These companies declare efficiency in "db@1v", except for the HD600 whose efficiency is declared in db/mw. 
   
  Im not sure about the AKG K701. it "looks and feels" like the declared efficiency (also given by AKG in db@1vrms) has been converted but Id double check by setting the "target spl" to whatever AKG says the K702 has@1v, and seeing what you get for voltage required 
   
  The gain you give in the far right column assumes that you have a 1v input signal. If you have quiet music you may only have a 0.25v signal or maybe even less with that same DAC. To achieve 115db with Hd800, and a quiet recording it could require boatloads of gain... If you want the amp to play LOUD there is no way around including the gain switch.


----------



## Armaegis

Can anyone provide the formula that converts from sensitivity in V to mW?


----------



## The Monkey

I'm a bit confused why there's a de facto assumption that this is designed to be a portable amp. From what I can glean from the designer's comments, the amp in its initial iteration is small, and therefore portable, but the designer also indicates that the amp also is suitable as a desktop amp (with bigger enclosure if wanted and other options). Regardless of whether the amp is used as a desktop or portable, it does not appear that there are any substantive differences in configuration. In other words, the amp designer appears to suggest that this amp is equally suited to desktop duties as it is to portable. So until someone offers a compelling reason to the contrary, I think limiting assumptions about the types of sources used to portables is inappropriate. Did the designer not use the Benchmark's amp as a comparator?


----------



## kwkarth

Quote: 





armaegis said:


> Can anyone provide the formula that converts from sensitivity in V to mW?


 

 Watts (W) or milliwatts (W/1000) are the product of Voltage (V) and Current (I) and  R=V(2)/I .  therefore...
   
  A sensitivity of 105dB / V is what is published for the AKG K702.  It has a published impedance of 62 ohms, so, our knowns are Voltage and resistance.  Since W=V(2)/R, then 1/62=0.01613, or roughly 16mW required for 105dB output from the AKG K702.


----------



## fishski13

Quote: 





the monkey said:


> I'm a bit confused why there's a de facto assumption that this is designed to be a portable amp. From what I can glean from the designer's comments, the amp in its initial iteration is small, and therefore portable, but the designer also indicates that the amp also is suitable as a desktop amp (with bigger enclosure if wanted and other options). Regardless of whether the amp is used as a desktop or portable, it does not appear that there are any substantive differences in configuration. In other words, the amp designer appears to suggest that this amp is equally to desktop duties as it is to portable. So until someone offers a compelling reason to the contrary, I think limiting assumptions about the types of sources used to portables is inappropriate. Did the designer not use the Benchmark's amp as a comparator?


 

 the performance goal posts keep moving to suit a particular line of argument.
   
  i generally recommend keeping the gain as reasonably low as possible for improved noise and giving you more play/adjustment with the volume.  also, a lower gain will give you better distortion numbers with increased negative feedback.  while the above table re: HP power requirements is handy, i would caution and reiterate that the source recording may not output enough V to achieve modest volumes, much less silly 115dB, under what i consider to be 'real world'/common playback situations.  choose your source and HPs carefully.


----------



## Armaegis

Quote: 





kwkarth said:


> Watts (W) or milliwatts (W/1000) are the product of Voltage (V) and Current (I) and  R=V(2)/I .  therefore...
> 
> A sensitivity of 105dB / V is what is published for the AKG K702.  It has a published impedance of 62 ohms, so, our knowns are Voltage and resistance.  Since W=V(2)/R, then 1/62=0.01613, or roughly 16mW required for 105dB output from the AKG K702.


 

 That part I know. I was wondering about the conversion from 1db/V to 1db/mW, which I'm pretty sure has a log or two in there. I could probably do it, but I'm a little too sleep deprived to crunch numbers right now. 
   
  ... doubling power... roughly 6dB... 2^x... equals P... zzzzzz


----------



## The Monkey

fishski13 said:


> the performance goal posts keep moving to suit a particular line of argument..




Spot on.


----------



## bcg27

Quote: 





armaegis said:


> That part I know. I was wondering about the conversion from 1db/V to 1db/mW, which I'm pretty sure has a log or two in there. I could probably do it, but I'm a little too sleep deprived to crunch numbers right now.
> 
> ... doubling power... roughly 6dB... 2^x... equals P... zzzzzz


 
   
  Someone should double check this to make sure I didn't make a mistake but:
   
  Sensitivity @1mW=sensitivity @1V - 10*log(P(1V in mW))
   
  if you want to substitute in the formula to get power from 1 volt you get
  Sensitivity @1mW=sensitivity @1V - 10*log(1/R*1000) = sensitivity @1V - (10*log(1/R)+30)
   
  logs are base 10 logarithm


----------



## Shike

Quote: 





fishski13 said:


> the performance goal posts keep moving to suit a particular line of argument.


 

 How so?  It's made mostly for either or - pick your gain based on how you're going to use it.  I don't see what the problem here is


----------



## kwkarth

Quote: 





armaegis said:


> That part I know. I was wondering about the conversion from 1db/V to 1db/mW, which I'm pretty sure has a log or two in there. I could probably do it, but I'm a little too sleep deprived to crunch numbers right now.
> 
> ... doubling power... roughly 6dB... 2^x... equals P... zzzzzz


 

 20x log(x/y) for voltage ratio
   
  From Wiki:
_dBm_ indicates that the reference quantity is one milliwatt, while _dBu_ is referenced to 0.775 voltsRMS.[2]


----------



## kwkarth

More on topic here:
   
  How does this amp "sound?"  Or does that not matter as long as somebody is happy with a few selective measurements?


----------



## bcg27

Quote: 





kwkarth said:


> More on topic here:
> 
> How does this amp "sound?"  Or does that not matter as long as somebody is happy with a few selective measurements?


 

 Has anyone built it yet? I was under the impression the designer himself only just got the updated pcbs


----------



## Head Injury

Quote: 





kwkarth said:


> More on topic here:
> 
> How does this amp "sound?"  Or does that not matter as long as somebody is happy with a few selective measurements?


 

 It sounds uncolored, with low distortion and noise.


----------



## kwkarth

Quote: 





bcg27 said:


> Has anyone built it yet? I was under the impression the designer himself only just got the updated pcbs


 
  We've all sure been flapping a lot of gums without any flapping of ears...
   
  One report I recall in this thread of someone who built point to point from schematic (& I have no idea about what the lead dress looked like) that review was mixed, as I recall.  Real world dynamic range vs. gain was mentioned as a concern, again, if I recall correctly.


----------



## kwkarth

Quote: 





head injury said:


> It sounds uncolored, with low distortion and noise.


 
  Great!  Can you be more specific?


----------



## fishski13

Quote: 





shike said:


> How so?  It's made mostly for either or - pick your gain based on how you're going to use it.  I don't see what the problem here is


 

 there is no problem as long as you understand the performance limitations and keep them in context.  i think some have glossed over the limitations.


----------



## Head Injury

Quote: 





kwkarth said:


> Great!  Can you be more specific?


 
   
  Specific how? It's not supposed to sound like anything.


----------



## kwkarth

Quote: 





head injury said:


> Specific how? It's not supposed to sound like anything.


 

 Well, since this isn't the sound science forum...  I forgot we had some flat earthers here.
   
  How about what was your source?  What were your headphones.  What sort of music?  Did you have it turned on?  Battery PS or AC?  You know, that sort of stuff.


----------



## Head Injury

Quote: 





kwkarth said:


> Well, since this isn't the sound science forum...  I forgot we had some flat earthers here.
> 
> How about what was your source?  What were your headphones.  What sort of music?  Did you have it turned on?  Battery PS or AC?  You know, that sort of stuff.


 

 I haven't heard it. Flat frequency response and low noise/distortion/crosstalk/etc. means that, when paired with a similarly flat DAC, it should sound like the headphones and nothing else. Provided there's no clipping, obviously.
   
  I will remind you that, though this isn't the Science forum, the thread is designed to be an objective discussion of the amp's capabilities. The amp itself was designed for objective performance, not subjective sound quality. Subjective impressions beyond measurable phenomena don't matter for this amp. Not for the people it's designed to please.
   
  If you'd like to provide a reason why it wouldn't sound like nothing, when not driven to clipping or otherwise used in a way it isn't meant to be, please do.


----------



## fishski13

Quote: 





head injury said:


> I haven't heard it. Flat frequency response and low noise/distortion/crosstalk/etc. means that, when paired with a similarly flat DAC, it should sound like the headphones and nothing else. Provided there's no clipping, obviously.
> 
> I will remind you that, though this isn't the Science forum, the thread is designed to be an objective discussion of the amp's capabilities. The amp itself was designed for objective performance, not subjective sound quality. Subjective impressions beyond measurable phenomena don't matter for this amp. Not for the people it's designed to please.
> 
> If you'd like to provide a reason why it wouldn't sound like nothing, when not driven to clipping or otherwise used in a way it isn't meant to be, please do.


 
   
  what does nothing sound like?


----------



## Steve Eddy

Quote: 





kwkarth said:


> More on topic here:
> 
> How does this amp "sound?"  Or does that not matter as long as somebody is happy with a few selective measurements?


 

 But the topic is the Objective2 headphone amp, the objective of which was objective performance, hence the name Objective2. Objectively speaking of course. 
	

	
	
		
		

		
		
	


	



   
  Edit: Oops. Didn't see HE's post. Took a short break while writing my post.
   
  se


----------



## Head Injury

Quote: 





fishski13 said:


> what does nothing sound like?


 

 The headphones.


----------



## kwkarth

Quote: 





steve eddy said:


> But the topic is the Objective2 headphone amp, the objective of which was objective performance, hence the name Objective2. Objectively speaking of course.
> 
> 
> 
> ...


 
  You're right, I forgot that objective and substantive are sort of antonyms in this thread.


----------



## Steve Eddy

Quote: 





> Originally Posted by *kwkarth* /img/forum/go_quote.gif
> 
> You're right, I forgot that objective and substantive are sort of antonyms in this thread.


 
   
  Substantive? Or did you mean to say subjective?
   
  se


----------



## Shike

Quote: 





kwkarth said:


> Well, since this isn't the sound science forum...  I forgot we had some *flat earthers* here.


 

 Why are you insulting people now?


----------



## Maxvla

Lots of attitude flowing around here. If you are interested in the amp, build one or wait for listeners impressions. Let the amp stand on it's own merits, or lack thereof if it is in fact the case. This isn't an expensive project, so anyone experimenting with it shouldn't be surprised if it doesn't suit them. They know the risks when investing in the design. Is the design limited with input voltage? Yes, but it can be adjusted for to a degree. That's the best part of DIY.

Who cares who designed it. Build it or don't. It's your call.


----------



## kwkarth

Quote: 





steve eddy said:


> Substantive? Or did you mean to say subjective?
> 
> se


 
  No, I meant exactly what I said, substantive.


----------



## kwkarth

Quote: 





shike said:


> Why are you insulting people now?


 
  Why do you choose to interpret that as an insult?


----------



## kwkarth

Quote: 





maxvla said:


> Lots of attitude flowing around here. If you are interested in the amp, build one or wait for listeners impressions. Let the amp stand on it's own merits, or lack thereof if it is in fact the case. This isn't an expensive project, so anyone experimenting with it shouldn't be surprised if it doesn't suit them. They know the risks when investing in the design. Is the design limited with input voltage? Yes, but it can be adjusted for to a degree. That's the best part of DIY.
> 
> Who cares who designed it. Build it or don't. It's your call.


 
   
  Well said!


----------



## Steve Eddy

Quote: 





> Originally Posted by *kwkarth* /img/forum/go_quote.gif
> 
> No, I meant exactly what I said, substantive.


 
   
  Ok.
   
  se


----------



## limpidglitch

Quote: 





steve eddy said:


> Substantive? Or did you mean to say subjective?
> 
> se


 


  I think he meant to say noun.
   
  This thread is only getting better and better.


----------



## kwkarth

I'm not so sure about folks who claim this amp sounds like "nothing," without ever having heard it.  I believe that lacks a bit, no, a lot, of substance.


----------



## Head Injury

Quote: 





kwkarth said:


> I'm not so sure about folks who claim this amp sounds like "nothing," without ever having heard it.  I believe that lacks a bit, no, a lot, of substance.


 

 Then would you please, as I requested, explain why it wouldn't when the measurements say it will? That's the least you can do if you're going to bring the topic up.


----------



## kwkarth

Quote: 





head injury said:


> Then would you please, as I requested, explain why it wouldn't when the measurements say it will? That's the least you can do if you're going to bring the topic up.


 

 I'll be happy to wait for actual subjective and substantive, as well as objective measurement reports.  If modeling were a perfect predictor in any discipline, there would never be a need for prototyping anything, from amplifiers to airplanes.
   
  What does your experience tell you?


----------



## Satellite_6

Quote: 





kwkarth said:


> More on topic here:
> 
> How does this amp "sound?"  Or does that not matter as long as somebody is happy with a few selective measurements?


 


  "few selective measurements" Can you explain what you mean by this? 
   
  There are pages of measurements.


----------



## kwkarth

Quote: 





satellite_6 said:


> "few selective measurements" Can you explain what you mean by this?
> 
> There are pages of measurements.


 
  It doesn't need to be rehashed, yet again.  I'll wait for the proof of the pudding.  Thanks.  You can always re-read the thread.


----------



## Head Injury

Quote: 





kwkarth said:


> I'll be happy to wait for actual subjective and substantive, as well as objective measurement reports.  If modeling were a perfect predictor in any discipline, there would never be a need for prototyping anything, from amplifiers to airplanes.
> 
> What does your experience tell you?


 

 "subjective and substantive" is an oxymoron in this case.
   
  Of course a prototype is needed. The measurements we've been given are _not_ models. They _are_ measurements of the prototype.
   
  What do you mean, my experience? With audio equipment? My experience tells me that a low distortion headphone and a low distortion DAC/amp is _heavenly_.
   
  You continue to dodge my request. Would it be too much to ask an administrator to stop trolling?


----------



## kwkarth

Quote: 





head injury said:


> "subjective and substantive" is an oxymoron in this case.
> 
> Of course a prototype is needed. The measurements we've been given are _not_ models. They _are_ measurements of the prototype.
> 
> ...


 
  We see what we look for.


----------



## Shike

Quote: 





kwkarth said:


> Why do you choose to interpret that as an insult?


 
   
  How should it be interpreted?  More importantly, what do YOU associate with flat earthers, since that's the term you used.


----------



## kwkarth

Quote: 





shike said:


> How should it be interpreted?  More importantly, what do YOU associate with flat earthers, since that's the term you used.


 

 Read Discworld.  Wonderful series.


----------



## JamesMcProgger

this thread went to the crapper. shame. I enjoying reading the first 10 pages somebody drop me a shout when the final design or group buy is out plz..


----------



## Shike

Quote: 





jamesmcprogger said:


> this thread went to the crapper. shame. I enjoying reading the first 10 pages somebody drop me a shout when the final design or group buy is out plz..


 


  Agreed, I'll do my best to inform you though.  I'll be reviewing it when I have mine built with PCB.


----------



## Anonanimal

Quote: 





nikongod said:


> Nice chart!
> 
> Your numbers for Beyer and Sennhesier are off. These companies declare efficiency in "db@1v", except for the HD600 whose efficiency is declared in db/mw.
> 
> ...


 


  Thanks for the input, all.  Will revisit the questionable numbers.
   
  Edit:
   
  Okay I've revisited all of the numbers and corrected the sensitivities that were originally 1dB/V.  I have added a calculator to the spreadsheet to do that.
   
  Nikongod- actually the gain column is using the input Vrms@0dBFS, which is set to 1.40Vrms for the gamma2 DAC.  It was performing a roundup operation to give an integer gain number with some extra headroom.  I've removed the roundup to make it more exact.  This should help shed some light on how little gain most headphones really need.
   
  The Beyer T1 numbers were correct, per this datasheet: http://north-america.beyerdynamic.com/shop/media//datenblaetter/T1_DB_E_A2.pdf
   
  Also, I've moved it to Google Docs-  Give this link a try: https://docs.google.com/spreadsheet/ccc?key=0ArBLkTRCqzhSdENZVW9kYTA3VUlMMV9UODIxLUpPVnc&hl=en_US#gid=0
   
  I can confirm at least the T1 numbers, as my B22 has a gain of 2 (fed by gamma2) and I have not run into volume limitations on a single recording.  The spreadsheet recommends a gain of 2 for 110dB peak levels.


----------



## chinesekiwi

Quote: 





fishski13 said:


> what does nothing sound like?


 
   
  The Benchmark DAC1's headphone amp. An amp and source is not supposed to 'sound' like anything...it should be as transparent as possible.
  However better sound results from less distortion unless you are recreate a  speaker surrounding, in which of course, there always have more distortion than headphones, which is why a lot of people prefer 'warmth' in their music.


----------



## Head Injury

I browsed through the diyAudio thread and, in light of concerns about clipping with 3x gain and hot sources, NwAvGuy has dropped the default gain to 2.5x. I thought I would pass this on, to maybe elicit constructive discussion again.


----------



## Beefy

Quote: 





kwkarth said:


> I'm not so sure about folks who claim this amp sounds like "nothing," without ever having heard it.  I believe that lacks a bit, no, a lot, of substance.


 

 I can't believe that I agree with kwkarth on something.
   
  For reference, I am a scientist and skeptical of many audiophool traditions...... but I strongly believe that anyone who thinks an amp is perfectly transparent because of a select and limited group of measurements is wrong. It shows a substantial amount of arrogance, and a strong underestimation (or misunderstanding) of the complexities of both the electronics and the human brain.
   
  The amp needs to be ABX'ed, double blinded, some sort of proper listening test. Until then, both the objectivists and the subjectivists are full of it.
   
  *
   
  The gain issue is still not solved adequately to my mind. I cannot fathom why the designer is introducing such significant potential problems for the sake of a few dB of SNR. We all know how many noobs are going to end up with one of these, switch to a MOAR BETTAR GAINZ and wonder why it sounds bad. Seriously, even if the SNR was dropped by 30dB by moving the pot, it would still measure very well, and the problem is gone.


----------



## mikeaj

If you believe the designer, he says he did blind listening tests between his Benchmark DAC1 and the O2 and found them to sound the same.
   
  From the first article:
   
  "*SUBJECTIVE COMPARISONS:* I’m more than a little biased, so that’s why I broke out the blind testing gear. And, as near as I and a few others can tell so far, the O2 sounds so similar to the well regarded Benchmark DAC1 Pre’s headphone amp we can’t tell them apart. See _The Subjectivist Pitch_ above. I also believe those currently listening to amps with significant problems, be it higher output impedance, high distortion, audible noise, insufficient power, etc, might be in for a real treat (unless they _like_ those things). I’m looking forward to more blind tests with the O2!"


----------



## Satellite_6

[redundant quote removed]
   
  NwAvGuy has claimed to have done a blind test already. I don't see how the designer is responsible for the user's ignorance. He even has a whole section on how to operate the O2 properly. 
   
  It sounds good, but I would like to see more details and more tests of course. 
   
  I hope I haven't broken any unwritten rules this time . . .


----------



## Head Injury

Quote: 





beefy said:


> The gain issue is still not solved adequately to my mind. I cannot fathom why the designer is introducing such significant potential problems for the sake of a few dB of SNR. We all know how many noobs are going to end up with one of these, switch to a MOAR BETTAR GAINZ and wonder why it sounds bad.


 

 At that point it's builder error, though. If you build it within spec, is there really a problem?
   
   


> Seriously, even if the SNR was dropped by 30dB by moving the pot, it would still measure very well, and the problem is gone.


 
   
  Ouch! I'll take the better SNR.
   
  A stern warning to any potential builders (as a preface to the schematic perhaps) would prevent (almost) anyone from turning the gain too high, and won't lower SNR.
   
  Luckily for my uses a 2.5x gain is plenty high enough without causing clipping.
   
  ----------
   
  Note to the above posters: Blind tests really only work if the listeners expect to hear a difference. If you don't expect (or want) a difference, then even if there is one you might bias yourself into thinking there isn't. I can't speak for the others NwAvGuy tested, but his own blind test is definitely flawed.


----------



## Beefy

Quote: 





mikeaj said:


> If you believe the designer, he says he did blind listening tests between his Benchmark DAC1 and the O2 and found them to sound the same.


 
   

  Well firstly, I don't believe that the Benchmark is a good comparison. Most people whose opinion I trust think it sounds shrill and metallic.
   
  Secondly, I don't know good his hearing is. I want to see more of these in the wild.
   

  Quote: 





head injury said:


> At that point it's builder error, though. If you build it within spec, is there really a problem?


 

 Because it isn't the builder I am worried about, but the end user. Accounting for people's stupidity is a better design decision than taking SNR beyond the range of human perception.


----------



## dsavitsk

beefy said:


> The gain issue is still not solved adequately to my mind. I cannot fathom why the designer is introducing such significant potential problems for the sake of a few dB of SNR.




I don't think this is nearly as big a deal as people are making it out to be, but, I do think there are two different issues that have been aggregated into one. The first issue is whether having an input limit is an inherently bad thing, and the second is whether the input limit of this amp is too low.

1. To address the first, all amps have an input limit. This is particularly noticeable in an amp with an input transformer where it will saturate if the signal level is too high. But, it is also true with something like a B22 where a very high level input could damage the pot (and in some cases, such as with a stepper, that level is exceedingly high, but it does exist). 

So, input limits are inherent in designing a headphone amp. But, with an IPT, or the opamp before the volume control, there are concrete objective benefits to doing it such as CMRR, isolation from ground loops, and lower SNR. There are also trade-offs, such as the fact that badly behaved sources (those with too high of an output) may not be compatible. The fact that not all sources are compatible with all amps should not be a surprise to anyone, particularly in an area where there are no hard and fast standards. Indeed, I try to keep my sources at 1Vrms or lower which works well as I tend to transformer couple most amps. Further, while this amp may not be able to handle a high source level, it seems to be, with perhaps some tweaking, able handle a higher source impedance than many other amps.

2. The second issue is that this amp may have a particularly low signal input limit. OK. So, as I say, not all amps are useful in all situations. Use something else. This is a different and new-ish topology to the headphone world. Like all circuits, it has benefits and drawbacks, and will work in only limited situations. This does not make it any different than any other amplifier out there, AMB's designs included. The flaw here seems to be not in having a limit, but in the designer's contention that it is perfect and better than everything else in every situation. Clearly this is not the case, so, use it where it is appropriate. In places where it is not, use a resistor divider (or another pot) in front of the first opamp, or use a different transformer to increase the power supply.

Finally, so I can avoid posting in this thread again, for an amp with a lot of feedback, the THD numbers don't strike me as being off the chart. They are fine, but not spectacular. My soundcard does better than that, and it sounds terrible. And, that's the last issue -- contrary to what at least one poster believes, not much can be gleaned from the numbers posted in the first post. All you can say is that the amp is working within expected specs. There is a lot about audio design, how an amp reacts with a real world load (back EMF injected into a feedback loop, for instance) and human perception that is not captured in those measurements.


----------



## mikeaj

Quote: 





head injury said:


> Note to the above posters: Blind tests really only work if the listeners expect to hear a difference. If you don't expect (or want) a difference, then even if there is one you might bias yourself into thinking there isn't. I can't speak for the others NwAvGuy tested, but his own blind test is definitely flawed.


 

 I totally agree here, and it's more than likely that the other listeners are also biased.  Blind testing is really best for determining that a difference exists, not confirming the opposite.  This is the caveat I neglected to point out.  It also depends on the kind of blind testing done and the amount of honest effort put into the testing, though we can't be sure about either.  It's a shame that this sums up all the listening we know about so far, but...time to wait for the v1.1 board to get into peoples' hands.
   
   
  I also agree with the sentiment of a limited set of measurements not telling the whole story, but with the number of different THD tests, different IMD tests, square waves into different loads (including real headphones and real headpones + capacitor), blind listening with a variety of headphones, and so on, as well as all the other unpublished results, it just seems kind of unlikely that the real-world performance would be noticeably poor in some way.  Some things that humans perceive don't really map well to these standard metrics and benchmarks.  Anyway, maybe when somebody builds one they can do a line-out -> O2 -> line-in recording with the O2 driving some real headphones, and do a differencing test against the recording that was played?  You'd probably need a really really good ADC though, as well as DAC.
   
  Most likely it will sound similar to the Benchmark...which in turn probably sounds like nothing really (i.e. like not much was added to the input signal).  Whether or not a high-fidelity signal sounds shrill and metallic, is up for the listener to decide.  But doesn't that depend on the music that is being played?


----------



## Beefy

Quote: 





dsavitsk said:


> Finally, so I can avoid posting in this thread again.......
> 
> ...... how an amp reacts with a real world load (back EMF injected into a feedback loop, for instance) and human perception that is not captured in those measurements.


 

 Please stick around, because this point you have raised is something I am very interested in.
   
  I've been speaking with other folk on another non-DIY forum, lamenting that the vast majority of amp testing is done with purely resistive loads which are a LONG way from real-world headphones. Do you think that testing with actual headphones connected to the amp instead of simulated loads would be beneficial? Or can you think of a better simulated load than just a resistor? Or are your ears the best decider?


----------



## Beefy

Quote: 





mikeaj said:


> square waves into different loads (including real headphones and real headpones + capacitor)


 

 Correct me if I am wrong, but the real headphone load was Sennheiser CX300 IEM's. I really don't think that such a sensitive load is a good indication of what happens with your a full size, lower sensitivity dynamic headphone, which requires much larger voltage and current swing, has frequency dependent resonances, etc.


----------



## SpaceTimeMorph

With as low an output impedance as this amp has measure though, the voltage swing across the output stage (due to varying headphone impedances) should be minimized.  Also, back EMF from the headphone would be better dissipated with a low impedance output from the amp (better damping factor).  Both points making this less of an issue.  That being said, running a test using a reactive load would be good from an empirical standpoint, just to prove that theory and execution are as close as possible.


----------



## Armaegis

Quote: 





bcg27 said:


> Someone should double check this to make sure I didn't make a mistake but:
> 
> Sensitivity @1mW=sensitivity @1V - 10*log(P(1V in mW))
> 
> ...


 


  Seeing as I asked the original question... but yeah now that I've crunched through the formulae myself that looks right.


----------



## digger945

from a thread here:
http://www.head-fi.org/forum/thread/168037/db-per-milliwhat-efficiency-vs-sensitivity-vs-how-loud-do-they-really-go/15
   
   
   
   Convert sensitivity in dB/V to sensitivity in dB/mW. Another good sensitivity thread.

   Quote:


  Originally Posted by *T_Schmidt* 


_ hey, sorry to bringing to life a very dead thread, but I have been searching for hours and have not been able to find the SPL dB / mW rating for the AKG K701's (or an actual conversion formula, either). I just bought a pair and would like to know the sensitivity to pair it up with a respective amplifier._




 I just replied to a thread (see post #37) where I put "an actual conversion formula" to convert sensitivity in dB/V and impedance to sensitivity in dB/mW.

 The formual gets the same results as post #18 above. I'll repeat the equation here for reference.


[size=medium]==== Extra Credit =============
[size=medium]For the geeks out there, the equation to convert dB/V to dB/mW is[/size]

 [size=medium]dB/mW = dB/V + 10*log(R*P/V^2)[/size]

[size=medium]where[/size]
[size=medium]dB/V is the sensitivity in dB (SPL) at 1 Vrms of voltage into impedance R, 103 dB/V into 300 ohms in this case[/size]
[size=medium]R is the nominal impedance, 300 ohms in this case[/size]
[size=medium]V is the reference voltage, 1 Vrms in this case[/size]
[size=medium]P is the reference power, 0.001 watt in this case[/size]
[size=medium]dB/mW is the sensitivity in dB (SPL) at 0.001 watt of power (that is 1 milliwatt)[/size]
[size=medium]log is the logarithm base 10[/size]

[size=medium]In the above example we have:[/size]

[size=medium]dB/mW = 103+10*log(300*0.001/1^2) = 98.7[/size][/size]


----------



## Steve Eddy

se


----------



## SpaceTimeMorph

It's easier than that though
   
  Smw = Srms + 10*log(Z/1000)
   
  Where
   
  Srms = sensitivity in dB/Vrms
  Smw = sensitivity in dB/mW
  Z = headphone impedance in ohms
   
  This of course assumes 1Vrms is the reference...


----------



## SpaceTimeMorph

Quote: 





> Originally Posted by *Steve Eddy* /img/forum/go_quote.gif
> 
> se


 
   
  Ha, didn't know that's how you felt


----------



## Steve Eddy

Quote:  





> Ha, didn't know that's how you felt


 

 Not feeling much of anything now that the morphine's kicked in. 
	

	
	
		
		

		
		
	


	



   
  se


----------



## DingoSmuggler

Quote: 





spacetimemorph said:


> It's easier than that though
> 
> Smw = Srms + 10*log(Z/1000)
> 
> ...


 

 You've got that a bit mixed up.
  using your same units it would be
   
  Smw = Srms - 10*log(1000/Z)


----------



## b0ck3n

Quote: 





amb said:


> For 1Vrms into 32 ohms, the power being delivered is a bit over 31mW.  To get 1mW into 32 ohms, you need only 0.18Vrms. Doing a conversion from one to the other. the PX100's sensitivity becomes 99dB/mW.  I mention all this to show that it's not the most efficient portable headphones compared to many others.  Yet it is an immensely popular model so it's appropriate to use as an example.
> 
> _*Where do you get 0.18 V from? You need 1 volt RMS at 32 ohms to get 31 mW.*_
> 
> ...


 

  
  Quote: 





fishski13 said:


> i would echo the above response from Ti and heed the concerns about having a very limited input source V and gain to drive multiple headphones.  having some headroom for differences in recording volume is not about placebo or expectation bias.  it's real.
> 
> *If you look at commercial desktop amps, including the high-end models, most have a low gain setting in the 2X - 4X range to use with home sources. The HeadAmp GS-1, for example, is 3X.*
> 
> ...


 

 You forced me to get some books out to disprove your claims, and I don't appreciate that at all. I've enough on my plate as it is without having to devout hours of my time to this forum thread. In the future I'd suggest people look at claims that seem backed by math and physics with suspicion - unless you can verify the numbers for yourself, don't trust them to be accurate.


----------



## b0ck3n

The O2 is as suitable as a desktop amp as it is as a portable/transportable because of it's performance - low output impedance (0.58 ohms), gobs of power (relative to it's size) and very respectable distortion levels. You can't do better within the audible range.
   
  Discussion on how to avoid the input/gain issue at your computer rose on another forum. You can just put the O2 volume at max and use the audio player's volume controls.
   
  Like I've said the O2 was designed around the measurements. Given that a particular pair of headphones was designed for use with an output impedance as close to 0 as possible, the O2 (paired with an equally transparent source) will let you hear your pair of headphones the way they were intended to sound. The amp in itself has no sound signature. This might relate to "shrill and mechanic" with some headphones - if you don't like your headphones, try another pair.
   
   
  Quote:


kwkarth said:


> Well, since this isn't the sound science forum...  I forgot we had some flat earthers here.


 


 Humans believed the earth was flat because that's how we perceived it while standing on it. If all the evidence suggests that the O2 is "transparent" and "sounds like nothing", and you suggest that's not true, then in this case you're the flat earther. That's not to say that different people won't perceive different things when listening to the O2, perception is still very much real, it's just pointless talking about it in absolute terms as one's perception doesn't always relate to the same as another's.


----------



## kwkarth

Quote: 





b0ck3n said:


> The O2 is as suitable as a desktop amp as it is as a portable/transportable because of it's performance - low output impedance (0.58 ohms), gobs of power (relative to it's size) and very respectable distortion levels. You can't do better within the audible range.
> 
> Discussion on how to avoid the input/gain issue at your computer rose on another forum. You can just put the O2 volume at max and use the audio player's volume controls.
> 
> ...


 

 It really seems to me that a great many people are talking about how this amp should sound based upon the measured and predicted measurements.  I would very much rather see/read reports of how it actually sounds in real life, not just on discworld.  I suspect Pratchett would agree.


----------



## n3rdling

Gonna have to wait until the boards start getting into people's hands for that.  In the meantime I think the objective discussion is very entertaining/insightful.


----------



## Steve Eddy

Quote: 





> Originally Posted by *kwkarth* /img/forum/go_quote.gif
> 
> I would very much rather see/read reports of how it actually sounds in real life, not just on discworld.


 
   
  But how do you know how something "actually sounds" given that how something sounds is a highly subjective thing and can vary dramatically among listeners?
   
  Some think Julia Roberts is absolutely gorgeous. Others think she's rather ugly. So how does Julia Roberts "actually look"?
   
  From the O2's designer's perspective, its objective performance is such that what alterations it does make to the signal are so far below known audible thresholds that by all evidence, it should not impart any sound of its own.
   
  se


----------



## Head Injury

Quote: 





steve eddy said:


> But how do you know how something "actually sounds" given that how something sounds is a highly subjective thing and can vary dramatically among listeners?
> 
> Some think Julia Roberts is absolutely gorgeous. Others think she's rather ugly. So how does Julia Roberts "actually look"?
> 
> ...


 

 Don't take the bait, Steve!


----------



## Steve Eddy

Quote: 





head injury said:


> Don't take the bait, Steve!


 

 Bait? That was the most delicious brownie I've ever eaten! Who in their right mind would use something so scrumptious as bait?
   
  se


----------



## Achmedisdead

Quote: 





steve eddy said:


>


 
  +1


----------



## The Monkey

Quote: 





b0ck3n said:


> The O2 is as suitable as a desktop amp as it is as a portable/transportable because of it's performance - low output impedance (0.58 ohms), gobs of power (relative to it's size) and very respectable distortion levels. You can't do better within the audible range.


 
   
  Well, it _purports_ to be for now.  But I agree with the premise.  So for those people who are limiting comparisons to portable amps or dismissing hot sources because no portables are that hot--knock it off.


----------



## amb

Quote: 





b0ck3n said:


> Quote:
> 
> 
> 
> ...


 
   
  Yes, P = 1V ^2 / 32 = 31.3mW.  Isn't that exactly what I said (bold green above)?
  The 0.18Vrms is how much voltage is needed to deliver 1mW into 32 ohms (bold blue above).  0.18V ^2 / 32 = 0.001W = 1mW.
  In my original post I said that I calculated the dB/mW figure in order for the PX100's sensitivity to be directly comparable to other headphones.
   
  Please read carefully first before acting as if you found a mistake.  I don't make such posts haphazardly.
   
  Quote: 





> Quote:
> 
> 
> 
> ...


 
   
  That's all fine, but you fail to notice what I wrote in bold and take into account the 15dB headroom I added...  The point is not to play above 110dB, but to have enough gain to compensate for quiet recordings.  It would be incorrect to design the gain structure of your system based purely on 0dBFS numbers.  Music recordings are not a full-scale amplitude sine wave.
   
  Quote: 





> ...
> *Even with a 0.5 V RMS source 5X gain is ridiculous with the PX100.*


 
   
  Yes, 0.5Vx5 = 2.5Vrms would be more than loud on the PX100, but there is a volume control to let you regulate the actual volume.  Let me _repeat yet another time_ in case it still hasn't sunk in, the point of the gain is not to actually play at loud levels with a 0dBFS signal, but to allow quiet recordings to reach loud levels without max-ing out the volume pot and left with no more room to adjust.
   
  Quote: 





> You forced me to get some books out to disprove your claims, and I don't appreciate that at all. I've enough on my plate as it is without having to devout hours of my time to this forum thread. In the future I'd suggest people look at claims that seem backed by math and physics with suspicion - unless you can verify the numbers for yourself, don't trust them to be accurate.


 
   
  We _forced_ you?


----------



## b0ck3n

People seem to also forget that the O2 has the same distortion levels from 0 to max volume, meaning that as long as you've got a volume control on your source or DAC you can make sure to stay within the limits of the amp clipping very easily. The misconception that the O2 clips before getting loud enough is just that, a misconception.


----------



## b0ck3n

Quote:


amb said:


> Yes, P = 1V ^2 / 32 = 31.3mW.  Isn't that exactly what I said (bold green above)?
> The 0.18Vrms is how much voltage is needed to deliver 1mW into 32 ohms (bold blue above).  0.18V ^2 / 32 = 0.001W = 1mW.
> In my original post I said that I calculated the dB/mW figure in order for the PX100's sensitivity to be directly comparable to other headphones.
> 
> ...


 

 Read my last post: max out the O2 volume and use the volume control on your source or DAC. The O2 will play louder than the Mini3 so you really don't have to worry about headroom.


----------



## amb

Quote: 





b0ck3n said:


> People seem to also forget that the O2 has the same distortion levels from 0 to max volume, meaning that as long as you've got a volume control on your source or DAC you can make sure to stay within the limits of the amp clipping very easily. The misconception that the O2 clips before getting loud enough is just that, a misconception.


 
   
  Other than something like the _headphone output_ on portable audio players or software volume control on the computer, how many sources (i.e., CD players, DACs) actually have a volume control on it?  Yeah, Benchmark DAC1 has one that could be optionally enabled, but look at the field of sources currently available, commercial or DIY, you'll find that assuming a source with a volume control is not a good plan.
   
  And to play "devil's advocate"... even if the source has a volume control, the moment you use it to turn down the signal volume prior to it entering the amp's input stage, you've reduced some S/N ratio right there.  If you then have to turn up the volume on the amp to make up for the lost volume, then wouldn't that be quite the antithesis of what the designer was trying to do with the volume pot after the output of the gain stage?


----------



## Shike

Add a passive preamplifier like the NHT PVC or set the gain properly for the source you'll be using - problem solved.  This isn't hard or something that can't be worked around unlike certain (and IMO larger) issues with other designs.


----------



## Anaxilus

Quote: 





beefy said:


> I can't believe that I agree with kwkarth on something.
> 
> For reference, I am a scientist and skeptical of many audiophool traditions...... but I strongly believe that anyone who thinks an amp is perfectly transparent because of a select and limited group of measurements is wrong. It shows a substantial amount of arrogance, and a strong underestimation (or misunderstanding) of the complexities of both the electronics and the human brain.
> 
> The amp needs to be ABX'ed, double blinded, some sort of proper listening test. Until then, both the objectivists and the subjectivists are full of it.


 

 Thank goodness.  Well said.


----------



## Head Injury

amb, I was thinking the same thing about source volume. Not many have it, it's hardly a solution at all.
   
  Quote:


amb said:


> If you then have to turn up the volume on the amp to make up for the lost volume, then wouldn't that be quite the antithesis of what the designer was trying to do with the volume pot after the output of the gain stage?


 

 Yes, but it's sort of a worst case solution. Not that many source/headphone combinations will have a hot enough line out and need enough gain to cause clipping in the first place. With a 2Vrms source on AC power you can get a gain of what, 3.5x? That's enough to drive the HE-6 to 110dB. The new default of 2.5x gain is enough to handle a 2.8Vrms source, and drive the HE-6 to 107dB. At least according to Anonanimal's awesome spreadsheet.
   
  If you're building it for portable use, set a low gain. You won't need the extra power, and you'll give the batteries a breather. Then you won't have to mess with the source volume.


----------



## kwkarth

Quote: 





steve eddy said:


> But how do you know how something "actually sounds" given that how something sounds is a highly subjective thing and can vary dramatically among listeners?
> 
> Some think Julia Roberts is absolutely gorgeous. Others think she's rather ugly. So how does Julia Roberts "actually look"?
> 
> ...


 

 In the context we find ourselves with respect to this amp, the "objectivity" that is being represented, isn't.  So give me some subjective listening impressions.  At least those may be off discworld.


----------



## Shike

Quote: 





kwkarth said:


> In the context we find ourselves with respect to this amp, the "objectivity" that is being represented, isn't.


 

 If the measurements are factual I fail to see where you're coming from, if it's accurate to the signal it's accurate to the signal - what else do you want people to say?


----------



## kwkarth

Quote: 





shike said:


> If the measurements are factual I fail to see where you're coming from, if it's accurate to the signal it's accurate to the signal - what else do you want people to say?


 
  Tell me all about the measurements you made.


----------



## Currawong

I think AMB's point is that, even if the amp measures well in the lab, once people start using it in a variety of situations, due to various factors about the source used, they may not be able to use in in a manner that gets the best results, both measurable and audible, so the measurements may be moot. 
   
  This has come because I think nwavguy has pitched it in a "Fight the man!" manner, which appeals to some people here, suggesting that for $35 (or whatever the total is) you can have an amp that will be good enough for everything. Now the people who know what they are talking about have come in and started telling it like it is, some of you don't want to hear it.  I suggest some of you should ditch the battle mindset, as anyone building this will need to know as much as they can and any issues found now will only benefit everyone in the long run.


----------



## khaos974

Nice post Curra, this thread has turned too confrontational; anyway, the 1.1 PCB design has been released, default gain is now 2.5.x.


----------



## Maxvla

kwkarth said:


> Well said!




I was mostly referring to your posts, actually.


----------



## b0ck3n

Well, the designer has been forward with the "input/gain issue", if you want to call it an issue, from the beginning. It's not something that's been brought to light by AMB, as were it a carefully concealed problem. If someone would detect an issue that would seriously impede normal use, or be an obvious deficiency, I'm sure the designer would try to solve that issue - such as the gain switch, which was added due to popular demand.

The measurements already provided are the most exhaustive I've ever seen from a designer, and every compromise and trade-off explained in great detail, and I still think some of the concerns people on this thread have would've been put to rest by just reading the articles. Instead things are taken out of context and questioned, obscuring the bigger picture.


----------



## b0ck3n

For those who want to use hot sources at home a desktop version of the O2 has been announced that eliminates the input overload issue.


----------



## deadlylover

Quote: 





b0ck3n said:


> For those who want to use hot sources at home a desktop version of the O2 has been announced that eliminates the input overload issue.


 

 Fantastic, just after I 'fixed up' the gain issue on my obj2........ It still spazzes out every now and then =/.
   
  FFFFFFFFFFFUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU.


----------



## khaos974

deadlylover said:


> Fantastic, just after I 'fixed up' the gain issue on my obj2........ It still spazzes out every now and then =/.
> 
> FFFFFFFFFFFUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU.




Design issues or building issues?


----------



## deadlylover

Quote: 





khaos974 said:


> Design issues or building issues?


 
   
  I prolly let out a little bit of the magic pixie dust from the 2068 when it ate my source. I've got a spare but I'll have to wait anyway to borrow a LCD-2 to run it through it's paces.
   
  So I think I'm the first person on head-fi with a (mostly) working obj2? I'm probably also one of the only people who doesn't own a proper flippin' dynamic to use it with.


----------



## Armaegis

I do all my DIY testing on a pair of cheap airline earbuds. Not much for sound quality (though better than the $1store), but they sit at 300 ohms and I've cranked nearly 2V offset into them without frying.


----------



## The Monkey

b0ck3n said:


> For those who want to use hot sources at home a desktop version of the O2 has been announced that eliminates the input overload issue.





So now it is a portable? Kind of a moving target, this amp.


----------



## khaos974

It always was a portable, why would it have batteries otherwise?


----------



## Beefy

Quote: 





b0ck3n said:


> Quote:
> 
> Read my last post: max out the O2 volume and use the volume control on your source or DAC. The O2 will play louder than the Mini3 so you really don't have to worry about headroom.


 

 To mirror and expand on what others have said about most sources lacking volume control on their line outs...... many of us use ASIO on our PC's that disables software volume control as well. So this strategy will not prevent the issue in many cases.
   
   
  Quote: 





shike said:


> Add a passive preamplifier like the NHT PVC or set the gain properly for the source you'll be using - problem solved.  This isn't hard or something that can't be worked around unlike certain (and IMO larger) issues with other designs.


 
   

  You are seriously suggesting that somebody would spend $119 as safety factor on a "$30" amp, by putting a second volume control in the signal chain, and putting pot noise back in front of the input stage anyway, rather than changing the design to be more traditional?
   
  Yeah, that makes a LOT of sense.
   
  Quote: 





khaos974 said:


> It always was a portable, why would it have batteries otherwise?


 

 So will _you_ be carrying one around in your _pocket_?
   
  Frankly, I cannot understand why it has batteries, other than an attempt to try and one-up other portables - despite being far larger than the competition, and certainly too large to actually carry around with you.


----------



## khaos974

Actually, I don't care about it portable performance at all, I consider anything bigger that 0 cubic inch to much of hassle to carry around, it's just one thing too much in my pocket. But 've see quite humonguous portable rigs around, it's just one more big portable rig.


----------



## The Monkey

Quote: 





khaos974 said:


> It always was a portable, why would it have batteries otherwise?


 


  Wrong.


----------



## b0ck3n

Quote:


beefy said:


> To mirror and expand on what others have said about most sources lacking volume control on their line outs...... many of us use ASIO on our PC's that disables software volume control as well. So this strategy will not prevent the issue in many cases.
> 
> _*Well, it's only an issue if you've got a hot source AND you can't be bothered to adjust gain accordingly. *_
> 
> ...


----------



## Currawong

Quote: 





b0ck3n said:


> _*Heck, it one-ups desktop amps*_


 

 You need to stop with this weasel-wording (only two "desktop amps" are mentioned when he lists the measurement comparisons) and other crap and stop trying to defend the amp design the way you are, as you're ruining it not only for everyone else, but for him included.


----------



## khaos974

the monkey said:


> Wrong.




It was always designed as a portable amp, you could argue that it wasn't successful, but it the aim was portability. It's about the same size as the RSA SR-71, the iQube and much smaller than the Lisa III.


----------



## fishski13

Quote: 





b0ck3n said:


> You forced me to get some books out to disprove your claims, and I don't appreciate that at all. I've enough on my plate as it is without having to devout hours of my time to this forum thread. In the future I'd suggest people look at claims that seem backed by math and physics with suspicion - unless you can verify the numbers for yourself, don't trust them to be accurate.


 

 i was referring to the AKG 240DF.  they're fairly popular. 
   
  like i said more than once, you need to consider the source recording volume it was mastered at.  i have amps here that can swing more V and higher gain a 5x that can be maxxed on volume driving these recordings.  i also have some older ECM label stuff that are the same.  the power requirements only tell you part of the story.  and no, the mini3 couldn't do it either, but it is a portable amp.
   
  defining the performance limits of a design is de rigeur here on the DIY forum as well as heeding the real world experience of people with experience.


----------



## limpidglitch

Quote: 





beefy said:


> To mirror and expand on what others have said about most sources lacking volume control on their line outs...... many of us use ASIO on our PC's that disables software volume control as well. So this strategy will not prevent the issue in many cases.
> 
> You are seriously suggesting that somebody would spend $119 as safety factor on a "$30" amp, by putting a second volume control in the signal chain, and putting pot noise back in front of the input stage anyway, rather than changing the design to be more traditional?
> 
> ...


 

  
  I really do not see the problem here. If you have a particularly hot source, then just select a lower gain. If you have an insanely hot 4Vrms source, f.ex a tube output CD player (disregarding the silliness of such contraptions) max gain running on batteries will be ~1X. This will give you enough output to drive, say the LCD-2, to 115dB (following Ananominals most excellent spreadsheet, thanks a lot for the effort, dude). So you choose 1X as the low gain setting, and maybe 8X as the high gain setting, so you can drive your LCD-2s to the same level using an iPod as source.
  What more can you reasonably ask for?
   
  There really are no problems here other than what you make yourself, so if you can refrain from doing so, all should be fine.


----------



## Beefy

Quote: 





b0ck3n said:


> _*Have you seen some of the popular portable rigs right now?*_


 

 Indeed! Lets do a Sizeasy comparison, just to see how the O2 compares to the 'competition'......
   
*http://www.sizeasy.com/page/size_comparison/32684-O2-in-B2-080-vs-Mini3-in-1455C801-vs-Headamp-Pico*
   
  Quote: 





limpidglitch said:


> There really are no problems here other than what you make yourself, so if you can refrain from doing so, all should be fine.


 

 The problem is that it won't be the builders who deal with this, but clueless noob end users who don't understand the problem. You shouldn't have to use the gain knob like a volume control to avoid problems or account for quieter recordings. That is why we have a volume control.


----------



## limpidglitch

Quote: 





fishski13 said:


> defining the performance limits of a design is de rigeur here on the DIY forum as well as heeding the real world experience of people with experience.


 


  And as Nw has done this repeatedly, all should be fine, right?


----------



## The Monkey

khaos974 said:


> the monkey said:
> 
> 
> > Wrong.
> ...




Go back and read his site--carefully. He makes clear that this can be used as a portable or desktop. It is clear from the actual words he uses, despite the fact that his writing is far from the model of clarity. 

What is also clear is that some people are changing the stated goals of the amp and thereby the universe of comparators and criticisms as an exercise in obfuscation. Why?


----------



## Focal1

Quote: 





the monkey said:


> So now it is a portable? Kind of a moving target, this amp.


 


   


  Quote: 





beefy said:


> To mirror and expand on what others have said about most sources lacking volume control on their line outs...... many of us use ASIO on our PC's that disables software volume control as well. So this strategy will not prevent the issue in many cases.
> 
> 
> 
> ...


 


  As far as the size, portable doesn't have to mean it's meant to be carried around in your pocket and used while walking or on a bus, I think to me portable is something I can throw in a bag to use at work, at home, or while out of town where I wouldn't be able to bring a full-sized amp.


----------



## nikongod

Quote: 





shike said:


> Add a passive preamplifier like the NHT PVC or set the gain properly for the source you'll be using - problem solved.  This isn't hard or something that can't be worked around unlike certain (and IMO larger) issues with other designs.


 

 It seems extremely counterproductive to put a piece of gear like the NHT PVC (I actually own one) before a measurements first amplifier. 
   
  Another analog volume control adding its distortions and noise, and a transformer with inherent bandwidth limitations, phase shifts, and distortions. Next thing you know people will be designing their own amps, for themselves, that sound great despite not measuring so well. 
   
  Also, my PVC has 0.5db channel matching at best. Despite all of that, I actually like it quite a lot. It makes a quick and dirty test-bed for figuring out how much too much gain you have, and is an adequate band-aid fix when you have no real control over the gain. 
   
  Quote: 





b0ck3n said:


> People seem to also forget that the O2 has the *same* distortion levels from 0 to max volume, meaning that as long as you've got a volume control on your source or DAC you can make sure to stay within the limits of the amp clipping very easily. The misconception that the O2 clips before getting loud enough is just that, a misconception.


 
   
  Your full of it. 
   
  Have you seen a graphs of output power (or voltage into resistance, may be better for headphones) VS THD+n for a variety of loads? I have NEVER seen a flat curve for Power VS THD+n. Ever. I think this curve actually has a lot to do with how an amp sounds. Amplifiers whose THD+n rises like whoa as power drops make me laugh. Lowest distortion at 20W, but we only use 2. Jokes on you!
   
  I have often wondered if the characteristic V-shaped THD VS power curve is part of why so many "perfect amps" could suck a golf ball through a garden hose. Its probably a combination of that, and something else that the designer overlooked.
   
  "everything I thought of is perfect" 
  "umm, what about that turd you gave me"
  "I didnt think of that"
   
  Keep trying.


----------



## khaos974

the monkey said:


> khaos974 said:
> 
> 
> > the monkey said:
> ...




It's an amp that can be used as a portable, thus it was designed as a portable and desktop amp. The portable criterion is included in the portable and desktop criteria. It's designed to be a portable amp.


----------



## limpidglitch

Quote: 





the monkey said:


> Go back and read his site--carefully. He makes clear that this can be used as a portable or desktop. It is clear from the actual words he uses, despite the fact that his writing is far from the model of clarity.
> 
> What is also clear is that some people are changing the stated goals of the amp and thereby the universe of comparators and criticisms as an exercise in obfuscation. Why?


 


  You're not exactly the epitome of clarity yourself. He says it can be used as a portable, and so it can. Yet somehow it can't?
   
  It can be used without a tether and fits in the palm of your hand, thats portable enough for me.


----------



## The Monkey

lol, you people continue to surprise and delight.  Let's try this another way.  Based on the designer's initial treatise, the only difference between the amp in portable form and desktop form is the size of the enclosure.  However, when amps are discussed on this site, there is a distinction drawn between portable and desktop amps that loosely can be described as portables are not as "good" as desktops, and they should not be expected to have such performance.  Right or wrong, that is the general perception.  My understanding of the designer's goal is that there should be no such distinction except for the size of the enclosure.  However, several people in this very thread already are trying to define it as a portable and either explicitly or implicitly state that it should be used as such (e.g., someone mentioning that it will be used with portable sources only).
   
  I'm curious why people want to categorize this as a portable amp.  Is it merely to emphasize the convenience of it, or is a preemptive attempt to invalidate comparisons to desktop amps?


----------



## The Monkey

Quote: 





khaos974 said:


> It's an amp that can be used as a portable, thus it was designed as a portable and desktop amp. The portable criterion is included in the portable and desktop criteria. It's designed to be a portable amp.


 


  I have no idea what any of that means.


----------



## khaos974

the monkey said:


> I have no idea what any of that means.




Sorry, I was doing multiple things at the same time, the website claims it's designed as both portable and desktop. Since portable is included in the "portable and desktop", saying that the designer claimed from the beginning that it was designed as a portable amp is accurate.


----------



## The Monkey

Quote: 





khaos974 said:


> Sorry, I was doing multiple things at the same time, the website claims it's designed as both portable and desktop. Since portable is included in the "portable and desktop", saying that the designer claimed from the beginning that it was designed as a portable amp is accurate.


 


 Accurate (arguably), but potentially misleading.  And I don't think you're doing it on purpose.  But as I explained above, there are many here who expect different performance from a portable than from a desktop.  It seems to me that is one of the "myths" the designer is interested in debunking; a laudable goal in my opinion.  So for the purposes of the O2, unless someone corrects me, I believe the difference in the size of the enclosure is the only meaningful distinction between a desktop O2 and a portable O2.  The real problem, as I see it, is that people are already trying to excuse potential performance issues by leaning on the old crutch of "but it's only a portable!" (And therefore any performance limitations compared to desktops should be excused.)  My sole purpose in going on like this is that I would hope, when discussing performance, people would discuss the O2 as just an amp, the portable/desktop distinction is meaningless.  Unless the designer is changing his tune, which his recent comment indicates might be the case.


----------



## limpidglitch

Quote: 





the monkey said:


> lol, you people continue to surprise and delight.  Let's try this another way.  Based on the designer's initial treatise, the only difference between the amp in portable form and desktop form is the size of the enclosure.  However, when amps are discussed on this site, there is a distinction drawn between portable and desktop amps that loosely can be described as portables are not as "good" as desktops, and they should not be expected to have such performance.  Right or wrong, that is the general perception.  My understanding of the designer's goal is that there should be no such distinction except for the size of the enclosure.  However, several people in this very thread already are trying to define it as a portable and either explicitly or implicitly state that it should be used as such (e.g., someone mentioning that it will be used with portable sources only).
> 
> I'm curious why people want to categorize this as a portable amp.  Is it merely to emphasize the convenience of it, or is a preemptive attempt to invalidate comparisons to desktop amps?


 

  
  Only happy to be a source of surprice and delight 
	

	
	
		
		

		
			




   
  I'm a bit out of the loop when it comes to audiophile logic, but I'm doing my best. 
  Is the problem here that Head-Fi consensus does not allow an amplifier to be both 'portable' and 'desktop' at the same time, since a 'portable' amplifier must be inherently iferior to a 'desktop' amplifier, and the impossibility of an amplifier being simultaneously both inferior and superior to a given reference?
  If this is the case the remedy is very simple, as the dissonance is only imagined: The 'portable' and 'desktop' O2 aren't equal in performance.


----------



## nikongod

Beyond the higher voltage rails from wall power, it does not look like the O2 amp has any features that are intended for home use but not portable. 
   
  Pimeta springs to mind as an example where there are things that one would do for a home amp (Class-A bias op amp, higher idle current for output buffers) that one would not do in a portable, in the name of battery life.


----------



## khaos974

the monkey said:


> Accurate (arguably), but potentially misleading.  And I don't think you're doing it on purpose.  But as I explained above, there are many here who expect different performance from a portable than from a desktop.  It seems to me that is one of the "myths" the designer is interested in debunking; a laudable goal in my opinion.  So for the purposes of the O2, unless someone corrects me, I believe the difference in the size of the enclosure is the only meaningful distinction between a desktop O2 and a portable O2.  The real problem, as I see it, is that people are already trying to excuse potential performance issues by leaning on the old crutch of "but it's only a portable!" (And therefore any performance limitations compared to desktops should be excused.)  My sole purpose in going on like this is that I would hope, when discussing performance, people would discuss the O2 as just an amp, the portable/desktop distinction is meaningless.  Unless the designer is changing his tune, which his recent comment indicates might be the case.




Ok, I see what you mean, and I agree that performance wise it should be judged as simply an amp, since the designer hasn't restricted its use to portable source.

(Little explanation, you interjected a "Wrong" I was discussing with someone else whether the enclosure was too big for the O2 to be classified as portable, I interpreted that "wrong" as "it's too big for the designer to claim this is a portable amp", hence the following discussion where we were totally on different tracks )


----------



## nikongod

Quote: 





limpidglitch said:


> Is the problem here that Head-Fi consensus does not allow an amplifier to be both 'portable' and 'desktop' at the same time, since a 'portable' amplifier must be inherently iferior to a 'desktop' amplifier, and the impossibility of an amplifier being simultaneously both inferior and superior to a given reference?
> If this is the case the remedy is very simple, as the dissonance is only imagined: The 'portable' and 'desktop' O2 aren't equal in performance.


 

 Its not that head-fi doesn't allow for a portable amplifier to be better than a stationary one, its that it only very very rarely happens that way. Its not hard to build a stationary amplifier so bad that a portable bests it. A stationary Cmoy VS a portable Pimeta for example. 
   
  While the O2's performance is probably very very similar from portable and stationary use that does not mean that it is ever better than a dedicated stationary amplifier.


----------



## Beefy

Quote: 





limpidglitch said:


> Is the problem here that Head-Fi consensus does not allow an amplifier to be both 'portable' and 'desktop' at the same time, since a 'portable' amplifier must be inherently iferior to a 'desktop' amplifier, and the impossibility of an amplifier being simultaneously both inferior and superior to a given reference?
> If this is the case the remedy is very simple, as the dissonance is only imagined: The 'portable' and 'desktop' O2 aren't equal in performance.


 

 It depends on your definition of portable. As far as I am concerned, if it wouldn't fit in my pocket it isn't portable. The Mini3 is barely portable, the Pico slightly better, and a Pico Slim being the ideal portable form factor. So to my mind, the O2 will never be portable.
   
  So yes, in what I define as a portable form factor, a portable amplifier is generally inferior to a similarly well designed desktop amplifier. Sacrifices must be made on the power supply, grounding scheme, output stage and heat dissipation to fit within the space budget, which typically allows no more than a single 9V battery.
   
  The designer of this amp has simply made his 'portable' huge and with two batteries in order to avoid dealing with most of these issues.


----------



## The Monkey

Quote: 





limpidglitch said:


> Only happy to be a source of surprice and delight
> 
> 
> 
> ...


 

 Yes, my belief is that people at HF tend to hold portables to one standard and desktops to another, for any number of reasons I suppose, some valid given certain designs.  As for your last sentence, you mean that any difference in performance between a desktop O2 and a portable O2 would be imagined, correct?


----------



## SpaceTimeMorph

Quote: 





the monkey said:


> Accurate (arguably), but potentially misleading.  And I don't think you're doing it on purpose.  But as I explained above, there are many here who expect different performance from a portable than from a desktop.  It seems to me that is one of the "myths" the designer is interested in debunking; a laudable goal in my opinion.  So for the purposes of the O2, unless someone corrects me, I believe the difference in the size of the enclosure is the only meaningful distinction between a desktop O2 and a portable O2.  The real problem, as I see it, is that people are already trying to excuse potential performance issues by leaning on the old crutch of "but it's only a portable!" (And therefore any performance limitations compared to desktops should be excused.)  My sole purpose in going on like this is that I would hope, when discussing performance, people would discuss the O2 as just an amp, the portable/desktop distinction is meaningless.  Unless the designer is changing his tune, which his recent comment indicates might be the case.


 

 What is the difference between a portable O2 and a desktop one?  Good question!  Other than the enclosure difference, the main one is the voltage present on the power supply rails.  With AC Power connected, it is rated at 20Vpp.  However, when no AC source is connected the dual 9-V batteries provide a rated 14Vpp to the power supply rails.  One is kept from interfereing with the other through an auctioneering mechanism so that when the wall power is connected only the mains power will be present on the rails, and when it is disconnected, only the battery power will be.  The problem/design concern here is of course that it will output less power when on battery than connected to a wall.  Now, with normal portable sources and not using obscenely hard to drive headphones this won't be a problem because most portables won't output as much voltage as a desktop source would.  What do I mean by normal?  Redbook standard is 2Vrms.  Most portable sources are in the range from .5Vrms-1Vrms.  Some in both catagory are over, however, they are the minority.
   
  There are cases where a "hot source" (as it has been described) could overload the input stage if the gain is set too high.  Of course, lowering the gain might be a problem if you are using a hot source with a hard to drive headphone.  Again, for 99% of the people this won't be a problem.  For the extra 1%, it is a possibility to use a higher voltage output wall transformer in conjunction with a higher voltage output battery (lion of some sort, for example) in conjunction with higher voltage MOSFETs (the ones in the design are limited to 25V) in order to rectify this.  (You could also use a Zener clamp upstream of the MOSFETS)
   
  The reason why this wasn't done in the original design was in order to keep the DIY as simple and safe as possible.  Building a reliable lion power supply under DIY conditions would require surface mount soldering as well as certain safety features (CCCV shut-off for example); not to mention increased cost.  This didn't meet the original design criteria as specified in his article and in the above.
   
  Now you could argue that due to the lower power supply rails, this design isn't as one size fits all as the designer claims... and you would have a point.  However, since independent measurements haven't been forthcoming the best realistic answer would be that, according to the designers measurements, for 99% of the people this amp would perform equally well in a desktop scenario as it would in a portable one.  And for the outlier case, correct choice of differing gain structure/making some improvements to the power supply are available.
   
  Some would also argue that the amp cannot output 20Vpp/14Vpp.  However he has made measurements (on his website again) that clearly show the amp outputting a clear sine wave up to 20Vpp before it clips.  That suggests the opamps specified (NJM2068s) can drive closer to the supply rails than the spec sheet lists.  The designer has made many measurements/tests of many different opamps to arrive at the one he chose for the design.  Again, until someone independently peer checks his results none of this is 100%.
   
  Also, some in this thread are making the mistake of taking others assertions as the designers.  I would be careful with that, he has enough written about this amp on his website (no one is banned from going there AFAIK) and on other forums to debate the merits or shortcomings of this amp for a while.
   
  Hope this helps clear things up!


----------



## Shike

Quote: 





currawong said:


> This has come because I think nwavguy has pitched it in a "Fight the man!" manner, which appeals to some people here, suggesting that for $35 (or whatever the total is) you can have an amp that will be good enough for everything. Now the people who know what they are talking about have come in and started telling it like it is, some of you don't want to hear it.  I suggest some of you should ditch the battle mindset, as anyone building this will need to know as much as they can and any issues found now will only benefit everyone in the long run.


 

 It's perfectly clear NwAvGuy is aware of the limitations of designs, and knows very well what he's talking about.
   
  Quote: 





beefy said:


> You are seriously suggesting that somebody would spend $119 as safety factor on a "$30" amp, by putting a second volume control in the signal chain, and putting pot noise back in front of the input stage anyway, rather than changing the design to be more traditional?
> 
> Yeah, that makes a LOT of sense.


 
   
  Safety factor?  It wouldn't be a safety factor in the least, just prevent clipping on hot sources in this context.  You can build a volume control like the PVC cheap, it's just basically using a higher quality pot.
   
  He put the volume control where he did for achieving the best specs.  Other amplifiers have similar trade-offs like Fiio.  If you don't want to have to use a volume control either set the gain for your source or buy a source that actually conforms to redbook spec.
   
   
   
  The O2 is a portable amp that can be used as a desktop amp - I did the same with my Mini^3 before I sold it.  Personally, I wouldn't even use the Mini^3 as a pocket amp since there's sufficient amps that are plenty more pocketable and the O2 falls in the same category.  For travel though it was always brought along, and should the O2 live up to the hype it will fill that spot.  I fail to see what's hard to grasp here honestly . . .


----------



## fishski13

Quote: 





limpidglitch said:


> And as Nw has done this repeatedly, all should be fine, right?


 


  you quoted me out of context.  yes, he's measured the amp, but since not all recordings are equal in loudness, you need to have some headroom in volume adjustment.  i don't care how the amp 'measures', the gain and source restrictions limit its application.  i think the amp will be fine for my D2000 with 2Vrms from source and 3.1x gain, but barely enough for my K702 if i want to have adequate volume with my entire music collection.


----------



## bcg27

@SpaceTimeMorph While spec sheets are generally conservative, I think it would be a mistake to define the amplifiers output capabilities based on winning the tolerance lottery and getting a good chip. That would be like Intel saying it's processors work at 5 GHz because some people are able to overclock them to that. Sure, I imagine you could buy 10 or 20 of the chips and pick the one that can swing the most voltage, but the official specifications should definitely agree with the data sheets.


----------



## Shike

Quote: 





fishski13 said:


> you quoted me out of context.  yes, he's measured the amp, but since not all recordings are equal in loudness, you need to have some headroom in volume adjustment.  i don't care how the amp 'measures', the gain and source restrictions limit its application.  i think the amp will be fine for my D2000 with 2Vrms from source and 3.1x gain, but barely enough for my K702 if i want to have adequate volume with my entire music collection.


 

 As someone that also owns a K702, I beg to differ. 101dB at 1V isn't a a hard to drive headphone in the least, and since I'll be reviewing one I can put my money where my mouth is.  Give me one or two tracks you think there will be a problem with using this amp and the K702.

 PS: I use MP3 gain and replaygain my entire collection to retain dynamic range while making sure the peaks are roughly the same level and don't clip.


----------



## bcg27

Quote: 





shike said:


> The O2 is a portable amp that can be used as a desktop amp - I did the same with my Mini^3 before I sold it.  Personally, I wouldn't even use the Mini^3 as a pocket amp since there's sufficient amps that are plenty more pocketable and the O2 falls in the same category.  For travel though it was always brought along, and should the O2 live up to the hype it will fill that spot.  I fail to see what's hard to grasp here honestly . . .


 

 Every portable amp can be a desktop amp, but not all desktop amps can be a portable amp. Actually I personally don't consider any amp portable. Even an ipod by itself is a little too clunky for me to have extra in my pockets. For ordinary walking around I will either play off my phone or my clip. If I am going on a trip where I am carrying a bag then something the size of an ipod is acceptable, but I still wouldn't want to bother with an amp unless I am going on a long trip, like going to be somewhere for a couple weeks or more.
   
  Of course, a lot of people will disagree with me and I think that is part of the problem, that not everyone has the same definition of portable. If I were to build this amp, it would not be a portable for me, it would be a desktop amp. Perhaps a easily transportable desktop, but I would never use it on the go.


----------



## mikeaj

Quote: 





nikongod said:


> Have you seen a graphs of output power (or voltage into resistance, may be better for headphones) VS THD+n for a variety of loads? I have NEVER seen a flat curve for Power VS THD+n. Ever. I think this curve actually has a lot to do with how an amp sounds. Amplifiers whose THD+n rises like whoa as power drops make me laugh. Lowest distortion at 20W, but we only use 2. Jokes on you!
> 
> I have often wondered if the characteristic V-shaped THD VS power curve is part of why so many "perfect amps" could suck a golf ball through a garden hose. Its probably a combination of that, and something else that the designer overlooked.


 

 Yes definitely.  Obviously it's not flat as noise (which is really low) dominates on the left side and performance degrades on the right side.
   
  Click on the first article and search for:
*THD+N vs OUTPUT & MAX POWER ON AC*
  and also
*THD+N vs OUTPUT & MAX POWER ON BATTERY*
   
  It's purportedly well below 0.01% into any load tested, even on battery, just before distortion really ramps up on the right side near clipping.  It's kind of inconvenient not to be able to link relevant information, but sure...
   
   
  Quote: 





bcg27 said:


> Every portable amp can be a desktop amp, but not all desktop amps can be a portable amp. Actually I personally don't consider any amp portable. Even an ipod by itself is a little too clunky for me to have extra in my pockets. For ordinary walking around I will either play off my phone or my clip. If I am going on a trip where I am carrying a bag then something the size of an ipod is acceptable, but I still wouldn't want to bother with an amp unless I am going on a long trip, like going to be somewhere for a couple weeks or more.
> 
> Of course, a lot of people will disagree with me and I think that is part of the problem, that not everyone has the same definition of portable. If I were to build this amp, it would not be a portable for me, it would be a desktop amp. Perhaps a easily transportable desktop, but I would never use it on the go.


 
   
  Yeah these are my thoughts exactly regarding portable vs. desktop.  Good explanation.


----------



## Shike

Quote: 





bcg27 said:


> Of course, a lot of people will disagree with me and I think that is part of the problem, that not everyone has the same definition of portable. If I were to build this amp, it would not be a portable for me, it would be a desktop amp. Perhaps a easily transportable desktop, but I would never use it on the go.


 

 I think you hit the nail on the head, a new 'genre' of amp: transportable.
   
  I certainly wouldn't use this as a portable, and while it can it isn't exactly easy to do so.  On the other hand it's easy to transport.


----------



## limpidglitch

Quote: 





the monkey said:


> Yes, my belief is that people at HF tend to hold portables to one standard and desktops to another, for any number of reasons I suppose, some valid given certain designs.  As for your last sentence, you mean that any difference in performance between a desktop O2 and a portable O2 would be imagined, correct?


 

  
  No, I mean that the dissonance is imagined, as the 'portable' (battery) O2 measures slightly worse than the 'desktop' (AC) O2.
  F.ex 1% THD+N into 33 ohm is reached at 613mW by AC, and at 547mW by battery.
  There is no reason why Head-Fi'ers heads should start exploding; their dogma that stationary (in general) beats portable (in general) still holds true.


----------



## fishski13

Quote: 





shike said:


> As someone that also owns a K702, I beg to differ. 101dB at 1V isn't a a hard to drive headphone in the least, and since I'll be reviewing one I can put my money where my mouth is.  Give me one or two tracks you think there will be a problem with using this amp and the K702.
> 
> PS: I use MP3 gain and replaygain my entire collection to retain dynamic range while making sure the peaks are roughly the same level and don't clip.


 

 sure thing!  i'm glad to hear that you've decided to build this amp.


----------



## Beefy

Quote: 





shike said:


> Safety factor?  It wouldn't be a safety factor in the least, just prevent clipping on hot sources in this context.  You can build a volume control like the PVC cheap, it's just basically using a higher quality pot.
> 
> He put the volume control where he did for achieving the best specs.


 

 You still don't see it, do you? You are suggesting putting a volume control in front of the gain stage, to make up for the fact that the amp does not have a volume control in front of the gain stage.
   
  This is flat out dumb, because it completely negates the intended effect, and actually makes things worse than if there was a single volume pot where most other DIY other amps put it.
   
  Quote: 





shike said:


> I think you hit the nail on the head, a new 'genre' of amp: transportable.
> 
> I certainly wouldn't use this as a portable, and while it can it isn't exactly easy to do so.  On the other hand it's easy to transport.


 

 Which would be fine, if the designer weren't making such a strong comparison to the Mini3. I am like you in that I wouldn't pocket a Mini3...... but nevertheless, the Mini3 is in a _much_ smaller size range.


----------



## Shike

Quote: 





beefy said:


> You still don't see it, do you? You are suggesting putting a volume control in front of the gain stage, to make up for the fact that the amp does not have a volume control in front of the gain stage.
> 
> This is flat out dumb, because it completely negates the intended effect, and actually makes things worse than if there was a single volume pot where most other DIY other amps put it.


 

 Then don't buy a "flat out dumb" source that can't follow redbook due to poor design.  It's really that simple isn't it?  It's not the amp designer that needs to make sure your source is behaving itself.


----------



## nikongod

Quote: 





mikeaj said:


> Yes definitely.  Obviously it's not flat as noise (which is really low) dominates on the left side and performance degrades on the right side.
> 
> Click on the first article and search for:
> *THD+N vs OUTPUT & MAX POWER ON AC*
> ...


 

 Thanks for pointing it out. 
   
  Are they available on a logarithmic voltage scale? I own a few headphones that have never seen more than 100mv, and I cant read that section of the graph.


----------



## The Monkey

Quote: 





limpidglitch said:


> No, I mean that the dissonance is imagined, as the 'portable' (battery) O2 measures slightly worse than the 'desktop' (AC) O2.
> F.ex 1% THD+N into 33 ohm is reached at 613mW by AC, and at 547mW by battery.
> There is no reason why Head-Fi'ers heads should start exploding; their dogma that stationary (in general) beats portable (in general) still holds true.


 

 Would those differences be audible?  And, regardless, comparing the O2 in its "desktop" configuration to other desktops would be appropriate, correct?
   
  FWIW, HeadFi'ers heads regularly explode for no good reason.


----------



## Beefy

Quote: 





shike said:


> Then don't buy a "flat out dumb" source that can't follow redbook due to poor design.  It's really that simple isn't it?  It's not the amp designer that needs to make sure your source is behaving itself.


 


  Nice try to deflect away from the fact that your passive volume control was a stupid idea, but I will play along, and go through this very simply......
   
  Using a volume pot to control the volume is good. Misuse does not inherently cause clipping issues in most amps.
   
  Using a gain switch as a backup to account for soft vs loud recordings, while still maintaining good volume pot travel for both, is good. Misuse does not inherently cause clipping issues in most amps.
   
  Being _forced_ to change the gain with different sources and recording levels to prevent clipping and maintain adequate volume is bad.
   
  This is a considerable usability issue. No matter what the builder does, these amps will end up in the hands of people who aren't informed enough to understand why the amp sounds bad at high gain settings.


----------



## Steve Eddy

Quote:  





>





> FWIW, HeadFi'ers heads regularly explode for no good reason.


 

 "I don' know wuh happun'. Alla sudden, he haid, it jes' 'sploded!" --Eyewitness interview
   
  se


----------



## Steve Eddy

Quote: 





beefy said:


> This is a considerable usability issue. No matter what the builder does, these amps will end up in the hands of people who aren't informed enough to understand why the amp sounds bad at high gain settings.


 
   
  So what? Why must a designer be shackled by the ill-informed?
   
  se


----------



## The Monkey

Is this group defining anything greater than 2 Vrms (is that the right way to state it?) as being a "hot" source?


----------



## Head Injury

Quote: 





the monkey said:


> Is this group defining anything greater than 2 Vrms (is that the right way to state it?) as being a "hot" source?


 

 I believe we're defining it at about that for portable sources, and since 2.8Vrms is apparently clipping level at the default 2.5x gain on AC, that would be hot for desktop sources.
   
  I'm no good at the fancy math. At 2.5x gain, what input would cause clipping on the 9V batteries?


----------



## nikongod

Quote: 





steve eddy said:


> So what? Why must a designer be shackled by the ill-informed?
> 
> se


 
   
  I laughed. 
   
  You roxor!


----------



## The Monkey

Quote: 





head injury said:


> I believe we're defining it at about that for portable sources, and since 2.8Vrms is apparently clipping level at the default 2.5x gain on AC, that would be hot for desktop sources.
> 
> I'm no good at the fancy math. At 2.5x gain, what input would cause clipping on the 9V batteries?


 


  It's weird.  Taking a quick look at the specs of the various desktop DACs I've owned, they seem to be all over the place from 2.0 - 2.7.  Then again, half the time I don't know what the hell I'm reading.


----------



## Head Injury

Quote: 





the monkey said:


> It's weird.  Taking a quick look at the specs of the various desktop DACs I've owned, they seem to be all over the place from 2.0 - 2.7.  Then again, half the time I don't know what the hell I'm reading.


 

 Yes. In other words, with 2.5x gain there isn't a problem with clipping. At least on AC power.
   
  You could probably say that 2.8Vrms is "too hot", and 2.3Vrms+ (which I think was the clipping level at 3.1x gain?) is "hot".


----------



## Shike

Quote: 





beefy said:


> Nice try to deflect away from the fact that your passive volume control was a stupid idea, but I will play along, and go through this very simply......


 

  Nice try, but it isn't a stupid idea if it works.  You're going to need to provide evidence that the impacts are clearly audible first.  You can say "but this wouldn't be an issue", it still doesn't matter.  It wouldn't be an issue if the source makers developed their gear properly.  If a source shoved a crapload of DC voltage on the output and the amplifier outputted it whose fault is it?
   
   
  Quote: 





> Using a volume pot to control the volume is good. Misuse does not inherently cause clipping issues in most amps.
> Using a gain switch as a backup to account for soft vs loud recordings, while still maintaining good volume pot travel for both, is good. Misuse does not inherently cause clipping issues in most amps.
> 
> Being _forced_ to change the gain with different sources and recording levels to prevent clipping and maintain adequate volume is bad.
> ...


 
   
  People misusing a product now means we should limit the design?  That's stupid.  Let's all use plastic knives because someone may cut themselves otherwise.
   
  An apt comparison is a really nice sharp knife being used with a bamboo board losing its edge.  You can't say the knife is the problem when it's clearly not meant to be used with bamboo.  Sure enough someone is going to do it and complain about the knife when it's their own fault.  Most chefs would say the person using the board was incompetent and move on - the knife (amp) isn't the problem here.  The board (source) is.  The best thing is a disclaimer can be made, which it has, and move on.

  
  Quote: 





the monkey said:


> Is this group defining anything greater than 2 Vrms (is that the right way to state it?) as being a "hot" source?


 

  
  Pretty much.  It's just that some hot sources are closer to normal like the HRT streamer.  2.7V like the Audio-GD is no where near redbook standard.  IMO the smallest gain should be 2.5x, that way if the voltage is 2.5 it's safe.  Anything above that is closer to 3V anyway and is clearly disregarding standards being fringe cases.
   
   
  @Head Injury
   
  1.4V would cause clipping on low batteries - so a 2.5x gain is definitely safe for most portables - which tend to have volume control anyway so . . .


----------



## Beefy

Quote: 





steve eddy said:


> Why must a designer be shackled by the ill-informed?


 
   
  Because that is how products gain mass-market acceptance. Esoteric products that require OCD attention are why most of the world think audiophiles are pathetic.
   
  Following this, it really comes down to a question of why and when a gain switch should be used. In my opinion, it should only ever be need to be increased when you need more volume pot travel, or decreased when you have very little volume pot travel. Forcing users to switch gain depending on what source they have - in addition to the typical use case - is a defect of usability.


----------



## Beefy

Quote: 





shike said:


> Nice try, but it isn't a stupid idea if it works.  You're going to need to provide evidence that the impacts are clearly audible first.


 

 The designer put the volume pot after the gain stage to improve SNR, right?
   
  So putting another volume pot before the gain stage would decreases SNR, right?
   
  How can you not see the gaping holes in your own logic?


----------



## Head Injury

Quote: 





shike said:


> The best thing is a disclaimer can be made, which it has, and move on.


 

 Yep. Like I said, the problem would be solved with a warning at the top of the schematic which reads something like "DON'T SET GAIN TO X IF SOURCE OUTPUTS Y!" Then if someone does set the gain too high, it's nothing but their fault. They didn't read the instructions. It would be like if someone glued some tubes in where opamps are supposed to be. The design uses opamps, so it's your fault if you use anything else. The design uses a certain gain, so it's your fault if you set it too high.
   
  Quote: 





beefy said:


> Because that is how products gain mass-market acceptance. Esoteric products that require OCD attention are why most of the world think audiophiles are pathetic.


 

 It requires OCD attention to not mess with the specified gain?
   
   


beefy said:


> The designer put the volume pot after the gain stage to improve SNR, right?
> 
> So putting another volume pot before the gain stage would decreases SNR, right?
> 
> How can you not see the gaping holes in your own logic?


 

  Weren't you the one to suggest moving the volume pot to eliminate the issue, reducing SNR in the process? Shike's idea is the same in concept, but not permanent. If your source isn't too hot, you don't need the extra volume control. Your idea would reduce SNR for all sources, not just the troublesome ones.
   
  Here's a wild thought, but can we discuss some other aspect of the design now? Or is user error the only actual flaw?


----------



## Shike

Quote: 





beefy said:


> Because that is how products gain mass-market acceptance. Esoteric products that require OCD attention are why most of the world think audiophiles are pathetic.


 

 This currently isn't a mass market product, even $20 headphone amplifiers tend to fail at being "mass market" products.
   
  If we're talking about mass market products anyway, how many of them output over 2.5V?  I've seen one non-mass market one (unless you're calling Audio-GD a household audio name), and possibly a DIY dac.  That's hardly a deal breaker no matter how you look at it.
   
  Quote: 





> The designer put the volume pot after the gain stage to improve SNR, right?
> So putting another volume pot before the gain stage would decreases SNR, right?
> 
> How can you not see the gaping holes in your own logic?


 
   
  Which means it would have roughly the same SNR as putting it before the gain stage when maxing out the default volume control correct?
   
  This would only have to be done for maybe a handful of cases correct? 
   
  So it's a safe guess that most cases would see a benefit doing it his way, correct?
   
  Keep trying, you can use a Play-Doh knife with your steak if you want.


----------



## limpidglitch

Quote: 





the monkey said:


> Would those differences be audible?  And, regardless, comparing the O2 in its "desktop" configuration to other desktops would be appropriate, correct?
> 
> FWIW, HeadFi'ers heads regularly explode for no good reason.


 
   
  Running an HE-6 at ear-splitting levels, possibly?
  I think the comparison is appropriate. It will of course not beat all competitors in all categories, but if the measurements hold promise, it will kick well above it's weight.
   
  Edit: Obviously one cannot prepare dinner and argue with the interwebs at the same time.


----------



## nikongod

Quote: 





shike said:


> If we're talking about mass market products anyway, how many of them output over 2.5V?  I've seen one non-mass market one (unless you're calling Audio-GD a household audio name), and possibly a DIY dac.  That's hardly a deal breaker no matter how you look at it.


 
   
  By mass market product are you referring to sources? 
  Almost all professional/studio sources have outputs higher than 2.5v.


----------



## Steve Eddy

Quote: 





> Originally Posted by *Beefy* /img/forum/go_quote.gif
> 
> Because that is how products gain mass-market acceptance.


 

 I must have missed something. When did this turn into a mass-market product? Last I looked, it was a DIY project.
   
  When can we expect to see the O2 turn up on the shelves at Best Buy?
   
  Quote: 





> Esoteric products that require OCD attention are why most of the world think audiophiles are pathetic.


 
   
  Ok all you designers out there. From now on, whatever you design must be done under the assumption that these are the people who will be using them.
   





   
  se


----------



## khaos974

nikongod said:


> Thanks for pointing it out.
> 
> Are they available on a logarithmic voltage scale? I own a few headphones that have never seen more than 100mv, and I cant read that section of the graph.




Apparently the left sides on the graphs are ****ty because the dscope averages starts at 0.000 V where the noise obviously goes over 1%. He did a separate measure at 10 mV (called LOW LEVEL THD & THD+N), THD+N < 0.03% and THD = 0.0019%


----------



## Beefy

Quote: 





head injury said:


> Weren't you the one to suggest moving the volume pot to eliminate the issue, reducing SNR in the process? Shike's idea is the same in concept, but not permanent. If your source isn't too hot, you don't need the extra volume control. Your idea would reduce SNR for all sources, not just the troublesome ones.


 

 Indeed, that was me. To my mind, usability trumps any small gain made by this amp. The vast majority of other DIY designs manage good SNR with the volume pot before the gain stage, and there is absolutely no possibility of input stage clipping. So why the issue here, other than for self-indulgently clinging to measurements at the expense of usability?
   
  Quote: 





shike said:


> Which means it would have roughly the same SNR as putting it before the gain stage when maxing out the default volume control correct?


 

 Except for the fact that the second volume pot is still imposing an effect between the input and output stage. Two volume controls is a bad solution.
   
  Play Doh knives indeed, Shike.


----------



## Head Injury

Quote: 





beefy said:


> Indeed, that was me. To my mind, usability trumps any small gain made by this amp. The vast majority of other DIY designs manage good SNR with the volume pot before the gain stage, and there is absolutely no possibility of input stage clipping. So why the issue here, other than for self-indulgently clinging to measurements at the expense of usability?


 

 There is no expense of usability for 95% of people out there. 2.5x gain is enough to power an HE-6, the most demanding headphone, to 107dB. 2.5x gain itself is only necessary if you have a source which outputs around 2.8Vrms. Do you need your HE-6 louder, and do you have a source that's hotter? I haven't heard of any sources that output more than that single-ended.
   
  What is the usability issue?
   
  The point of my post was that you called Shike's idea of an external volume control "dumb", when you basically suggested the design itself do the same thing. I don't get that. How is one dumb and the other isn't?


----------



## Beefy

Quote: 





head injury said:


> The point of my post was that you called Shike's idea of an external volume control "dumb", when you basically suggested the design itself do the same thing. I don't get that. How is one dumb and the other isn't?


 

 Because a single volume control in front of the gain stage covers _100%_ of people, and is better than having two volume controls as Shike suggests.


----------



## Head Injury

Quote: 





beefy said:


> Because a single volume control in front of the gain stage covers _100%_ of people, and is better than having two volume controls as Shike suggests.


 

 And covers 100% of people with lower SNR, too.
   
  What would make it better than two volume controls? Shike's second volume control can be removed. Shike's suggestion covers 100% of people as well, but only 5% of them have reduced SNR.


----------



## The Monkey

Just checking some sources' outputs (some of this info is annoyingly hard to find).  For now, I've just been looking at DACs I have owned or borrowed.
   

 DACMagic - 2.1Vrms
 Parasound 1100HD - 3V
 Electrocompaniet ECD-1 - 1.6
 Bryston BDA-1 - 2.3V


----------



## Anonanimal

Quote: 





fishski13 said:


> you quoted me out of context.  yes, he's measured the amp, but since not all recordings are equal in loudness, you need to have some headroom in volume adjustment.  i don't care how the amp 'measures', the gain and source restrictions limit its application.  i think the amp will be fine for my D2000 with 2Vrms from source and 3.1x gain, but barely enough for my K702 if i want to have adequate volume with my entire music collection.


 

 I think you'd actually be fine for anything but a seriously variable collection.  The K702 is rated at 105dB/V, which translates into ~93 dB/mW efficiency @62 Ohms.  Based on your source you should only need a gain of 2-3 to get 115dB+ peak volume on normalized recordings.  How much quieter, in dB, are your 'quiet' recordings?
   
  https://docs.google.com/spreadsheet/ccc?key=0ArBLkTRCqzhSdENZVW9kYTA3VUlMMV9UODIxLUpPVnc&hl=en_US#gid=0


----------



## limpidglitch

Quote: 





the monkey said:


> Just checking some sources' outputs (some of this info is annoyingly hard to find).  For now, I've just been looking at DACs I have owned or borrowed.
> 
> 
> DACMagic - 2.1Vrms
> ...


 


  You wouldn't happen to know how much the Pico DAC outputs?
  The spec. section at HeadAmp is for some reason completely empty.


----------



## The Monkey

Dunno.  I'll try to find out.


----------



## Shike

Quote: 





nikongod said:


> By mass market product are you referring to sources?
> Almost all professional/studio sources have outputs higher than 2.5v.


 


  That could be a legitimate concern for those planning on using it with pro gear.  Do you have some specific examples handy?
   
  @The Monkey
   
  Would never have expected Parasound to be pushing 3v, that's crazy.
   
   
  At this point maybe the gain structure should be:
   
  1x - unity
  2x - normal
  3x - "high"
   
  That would eliminate just about the entire problem.  If your source is doing 4v unbalanced then it just can't be used period.  This would allow portable sources that have 1v out to go up to 3v, and almost any home source could get around 6v without an issue.


----------



## Bojamijams

So uhh.. has anyone built this thing yet?


----------



## Shike

Quote: 





bojamijams said:


> So uhh.. has anyone built this thing yet?


 


  DeadlyLover built it point to point, but his gain was too high.  He also thinks he may have damaged something.  I'll be reviewing one one way or another, but not until the PCB is in full production obviously.


----------



## c61746961

nikongod said:


> Almost all professional/studio sources have outputs higher than 2.5v.


[citation needed]


----------



## Avro_Arrow

Check here
  
  Quote: 





c61746961 said:


> [citation needed]


----------



## Satellite_6

Interesting, there will always be a case that doesn't work I guess.
   
  2.5X/2.8V seems like a good compromise though. . .


----------



## holland

One can possibly add a "clip" light for a visual indicator of clipping.  Or a light that is held high with circuitry indicating you've clipped instead of just blinking.
   
  It seems to me that much of the discussion is centered around an arbitrarily low gain stage, with potential for clipping, and enthusiasts arguing about how the gain is too low, or just right.  Everything can clip, if fed a high enough level, even power amps, which usually indicate the level of input they are expecting.
   
  One can also increase the amount of voltage available from +-12V to +-18V.  It may not measure as well, but perhaps the designer can measure it and see for sure.  I just sent him an email requesting such.  Especially if one is running off of AC, there's no real need to restrict to +-12V.  It seems to me that the designer should just do some measurement and changes to support +-18V.  Why not?  Just do it and measure it.  You know people will tweak it that way, I surely would.  Fry the pot?  perhaps, I haven't looked at pot specs lately, nor it's power capability.  With higher rails come the possibility for higher gain or gain without clipping, i.e., more headroom.
   
  *shrug*, it seems simple enough.  Pot after the gain isn't horribly new, I've seen it around before, particularly if you've dealt with DACs which may have a gain stage as part of it's output stages feeding into a Pot with just a unity gain or low-gain (2x) buffer after it.  That's really all this looks like to me.  In fact, I have a couple of DACs that do exactly that.
   
  IMO, unified DAC+amp is the way to go, with digital volume control.  You can then do a full-on design for best measurements controlling every single point because it can be limited at every stage.  It may not be portable, but I'm not really sure how much that really matters.  FWIW, IMHO, etc. etc.


----------



## Grahame

On the question of "hot" Line Level sources , some cynics might consider that one reason might be that such devices would come out on top, in non level matched comparisons (_because they are all just DAC's / line level sources, right?) , _given that louder sounds better, all things being equal.


----------



## limpidglitch

Quote: 





holland said:


> One can possibly add a "clip" light for a visual indicator of clipping.  Or a light that is held high with circuitry indicating you've clipped instead of just blinking.
> 
> It seems to me that much of the discussion is centered around an arbitrarily low gain stage, with potential for clipping, and enthusiasts arguing about how the gain is too low, or just right.  Everything can clip, if fed a high enough level, even power amps, which usually indicate the level of input they are expecting.
> 
> ...


 


  A dedicated desktop version is in the works.
  This will have a re-designed gain structure, and I expect, re-designed power supply.


----------



## Cain

Quote: 





shike said:


> Would never have expected Parasound to be pushing 3v, that's crazy.


 


  The Parasound "Pyrosound" JC1 is famous for randomly blowing up due to instability issues on the output stage, so I'm not surprised in the slightest.


----------



## fishski13

Quote: 





anonanimal said:


> I think you'd actually be fine for anything but a seriously variable collection.  The K702 is rated at 105dB/V, which translates into ~93 dB/mW efficiency @62 Ohms.  Based on your source you should only need a gain of 2-3 to get 115dB+ peak volume on normalized recordings.  How much quieter, in dB, are your 'quiet' recordings?
> 
> https://docs.google.com/spreadsheet/ccc?key=0ArBLkTRCqzhSdENZVW9kYTA3VUlMMV9UODIxLUpPVnc&hl=en_US#gid=0


 

 apples and oranges, but i have a M3 here with a gain of 8x.  i sat down for a listen this evening with my K702 and BM DAC1 (2Vrms).  with the pot mounted with pointer at about 7:30, i am hitting 2-2:30 with my ECM label recordings (new or old recordings) and the same for a couple of the Steely Dan albums i tried.  measured dB was 85 peaks with an analog Radio Shack meter stuck through a piece of cardboard to cover the driver housing.


----------



## agdr

Quote: 





holland said:


> One can also increase the amount of voltage available from +-12V to +-18V.  It may not measure as well, but perhaps the designer can measure it and see for sure.  I just sent him an email requesting such.  Especially if one is running off of AC, there's no real need to restrict to +-12V.  It seems to me that the designer should just do some measurement and changes to support +-18V.  Why not?  Just do it and measure it.  You know people will tweak it that way, I surely would.  Fry the pot?  perhaps, I haven't looked at pot specs lately, nor it's power capability.  With higher rails come the possibility for higher gain or gain without clipping, i.e., more headroom.


 
   
  I already suggested going to +/15V since the chips are all good for +/-18V. 
	

	
	
		
		

		
			





  His reply was the higher voltage would push the output chips slightly out of safe operating area with maximum output.  He says it would also make the battery charging circuit more complex and the board is out of space right now.  But who knows, he may yet find a clever way to do it on some future revision.
   
  Sounds like he might consider a higher voltage on the desktop version, if that unit comes to pass.

 The O2 seems like a very interesting design and looks like a good amp.  I'm also an enormous fan of AMB's mini^3.  This one seems to be in a different size category.  For super-small with one battery you have the mini^3, and that size pretty much dictates a virtual ground.   The O2 has the dual rails and dual batteries with clever protection circuit and real ground, but larger case.  Each amp hits its own market segment.


----------



## SpaceTimeMorph

Quote: 





agdr said:


> The O2 seems like a very interesting design and looks like a good amp.  I'm also an enormous fan of AMB's mini^3.  This one seems to be in a different size category.  For super-small with one battery you have the mini^3, and that size pretty much dictates a virtual ground.   The O2 has the dual rails and dual batteries with clever protection circuit and real ground, but larger case.  Each amp hits its own market segment.


 
   
  Definitely this... I haven't like the comparisons to the mini^3 from the moment they started.  Different beasts.
    
  Quote:


holland said:


> IMO, unified DAC+amp is the way to go, with digital volume control.  You can then do a full-on design for best measurements controlling every single point because it can be limited at every stage.  It may not be portable, but I'm not really sure how much that really matters.  FWIW, IMHO, etc. etc.


 

 I actually would like to integrate a DAC+O2 amp.  Do you have any suggestions on DACs use?  I don't have the proper tools to do a full on DIY so I would probably just be rolling with something premade.
   
  Oh, and to whomever posted it earlier (too lazy to go back and read).  Srms + 10*log(Z/1000) = Srms - 10*log(1000/Z).  They both work to convert dB/1Vrms to dB/mW; just use whichever one floats your boat.


----------



## The Monkey

Wouldn't it make more sense to chuck the whole battery concept and just concentrate on a desktop?  Fewer compromises that way, no?


----------



## Mong0

Quote: 





the monkey said:


> Wouldn't it make more sense to chuck the whole battery concept and just concentrate on a desktop?  Fewer compromises that way, no?


 


  Not exactly, you need to remember that he is aiming for a one-size-fits-all kind of design. It will be a desktop and portable DAC1-quality amp that costs very little, but yet will perform into the inaudible area of being able to tell the O2 and DAC1 apart. Removing the battery would compromise that design.


----------



## Steve Eddy

Quote: 





the monkey said:


> Wouldn't it make more sense to chuck the whole battery concept and just concentrate on a desktop?  Fewer compromises that way, no?


 

 How 'bout the best of both worlds?
   

   




   
  se


----------



## fishski13

Quote: 





steve eddy said:


> How 'bout the best of both worlds?
> 
> 
> 
> ...


----------



## kwkarth

Quote: 





steve eddy said:


> How 'bout the best of both worlds?
> 
> 
> 
> ...


 

 An orange power cord will color your sound.


----------



## bcg27

How about one of these
   
	

	
	
		
		

		
		
	


	



  http://www.lifelinebatteries.com/rvflyer.php?id=8
   
  connected to something like this
   
	

	
	
		
		

		
		
	


	



http://www.amazon.com/Power-Bright-PW2300-12-Inverter-2300/dp/B002AMPGE6/ref=pd_sbs_auto_3
   
  The ultimate in amp battery power


----------



## Steve Eddy

Quote: 





kwkarth said:


> An orange power cord will color your sound.


 
   
  Ok, smartass.
   

   




   
  se


----------



## Steve Eddy

Quote: 





bcg27 said:


> How about one of these
> 
> connected to something like this
> 
> The ultimate in amp battery power


 

 Now yer talkin'! Lugging that 162 pound battery will get your ass in shape in no time! Just one more benefit.
   
  se


----------



## Maxvla

beefy said:


> Indeed, that was me. To my mind, usability trumps any small gain made by this amp. The vast majority of other DIY designs manage good SNR with the volume pot before the gain stage, and there is absolutely no possibility of input stage clipping. So why the issue here, other than for self-indulgently clinging to measurements at the expense of usability?
> 
> 
> Except for the fact that the second volume pot is still imposing an effect between the input and output stage. Two volume controls is a bad solution.
> ...




Why shouldn't people be interested in building something that's different? If everyone used the same design principles there would never be innovation.


----------



## kwkarth

Quote: 





steve eddy said:


> Ok, smartass.
> 
> 
> 
> ...


 
  Now you're going to whitewash the sound.  Where's your sense of transparency man?


----------



## SpaceTimeMorph

You guys think so small...
   
http://www.fairbanksmorsenuclear.com/engine_colt-pielstickPA6B.php
   
  Can be skid mounted too!!


----------



## Armaegis

Quote: 





kwkarth said:


> Now you're going to whitewash the sound.  Where's your sense of transparency man?


 

 Get yourself a bundle of fibre optic cable, then do this: http://www.teralab.co.uk/Experiments/Conductive_Glass/Conductive_Glass_Page1.htm


----------



## Steve Eddy

Quote: 





> Originally Posted by *kwkarth* /img/forum/go_quote.gif
> 
> Now you're going to whitewash the sound.  Where's your sense of transparency man?


 
   
  We gotcher transparency right heah, pal!
   

   
  se


----------



## kwkarth

Quote: 





spacetimemorph said:


> You guys think so small...
> 
> http://www.fairbanksmorsenuclear.com/engine_colt-pielstickPA6B.php
> 
> Can be skid mounted too!!


 

 Is the model 20V suitable for portable use?


----------



## bcg27

Quote: 





armaegis said:


> Get yourself a bundle of fibre optic cable, then do this: http://www.teralab.co.uk/Experiments/Conductive_Glass/Conductive_Glass_Page1.htm


 
  Pretty neat but at 1.1 kOhms per cm I think it is a bit of a stretch to call it conductive. I wonder how much additional treatments improve the conductivity.


----------



## Currawong

Edit: Removed part of this post at someone's suggestion.
   
  Quote: 





shike said:


> Nice try, but it isn't a stupid idea if it works.  You're going to need to provide evidence that the impacts are clearly audible first.  You can say "but this wouldn't be an issue", it still doesn't matter.  It wouldn't be an issue if the source makers developed their gear properly.  If a source shoved a crapload of DC voltage on the output and the amplifier outputted it whose fault is it?


 

 The point seems to be that the design measures well (ie: as I just stated, pitched at people like yourself) and, unless I understand wrongly, putting the volume after the gain stage results in better measurements. Now you're talking about audibility (ie: how it sounds). You can't have your cake and eat it too always. This is why I've suggested to others who argue about this stuff that they go and design their own amp.

  
  Quote: 





maxvla said:


> Quote:
> 
> 
> 
> ...


 

 It's not about doing something different, it is about doing something that is usable.  I'd love a Firstwatt amp, for example, but that's not usable for me as it would murder my power bill and I don't listen that loud with speakers. I'm sure, likewise, many people wouldn't consider the D-class amps I use because they listen to big orchestral arrangements at loud volumes which they may not be as suitable for. This amp has been pitched as an all-round useful amp which, for little money DIY (but probably at least a couple of hundred dollars commercially) will perform as good or better than existing, more expensive commercial offerings.  That's a pretty tall order considering the large variety of headphones and sources it may be used with.


----------



## Armaegis

Quote: 





bcg27 said:


> Pretty neat but at 1.1 kOhms per cm I think it is a bit of a stretch to call it conductive. I wonder how much additional treatments improve the conductivity.


 

 So are you saying we should be making fiber optic resistors instead?


----------



## Satellite_6

Quote: 





currawong said:


> It's not about doing something different, it is about doing something that is usable.  I'd love a Firstwatt amp, for example, but that's not usable for me as it would murder my power bill and I don't listen that loud with speakers. I'm sure, likewise, many people wouldn't consider the D-class amps I use because they listen to big orchestral arrangements at loud volumes which they may not be as suitable for. This amp has been pitched as an all-round useful amp which, for little money DIY (but probably at least a couple of hundred dollars commercially) will perform as good or better than existing, more expensive commercial offerings.  That's a pretty tall order considering the large variety of headphones and sources it may be used with.


 

 Are you arguing it's not usable? It seems to be usable with like 99% of sources and 99% of headphones now, no? 
   
  I guess we will have to hear the thing to see if it's all really all that though. He is is promising a lot!


----------



## Shike

Quote: 





> The point seems to be that the design measures well (ie: as I just stated, pitched at people like yourself) and, unless I understand wrongly, putting the volume after the gain stage results in better measurements. Now you're talking about audibility (ie: how it sounds). You can't have your cake and eat it too always. This is why I've suggested to others who argue about this stuff that they go and design their own amp.


 
   
  First, the accusation here is that the second volume control will impart a worse specification even when maxed out than if it were just in front of the gain stage.  This is probably true, but it's a level of magnitude.  It STILL may measure better or in-line with higher performance gear anyway, and needs to be tested.  The final question is whether one wants to try and jumper it and use a pre-gain volume control anyway which is also possible, but should be measured.
   
  In regards to audibility, we're talking audibility as in "hey, can this be heard in an ABX" not "how it sounds" in the way you're probably most used to hearing it.  I'm not talking "does it sparkle", I'm saying "hey, is this distortion really audible?  What about channel balance", etc.  Other sub-$100 amps tend to have very audible issues, be quite power limited, or have other compromises some of us rather not make.  Once again, I'm not naming names - but for those of us that are aware of the current landscape in terms of objective performance this IS a breath of fresh air
   
  Lastly, and this is important, this "issue" can be fixed by using the appropriate gain setting anyway making it a null issue.  Speaking of cake and eating it too, why are people wanting an amazing performing amp for under $100 and infuriated that they may need to use a switch?  The horror!


----------



## anetode

Gain, shmain. Can it be shoved in an altoids tin and sold for 50$ on ebay? No? Then I have no desire to buy it.


----------



## limpidglitch

A group buy for the PCBs have been initiated over at DIYA.
   
Linky


----------



## Currawong

I've removed part of my post. Sorry, but it is frustrating to see people trying to make intelligent discussion about this amp yet have numerous peanut gallery replies to those people with genuine knowledge.  I'm going to leave it alone entirely from here. Good luck everyone getting something sane out of this.


----------



## milosz

I would be interested to see some A/B comparisons with this amp, especially some blind A/B comparisons.


----------



## deadlylover

Quote: 





milosz said:


> I would be interested to see some A/B comparisons with this amp, especially some blind A/B comparisons.


 

 You are going to look forward to this weekend, I promise I'll stop being lazy now ^^, all the hostility in this thread kinda puts me off from doing anything, that, and I've been a busy little bugger the past couple of days with no free time.


----------



## b0ck3n

Quote: 





nikongod said:


> Your full of it.


 
   
  You're right, I over-simplified. What I meant to say was that distortion levels are below audibility throughout the entire range.


----------



## phrosty

Very interested in this, but I don't know how to build my own.  I hope once it gets some testing, some enterprising individual will decide to start selling them pre-made.
   
  Now we need an Objective DAC.


----------



## arirug

Same here. I want this headphone amplifier as fast as possible!


----------



## bcg27

Quote: 





limpidglitch said:


> A group buy for the PCBs have been initiated over at DIYA.
> 
> Linky


 


   Thanks for the  link. I'm in for a couple of boards. Boards look like they will be really cheap so I won't feel bad if I don't actually end up building this thing.


----------



## Soaa-

Quote: 





phrosty said:


> Now we need an Objective DAC.


 

 NwAvGuy said that probably won't happen. It's a lot trickier to design a DAC than an amp, and there are already well engineered DACs on the market at fair price. He mentioned the Behringer DAC a few times, and although that alone isn't suitable to drive most headphones due to high internal impedance, the O2 presents a 10 kOhm load, which negates the side effects of internal impedance.
   
  I'd say Computer -> Behringer -> O2 would make a sweet setup.


----------



## Armaegis

Quote: 





milosz said:


> I would be interested to see some A/B comparisons with this amp, especially some blind A/B comparisons.


 


  As long as people will be comparing it agains the big boys, toss in a couple cheaper amps like the e5 and a well made cmoy, and also directly off source when listening to an easily driven headphone.


----------



## micmacmo

Quote: 





milosz said:


> I would be interested to see some A/B comparisons with this amp, especially some blind A/B comparisons.


 

 I, for one, would be interested in reading your A/B comparisons.


----------



## Anonanimal

Quote: 





fishski13 said:


> apples and oranges, but i have a M3 here with a gain of 8x.  i sat down for a listen this evening with my K702 and BM DAC1 (2Vrms).  with the pot mounted with pointer at about 7:30, i am hitting 2-2:30 with my ECM label recordings (new or old recordings) and the same for a couple of the Steely Dan albums i tried.  measured dB was 85 peaks with an analog Radio Shack meter stuck through a piece of cardboard to cover the driver housing.


 

 That's interesting.  Any idea what the relative dB difference is between those 'quiet' albums and louder albums at the same volume pot setting?  I think if we could come up with a reasonable range of 'headroom' needed for various recording levels, we could come up with some solid Low/High gain recommendations for this and other amps.


----------



## dfkt

Or you could simply use Replaygain.


----------



## nikongod

Quote: 





anonanimal said:


> Any idea what the relative dB difference is between those 'quiet' albums and louder albums at the same volume pot setting?  I think if we could come up with a reasonable range of 'headroom' needed for various recording levels, we could come up with some solid Low/High gain recommendations for this and other amps.


 

 12-20db of headroom is the general rule of thumb. 
  Quote: 





dfkt said:


> Or you could simply use Replaygain.


 

 Until it runs into digital clipping.


----------



## Anonanimal

Quote: 





nikongod said:


> 12-20db of headroom is the general rule of thumb.
> 
> Until it runs into digital clipping.


 

 Yeah I suppose- it's just that it seems there is always a question about gain from someone and the advice is always something anecdotal and often the source (DAC) isn't even cited.  I may take all this info and see if I can create something useful w/ it for people new to DIY and who lack an understanding of how to correctly set their gain.  Does it seem worth the time to do?


----------



## Achmedisdead

Quote: 





dfkt said:


> Or you could simply use Replaygain.


 


  Would that be "audiophile" ?


----------



## dfkt

Quote: 





nikongod said:


> Until it runs into digital clipping.


 

 You can prevent clipping with most proper Replaygain implementations.


----------



## nikongod

Quote: 





anonanimal said:


> I may take all this info and see if I can create something useful w/ it for people new to DIY and who lack an understanding of how to correctly set their gain.  Does it seem worth the time to do?


 

 It seems like a cool writeup. 
   
  A few months ago the DIYaudio newsletter and a thread afterwards were about setting up your system's gain structure. Very cool.


----------



## b0ck3n

dfkt said:


> Or you could simply use Replaygain.




Isn't that, like, cheating..?


----------



## Shike

Quote: 





b0ck3n said:


> Isn't that, like, cheating..?


 

  
  I replay gain my collection, and why not?  Retain dynamic range and control volume easily so you don't blow your eardrums switching from one album to the next.  Just make sure you use the proper player with the tracks and it's not an issue.

  
  Quote: 





nikongod said:


> Until it runs into digital clipping.


 

 Replay gain in Foobar can prevent clipping according to peak - usually considered the preferred method too.


----------



## Achmedisdead

Quote: 





shike said:


> I replay gain my collection, and why not?  Retain dynamic range and control volume easily so you don't blow your eardrums switching from one album to the next.  Just make sure you use the proper player with the tracks and it's not an issue.
> 
> 
> 
> Replay gain in Foobar can prevent clipping according to peak - usually considered the preferred method too.


 


  It sure works for me!


----------



## b0ck3n

Sorry, I was being sarcastic. I use foobar replaygain, I'll even EQ if need be. I never agreed that great sound has to be difficult to achieve to be worthwhile.


----------



## mikeaj

I'm not familiar with the ReplayGain algorithm, but the value in dB it outputs after a scan is some kind of measure of average (averaged how?) perceived loudness I presume. 
   
  Some albums reach -15dB (15dB above target level) or more required on ReplayGain, while some quiet ones are like +10dB.  Well, there are tracks significantly softer than the average in some albums, say even +20dB even for popular music back in the day.  Taking extreme cases, we're looking at something like 30 to 40dB difference between two different non-joke tracks, as a reference.


----------



## Olli1324

Crikey, didn't see this thread here.
   
  I just thought I'd pop over to mention that I am indeed hosting a group buy. It will be ending at the end of this month so don't dawdle - get signing up! I've noticed one or two head-fi members have already placed some orders 
   
  For those who want an O2 but don't want to build it? Be patient 
   
  http://www.diyaudio.com/forums/group-buys/194708-o2-headphone-amplifier-gb.html


----------



## BobSaysHi

Quote: 





olli1324 said:


> Crikey, didn't see this thread here.
> 
> I just thought I'd pop over to mention that I am indeed hosting a group buy. It will be ending at the end of this month so don't dawdle - get signing up! I've noticed one or two head-fi members have already placed some orders
> 
> ...


 

 Yeah, I bought two boards.


----------



## upstateguy

Quote: 





the monkey said:


> Wouldn't it make more sense to chuck the whole battery concept and just concentrate on a desktop?  Fewer compromises that way, no?


 
   
  +1
  
   
  Quote: 





olli1324 said:


> Crikey, didn't see this thread here.
> 
> I just thought I'd pop over to mention that I am indeed hosting a group buy. It will be ending at the end of this month so don't dawdle - get signing up! I've noticed one or two head-fi members have already placed some orders
> 
> ...


 

 How does the group buy work for those of us in the US?


----------



## Steve Eddy

Quote: 





upstateguy said:


> How does the group buy work for those of us in the US?


 
   
  Same as it does for everyone else. Just post a reply in the thread with how many you want and what region you're in.
   
  se


----------



## rembrant

I've signed up for two boards. I guess the proof will be in the pudding. Be warned though. The only sophisticated measuring tools I posses are my ears. I will AB with my Sony CDP-397 transport through the headphone out on Sony STR-V200 receiver and directly from the transport alone. Not really a fair battle. I will try to make it as objective as possible.


----------



## b0ck3n

@deadlylover: how do you like the O2 with the gain fixed?


----------



## Sorensiim

This thread made me change my signature. 
   
  Just ordered an O2 pcb, I'm really curious to hear this thing.


----------



## deadlylover

Quote: 





b0ck3n said:


> @deadlylover: how do you like the O2 with the gain fixed?


 
   
  I'm not telling. 
	

	
	
		
		

		
			




   
  It doesn't sound like absolute garbage with the AD900's (I think those are garbage though 
	

	
	
		
		

		
		
	


	




), you'll have to wait till the weekend where I can pay a visit to a friend where I'll be able to commandeer the beta22/LCD-2 combo.
   
  Turn off thump is kind of pissing me off, but it's no biggie, just take a leaf out of schiit's book and don't turn it off while the headphones are plugged in.
   
  Ugh, dynamics........


----------



## b0ck3n

The first commercial, fully built O2 can be acquired here: http://epiphany-acoustics.co.uk/7.html

(I apologize before-hand if the link is in violation with the TOS, if so remove it)


----------



## grokit

Quote: 





b0ck3n said:


> The first commercial, fully built O2 can be acquired here:


 
   
  Any idea what the form factor will be like on this production version?


----------



## Maxvla

Interested in a commercial home version. Would you need to run batteries like the RWA Isabellina HPA to get similar measurements as the O2 portable version?


----------



## b0ck3n

That particular version is actually the original design, built from the original BOM, right down to the enclosure.

Edit: a desktop version, the "ODA", is in development. The batteries are removed and the gain stage has been optimized for stationary use - there are no numbers yet available but I don't think you can load it too hot using any currently existing source.


----------



## rayuma

Any word of someone in the US manufacturing these?


----------



## b0ck3n

Quote: 





deadlylover said:


> Turn off thump is kind of pissing me off, but it's no biggie, just take a leaf out of schiit's book and don't turn it off while the headphones are plugged in.


 

 The turn on/off transient behavior (scope shots posted on the blog show 250 mV RMS (350 mV peak) and about half of one 25 Hz cycle worst case) should be tiny. If not it's likely you got something wrong, zapped one of the MOSFETs with ESD etc, as the designer warned against when building the O2 point-to-point. Try getting in contact with him, I'm sure he'd be eager to help you get everything working as it should.


----------



## Olli1324

Quote: 





grokit said:


> Any idea what the form factor will be like on this production version?


 
   
  It will be in the same box as the DIY version. There really isn't much scope for reducing the size of the enclosure.


----------



## bcg27

Quote: 





b0ck3n said:


> The turn on/off transient behavior (scope shots posted on the blog show 250 mV RMS (350 mV peak) and about half of one 25 Hz cycle worst case) should be tiny. If not it's likely you got something wrong, zapped one of the MOSFETs with ESD etc, as the designer warned against when building the O2 point-to-point. Try getting in contact with him, I'm sure he'd be eager to help you get everything working as it should.


 


   I would not consider 250 mV 'tiny' and should in fact yield an audible thump. With the AD900 @ a sensitivity of 100 dB/mW and 35 ohm impedance this results in about 1.8 mW into the headphones which is over 100 dB and would be quite loud.


----------



## mikeaj

Quote: 





bcg27 said:


> I would not consider 250 mV 'tiny' and should in fact yield an audible thump. With the AD900 @ a sensitivity of 100 dB/mW and 35 ohm impedance this results in about 1.8 mW into the headphones which is over 100 dB and would be quite loud.


 

 Indeed, not tiny at all.  It shouldn't be a headphones-damaging or ears-damaging level, but come back talking about a quantity measured in uV (uh, with say three or less digits) before you say something is tiny.


----------



## b0ck3n

bcg27 said:


> I would not consider 250 mV 'tiny' and should in fact yield an audible thump. With the AD900 @ a sensitivity of 100 dB/mW and 35 ohm impedance this results in about 1.8 mW into the headphones which is over 100 dB and would be quite loud.




Correct, but it's only for 0.02 seconds. With 35 ohm headphones it would be less significant than at the 600 ohms it was tested at because the charge left in the power supply caps discharges faster into a low impedance load.

It's about a 100th of the DC transient measured when powering off the Schiit Asgard (pre relay).


----------



## wakibaki

I'm relieved to see a thread on this subject as I stopped posting on this forum when my own O2 thread was deleted.
   
  All I have to say for the moment is that the price for a fully built version is not cheap. Oh, and point to point and dead-bug construction can be very good, but you can have a big impact on performance if you don't take care, I mean, you can quite readily produce an oscillator instead of an amplifier in an extreme case, so don't dismiss these considerations entirely. 
   
  w​


----------



## Shike

Quote: 





b0ck3n said:


> Correct, but it's only for 0.02 seconds. With 35 ohm headphones it would be less significant than at the 600 ohms it was tested at because the charge left in the power supply caps discharges faster into a low impedance load.
> 
> It's about a 100th of the DC transient measured when powering off the Schiit Asgard (pre relay).


 

 It's actually a little under a 7th 9th of the Asgard voltage (fixed).  Still, as long as it doesn't play havok with my AKG drivers I'm not worried - wait and see.


----------



## Shike

I see, well now I know.  All I can remember was discovering the Asgard transient was nightmare fuel, so I can understand why some are hesitant.  We'll definitely need reviews to see if this actually turns out to be an issue, but I doubt it at this point.  Wait and see I guess, wait and see ^_^


----------



## b0ck3n

Fortunately, since the designer has been so open about his design, criticism and concerns have been answered by others - everything, and I mean _everything_, is published for everyone to see on his blog.

I'm hoping that the thread can move on to providing information on how to get parts, kits or finished amps and later on, people's experiences using them.


----------



## Currawong

Quote: 





willakan said:


> I'm not complaining about that. I'm complaining about the fact that the design is being criticised, but any links that attempt to counter that criticism, even not to NwAvGuy's site, are being removed. Regardless of the vehemence or not with which the criticism is delivered, or indeed its prevalence, that is not a place I want my thread going (I know, technically not 'my' thread now, but hey)


 

 I think you are missing the point of DIY. If you or I designed an amp and posted it here, the first thing that would happen is that people with knowledge would post critique of the design and suggest improvements. This is normal. However, because of the nonsense perpetuated about this design and Head-Fi, you see criticism not as part of the design process but as some kind of attack, even when the critique is given by engineers with no personal interest whatsoever in the design.  This thread will be good if, as I said in a previous post, you can stop with all the (totally incorrect and easily disproven) conspiracy theories and focus on getting it built well and overcoming any shortfalls in the design that may arise when using it with different gear.


----------



## mikeaj

Criticism and feedback is part of the DIY design process, which is why there's a gain switch now and then later on why the default lower gain setting is 2.5X and not 3X.
   
  Anyhow, if the interest is in improving the design or helping the designer out, I'd think that the natural thing to do would be to post on one of the places where the designer can read and respond to potential concerns.  Serious accusations or differences in opinion are fine, but they seem small and petty if only posted here only and not in one of the other places.  (That is, unless people legitimately don't realize those places exist, since any mention of them is put on lockdown.)  Is one of the themes in this thread questioning other peoples' motives?


----------



## deadlylover

I just spent about 3 hours at a friend's place ping ponging back and forth in a level matched comparison between the Obj2 and beta22, using the LCD-2. I was unable to discern any large differences in sound between either amps, so any differences I heard were small, and may very well have been my imagination.
   
  There was practically no difference tonality wise, but I felt that the beta22 sounded a little less congested, that's pretty much the best I can put it. Since I kind of tunnel vision the vocals when listening to music, the main difference for me was the vocal separation with the rest of the track.
   
  Anyway, I don't claim to have a large amount of experience with the LCD-2, and I realise some differences may only show up after an extended audition, so that's why I left the Obj2 with my friend, so I can forward his impressions eventually. I'm no audiophile, I've never heard any real live music, I have tin ears and I don't particularly care how things sound as I am not nearly as passionate about music as most of you guys. I also loathe dynamics, so I was really trying to pick between the lesser of two evils here, so please take my impressions with a grain of sugar, spice and everything nice.
   
  On the other hand, I may very well be a sucker for subjective bias, as the comparison was only volume matched, and not done blind. The beta22 was actually balanced, so it only had a 4pin xlr out, and I had to 'unbalance' it for this comparison. It was a pain having to switch the LCD-2's cable each time I went back and forth, which is why we couldn't be bothered to do a proper blind test. I would have liked to build a milosz style switcheroo box, but I was just too lazy.
   
  Do keep in mind that my Objective2 was not done on the proper PCB, and I very well may have ballsed up the amp, so again, don't take my impressions too seriously.
   
  Please don't hurt me.


----------



## Currawong

Thanks for the impressions. I tend to find the same thing, that better gear results in a more clear distinction between instruments and the vocals on recordings.
   
  A couple of questions: How loud were you listening? Is the Beta 22 single-ended or balanced?


----------



## deadlylover

Quote: 





currawong said:


> Thanks for the impressions. I tend to find the same thing, that better gear results in a more clear distinction between instruments and the vocals on recordings.
> 
> A couple of questions: How loud were you listening? Is the Beta 22 single-ended or balanced?


 
   
  About 70db or so, not terribly loud at all. The beta22 was configured for single ended operation (2ch) for a fair comparison, it's actually a balanced b22.


----------



## b0ck3n

Thanks for your straight up impressions, deadlylover. I find it extremely difficult to discern any difference between sources and amps when I can't make the switch instantly.


----------



## Willakan

The worldwide group buy over at DIYAudio has already got about 200 boards requested by various people. Many more impressions/reviews are looming on the horizon...
   
  EDIT: Also, whilst I'm at it, for those worried about turn-on transients, NwAvGuy has measured them into various loads and found them pretty benign - it has a little turn on thump, but it is well within safe bounds for even the most sensitive 'phones.


----------



## Costia

can anyone explain how the current limiting works in the O2?
  I understand how/why it  it will shutdown on low input voltage an the hysteresis, but i don't seem to figure out what actually limits the current.


----------



## b0ck3n

For anyone who's interested in the O2, but not quite ready to take the DIY plunge, MrSlim is offering a build service over at DIYaudio.
   
  Short info: a complete basic build using the portable case and FPE front panel at $114 (shipping excluded), with the option to add batteries at a cost of $11. A "desktop" case with 1/4 headphone jack and RCA input jacks can be had at an added cost of $15.


----------



## mikeaj

Quote: 





costia said:


> can anyone explain how the current limiting works in the O2?
> I understand how/why it  it will shutdown on low input voltage an the hysteresis, but i don't seem to figure out what actually limits the current.


 

 I think it's just the dual NJM4556 output stage.  They can't put out more than a certain amount of current, even though distortion into low impedances is pretty low just up until their limit.


----------



## qusp

better to leave the headphones plugged in if the thump is minimal is it not? i often wondered which would be more damaging, a small turn on thump, or shorting the outputs and headphones to to ground on the way in and out while the amp is on ie. hot plugging


----------



## Willakan

It is said to be more of a turn on click than thump, leave it plugged in.
  If you're worried, wait for the desktop version, which will have proper board mounted RCA inputs, better gain stage structure and also will be completely silent on turn-on/off.


----------



## Kibble Fat

subscribed.  Keep up the good work lads!


----------



## Reticuli2

Didn't two versions of a defective Cmoy and an E7 also blow your Mini3 away?

  
  Quote: 





amb said:


> The $30 figure is fallacious as has been mentioned in this thread.  It is also misleading for the designer to claim that a Mini³ is "more costly" than the O2, when the price figure for the Mini³ is a professionally-built unit with labor costs added.
> 
> 
> Simple.  He had been abusive to me on my own forum and in several other forums, not to mention his blogs, repeatedly.  What makes you think it would be different now?  I don't see anything constructive in me engaging him directly.  His fanboys could do me the favor and spare me the grief.
> ...


----------



## Reticuli2

Since when is 2.5 Volts input with low distortion considered "a weak source"?  The designer is protecting the O2 from up to 4V of input.  How does that not seem rational?  What are you expecting to be inputed into your amps?  Consumer nominal is 200-2000mV max, and anything with a 2V output lets you attenuate it.  Usually it's only in the 200-500mV range.  Pro Nominal is usually 1-1.3V.  I have never seen any portable player that could come anywhere close to 4V, in fact most can't even REACH pro nominal levels, let alone 2V. 
   
  Even on battery power at either gain setting, this amp's design appears to measure as well or better than most the stuff out there.
  Quote: 





amb said:


> No, I am not interested in discussing this directly with the designer.  If he is the brilliant engineer that he makes himself out to be, then he _must_ know these limitations.  Must use a weak source, must use low gain, must use AC power... too many ifs, ands and buts.  None of the amps that he lists as "competition" have these problems.


----------



## Reticuli2

And the O2 has been designed to accept those levels.  What are people going on about here?
  Quote: 





beftus said:


> Quote:
> 
> 
> b0ck3n said:
> ...


----------



## Satellite_6

The original gain was 3.1X which was a problem for unusual sources. It has been changed. This was the only legit criticism in a thread full of BS as far as I can tell, and the problem was blown out of proportion.


----------



## Reticuli2

[size=10pt]Truly bizarre. But some other shenanigans going on around here probably top that. I think my TV is staring at me.[/size]


----------



## Reticuli2

And you should be sending test waveforms into your gear and checking its output to check clipping, anyway.  That's a very basic thing to do, simple, and immediately tells you how hot to make the input.  For all the dissing of Rightmark on here, it's very easy to use the scope on it.
  
  Quote: 





odigg said:


> That makes sense.  Thanks.  I think most every portable device I use outputs less than 1Vrms, so I guess I don't have to worry too much.


 


 And ALL measuring equipment works best when you use them on the same pieces of gear and then compare the gear with the results from that measuring equipment.  Doesn't matter whether it's an expensive standalone analyzer or the input of a Sound Blaster.


----------



## Reticuli2

It's pretty easy to see when distortion begins on any simple waveform on a scope when passed through any preamp/mixer/headphone-amp, real or virtual, then just back the volume down on the source whatever amount you're comfortable with.  Considering none of this would happen unless you went over normal volume levels for normal gear, even the hottest gear's output as it distorts could be backed off by 50% and still be sending a very hot signal (around pro nominal) that by any measure should be getting the most out of the equipment.  Unless it's some wonky design that only has good performance at 3V, or something.  Then you should probably complain to the designer.
  
  Quote: 





odigg said:


> You could measure the output voltage.  All you need to do is play a 1khz tone file through Foobar at full volume and measure the output voltage of the DAC.  You also need to make sure it's not clipping - I'll let somebody else tell you how to do that as I don't want to give you the wrong information.


----------



## Willakan

NwAvGuy actually responded to Ti's criticism elsewhere. To paraphrase his points:
  1. Ti is using the wrong values for both the diode drop (this is backed up by datasheet of aforementioned diode) and the peak to peak voltage.
  2. It's a straw man of an argument anyway as it seems unlikely that you would use batteries with the amp when you're using home sources - and even if you did you should be fine with reasonably charged batteries.
  3. Finally, to accommodate the really marginal sources (above about 2.5V if memory serves) he has slightly lowered the default gain.
   
  He also expressed amusement that Ti would rigidly declare, when both the Mini3 and his design use the same battery type, that the batteries output 8.4V, as whilst trying to defend his own designs he insisted they output considerably more.
   
*So to paraphrase that, the maths is wrong, the argument is wrong and Ti appears slightly contradictory to the uneducated observer.*


----------



## Reticuli2

[size=10pt]Interesting, but if a given amp tests much better on the same measuring equipment (whether by your sound card input or stand alone pro test gear) than several other amps, regardless of what other unknowns are unaccounted for, isn't it likely that the knowns that have been measured indicate the much-better-testing amp will sound more accurate & transparent to the original signal? And if the measuring metrics used are numerous, rather than, say, just one (like S/N ratio or THD), that this probability drastically increases as the number of different measurements and the multiplicity of better measurements increases?[/size]
   
  [size=10pt]I would certainly agree it's possible for two pieces of gear that measure reasonably similarly (and we can argue about how similar that has to be) can sound different.  But the more measurements you add or the greater the resolution used in the tests, the less likely this is to be the case.[/size]
   
  Quote: 





beefy said:


> I can't believe that I agree with kwkarth on something.
> 
> For reference, I am a scientist and skeptical of many audiophool traditions...... but I strongly believe that anyone who thinks an amp is perfectly transparent because of a select and limited group of measurements is wrong. It shows a substantial amount of arrogance, and a strong underestimation (or misunderstanding) of the complexities of both the electronics and the human brain.
> 
> ...


----------



## Reticuli2

Which of this gear DOESN'T have a volume control on that output, though?
  
  Quote: 





shike said:


> That could be a legitimate concern for those planning on using it with pro gear.  Do you have some specific examples handy?
> 
> @The Monkey
> 
> ...


----------



## Beefy

Quote: 





reticuli2 said:


> [size=10pt]Interesting, but if a given amp tests much better on the same measuring equipment (whether by your sound card input or stand alone pro test gear) than several other amps, regardless of what other unknowns are unaccounted for, isn't it likely that the knowns that have been measured indicate the much-better-testing amp will sound more accurate & transparent to the original signal?[/size]


 
   
  That assumes that more accurate, better testing, and truthful to the original signal actually sounds better to the end user - and thus makes it a better amp. It is an interesting problem that I can't be arsed to solve.
   
   
  Quote: 





reticuli2 said:


> [size=10pt]And if the measuring metrics used are numerous, rather than, say, just one (like S/N ratio or THD), that this probability drastically increases as the number of different measurements and the multiplicity of better measurements increases?[/size]


 
   
  To the pure objectivist, yes, that should be the case. But as a skeptic - of both pure the pure objectivist and subjectivist positions - I still don't think that measurements will ever be able to cover every audible performance aspect. You can't listen to measurements any more than you should listen to a boutique power cable.
   
  *
   
  One last thing....... PLEASE, FOR THE LOVE OF GOD, USE MULTIQUOTE.


----------



## Satellite_6

He has a point. Digging up old posts and posting over and over again isn't very helpful. You've missed the fireworks.


----------



## Reticuli2

Some serious pro gear have specific main outputs that are capable of going very hot, that are capable of but not normally intended to run at, say 8Vrms before they might start clipping.  You don't run a mixing board that has a non-record "amp" out at 7Vrms just because it can theoretically handle 8.  Everyone with any familiarity with the stuff would know you wouldn't expect much of anything to be capable of using that hot a signal, except certain amps that... yes... have a volume pot before the gain stage.  And if you really need to crank your main board that hot, then your amp is way way too weak for the application.  In that case, you either get a bigger amp or more sensitive speakers.  Point of fact, those sorts of "amp" outs from mixing boards are meant to feed into mono pro amps that don't have volume pots and will have their own volume control anyway on the board.  And I suspect most of the gear being cited is exactly like that.  Name one pro device that goes over 2.5Vrms for its nominal output that doesn't have a volume control on that output.  If you find one, you'll probably want to shoot an email to the maker and ask them why (as one person liked to say in this thread) they did such a 'tarded thing.
  Quote: 





c61746961 said:


> [citation needed]


----------



## Reticuli2

[size=10pt]Oh, I don't think measurements will ever be able to totally describe what we hear either, but I think what I posted there still stands.[/size]
  [size=10pt]Funny you should mention cables. In blind tests run by Thiel once at CES, I was the only one in the audience who could repeatedly call them out when they tried to trick us by swapping or not swapping the cables. But those were very special, electrically-charged-dialectic cables. And like as big as a fire-hose and had their own power supplies. Not for resale. I do like Teflon dielectrics, though... and short cables. [/size]
  [size=10pt]hah hah... first, how do I see the entire thread in one long scrollable page? That would make multi-quote possible for me.[/size]


----------



## Steve Eddy

Quote: 





reticuli2 said:


>





> [size=10pt]first, how do I see the entire thread in one long scrollable page? [/size]


 
   
  You can't. It's limited to a measly 15 posts per page.
   
  se


----------



## particleman14

autopager u noobs


----------



## Reticuli2

Don't know what that is.  Point me to it or explain.


----------



## Steve Eddy

Quote: 





reticuli2 said:


> Don't know what that is.  Point me to it or explain.


 

 Ultimately, it's a kludge that tries to do what the forum software should be doing in the first place.
   
  https://addons.mozilla.org/en-US/firefox/addon/autopager/
   
  se


----------



## amb

Quote: 





willakan said:


> NwAvGuy actually responded to Ti's criticism elsewhere. To paraphrase his points:
> 1. Ti is using the wrong values for both the diode drop (this is backed up by datasheet of aforementioned diode) and the peak to peak voltage.


 
   
  Au contraire.  The 1N5818 diode's forward drop is 0.5V (STmicro version) or 0.55V (Vishay version).  There are two of them, so the total diode drop is 1V or 1.1V.  I quoted the former figure in my original post.
   
*FACT*: ST datasheet snapshot:

   
*FACT*: Vishay datasheet snapshot:

   
*FACT*: The NJM2068 opamp is not rail-to-rail, and could swing only to about 1V below the positive rail and 2V above the negative rail when driving a light load (which the volume pot is).  Here's proof from its datasheet, see the left diagram for RL = 10K ohms and +/-12V rails, what the voltage swing is.  The negative signal peak will clip first.  Thus when calculating maximum output swing for a given input voltage, this loss has to be accounted for.
   

   
  Quote: 





> 2. It's a straw man of an argument anyway as it seems unlikely that you would use batteries with the amp when you're using home sources - and even if you did you should be fine with reasonably charged batteries.


 
   
  You don't seem to read all my posts before quoting this out of context.  Lowering the gain certainly helps to increase headroom, but for high-impedance or low efficiency headphones, you may *need* more gain, especially when taking account the additional gain necessary (15dB is a good figure) for quiet recordings, so you don't run out of volume control rotation and still have insufficient volume for real music, not 0dBFS sine waves.
   
  Quote: 





> 3. Finally, to accommodate the really marginal sources (above about 2.25V if memory serves) he has slightly lowered the default gain.


 
   
  See above, lowering the gain is a band-aid solution for efficient headphones, but does not deal with many other headphones.  The fact that the designer has decided to fix the issue with a separate desktop version (with higher voltage rails) actually proves my point.  I am glad that I was able to contribute to a positive change to his design. 
	

	
	
		
		

		
			




   
  But, by putting his volume control after the gain stage for a small gain in S/N ratio (which, in actual use, is mostly inconsequential unless the headphones are extraoridinarily efficient), he has also made the amp difficult to mix and match with different sources and headphones.  I did the math, _show me_ where I did wrong.
   
  Quote: 





> He also expressed amusement that Ti would rigidly declare, when both the Mini3 and his design use the same battery type, that the batteries output 8.4V, as whilst trying to defend his own designs he insisted they output considerably more.


 
   
  I never said that the Mini³ outputs more voltage swing than the O2.  He has the advantage of two batteries vs. the one in the Mini³.  But the O2 is also more than twice the size of Mini³ (same depth, twice as wide and a bit taller) which makes it less than portable.
   
  But the more important point is not the absolute output voltage, but adaptability to various sources and headphones without clipping.  The Mini³ has no problem with input overload with hot sources and/or high gain, nor does the cmoy or Benchmark DAC1 or any other amps that he used for comparison purposes.
   
  Quote: 





> *So to paraphrase that, the maths is wrong, the argument is wrong and Ti appears slightly contradictory to the uneducated observer.*


 
   
  You're making a baseless comment.  Again, go read my posts again_, and show me what I did wrong_.
   
  It's amazing how many of NwAvGuy's fans would ignore the issue and just try to sweep all criticisms under the rug.  I wasn't even the first one to mention this -- nikongod did.  I merely provided the calculations to show that it's a real problem.


----------



## Reticuli2

Will autopager let me quote multiple pages, or is the quoting system not available on it?
   
  [size=10pt]You know what I'd really like? Just a very high performing 0dB gain "buffer" like that defective cmoy NwAVguy tested. I've got so many jacks already (some pretty good), and I just need to add potential current and near-zero output impedance. I don't really need any gain. All my cans are 100ohms or less and get plenty loud out of all those jacks. But it looks like the best budget choices are the E7, Grado clones, and this O2. I don't like the idea of paying for something with a DAC built in that's only 16bit. But I don't love the idea of a gain-adding headphone amp nowadays to not have a DAC built in. So the choice seems to be either settle for a $100 compromised amp on a compromised DAC (but which is a great price for that combo, apparently), get an equally good amp with no DAC at half the price, or get a great amp built at just over the $100 mark that has no DAC built in. If I go for one without the DAC, it might as well just be a high-performing cheap 0dB gain buffer, because I'll just be using it from headphone jacks of a laptop, mp3 players, and those on the front of DJ controllers that already have more gain than I even need. At least with a DAC you bypass the jacks and solve the problem of having nothing with a dedicated line-out while at college... at least for the laptop. [/size]


----------



## Costia

i think you have different purposes in building the amps
  nwavguy stated he wants the best specs . i did not see "ease of use" in his requirements list
  While other amps might be more versatile, smaller and easier to use (1 less switch). his has the better specs
   
  I do think that for consumer electronics usability should sometimes come at the expense of quality
  i.e. putting the pot at the first stage is more comfortable than a gain switch + pot at the second stage
  By doing that you would loose some quality. but going from 100db snr to 80-70db will have no audible impact for 99.9% of the consumers. while the comfort effects everyone
  A commercial designer would have made this compromise.
  But what nwavguy wanted to prove is you can get near studio quality gear for ~30$ - moving the pot would hurt this goal
  For the purpose of proving his point, and meeting the requirements set for the O2 - any gain in quality is more important than usability and comfort
  I dont think O2 was meant to be a commercial amp
   
  edit:
  TLDR: its unfair to judge his amp by your requirements. Look at his set goal/requiremns and check if he met them.


----------



## amb

From the designer's own blog: "ONE SIZE (nearly) FITS ALL".  When there are so many constraints to avoid clipping, then I think that goal is not met.
   
  Also, to put things in perspective, the noise difference (at half volume, which is basically the worst case where there is maximum difference between having the pot before or after the gain stage) is about 10dB.  From his own measurement of the Mini³, if you look at the noise graph, the noise floor approximately hugs the -135dB line or so, whereas the O2 about -145dB.  The displayed numeric figures are integrated over the range of audio frequencies and shows as Mini³ -97.5dB vs. O2 -107.9dB (both with A-weighting).  Oh and by the way, the Mini³ he tested has a gain of 5.3x, if it was lowered to 2x to be comparable to the O2's low gain mode, the Mini³ would have another -8.xdB less noise.  That brings the noise floors within a couple dBs of each other.
   
  But what price he has to pay for those measly few inaudible dBs of noise floor?


----------



## fishski13

Quote: 





reticuli2 said:


> Didn't two versions of a defective Cmoy and an E7 also blow your M3 away?


 
   
  what are you talking about?  blow away based on what parameters?  do you have measurements of "my M3" or anecdotal/subjective evidence?  i've only built one M3 for a customer, and other than me, only 2 people have heard "my M3". 
   
  after reading your PM to me and now this, it seems you're just picking a fight.


----------



## Satellite_6

Quote: 





amb said:


> From the designer's own blog: "ONE SIZE (nearly) FITS ALL".  When there are so many constraints to avoid clipping, then I think that goal is not met.
> 
> Also, to put things in perspective, the noise difference (at half volume, which is basically the worst case where there is maximum difference between having the pot before or after the gain stage) is about 10dB.  From his own measurement of the Mini³, if you look at the noise graph, the noise floor approximately hugs the -135dB line or so, whereas the O2 about -145dB.  The displayed numeric figures are integrated over the range of audio frequencies and shows as Mini³ -97.5dB vs. O2 -107.9dB (both with A-weighting).  Oh and by the way, the Mini³ he tested has a gain of 5.3x, if it was lowered to 2x to be comparable to the O2's low gain mode, the Mini³ would have another -8.xdB less noise.  That brings the noise floors within a couple dBs of each other.
> 
> But what price he has to pay for those measly few inaudible dBs of noise floor?


 
  No sources over 3V.


----------



## Reticuli2

That was directed at amb.  I've deleted the accidental multiquote of you before him.  Odd, considering I didn't even know how to multiquote at the time.  The PM had nothing to do with the M3.
  
  Quote: 





fishski13 said:


> what are you talking about?  blow away based on what parameters?  do you have measurements of "my M3" or anecdotal/subjective evidence?  i've only built one M3 for a customer, and other than me, only 2 people have heard "my M3".
> 
> after reading your PM to me and now this, it seems you're just picking a fight.


----------



## Beefy

Quote: 





reticuli2 said:


> That was directed at amb.  I've deleted the accidental multiquote of you before him.  Odd, considering I didn't even know how to multiquote at the time.


 

 Perhaps you should go back and edit it to properly specify the Mini3 then. The M3 is a desktop amp.


----------



## Reticuli2

Done.  Thanks.
  Quote: 





beefy said:


> Perhaps you should go back and edit it to properly specify the Mini3 then. The M3 is a desktop amp.


----------



## skeptic

Quote: 





> Originally Posted by *amb* /img/forum/go_quote.gif
> 
> Also, to put things in perspective, the noise difference (at half volume, which is basically the worst case where there is maximum difference between having the pot before or after the gain stage) is about 10dB.  From his own measurement of the Mini³, if you look at the noise graph, the noise floor approximately hugs the -135dB line or so, whereas the O2 about -145dB.  The displayed numeric figures are integrated over the range of audio frequencies and shows as Mini³ -97.5dB vs. O2 -107.9dB (both with A-weighting).  Oh and by the way, the Mini³ he tested has a gain of 5.3x, if it was lowered to 2x to be comparable to the O2's low gain mode, the Mini³ would have another -8.xdB less noise.  That brings the noise floors within a couple dBs of each other.
> 
> But what price he has to pay for those measly few inaudible dBs of noise floor?


 

 Of the measurements discussed by nwavguy, noise is hardly the chief concern when it comes to comparing the mini3 and O2, amb - as you well know.  How bout the 25db difference in measured crosstalk between the mini3 and o2 at 15 ohms?  How about the THD at 20khz?


----------



## agdr

Quote: 





reticuli2 said:


> [size=10pt]You know what I'd really like? Just a very high performing 0dB gain "buffer" like that defective cmoy NwAVguy tested. I've got so many jacks already (some pretty good), and I just need to add potential current and near-zero output impedance. I don't really need any gain.[/size]...


 


 Here you go:
   
http://www.diyaudio.com/forums/headphone-systems/179298-wire-ultra-high-performance-headphone-amplifier-pcbs.html
   
  The current group buy info starts at post #364 (this is the second run) but is stalled out at the moment until the designer gets some more free time.  Shouldn't be long.
   
  This is just a (250mA each) LME49600 current buffer in a 1x gain loop with a LME49990.  All surface mount so you would have to do smd soldering.  His original was a balanced-in single-end out design that got some rave reviews from the builders.  The new run is the same plus a SE-SE version and a SE-bal version.  Looks like he is even going to use 0.01% SMD resistors in this one.  It is just a current buffer - you add your own power (looks like he is doing a small PS board too) and everything else.  No pot, not even any jacks just pins to connect out to whatever you want, no gain stage so your source has to put out at least the voltage you need on the output.  He has measurements done with an Audio Precision in posts #2 and #3 for balanced in, and post #106 with one balanced input grounded for single-ended testing.
   
http://www.national.com/profile/snip.cgi/openDS=LME49600
   
http://www.national.com/profile/snip.cgi/openDS=LME49990
   
  The 49600s alone are about $11 each and the 49990s are about $5 each at Digikey, and the board will probably be around $20 in low quantities.  NwAvGuy knows about this amp - he has posted in that thread - but it is really a different thing from the O2 or mini^3.  Like you posted it is just a current buffer board.  No power supply, no gain stage, no pot, no batteries, not even a specific case in mind and all surface mount parts instead of through-hole.  The quiescent (idle) current of the 49600s is also huge, up to 18mA each, so these are not battery-friendly parts.


----------



## mikeaj

Quote: 





amb said:


> Au contraire.  The 1N5818 diode's forward drop is 0.5V (STmicro version) or 0.55V (Vishay version).  There are two of them, so the total diode drop is 1V or 1.1V.  I quoted the former figure in my original post.
> 
> *FACT*: ST datasheet snapshot:
> 
> ...


 
   
  Why did you not quote the more relevant part of the datasheet?
   
  Here's the relevant graph for the STmicro one, at least from the datasheet on the STmicro website:

   
  Current is less than 0.1A, not 1A (at least according to the designer, when running the clipping tests).  So the voltage drop with 1A is not relevant.  Dare I say that you were mistaken here?
   
  Anyway, measured results show much higher than 11.8V peak-to-peak, at least when batteries on a full charge are more like 9V.  Are you suggesting that the measured result of 5.5V rms (@ 1% THD) into 150 ohms on battery is invalid?  Obviously that max output depends on the battery charge, which was apparently pretty full at a high 9V.  I ask this as a serious question since the NwAvGuy's called some of your figures into question as well.  (But let's recall that some of the confusion regarding the Mini3 was about testing into one channel as opposed to both, where the demands on the "ground" channel op amp are higher.  NwAvGuy assumed that the tested max power there was into both channels.)
   
   
  Quote: 





amb said:


> You don't seem to read all my posts before quoting this out of context.  Lowering the gain certainly helps to increase headroom, but for high-impedance or low efficiency headphones, you may *need* more gain, especially when taking account the additional gain necessary (15dB is a good figure) for quiet recordings, so you don't run out of volume control rotation and still have insufficient volume for real music, not 0dBFS sine waves.


 
   
  Part of this whole clipping and gain thing boils down into a disagreement over how much gain and voltage is enough, particularly with regards to recordings that are mastered really really soft.  If a certain part is supposed to be very soft like -50 dBfs, I'm not going to try to play it at 80 dB SPL and have my ears blasted off or have massive clipping whenever it gets louder.  But that's just me (and I mean this without sarcasm).


----------



## fishski13

Quote: 





skeptic said:


> Of the measurements discussed by nwavguy, noise is hardly the chief concern when it comes to comparing the mini3 and O2, amb - as you well know.  How bout the 25db difference in measured crosstalk between the mini3 and o2 at 15 ohms?  How about the THD at 20khz?


 

 THD and cross-talk increase with gain.


----------



## mikeaj

Quote: 





fishski13 said:


> THD and cross-talk increase with gain.


 
   
  Indeed.  However, the differences skeptic quoted are more or less apples-to-apples, at the same output level into the same loads with typical default gains set.
   
  Most of the published results are at that 3.1X or maybe 2.5X gain, which is important to note.  The difference in THD+N is given in one graph for 1X gain as opposed to 6X gain at 2V rms, and this shows a pretty small difference in performance (less than double THD+N at any frequency and generally much less than double, so still below accepted levels of audibility) but this is for a relatively easy 600 ohms load.  Then again, you probably won't be wanting to use 6X gain with most 16 ohms headphones.


----------



## Shike

Use a gain of 2 and 6, or 2 and 3 if no low voltage (sub 2V units) are used.  Congrats, you've covered just about every headphone and source.  If a gain of two is too high, then your source is either a very special case (some tube designs) or just plain built way out of standards.
   
  It's really a non-issue with even a moment of forethought.


----------



## amb

Quote: 





skeptic said:


> Of the measurements discussed by nwavguy, noise is hardly the chief concern when it comes to comparing the mini3 and O2, amb - as you well know.  How bout the 25db difference in measured crosstalk between the mini3 and o2 at 15 ohms?  How about the THD at 20khz?


 
   
  The whole premise of placing the volume pot after the gain stage instead of before is about lowering noise, hence the focus on that subject.  The rest is red herring.  The point is not to compare the Mini³ against the O2, only to illustrate that the supposed noise advantage of having the pot after the gain stage is small and negligible.
    
  Quote:


mikeaj said:


> Current is less than 0.1A, not 1A (at least according to the designer, when running the clipping tests).  So the voltage drop with 1A is not relevant.  Dare I say that you were mistaken here?


 

 OK, you have a point.  The forward voltage changes with current, and is lower at low currents.  But we're talking about about 0.2V difference each here, which is small compared to the losses in the NJM2068 opamp.


----------



## Willakan

Wait a second, I thought we were discussing power output primarily, not pot position. What happened to that?
  To cut to the chase, here is graph showing power output.* Is it wrong/impossible? *Sorry for the Mini3 figures, but I can hardly edit them out of the graph.
  The designer has since responded again at ABI - NwAvGuy politely suggests that respond to him there instead if you still think your argument has merit.


----------



## Maxvla

Will a desktop version of this amp put out much heat? My desk is in a corner and tubed amps make it rather toasty over there.


----------



## Anaxilus

Quote: 





maxvla said:


> Will a desktop version of this amp put out much heat? My desk is in a corner and tubed amps make it rather toasty over there.


 

 No worries.  Any heat will be negligible compared to the tubes.  Heat is absolute and not additive so you should notice little to no effect to your ambient temps.  To be more clear, you won't exceed your current tube amps maximum heat output but your total ambient might tick up a degree (F) depending.  More than likely whatever monitor or TV you are using is outputting more heat than the O2 unless you're on your laptop (depending on the laptop).


----------



## Maxvla

Getting more and more interested in the desktop O2. Great for sensitive IEMs, low(er) heat, low price, stackable (no tubes), and more. Just give me a case that doesn't look like shambles (a good portion of the DIY stuff) from a competent maker and I'm sold on trying one.


----------



## Reticuli2

You mean it's absolute when not considering a confined space, right?  So in his little corner heat will not build up, but in the entire room it will.  Unless I misunderstand something about heat so that "heat is absolute and not additive" is completely correct.  I thought the opposite was true.
  
  Quote: 





anaxilus said:


> No worries.  Any heat will be negligible compared to the tubes.  Heat is absolute and not additive so you should notice little to no effect to your ambient temps.  To be more clear, you won't exceed your current tube amps maximum heat output but your total ambient might tick up a degree (F) depending.  More than likely whatever monitor or TV you are using is outputting more heat than the O2 unless you're on your laptop (depending on the laptop).


----------



## Steve Eddy

Quote: 





> Originally Posted by *Willakan* /img/forum/go_quote.gif
> 
> The designer has since responded again at ABI...


 

 ABI? What's ABI?
   
  se


----------



## chinesekiwi

Anythingbutipod.com


----------



## khaos974

steve eddy said:


> ABI? What's ABI?
> 
> se




http://anythingbutipod.com/forum/index.php


----------



## Steve Eddy

Ah, thanks! Only other place I'd been following it is over at diyAudio.
   
  se


----------



## purrin

Quote: 





reticuli2 said:


> Didn't two versions of a defective Cmoy and an E7 also blow your Mini3 away?


 
   
  Quote: 





willakan said:


> ...He also expressed amusement that Ti would rigidly declare, when both the Mini3 and his design use the same battery type, that the batteries output 8.4V, as whilst trying to defend his own designs he insisted they output considerably more.
> 
> *So to paraphrase that, the maths is wrong, the argument is wrong and Ti appears slightly contradictory to the uneducated observer.*


 
   
  Quote: 





skeptic said:


> Of the measurements discussed by nwavguy, noise is hardly the chief concern when it comes to comparing the mini3 and O2, amb - as you well know.  How bout the 25db difference in measured crosstalk between the mini3 and o2 at 15 ohms?  How about the THD at 20khz?


 

       Quote:


willakan said:


> * *Sorry for the Mini3 figures, but I can hardly edit them out of the graph.


 
   
  ---
   

This is really wierd, how did this thread become O2 > mini3? From my reading, it appears that Ti threw the mini3 into the ring for purposes of illustrating the (small) noise differences related to the placement of the pot.
   
It seems the "friends" of nwavguy or nwavguy himself have some kind of axe to grind with Ti - using pseudo authoritative statements such as "*So to paraphrase that, the maths is wrong, the argument is wrong and Ti appears slightly contradictory to the uneducated observer." *Hmm, this sounds a little bit like nwavguy himself. This seems like a very aggressive method of discourse, keeping in mind that no one forced the topic of the O2 design in these forums.
   
I thought this thread was meant as sort of a public commentary on the design of the O2. Why can't the "friends" of nwavguy just politely acknowledge Ti's criticisms, i.e. "We've spoken with nwavguy, and he has taken Ti's design concerns into account and lowered the gain. (Thank You!) Nwavguy's real-world measurements of the opamps voltage swing exceed those of the spreadsheets. Therefore Nwavguy feels that this will adequately address the expected use and scenarios of the typical user." 

Case closed.
   
Geez!


----------



## Willakan

The graph is NwAvGuy's. It is the only graph showing power output. It compares it to the Mini3 and there is nothing I can do about that. Feel free to make something irrational of it.
  As to Ti's criticism, I am simply passing on what NwAvGuy has to say about it. Don't shoot the messenger. The slight gain decrease is to allow for the use of some extremely hot sources (by consumer standards) with the amplifier. The bulk of Ti's criticism about headphone driving capability is strongly contested by NwAvGuy - I am reproducing what he said - otherwise it might appear to people on such a popular website as Head-Fi that the design is flawed - especially considering the prohibition of links to other areas in which it is discussed.
   
  As repeating what NwAvGuy says appears to lead to considerably..erm...friction, I would recommend Ti heads over to ABI to read and respond for himself.
   
  EDIT: NwAvGuy has added a section on the input stage to the most recent article on his site.


----------



## SpaceTimeMorph

Just to reiterate:
   

   
  The above graph indicates fairly symmetrical (i.e. almost identical +/- peaks) clipping performance running from an AC source.  +10Vp -> -10.5Vp for a total of 20.5Vpp.  This is the maximum the O2 can put out before clipping, and it shows great linearity with respect to the input sweep right up until it clips.  Therefore, by this graph you are seeing the voltage on the power supply rails of the O2; 20.5Vpp.  That's precisely 7.24675Vrms.
   
  Now calculating the dB equivalent of this into a 1000ohm load (note the 1000ohms and the *1000 to convert to mW cancel out):
   
  10*log(7.24675^2) = 17.2 dB.
   
  Therefore, with a 1000ohm headphone you would need a sensitivity of <93 dB/mW to find a set of headphones this couldn't drive off of AC power.  Move this value down to 600ohm:
   
  10*log[(7.24675^2/600)*1000] = 19.4 dB.
   
  This needs a sensitivity of <91 dB/mW before it becomes a problem.
   
  300 ohm:
   
  10*log[(7.24675^2/300)*1000] = 22.4 dB.
   
  Sensitivity < 87 dB/mW. 
   
  So, all that being said, what's the problem here?  Even if you want to discount the designers comments about "one size fits all", etc... this is still a <$100 DIY project that can rival amps many times its price.  You are going to struggle to find a gain structure/source voltage/headphone combination that clips.
   
  AMB, you claimed you needed a 5.6 Vrms signal to reach 114 dB with your headphones.  The O2 was designed to reach a target spec of 110dB.  That's a little over half the voltage that you are claiming you need.  So even if you want that much headroom, you would only need 3.53 Vrms, which would give you >100% headroom until you hit the power supply rails.  (This still gives you plenty of headroom on battery power: ~5 Vrms supplied).
   
  (I will message NwAvGuy to see if he has graphs for the clipping point on battery power, however, he claims 14Vpp here which would still be enough if you actually run a "normal" portable source.)
   
  The comments about other amps being able to accommodate any input voltage are fallacious.  Every amp (no matter the topology) is going to clip at a value roughly corresponding to what the power supply will be able to supply to it.  This means that every amp with a specific gain setting will clip with a specific voltage source.  There is no magic that will allow an amp to suddenly not clip if the input exceeds the max allowed.  Even if you are talking about a Class G or H amp, there is still a clip point involved.  The O2 has a relatively high clip point compared to the competition even considering the input overload "issue."  Again, this is an amp that costs <$100 as a DIY project.


----------



## Reticuli2

Quote: 





purrin said:


> Quote:
> 
> ---
> 
> ...


 


  
   
  [size=10pt][size=10pt]Little too ad homonym to go after a design's overall performance when they only want to talk about one teeny tiny aspect of it juxtaposed to the other design that trounced its measurements and didn't include any wanky crosstalk measurements that were kinda absurd even to laymen like me? Yeah, sorry. You're probably right. It is kinda like going after low-hanging fruit or the proverbial fish in the barrel. But how do you expect people to naturally respond? The 02 was designed to test better than many others and most people who build one or buy one will easily be able to use it properly even without this latest alteration. It’s kind of insulting us potential users. It's not like we said the guy or his amp was ugly, or anything. That would just be great fun...err... I mean out of line.[/size][/size]
  [size=10pt][size=10pt]That said, I was told in 2009 to never put a volume pot (like, say, an in-line volume control) between the headphone jack and the headphone. Essentially isn't that what NwAvGuy is doing, but with it having no other pot anywhere else? Or is there more to it? I seem to remember something about being told the impedance load is changed as the pot is reduced with an in-line volume.[/size][/size]


----------



## Head Injury

Quote: 





spacetimemorph said:


> This amp will even drive (not that it was designed to) a Stax SR-009 to ~78 dB.


 

  You hear that deadlylover? Get working on an adapter


----------



## SpaceTimeMorph

Just to show, here are some graphs taken by NwAvGuy that show performance while overloaded on battery and again on AC power:
   
*INPUT OVERLOAD ON BATTERY – *Here’s the V1.1 O2 running on batteries at about 80% charge. The battery voltage was 9.2V. At 2.5X gain it can still handle a 2 volt RMS input signal, which is the Redbook standard for home digital audio equipment. On AC power it can handle 2.8 V RMS which is well in excess of the Fiio E9 which overloads at 2.1V input. So even on reasonably charged batteries the O2 is fine on battery power:

   
*INPUT OVERLOAD ON BATTERY – *Here’s the V1.1 O2 running on AC power with 2.9 V RMS in at 2.5X gain and half volume. No signs of overload:


----------



## SpaceTimeMorph

Quote: 





head injury said:


> You hear that deadlylover? Get working on an adapter


 

 hehe... yea, bored at work one day... what can I say.


----------



## Reticuli2

At what reduction of charge on the battery powered one would the 2V redbook standard voltage cause it to clip?  I don't need it to be portable, but I have to decide whether I want to wait for the desktop version or go with the portable now.


----------



## mikeaj

Quote: 





> Originally Posted by *Reticuli2* /img/forum/go_quote.gif
> 
> [size=10pt][size=10pt]That said, I was told in 2009 to never put a volume pot (like, say, an in-line volume control) between the headphone jack and the headphone. Essentially isn't that what NwAvGuy is doing, but with it having no other pot anywhere else? Or is there more to it? I seem to remember something about being told the impedance load is changed as the pot is reduced with an in-line volume.[/size][/size]


 
   
  Pardon me if I missed what you were saying, but in the O2 the volume pot is between the gain stage and the output stage.  Others are saying they'd prefer the pot to be before the gain stage, so clipping can be avoided with very high sources and high gains, by turning the position of the pot.  I'm not sure what this has to do with adding impedance between the headphone jack (or after the output stage, even if on the board) and the headphones.


----------



## Reticuli2

O.k.


----------



## mikeaj

Quote: 





reticuli2 said:


> At what reduction of charge on the battery powered one would the 2V redbook standard voltage cause it to clip?  I don't need it to be portable, but I have to decide whether I want to wait for the desktop version or go with the portable now.


 
   
  Change the low gain to 2X or lower (just pick a different resistor value) and it will never clip with a 2V source until about maybe 5-10 minutes before it cuts off.  On like 1X to 1.5X it certainly won't have an issue straight until shutdown.  Keep in mind that if you're using it on battery, will you be using portable sources or home sources?  Most portable sources will not output 2V rms.  If running on AC power there is no problem with 2V sources.  You need to be running on low batteries with high output sources and higher gain settings (that can be reduced), or potentially a very high output source with higher gain settings, for there to be clipping.


----------



## SpaceTimeMorph

Quote: 





> Originally Posted by *Reticuli2* /img/forum/go_quote.gif
> 
> [size=10pt][size=10pt]That said, I was told in 2009 to never put a volume pot (like, say, an in-line volume control) between the headphone jack and the headphone. Essentially isn't that what NwAvGuy is doing, but with it having no other pot anywhere else? Or is there more to it? I seem to remember something about being told the impedance load is changed as the pot is reduced with an in-line volume.[/size][/size]


 
  Actually the general rule is "don't amplify then attenuate", the best answer is to raise the signal level to the nominal preferred as soon as the signal enters the amp.  That way you aren't choosing between loss of headroom and noise as your two poisons.  However, given the space and price considerations, he choose to put it between the gain stage and the output stage.  You are always going to want something in front of your volume pot (a buffer at least) that way you aren't required to use a higher resistance to attenuate the signal (you would be forced to use roughly half the source impedance to drop a signal by 6 dB otherwise, which would greatly increase Johnson noise).  The O2 achieves this to a degree by using the 2068's for the gain stage, which allow a lower impedance into the volume pot => giving less noise while at the same time stepping up the voltage to what is needed for the output stage.  This is in addition to the lower noise due to not amplifying the Johnson noise from the pot.
   
  All of that being said, I think we've beaten a dead horse into the pavement with the fact that there is plenty of headroom.
   
   Quote:


reticuli2 said:


> At what reduction of charge on the battery powered one would the 2V redbook standard voltage cause it to clip?  I don't need it to be portable, but I have to decide whether I want to wait for the desktop version or go with the portable now.


 
   
  He has revised his assessment of the low voltage situation with batteries and is claiming a 4.5V figure now.  Thusly his gain calculation is now 4.5/Vin on battery.  My reccomendation is if you want the desktop flavor, wait for that.


----------



## Steve Eddy

Just a quick comment.
   
  Much criticism has been levied at the O2 for the designer's decision to place the volume control between the input/amplification stage and the output stage. The basis of this criticism has been that the O2 would tend to overload when fed from sources with full scale outputs greater than a couple of volts RMS.
   
  I ask, why isn't the criticism being levied at the designers of source components which have full scale outputs greater than a couple of volts RMS?
   
  For many years there have been standards for line level outputs. In the consumer world, it is -10dBu, or about 0.316 volts RMS. In the pro audio world, it is +4 dBu, or about 1.23 volts RMS. When the Compact Disc came on the scene, Sony and Philips set the "Red Book" standard 0dBFS level at 2 volts RMS, or about +8.24dBu.
   
  I really don't see why any source component's fulls scale line level outputs should be any greater than this. To do so is just plain stupid in my opinion. And when you accommodate stupidity, all you do is just encourage more of it in the future.
   
  So I think the criticism of the placement of the O2's volume control is entirely misplaced.
   
  se


----------



## amb

Quote: 





> Originally Posted by *Steve Eddy* /img/forum/go_quote.gif
> 
> I ask, why isn't the criticism being levied at the designers of source components which have full scale outputs greater than a couple of volts RMS?


 
   
  Sources that could output more than a couple of volts RMS is not a recent phenomenon.  In the analog days, "0dB" is only a reference but signal peaks routinesly exceed that by large margins.  For example, almost all Nakamichi cassette decks output 1Vrms at "0dB" as displayed on its level meters, but cassettes can be recorded at levels much higher than that, with peaks reaching as high as +10dB.  At that level, the deck would be putting out 3.2Vrms.  Same goes for phono stages -- depending on the recorded level on the LP, the output voltage of the cartridge, and the gain of the phono stage, it too could produce high output voltage swings.
   
  At any rate, placing the blame on the source components is not fruitful -- they already exist in the market and the choice is to design an amp that could work with them, or not.


----------



## Anaxilus

Quote: 





reticuli2 said:


> You mean it's absolute when not considering a confined space, right?  So in his little corner heat will not build up, but in the entire room it will.  Unless I misunderstand something about heat so that "heat is absolute and not additive" is completely correct.  I thought the opposite was true.


 

 Should have worded it a bit differently.  Regardless, it's not rocket science in the context here so I thought it would be self explanatory.  Unless he lives outdoors in the desert at high noon, placing it in the corner has no effect to the absolute maximum but it has a minor impact to the rest of the room assuming the ambient temp is lower than the O2.


----------



## wakibaki

I've seen a lot of people here trying to tear down what RocketScientist has done. Your efforts would be better spent trying to match or exceed what he has done. People have reacted very defensively when the flaws in certain designs have been pointed out. They have switched to the attack now that the opportunity presents itself. This is far from admirable. 
   
  Having designed a lot of circuits myself, I appreciate the difficulties involved, particularly where objective test is involved. Test equipment, particularly calibrated test equipment, is not cheap. If, however, some of the designers who now find themselves at a disadvantage had had the foresight to reinvest some of their profits in creating designs which were a true improvement on the foregoing, instead of adopting dubious topologies on a speculative basis more for their advertising benefits and novelty (as it turns out) than any demonstrated technical advantage they would have been less vulnerable to soundly-based criticism.
   
  The answer is to change. Not to try to run down the O2, not to try to step up the advertising, but simply to try to produce better-performing designs, either in terms of cost (unlikely), performance (possible), features (entirely possible), useability (entirely possible), cosmetics (?) or DIY-appeal. What is certainly necessary is to stop pretending that there is some ineffable quality (sound) that that some amplifiers might possess in contrast to the O2, despite its superior measurements.
   
  As technology and circuit design progresses I anticipate that some of the designers of excellent full-power amps in the past will continue to publish new designs. Douglas Self was not discouraged from publishing his recent parallel NE5532 design by the fact that there are many excellent designs with flaws probably below the threshold of audibility already extant. I, for one, while not counting myself in that company, have not given up generating new designs simply because the O2 has appeared.
   
  Come on guys, put your shoulders to the wheel and do something creative instead of being destructive. It's in your own interests, because if you don't you will undoubtedly find your sales being eroded in the future, as they probably are being already.
   
  Perhaps it will be possible to persuade the nwavguy to review your future products, I can think of few things more beneficial than a favourable review from him.
   
  w


----------



## Anaxilus

Quote: 





spacetimemorph said:


> Therefore, with a 1000ohm headphone you would need a sensitivity of <93 dB/mW to find a set of headphones this couldn't drive off of AC power.  This amp will even drive (not that it was designed to) a Stax SR-009 to ~78 dB.


 
   
  Pardon my ignorance and apologies for detracting from the specific commentaries here.  I'm the first to admit to being out of my depth here wrt EE but is this a statement for the sake of Hyperbole?  Stax and Koss run their stats w/ a bias of 580v/600v respectively.  I'm not getting how the O2 is now an Energizer or did something just pass right over my head.  Sorry for the aside.


----------



## Steve Eddy

Quote: 





> Originally Posted by *amb* /img/forum/go_quote.gif
> 
> Sources that could output more than a couple of volts RMS is not a recent phenomenon.  In the analog days, "0dB" is only a reference but signal peaks routinesly exceed that by large margins.  For example, almost all Nakamichi cassette decks output 1Vrms at "0dB" as displayed on its level meters, but cassettes can be recorded at levels much higher than that, with peaks reaching as high as +10dB.  At that level, the deck would be putting out 3.2Vrms.  Same goes for phono stages -- depending on the recorded level on the LP, the output voltage of the cartridge, and the gain of the phono stage, it too could produce high output voltage swings.


 
   
  Never said they were. But it doesn't make them any less silly. Especially where digital audio is concerned.
   
  Quote: 





> At any rate, placing the blame on the source components is not fruitful -- they already exist in the market and the choice is to design an amp that could work with them, or not.


 
   
  So you admit it's a choice. Then why bust someone's chops just because they may make a choice that's different from the choice you may make?
   
  And I didn't suggest placing the blame on the source components. I suggested placing it on the _designers_ (and/or manufacturers) of the source components.
   
  se


----------



## limpidglitch

Quote: 





amb said:


> Sources that could output more than a couple of volts RMS is not a recent phenomenon.  In the analog days, "0dB" is only a reference but signal peaks routinesly exceed that by large margins.  For example, almost all Nakamichi cassette decks output 1Vrms at "0dB" as displayed on its level meters, but cassettes can be recorded at levels much higher than that, with peaks reaching as high as +10dB.  At that level, the deck would be putting out 3.2Vrms.  Same goes for phono stages -- depending on the recorded level on the LP, the output voltage of the cartridge, and the gain of the phono stage, it too could produce high output voltage swings.
> 
> At any rate, placing the blame on the source components is not fruitful -- they already exist in the market and the choice is to design an amp that could work with them, or not.


 

 Two other options remain:
   
  -Buy a proper DAC
  -Use ReplayGain
   
  People who insist on living in the dark ages just cannot be helped, the O2 isn't for them.


----------



## Costia

Quote: 





anaxilus said:


> Pardon my ignorance and apologies for detracting from the specific commentaries here.  I'm the first to admit to being out of my depth here wrt EE but is this a statement for the sake of Hyperbole?  Stax and Koss run their stats w/ a bias of 580v/600v respectively.  I'm not getting how the O2 is now an Energizer or did something just pass right over my head.  Sorry for the aside.


 
   
  You could attach a transformer to the output and maybe get the needed 500ish volt
   
  Anyway , why are you talking about Vrms in the context of clipping
  You should be talking about peak to peak
  unless you generally listen to sine waves Vrms has no connection to Vrms
   
  Scenario 1:
  classical music with loud parts/drums
  User will put the gain on the high setting - the loud part will clip

 Scenario 2:
  Unequalized mp3 library
  Will have to switch gain between songs and re-adjust volume


----------



## mikeaj

Peak-to-peak is more correct, but it's understood that the clipping tests are done with pure sine waves and the factor of 2*sqrt(2) is trivial.  It's more convenient to compare with output sources, which are less frequently quoted with the peak-to-peak output voltage figures?  Obviously the peak-to-rms value will not be the same ratio for many signals other than pure sine waves.


----------



## deadlylover

Quote: 





spacetimemorph said:


> This amp will even drive (not that it was designed to) a Stax SR-009 to ~78 dB.


 
   
  No it won't. 
	

	
	
		
		

		
			




   
  Quote: 





head injury said:


> You hear that deadlylover? Get working on an adapter


 
   
  I could if I wanted to, hook up some backwards transformers, generate the bias from another small transformer......
   
  Spritzer has already done something similar, and I think he described it as "it made noise".


----------



## upstateguy

Quote: 





			
				SpaceTimeMorph said:
			
		

> This amp will even drive (not that it was designed to) a Stax SR-009 to ~78 dB.


 

  
  Quote: 





deadlylover said:


> No it won't.


 

 Oh please, you could jump start a car with it.


----------



## khaos974

anaxilus said:


> Pardon my ignorance and apologies for detracting from the specific commentaries here.  I'm the first to admit to being out of my depth here wrt EE but is this a statement for the sake of Hyperbole?  Stax and Koss run their stats w/ a bias of 580v/600v respectively.  I'm not getting how the O2 is now an Energizer or did something just pass right over my head.  Sorry for the aside.




Don't worry, you missed nothing, it's just a figure to illustrate a point, on a pure theoretical point of view, that voltage will drive a SR-009 to 78 dB, but in practice, that's nothing useful.
First of all, you would need to rework the circuitry to make it work with an electrostat, and also 78 dB peak is ridiculously low, with classical music and 20 dB peaks, the average volume would be 58 dB, that's the level of a murmur in real life.


----------



## deadlylover

Quote: 





upstateguy said:


> Oh please, you could jump start a car with it.


 
   
  One mustn't underestimate the mightiness of TWO 9V batteries!


----------



## Anaxilus

Quote:  

 Thank you.


----------



## SpaceTimeMorph

Quote: 





khaos974 said:


> Don't worry, you missed nothing, it's just a figure to illustrate a point, on a pure theoretical point of view, that voltage will drive a SR-009 to 78 dB, but in practice, that's nothing useful.
> First of all, you would need to rework the circuitry to make it work with an electrostat, and also 78 dB peak is ridiculously low, with classical music and 20 dB peaks, the average volume would be 58 dB, that's the level of a murmur in real life.


 

 Sorry guys, didn't mean to distract from the conversation.  Yes it was a bit of hyperbole, I will deliver it better in the future


----------



## Reticuli2

That is probably a sound choice going with 2X gain for those that might use the portable version with home gear from time to time.  Occassionally you will see home sources at 2V with no volume attenuator.  I don't have one, but they're out there.

  
  Quote: 





mikeaj said:


> Change the low gain to 2X or lower (just pick a different resistor value) and it will never clip with a 2V source until about maybe 5-10 minutes before it cuts off.  On like 1X to 1.5X it certainly won't have an issue straight until shutdown.  Keep in mind that if you're using it on battery, will you be using portable sources or home sources?  Most portable sources will not output 2V rms.  If running on AC power there is no problem with 2V sources.  You need to be running on low batteries with high output sources and higher gain settings (that can be reduced), or potentially a very high output source with higher gain settings, for there to be clipping.


----------



## Shike

I just posted a review guys:
   
http://www.head-fi.org/t/568705/review-nwavguy-s-o2-diy-amplifier#post_7708264
   
  Let me know your thoughts.


----------



## deadlylover

Quote: 





shike said:


> I just posted a review guys:
> 
> http://www.head-fi.org/t/568705/review-nwavguy-s-o2-diy-amplifier#post_7708264
> 
> Let me know your thoughts.


 
   
  Nice review, but no comparisons?
   
  It's about time somebody else on head-fi has built one of these things. I almost thought the sound science gang were all talk and no substance.
  
  Take the batteries out, switch the amp on then switch off the AC wallwart, do your regulators come down evenly or do you get a massive spike at the output?


----------



## Shike

Quote: 





deadlylover said:


> Nice review, but no comparisons?


 


 It's mostly about the O2 - I did mention the disappointing crosstalk of the M^3 and the formerly dangerous off transient of the Asgard.  I may add more though in terms of direct comparisons if people are interested.
   
  As for the off transient, my DMM is really slow so it isn't going to catch anything extremely fast.  I couldn't catch any spike in voltage on/off using my DMM - they just aren't high enough or long enough for me to pick up.
   
  It's also worth noting that this is actually a full PCB build.


----------



## deadlylover

Quote: 





shike said:


> It's mostly about the O2 - I did mention the disappointing crosstalk of the M^3 and the formerly dangerous off transient of the Asgard.  I may add more though in terms of direct comparisons if people are interested.
> 
> As for the off transient, my DMM is really slow so it isn't going to catch anything extremely fast.  I couldn't catch any spike in voltage on/off using my DMM - they just aren't high enough or long enough for me to pick up.
> 
> It's also worth noting that this is actually a full PCB build.


 
   
  Are you testing it without the batteries and switching it from the AC (and not the proper power switch)?
   
  Grats on the first PCB build, did you do a small run for yourself or something?


----------



## Shike

Quote: 





deadlylover said:


> Are you testing it without the batteries and switching it from the AC (and not the proper power switch)?
> 
> Grats on the first PCB build, did you do a small run for yourself or something?


 

 Ah, you meant like a power strip switch.  Just tested it an now I see what you're saying, it fits the expected 250mv or so NwAvGuy tested.  I have it too.
   
  A friend built it for me, but the PCB was done through a small run.


----------



## deadlylover

Quote: 





shike said:


> Ah, you meant like a power strip switch.  Just tested it an now I see what you're saying, it fits the expected 250mv or so NwAvGuy tested.  I have it too.
> 
> A friend built it for me, but the PCB was done through a small run.


 
   
  Ah thanks for that, my fairchild regulators don't come down evenly, stay away from those. 
	

	
	
		
		

		
			




   
  I think nwavguy tested it under battery power, and not AC, but I'm not sure. If your DMM caught that and not the 250mv-odd that one is supposed to get normally from battery power....
   
  Bah forget about it.


----------



## Shike

Quote: 





deadlylover said:


> Ah thanks for that, my fairchild regulators don't come down evenly, stay away from those.
> 
> 
> 
> ...


 


  All I can say is my DMM is just wonky all around so I don't put huge amounts of faith in it, I really need to get a battery for my newer one soon - I'll comment on it more then if I find problems, but the off thump isn't crumpling my drivers so I'm not all that worried.


----------



## deadlylover

Quote: 





shike said:


> All I can say is my DMM is just wonky all around so I don't put huge amounts of faith in it, I really need to get a battery for my newer one soon - I'll comment on it more then if I find problems, but the off thump isn't crumpling my drivers so I'm not all that worried.


 
   
  No probs, I wasn't really trying to suggest that the Obj2 blows headphones up or anything, I just wanted to see if anyone else had dodgy regulators.


----------



## The Monkey

reticuli2 said:


> That is probably a sound choice going with 2X gain for those that might use the portable version with home gear from time to time.  Occassionally you will see home sources at 2V with no volume attenuator.  I don't have one, but they're out there.




They're not as rare as you seem to think they are.


----------



## Beefy

Quote: 





shike said:


> I did mention the disappointing crosstalk of the *M^3*


 

  
*Mini*3. The M^3 is a desktop amplifier.


----------



## mikeaj

Indeed, Mini^3 and M^3 are not the same, though both are three-channel (err, L/R plus active ground channel) amps I think.  I hope I haven't gotten it wrong too. 
   
  M^3 (desktop):
http://www.amb.org/audio/mmm/
   
  Mini^3 (portable):
http://www.amb.org/audio/mini3/
   
  At first I did a double take with those links before realizing that _these_ are allowed.


----------



## Shike

Quote: 





beefy said:


> *Mini*3. The M^3 is a desktop amplifier.


 
   
  Sorry for the freudian slip.  I did reference it properly in the review though.
   
  Still, I wouldn't be surprised if the M^3 had the same problems honestly.


----------



## Beefy

Quote: 





shike said:


> Still, I wouldn't be surprised if the M^3 had the same problems honestly.


 

 Any time you want to support that with hard data, then go right ahead.


----------



## Reticuli2

What, like -93dB crosstalk into an 8ohm load kind of hard data? 
	

	
	
		
		

		
		
	


	




  
  Quote: 





beefy said:


> Any time you want to support that with hard data, then go right ahead.


----------



## Shike

Quote: 





beefy said:


> Any time you want to support that with hard data, then go right ahead.


 

 I'm pretty sure I said I "wouldn't be surprised", not that it immediately was since I haven't measured it.  Still, if you want to know it's mathematically impossible, his output impedance would need to be even less than 0.0013 ohms (which is what would have been necessary for his 88dB into 33 ohm spec for the Mini^3).  I'd have to check the datasheet, but I'm pretty sure the headphone jack alone has more than that.
   
  You're perfectly free to create a dummy load and test it yourself though if you really want.


----------



## Beefy

Quote: 





reticuli2 said:


> What, like -93dB crosstalk into an 8ohm load kind of hard data?


 

 Indeed. Congratulations on completely missing the point


----------



## Costia

looks like this thread is becoming the "DIY forum" version of the "getting called out for not wearing the beats" thread


----------



## digger945

Quote: 





shike said:


> Sorry for the freudian slip.  I did reference it properly in the review though.
> 
> Still, I wouldn't be surprised if the M^3 had the same problems honestly.


 

 ^^^^^^ this really stinks. You put a bad name on this forum. Slinging mud at an established member's free-to-the-public designs. How is this useful in the context of this thread?
   


  Quote: 





shike said:


> I'm pretty sure I said I "wouldn't be surprised", not that it immediately was since I haven't measured it.  Still, if you want to know it's mathematically impossible, his output impedance would need to be even less than 0.0013 ohms (which is what would have been necessary for his 88dB into 33 ohm spec for the Mini^3).  I'd have to check the datasheet, but I'm pretty sure the headphone jack alone has more than that.
> 
> You're perfectly free to create a dummy load and test it yourself though if you really want.


 


  Would you please explain to me how output impedance affects crosstalk, or how feedback affects output impedance?


----------



## SpaceTimeMorph

Quote: 





deadlylover said:


> Ah thanks for that, my fairchild regulators don't come down evenly, stay away from those.
> 
> 
> 
> ...


 

 Yea, he's been having problems with the negative fairchild regulator responding slower than the positive one.  He's gotten better results with the on-semi regulators I do believe.


----------



## deadlylover

Quote: 





spacetimemorph said:


> Yea, he's been having problems with the negative fairchild regulator responding slower than the positive one.  He's gotten better results with the on-semi regulators I do believe.


 
   
  Cool, thanks. Everybody seems to know everything about this amp, apart from me, despite building one.


----------



## SpaceTimeMorph

Quote: 





deadlylover said:


> Cool, thanks. Everybody seems to know everything about this amp, apart from me, despite building one.


 

 Naw, as stated earlier, I'm too busy at work right at the present.  So I just get my fix by reading everything I can about this thing.  Otherwise I would've built one myself.  September will be a much better month as far as that goes.


----------



## deadlylover

Quote: 





spacetimemorph said:


> Naw, as stated earlier, I'm too busy at work right at the present.  So I just get my fix by reading everything I can about this thing.  Otherwise I would've built one myself.  September will be a much better month as far as that goes.


 
   
  Ahaah good luck dude.
   
  Don't worry, you can stuff the boards on the proper pcb in like 30 minutes no probs. I think the perfboard version took less than 2 hours, the p-p one took about 4-5 hours, mostly because I'm bad at stripping wire.


----------



## Shike

Quote: 





digger945 said:


> ^^^^^^ this really stinks. You put a bad name on this forum. Slinging mud at an established member's free-to-the-public designs. How is this useful in the context of this thread?


 

 Beefy wanted me to prove that Ti's M^3 measurements are incorrect, and checking the math they most likely are.  Just because it's free of charge doesn't mean it's excluded from fact checking now does it?
   
  Quote: 





> Would you please explain to me how output impedance affects crosstalk, or how feedback affects output impedance?


 
   
  Output impedance effects crosstalk because it acts like a voltage divider, as for output impedance and feedback: http://en.wikipedia.org/wiki/Negative_feedback_amplifier


----------



## Olli1324

For those head-fiers on the Group Buy list, payments are now being taken (inc. from US/CAN).
   
  Cheers


----------



## Parall3l

Interesting amp, looks fairly easy to assemble, I'm putting this on my "to try" list


----------



## Costia

Quote: 





shike said:


> Beefy wanted me to prove that Ti's M^3 measurements are incorrect, and checking the math they most likely are.  Just because it's free of charge doesn't mean it's excluded from fact checking now does it?
> 
> 
> Output impedance effects crosstalk because it acts like a voltage divider, as for output impedance and feedback: http://en.wikipedia.org/wiki/Negative_feedback_amplifier


 

 My calculation shows different results
  If there was no impedance between the jack's ground and the actual ground - crosstalk should theoretically be 0 (-Inf db)
  The result i got is : crosstalk= (Rout+Rheadphone)/Rground (or the inverse of this, depends what sign you wand on the db)
  This actually means that by increasing the output impedance you can decrease crosstalk
  http://i.imgur.com/vOmLT.png
   
  for crosstalk=93db , Rout=0.5ohm and Rheadphone=8 ,Rgnd should be 0.2mOhm. sounds improbable to me


----------



## digger945

I'm struggling to try and wrap my head around how exactly you can use any formula to calculate crosstalk, without actually performing a test to measure it.

How do you calculate the impedance of an active ground channel that is referenced to the power rails?


----------



## Costia

doublepost


----------



## Costia

1) its a model. you this kind of stuff while you are designing. before you actually build the amp. you cant just throw in a bunch of parts and say i will measure it when its all done and hope for the best
  2) he has an active ground? i thought the O2 used the connecting point of 2 batteries as its ground ( and if not, you need to add the acive ground op-amp output resistance to Rgnd)
   
  you can never get the real life results from models but they are very good approximations.
  Even F=ma is wrong, and we still use it...
  Edit: and V=IR is a first order approximation of some very complex EM fields calculations


----------



## digger945

Wrt EM fields, how can you have a proper "guess" without any specifics of the topology of the pcb, or measurements between traces and devices, or EM fields of either?

I am referring to the any amp, of any design.


----------



## Costia

I was referring to the O2. I did looks at its PCB layout (~15cm battery to jack, and 1-2cm capacitor to jack)
  my calculation is a response to shike's comment about the voltage divider theory -* not a comprehensive analysis *of the O2 or any other amp.
  I did not take into consideration all possible crosstalk sources
  What i intended to show is that with 8ohm load and 0.5ohm Rout you would need the resistance to the ground to be 0.2mOhm to reach 93db crosstalk
  in other words if Rgnd=0.2mOhm or higher, the *best possible* crosstalk would be 93db. it can be worse
  And it will, since the resistance of the headphone cord should be added to Rgnd as well (so the 93db figure is for the scope's ears only. AFAIK a human can hear crosstalk only when it reaches ~40ish db)
  There are many additional potential sources for noise/distortion/crosstalk. You need to pick the ones you consider most significant and design according to that.
  This choice might be wrong and you will end up with a bad amp.
  Then you go back to the drawing board and try again (or read a book that tells you were to look for problems)
   
  I think most of the figures provided by nwavguy are well beyond what an average person can hear - i.e. meaningless for practical reasons for use as a headphone amp (more practical if this amp will be connected as a part of a really long chain of audio equipment.)


----------



## Shike

Quote: 





costia said:


> I was referring to the O2. I did looks at its PCB layout (~15cm battery to jack, and 1-2cm capacitor to jack)
> my calculation is a response to shike's comment about the voltage divider theory -* not a comprehensive analysis *of the O2 or any other amp.
> I did not take into consideration all possible crosstalk sources
> What i intended to show is that with 8ohm load and 0.5ohm Rout you would need the resistance to the ground to be 0.2mOhm to reach 93db crosstalk
> ...


 


  The 93dB crosstalk figure is what AMB quotes for the M^3 --  and is likely impossible (pretty sure you agreed?).  The O2's quoted crosstalk is ~70dB, which I even measured and in comparison is much easier to reach.
   
  Are you sure we're on the same page here?


----------



## Costia

thought you were talking about the O2
  I do agree reaching 93db is very unlikely
  but i don't see what a voltage divider between Rheadphone and Rout has to do with it... 
  The most influential figure seems to be the resistance between the jack and the ground
  If it uses active ground, it could be even worse. depends on where the caps are and the op amp of the ground circuit.
   
  Edit:
  you also mentioned the negative feedback gain, that has nothing to do with Rout or crosstalk


----------



## Shike

Quote: 





costia said:


> thought you were talking about the O2
> I do agree reaching 93db is very unlikely
> but i don't see what a voltage divider between Rheadphone and Rout has to do with it...
> The most influential figure seems to be the resistance between the jack and the ground
> If it uses active ground, it could be even worse. depends on where the caps are and the op amp of the ground circuit.


 

 A resistor divider is created that uses the shared output impedance, it's why we're able to calculate expected crosstalk.
   
   
  Quote: 





> Edit:
> you also mentioned the negative feedback gain, that has nothing to do with Rout or crosstalk


 
   
  digger 945 was asking how output impedance and feedback correlate so I linked him to the Wiki article.
   
   
  Seems you jumped the gun a bit on this one, eh?


----------



## Costia

the output impedance isn't shared...
  and feedback doesnt affect output impedance as well
  edit: looks like the output resistance of the amp is related to the gain. hmm.
   
  looked at a datasheet of opa552.
  no output impedance is mentioned. Looks like its dependent on the actual current drawn from the amp rather than the gain (there is a graph)
  and the input impedance is 10^13


----------



## digger945

Quote: 





costia said:


> edit: looks like the output resistance of the amp is related to the gain. hmm.


 
  ...and gain is controlled by? (in this case using an IC opamp)


----------



## Shike

Quote: 





costia said:


> the output impedance isn't shared...


 

 I'm just going to focus on this right now.  The active grounds output impedance can't be fixed using feedback, so it gets shared between the L/R channels forming the voltage divider.
   
  NwAvGuy goes into a lot more depth about this on ABI, and will probably explain it infinitely better than I could hope.


----------



## Costia

I thought you were talking about the output impedance of the op amps that actually do the amplifying not the one used as a buffer for the active ground - which is shared
  I did read nwavguy's post on active grounds. not really convinced about the degradation. with a gain of x1 most op-amps should cope fairly well. (i.e. measurable but not audible difference)
  But it does seems like a waste of parts\space when it is not necessary (such as a single battery)
  I guess when you are talking about a required impedance of a few mOhm to get the 90db separation, the ground channel buffer's resistance will be the dominant one.
   
  I find it quite strange that TI don't have output impedance in the sheets of opa132 and opa552/1 although their op-amp guide states that it could be significant
  And i actually didn't know that an op amp's output impedance depends on the closed loop gain. learned something new


----------



## fubar3

Just looked at the schematic. Interesting design but I am wondering if it is good to have a diode between the regulator and the load. I don't know.. just asking.  It is possible to improve the power supply using adjustable regulators, instead of fixed which tend to be imbalanced. Adjustable regulators are flexible since they allow slow turn-on and other tweaks.  A resistor between the large caps on the input side might be helpful since it becomes an R/C filter.  Of course, I have forgotten the design details.. just relying on intuition.


----------



## Willakan

NwAvGuy said that the power supply regulators are not really a "bottleneck" in the design, so better ones wouldn't offer any real measurable improvements. It also already incorporates input filtering, although the AC filtering cap was removed.


----------



## anetode

After reading up a bit more on the design and the background debates, I've noticed an interesting parallel. The power output criticism of nwavguy's O2 amp kind of mirrors his own concerns over the Mini3's power output discrepancies among different test setups. Whereas amb's specs were the culmination of a long design cycle and the optimum setup for the greatest measured performance, nwavguy's methodology aims at the average user and uses average componentry. By amb's exacting standards, the O2 has a very low usable gain range that the predetermined (though since revised) figures would have pushed to clipping. Contrarily, by nwavguy's standards we have an amp that would work across the greatest practical range of headphone impedances and sensitivities to very low distortion, but sacrificing the usable output to meet a very exacting crosstalk spec. A kind of reverse situation from when nwavguy challenged the mini3's crosstalk due to the OPA690 3-channel output decision. So, from an outside perspective it seems like a fanatical resolve was placed to designing to a specific ideal. Personally, I don't quite see how a possible difference from inaudible but otherwise unexemplary crosstalk to an equally inaudible but altogether impressive crosstalk justifies the inherent limitation in design choices. Sure, O2 is a concept amp built on achieving great measurements, but also a budget and wide usability. Both amplifiers appear to be the product of carefully weighed design consideration.
   
  Unfortunately, what with the unfortunate subjective/objective rift in the head-fi camp and nwavguy's holy crusade and the designer egos, it almost seems like these approaches are somehow adversarial, rather than complementary.


----------



## SpaceTimeMorph

Quote: 





anetode said:


> After reading up a bit more on the design and the background debates, I've noticed an interesting parallel. The power output criticism of nwavguy's O2 amp kind of mirrors his own concerns over the Mini3's power output discrepancies among different test setups. Whereas amb's specs were the culmination of a long design cycle and the optimum setup for the greatest measured performance, nwavguy's methodology aims at the average user and uses average componentry. By amb's exacting standards, the O2 has a very low usable gain range that the predetermined (though since revised) figures would have pushed to clipping. Contrarily, by nwavguy's standards we have an amp that would work across the greatest practical range of headphone impedances and sensitivities to very low distortion, but sacrificing the usable output to meet a very exacting crosstalk spec. A kind of reverse situation from when nwavguy challenged the mini3's crosstalk due to the OPA690 3-channel output decision. So, from an outside perspective it seems like a fanatical resolve was placed to designing to a specific ideal. Personally, I don't quite see how a possible difference from inaudible but otherwise unexemplary crosstalk to an equally inaudible but altogether impressive crosstalk justifies the inherent limitation in design choices. Sure, O2 is a concept amp built on achieving great measurements, but also a budget and wide usability. Both amplifiers appear to be the product of carefully weighed design consideration.
> 
> Unfortunately, what with the unfortunate subjective/objective rift in the head-fi camp and nwavguy's holy crusade and the designer egos, it almost seems like these approaches are somehow adversarial, rather than complementary.


 

 Do we really have to go here again?  A lot has been written on the input overload "issue" already.  I recommend you go over this thread again, some pertinent information is pretty recent with regards to what you are talking about.  To summarize, however: the only way in which you will push this to clipping is with a "hot" source driving too high of a gain or if you are driving a rather extreme set of headphones you may have to lower the gain so that you will have lower volume on certain recordings.  Both of these are rather extreme examples and hardly limitations of the design that you will be encountering every time you power the amp up.  There's a difference between this amp's power output capabilities on AC vs. on battery... make sure you understand that as well as it bears importantly to this topic.  Any other questions, feel free to ask them.  Also, NwAvGuy has a good summary article that talks about this issue as well as some other things, I recommend reading that.
   
  As for the comparisons between NwAvGuy's and AMB's "philosophy" on design...  Frankly, that isn't the point of this discussion; this is a thread about the O2 amp.  However, if you want to know more, check this thread out before you criticize NwAvGuy too much:
http://www.diyaudio.com/forums/headphone-systems/188983-3-channel-headphone-amps-virtual-grounds-5.html#post2572899
   
  The fact is, there has been some debate over the validity of AMB's crosstalk figure, and there have been independent measurements taken that show it is within an audible range(~-33dB to ~-46dB), so make of that what you will.


----------



## anetode

Quote: 





spacetimemorph said:


> Do we really have to go here again?  A lot has been written on the input overload "issue" already.  I recommend you go over this thread again, some pertinent information is pretty recent with regards to what you are talking about.  To summarize, however: the only way in which you will push this to clipping is with a "hot" source driving too high of a gain or if you are driving a rather extreme set of headphones you may have to lower the gain so that you will have lower volume on certain recordings.  Both of these are rather extreme examples and hardly limitations of the design that you will be encountering every time you power the amp up.  There's a difference between this amp's power output capabilities on AC vs. on battery... make sure you understand that as well as it bears importantly to this topic.  Any other questions, feel free to ask them.  Also, NwAvGuy has a good summary article that talks about this issue as well as some other things, I recommend reading that.
> 
> As for the comparisons between NwAvGuy's and AMB's "philosophy" on design...  Frankly, that isn't the point of this discussion; this is a thread about the O2 amp.  However, if you want to know more, check this thread out before you criticize NwAvGuy too much:
> http://www.diyaudio.com/forums/headphone-systems/188983-3-channel-headphone-amps-virtual-grounds-5.html#post2572899
> ...


 

 Quite. As I said, I just spent a couple of hours reading up on it. I meant to offer a reflection on some of the controversy behind the amp's development which was relevant to the prior contents of this thread, regardless of the multitude of other takes on what this thread should really be about. I don't mean to seriously criticize NwAvGuy's work, or AMB's for that matter, as I simply don't have the requisite engineering knowledge to do so. The previous comment was just a helpful generalization I came by while tying up a number of disparate threads in my mind.


----------



## SpaceTimeMorph

^ Fair enough.


----------



## mikeaj

Quote: 





anetode said:


> After reading up a bit more on the design and the background debates, I've noticed an interesting parallel. The power output criticism of nwavguy's O2 amp kind of mirrors his own concerns over the Mini3's power output discrepancies among different test setups. Whereas amb's specs were the culmination of a long design cycle and the optimum setup for the greatest measured performance, nwavguy's methodology aims at the average user and *uses average componentry *[emphasis added]. By amb's exacting standards, the O2 has a very low usable gain range that the predetermined (though since revised) figures would have pushed to clipping. Contrarily, by nwavguy's standards we have an amp that would work across the greatest practical range of headphone impedances and sensitivities to very low distortion, but sacrificing the usable output to meet a very exacting crosstalk spec. A kind of reverse situation from when nwavguy challenged the mini3's crosstalk due to the OPA690 3-channel output decision. So, from an outside perspective it seems like a fanatical resolve was placed to designing to a specific ideal. Personally, I don't quite see how a possible difference from inaudible but otherwise unexemplary crosstalk to an equally inaudible but altogether impressive crosstalk justifies the inherent limitation in design choices. Sure, O2 is a concept amp built on achieving great measurements, but also a budget and wide usability. Both amplifiers appear to be the product of carefully weighed design consideration.
> 
> Unfortunately, what with the unfortunate subjective/objective rift in the head-fi camp and nwavguy's holy crusade and the designer egos, it almost seems like these approaches are somehow adversarial, rather than complementary.


 

 In my opinion one of the most compelling points here is that you can get very accurate performance driving headphones-level impedances with relatively low-cost components.  If you check the op amp article, you'll see that many of the more expensive alternatives seem to behave worse.  This is especially true if you use expensive parts with great specifications for some applications but not so much for audio, and if you aren't diligent in designing the circuits around them properly.
   
  Maybe I misinterpreted you, but the crosstalk has little to do with the design decisions regarding input clipping, so it's not like there's a design tradeoff there.
   
  I do agree there's too much ego involved and things getting personal.  But unfortunately, good intents and good efforts don't always result in the best designs.  It's best if you call it like you see it, but some of the reactions to that were not ideal.


----------



## Olli1324

A little note about the group buy...
   
  Tomorrow is the last full day before the GB closes and the order is placed.

 Please make sure that your order is placed in time so that you don't miss out. Also, if you haven't paid yet then please make sure that you check the online spreadsheet and send meyour payment asap.

 Many thanks!


----------



## Reticuli2

[size=10pt][size=10pt]AMB made large mistakes in its crosstalk measurements. I don't think it's appropriate to be drawing some equivalency, attempting to defend that mistake, and thereby bring further criticism when AMB itself is no longer attempting to defend it, either. Furthermore, AMB itself says they do not believe moving the pot back has that much of an effect on the specs, and therefore your parallel is even weaker.  It was probably a bad choice on their part to make that argument using the Mini3 as an example, but that’s water under the bridge.  The gain changes in the stated design of the O2 were always capable of being done by anyone building one and the limitations and possible remedies were disclosed pretty early on. That's very different than making measurement mistakes or using a virtual ground. Even if you just made an honest bad analysis with this parallel, if anyone else tries to bring this up again, we should just assume it's some provocateur trying to push the conversation to bashing AMB. It's not necessary. Give it a rest. [/size][/size]
  Quote:


anetode said:


> After reading up a bit more on the design and the background debates, I've noticed an interesting parallel. The power output criticism of nwavguy's O2 amp kind of mirrors his own concerns over the Mini3's power output discrepancies among different test setups. Whereas amb's specs were the culmination of a long design cycle and the optimum setup for the greatest measured performance, nwavguy's methodology aims at the average user and uses average componentry. By amb's exacting standards, the O2 has a very low usable gain range that the predetermined (though since revised) figures would have pushed to clipping. Contrarily, by nwavguy's standards we have an amp that would work across the greatest practical range of headphone impedances and sensitivities to very low distortion, but sacrificing the usable output to meet a very exacting crosstalk spec. A kind of reverse situation from when nwavguy challenged the mini3's crosstalk due to the OPA690 3-channel output decision. So, from an outside perspective it seems like a fanatical resolve was placed to designing to a specific ideal. Personally, I don't quite see how a possible difference from inaudible but otherwise unexemplary crosstalk to an equally inaudible but altogether impressive crosstalk justifies the inherent limitation in design choices. Sure, O2 is a concept amp built on achieving great measurements, but also a budget and wide usability. Both amplifiers appear to be the product of carefully weighed design consideration.
> 
> Unfortunately, what with the unfortunate subjective/objective rift in the head-fi camp and nwavguy's holy crusade and the designer egos, it almost seems like these approaches are somehow adversarial, rather than complementary.


----------



## Reticuli2

[size=10pt]Interestingly, we've known this in the DJ and studio mixer genres for a long time. Some of the best designs in history of "boards" use some of the cheapest, easiest-to-find, and ubiquitous opamps, resistors, and caps. It's what you do with them, and many designers apparently don't know how to "support" the parts with the right stuff immediately adjacent and feeding them the right juice or use good isolated circuit paths. However, you do not want to skimp on the faders, pots, and the power supply on them. And it doesn't hurt if the case weighs almost as much as a tank![/size]
   
  Quote: 





mikeaj said:


> In my opinion one of the most compelling points here is that you can get very accurate performance driving headphones-level impedances with relatively low-cost components.  If you check the op amp article, you'll see that many of the more expensive alternatives seem to behave worse.  This is especially true if you use expensive parts with great specifications for some applications but not so much for audio, and if you aren't diligent in designing the circuits around them properly.
> 
> Maybe I misinterpreted you, but the crosstalk has little to do with the design decisions regarding input clipping, so it's not like there's a design tradeoff there.
> 
> I do agree there's too much ego involved and things getting personal.  But unfortunately, good intents and good efforts don't always result in the best designs.  It's best if you call it like you see it, but some of the reactions to that were not ideal.


----------



## anetode

Quote: 





reticuli2 said:


> [size=10pt][size=10pt]AMB made large mistakes in its crosstalk measurements. I don't think it's appropriate to be drawing some equivalency, attempting to defend that mistake, and thereby bring further criticism when AMB itself is no longer attempting to defend it, either. Furthermore, AMB itself says they do not believe moving the pot back has that much of an effect on the specs, and therefore your parallel is even weaker.  It was probably a bad choice on their part to make that argument using the Mini3 as an example, but that’s water under the bridge.  The gain changes in the stated design of the O2 were always capable of being done by anyone building one and the limitations and possible remedies were disclosed pretty early on. That's very different than making measurement mistakes or using a virtual ground. Even if you just made an honest bad analysis with this parallel, if anyone else tries to bring this up again, we should just assume it's some provocateur trying to push the conversation to bashing AMB. It's not necessary. Give it a rest. [/size][/size]


 

 Yes on the drawing some equivalency, no on attempting to defend anything and no on further criticism. Thank you for acknowledging both the honesty and the badness of my analysis, as well as warning against anyone else offering their input.
   
   
  Quote: 





mikeaj said:


> Maybe I misinterpreted you, but the crosstalk has little to do with the design decisions regarding input clipping, so it's not like there's a design tradeoff there.


 

 Then the misinterpretation was on my behalf, I recall reading that there pot placement was to optimize crosstalk and that it left less flexibility in configuring the design. I'll go back and take another look. Anyway, I agree that O2 is perfectly suited for portable use given the typical DAP voltages where higher gain would not be a problem.
   
  The time to market is also remarkable. Given a couple of months I expect to see a multitude of different builds available from DIYers. And a while after that the new toy syndrome will die down a bit and production might scale to allow for some even nicer pricing.


----------



## koolkat

As I blow at anything DIY, I figured I could buy one of these O2s to test them out but was discouraged by the price..
   
  The maker of O2 said that the cost of parts wouldn't exceed 50 dollars. It's selling for about 120.
   
  Meh.


----------



## deadlylover

Quote: 





koolkat said:


> As I blow at anything DIY, I figured I could buy one of these O2s to test them out but was discouraged by the price..
> 
> The maker of O2 said that the cost of parts wouldn't exceed 50 dollars. It's selling for about 120.
> 
> Meh.


 
   
  Lol, it cost me about $85 to build the "$30" amp, and that's without proper casework or batteries.
  
  It's funny how he compares the value of the "$30" amp to the "$1000+" beta22, where really, it's like $120 to $500. And that's really not so bad when you say hello to diminishing returns and the fact that the beta22 can power speakers and the harder to drive headphones with more headroom.
   
  If anything, it's poor value to pay $120 for $23 worth of chips.


----------



## khaos974

What? 5 times the price of the production cost is rather common for electronics, if anything charging $120 for $75 of components [that's the official cost, battery and case included] is quite reasonable.


----------



## deadlylover

Quote: 





khaos974 said:


> What? 5 times the price of the production cost is rather common for electronics, if anything charging $120 for $75 of components [that's the official cost, battery and case included] is quite reasonable.


 
   
  I wish I lived in a magical land where I didn't have to pay kangaroo shipping costs. I was talking about the costs for me to DIY by the way, you know, since this is a DIY project.


----------



## khaos974

deadlylover said:


> I wish I lived in a magical land where I didn't have to pay kangaroo shipping costs. I was talking about the costs for me to DIY by the way, you know, since this is a DIY project.




Well, it a bit more expensive if you use kangaroo instead of humans as delivery men, the cost of training them alone would inflate delivery costs


----------



## koolkat

I figured the O2 would sell for a rather low price. If the components costed <50 bucks, including the casing and jacks, then 70-80 would be a reasonable price.
  The guy who's offering to build the amps didn't even design the amp, so RnD costs and everything else that factor in to the cost of regular amps are nil..
   
  Meh.
   
  /rant


----------



## Steve Eddy

Quote: 





koolkat said:


> I figured the O2 would sell for a rather low price. If the components costed <50 bucks, including the casing and jacks, then 70-80 would be a reasonable price.
> The guy who's offering to build the amps didn't even design the amp, so RnD costs and everything else that factor in to the cost of regular amps are nil..


 

 While there's no R&D costs, the guy still has to build them, yes? Which means stuffing and soldering the boards, assembling them into the cases, testing them, packaging them for shipping, writing or printing out the shipping labels (and customs forms if it's going overseas), etc., and you think his asking $120 is unreasonable? Really?
   
  se


----------



## Head Injury

Quote: 





koolkat said:


> I figured the O2 would sell for a rather low price. If the components costed <50 bucks, including the casing and jacks, then 70-80 would be a reasonable price.
> The guy who's offering to build the amps didn't even design the amp, so RnD costs and everything else that factor in to the cost of regular amps are nil..
> 
> Meh.
> ...


 
   
  You must not know how this market works 
	

	
	
		
		

		
		
	


	



   
  If NwAvGuy was taking a cut like other developers take, not just for his R&D but his name on the case, this thing would be $200. Then considering how it performs, all it would take is name-dropping some fancy science and pseudo-science, and he could charge even more.


----------



## upstateguy

Quote: 





steve eddy said:


> While there's no R&D costs, the guy still has to build them, yes? Which means stuffing and soldering the boards, assembling them into the cases, testing them, packaging them for shipping, writing or printing out the shipping labels (and customs forms if it's going overseas), etc., and you think his asking $120 is unreasonable? Really?
> 
> se


 

 I thought nwavguy posted that the parts + the case + a front panel from Front Panel Express was $75?


----------



## Steve Eddy

Oh yeah, and I forgot to add that even before all the above happens, he still has to take the time to order the parts (which includes shipping costs), and when they arrive, he has to unpack them, sort them and store them away, and deal with the shipping materials. Then there's the time spent interfacing with his customers. And of course PayPal is going to take their cut out of that $120 so at the end of the day, he doesn't even end up with $120 in his pocket.
   
  se


----------



## Steve Eddy

Quote: 





upstateguy said:


> I thought nwavguy posted that the parts + the case + a front panel from Front Panel Express was $75?


 
   
  I believe so, yes. The original $30 figure that he was first bandying about was just for the board and the parts I believe. But yeah, if you're looking at $75 for parts, case and front panel, asking only $120 for a finished product is downright benevolent if you ask me.
   
  se


----------



## upstateguy

Quote: 





steve eddy said:


> I believe so, yes. The original $30 figure that he was first bandying about was just for the board and the parts I believe. But yeah, if you're looking at $75 for parts, case and front panel, asking only $120 for a finished product is downright benevolent if you ask me.
> 
> se


 

 Downright Benevolent !  Now all it has to do is actually sound good........  
	

	
	
		
		

		
		
	


	



   
  Speaking of sounding good, are there any price figures 'bandying about' for the transformer amp?
   
  e


----------



## koolkat

In the early stages of production, Nwav said the cost of the components would be _very_ low. $30 ish iirc. 
   
  I figured it would be a good competitor in the sub $100 portable amp market. E11, Cmoys, PA2V2, A10 all retailing at about 70-90 bucks.
   
  Re-read the latest article again, and he said the average cost of production (casing, jacks, components, shipping, putting everything together) would be roughly below $150.
   
   
  I suppose $150 is very little since the O2 can supposedly power many high impedance cans sufficiently. Especially when compared to some Ray Samuel amps and Fostex HP-P1, etc. 
   
  Hmm.


----------



## i_djoel2000

Quote: 





koolkat said:


> I figured the O2 would sell for a rather low price. If the components costed <50 bucks, including the casing and jacks, then 70-80 would be a reasonable price.
> The guy who's offering to build the amps didn't even design the amp, so RnD costs and everything else that factor in to the cost of regular amps are nil..
> 
> Meh.
> ...


 

 just try to build one for yourself..complete with the enclosure and custom panel, we'll see how much it cost you at the end. i bet it will only slightly below $100


----------



## Head Injury

Quote: 





koolkat said:


> In the early stages of production, Nwav said the cost of the components would be _very_ low. $30 ish iirc.


 

 The components being the board and all the circuitry. Not the enclosure or the batteries. It's funny how that stuff actually costs more than the "real" amp, huh? Makes you wonder about all these $500+ amps, what's in them and what it all costs.
   
  ...how safe would it be to build the desktop version without an enclosure?


----------



## deadlylover

Quote: 





i_djoel2000 said:


> just try to build one for yourself..complete with the enclosure and custom panel, we'll see how much it cost you at the end. i bet it will only slightly below $100


 

 Depends where you live, it would cost me AT LEAST $120 to build one without taking advantage of any group buys and what not.
   
  Mouser wants 30$ to ship internationally, 20$ more than the $10 estimate from the magical $100 BOM figure. The other 2 vendors will probably charge an extra $15 between the two of them. A 230V wallwart is about $24 (nwavguy approved =P) which is almost $20 more than the $5 one in the BOM.
   
  Wow that's like ~$50 bucks more than you lucky folk who don't have to spring out for kangaroo shipping.
  
  Quote: 





head injury said:


> The components being the board and all the circuitry. Not the enclosure or the batteries. It's funny how that stuff actually costs more than the "real" amp, huh? Makes you wonder about all these $500+ amps, what's in them and what it all costs.
> 
> ...how safe would it be to build the desktop version without an enclosure?


 
   
  The first Obj2 built (except for the designer) lives in the cardboard mouser box that the parts came in ^^. I also could not for the life of me find the proper AC wall transformer, so I just threw a normal transformer in the box and slapped on an IEC socket, ahahahha.
   
Safety was obviously my top priority Safety might have been one of my priorities.


----------



## i_djoel2000

Quote: 





deadlylover said:


> Depends where you live, it would cost me AT LEAST $120 to build one without taking advantage of any group buys and what not.
> 
> Mouser wants 30$ to ship internationally, 20$ more than the $10 estimate from the magical $100 BOM figure. The other 2 vendors will probably charge an extra $15 between the two of them. A 230V wallwart is about $24 (nwavguy approved =P) which is almost $20 more than the $5 one in the BOM.
> 
> Wow that's like ~$50 bucks more than you lucky folk who don't have to spring out for kangaroo shipping.


 

 actually i was just teasing koolkat, regardless how much the exact cost is 
	

	
	
		
		

		
			







   
  but i have done quick calculation with farnell, it costs me almost $100 with the enclosure, & custom front panel


----------



## Reticuli2

And here I thought_ I_ was a cheapskate!


----------



## mikeaj

In the US, the PCB (through group buy, so it hasn't been made yet), all components that go on the PCB, the AC/AC wall transformer, and the enclosure, plus shipping for all of those, have cost me something between $50-55.  I forget what the exact amounts were.  The enclosure itself was like $16 including shipping.  The enclosure (B2-080BK so black version to match most of my other stuff) does feel and look nice though.
   
  That $50-55 figure does not include the front panel or batteries.


----------



## arirug

I think Mr.Slim offers the O2 for a very good price! And it is great to be of the first people getting a completely new design from the very educated inventor of the O2.


----------



## Maxvla

Waiting for desktop version (unless I get the JH3A).


----------



## Satellite_6

<$150 built or <$100 DIY sounds good to me. . . about half the cost of my current amp. Me want. I just hope the desktop version is still fairly cheap (I imagine it will be).


----------



## i_djoel2000

Quote: 





satellite_6 said:


> <$150 built or <$100 DIY sounds good to me. . . about half the cost of my current amp. Me want. I just hope the desktop version is still fairly cheap (I imagine it will be).


 


  desktop version should be cheaper since we can omit the batteries from BOM


----------



## koolkat

That's what I thought..
   
  Quote: 





head injury said:


> The components being the board and all the circuitry. Not the enclosure or the batteries.* It's funny how that stuff actually costs more than the "real" amp, huh?* Makes you wonder about all these $500+ amps, what's in them and what it all costs.


 

 Good luck and have fun with your O2s, those who have ordered them.


----------



## redminibus

HI everyone my first post here. 
  Just want to say I built my O2 with total cost of $50 (include case, battery and adapter ) and 6 hours of my Sunday afternoon( lots of questions asked). And this is my first time ever building an amp or soldering any PCB. so I'm sure any experienced DIYer can be able to finish with less than half the time I used.


----------



## i_djoel2000

Quote: 





redminibus said:


> HI everyone my first post here.
> Just want to say I built my O2 with total cost of $50 (include case, battery and adapter ) and 6 hours of my Sunday afternoon( lots of questions asked). And this is my first time ever building an amp or soldering any PCB. so I'm sure any experienced DIYer can be able to finish with less than half the time I used.


 

 where did you source your components? i guess farnell sells stuffs more expensive than other places by a pretty big margin, then.. i


----------



## Willakan

Everywhere outside the US I looked at for component sourcing (in the UK myself) is more expensive, it's just a matter of degrees of overpriced. To be fair though, this amplifier is still cheaper than everything else I looked at.


----------



## mikeaj

Quote: 





i_djoel2000 said:


> where did you source your components? i guess farnell sells stuffs more expensive than other places by a pretty big margin, then.. i


 

 I'm curious where the PCB came from and how much it cost, if you don't mind me asking!


----------



## i_djoel2000

Quote: 





mikeaj said:


> I'm curious where the PCB came from and how much it cost, if you don't mind me asking!


 

 you can head over to diyaudio.com. there's currently a pcb group buy over there, but i'm not sure whether it's closed or not


----------



## Willakan

The group buy is not closed, as NwAvGuy is waiting on a prototype PCB to fit a wider range of pots. Once the performance of that has been verified, the group buy will close soon after. PCB arriving this week, so not a huge amount of time left.


----------



## fishski13

Quote: 





willakan said:


> The group buy is not closed, as NwAvGuy is waiting on a prototype PCB to fit a wider range of pots. Once the performance of that has been verified, the group buy will close soon after. PCB arriving this week, so not a huge amount of time left.


 


  looks like olli sorted out the issues with Paypal as well.


----------



## Lil' Knight

^ oh, that's horrible PP drama...

I have a couple of boards right here but haven't got chance to find the parts. Wallwarts are dirt cheap here, something like $3/ea, and I can pick up locally.


----------



## mikeaj

Quote: 





i_djoel2000 said:


> you can head over to diyaudio.com. there's currently a pcb group buy over there, but i'm not sure whether it's closed or not


 
   
  Ah thanks, I was just curious though.  I was already on the group buy at diyaudio.


----------



## maverickronin

I've got a short (by my standards anyway...) review posted here if anyone's interested.


----------



## chinesekiwi

Quote: 





arirug said:


> I think Mr.Slim offers the O2 for a very good price! And it is great to be of the first people getting a completely new design from the very educated inventor of the O2.


 


  NwAvguy is the inventor, Mr. Slim is just offering his services for a build. Anyway, same here


----------



## arirug

Yeah! I know NwAvguy is the inventor, but I thought I was not allowed to mention his name here


----------



## Willakan

Well, the GB is now well over 500 boards - 620 to be precise...


----------



## svyr

wonder if this can handle K340 (360ohm, 94 dB / mW) or K240DF (600ohm, 88 db/mW)... without horrible distortion, at high enough volumes or fr sags...


----------



## Soaa-

svyr said:


> wonder if this can handle K340 (360ohm, 94 dB / mW) or K240DF (600ohm, 88 db/mW)... without horrible distortion, at high enough volumes or fr sags...




Should handle the K 240 DF just fine. FR sags only occur with low impedance headphones and/or high internal impedance amps, and this is the opposite case. Distortion only occurs when there isn't sufficient voltage swing, and in this case, there is. I don't think the K 240 DF will be much of a problem.


----------



## svyr

soaa- said:


> Should handle the K 240 DF just fine. FR sags only occur with low impedance headphones and/or high internal impedance amps, and this is the opposite case. Distortion only occurs when there isn't sufficient voltage swing, and in this case, there is. I don't think the K 240 DF will be much of a problem.




interesting... i heard pretty odd things from amps near peak output, trying to drive k340 (fr wise)... But anyway, 240DF is harder to drive, so if the amp can take it, then it can take both


----------



## Willakan

Output power for the O2 is an ample 613mW at 33 ohms, but drops to 355mW at 150ohms. Looking at your headphones, you'll have absolutely no issues with the K340 - that only needs about 120mW worst case. With the K240 you'll be fine with most recordings, but could conceivably have problems with quieter recordings at higher volumes - but nothing ReplayGain can't fix.
   
  EDIT: Strikes me this amp would get on wonderfully with the LCD2s. Plenty loud with prettymuch anything and power to spare...


----------



## svyr

willakan said:


> Output power for the O2 is an ample 613mW at 33 ohms, but drops to 355mW at 150ohms. Looking at your headphones, you'll have absolutely no issues with the K340 - that only needs about 120mW worst case. With the K240 you'll be fine with most recordings, but could conceivably have problems with quieter recordings at higher volumes - but nothing ReplayGain can't fix.




Thanks. Well, I no longer have either, just curious, since those two are the most power hungry dynamic HP I know of (HE6 ortho is probably more so, but I'm not sure). I always shoot myself in the leg with the old classical music dvds... no replay gain there lol. (vol leveling plugins, or vanilla gain via eq i spose)


----------



## Armaegis

Quote: 





willakan said:


> Output power for the O2 is an ample 613mW at 33 ohms, but drops to 355mW at 150ohms. Looking at your headphones, you'll have absolutely no issues with the K340 - that only needs about 120mW worst case. With the K240 you'll be fine with most recordings, but could conceivably have problems with quieter recordings at higher volumes - but nothing ReplayGain can't fix.
> 
> EDIT: Strikes me this amp would get on wonderfully with the LCD2s. Plenty loud with prettymuch anything and power to spare...


 

 I've owned a few K340s and tried them out on numerous amps and receivers of all price points. Most of them had ample power, but very few sounded good with them and the K340 is still a weird and difficult headphone to drive. I have no beef against the O2, but I would hesitate to make the statement that it can drive such and such based purely on the numbers.


----------



## Soaa-

armaegis said:


> I've owned a few K340s and tried them out on numerous amps and receivers of all price points. Most of them had ample power, but very few sounded good with them and the K340 is still a weird and difficult headphone to drive. I have no beef against the O2, but I would hesitate to make the statement that it can drive such and such based purely on the numbers.




The K 340 is an oddball, being dynamic/electret dual driver cans. Expected performance can be extrapolated for simple configurations such as the K 240 DF though.


----------



## mikeaj

Actually I think the designer would say that the K240DF is at the fringe or outside the range of the O2.  You can only get 7.3V rms out (88 mW) on AC power into 600 ohms, at 1% THD; more like 7V rms (82 mW) if you're expecting it to maintain low THD like under 0.01%. 
   
  So with either figure that's about 107 dB SPL with 88 dB SPL / 1 mW headphones.  NwAvGuy mentions 110 dB SPL as the target, though that's very debatable.


----------



## SpaceTimeMorph

Another review posted, for those curious: http://www.head-fi.org/t/571317/small-objective-2-review#post_7746496


----------



## koolkat

I believe there's a debate somewhere on the boards about how a headphone should sound when it is well amplified versus an adequately amplified headphone.
   
  Some swear with good amplification, the soundstage expands, there is less congestion, etc. Is that true for high impedance headphones? From what I recall, an insufficiently amped headphone will clip at high volume. So that should be the sole determinant of a good amp right? To be able to drive the headphones without clipping. Or is a transparent amp not _unleashing the full potential of the headphones_? Scientifically speaking of course.
   
  Hope ^ makes sense.


----------



## Soaa-

An ideal amp is simply signal in, stronger signal out. Amps that add their own coloration are technically not amps anymore, but filters.


----------



## Steve Eddy

Quote: 





> An ideal amp is simply signal in, stronger signal out. Amps that add their own coloration are technically not amps anymore, but filters.


 
   
  Gimme some filters, baby! And make 'em go to "11"! 
	

	
	
		
		

		
			




   

   
  se


----------



## Willakan

Quote: 





koolkat said:


> I believe there's a debate somewhere on the boards about how a headphone should sound when it is well amplified versus an adequately amplified headphone.
> 
> Some swear with good amplification, the soundstage expands, there is less congestion, etc. Is that true for high impedance headphones? From what I recall, an insufficiently amped headphone will clip at high volume. So that should be the sole determinant of a good amp right? To be able to drive the headphones without clipping. Or is a transparent amp not _unleashing the full potential of the headphones_? Scientifically speaking of course.
> 
> Hope ^ makes sense.


 

  There is also a debate on how headphones sound with the "stock" cable versus one made with Iranian irradiated unicorn hair (or silver, or 99.999999% pure copper...ect). An amplifier can either adequately amplify a headphone to provide music, including peaks, of a given volume, or it can't. Beyond that, unless it's doing bizarre things to the audio (which is indicative of a terrible design IMO) there isn't really any room for improvement.


----------



## mikeaj

Sure there's always room for improvement, but whether or not that improvement is audible is a different matter.

An insufficient amp (with the headphones and volume you set) will clip, not the headphones. Or if you listen really really loud, the headphones themselves can run out of excursion and clip, but I don't think you were talking about that.

In this context, people say an amp is "transparent" if the output is so close in shape to the original (may be larger or smaller, depending on the volume set) that you can't tell them apart. From the perspective of achieving high fidelity reproduction, the goal is an amp that outputs something that matches the input as close as possible, regardless of what the input is as long as it's in the audio frequency range and regardless of the headphones. The O2 was designed towards that objective (har har).

Some amps and other devices are designed to intentionally add distortions on top of the signal, which can thicken the sound or otherwise alter the original. Arguably this can make things sound better, but that's a different design goal for sure, and one that's hard to define since different people will think different things sound better.


----------



## SpaceTimeMorph

That Iranian unicorn hair is some good stuff.  You should see how it sounds after a 5 year liquid nitrogen bath.  Brings out the mid-range like none other.


----------



## deadlylover

Easy there guys, it would be very short sighted to assume that anything that _doesn't_ sound like the Obj2 _must _be coloured/crap.
   
  Considering I'm the only living person who has compared it with a decent amp, you guys don't even have an opinion.


----------



## Willakan

Quote: 





deadlylover said:


> Easy there guys, it would be very short sighted to assume that anything that _doesn't_ sound like the Obj2 _must _be coloured/crap.
> 
> Considering I'm the only living person who has compared it with a decent amp, you guys don't even have an opinion.


 
  I'm afraid as far as opinions go, I regularly recommend stuff based entirely on the numbers (not manufacturer specs or RMAA stuff obviously)
  It may seem short-sighted, but neutrality isn't subjective IMHO. To turn it round, it would be very strange to assume that things that sound different than the O2 do not measure significantly differently - and the only audible type of difference you can get (as the modern body of evidence stands on the subject), assuming you're not trying to drive an astoundingly insensitive headphone, is deviation from neutrality - which involves objectively worse measurements.


----------



## deadlylover

Quote: 





willakan said:


> I'm afraid as far as opinions go, I regularly recommend stuff based entirely on the numbers (not manufacturer specs or RMAA stuff obviously)
> It may seem short-sighted, but neutrality isn't subjective IMHO. To turn it round, it would be very strange to assume that things that sound different than the O2 do not measure significantly differently - and the only audible type of difference you can get (as the modern body of evidence stands on the subject), assuming you're not trying to drive an astoundingly insensitive headphone, is deviation from neutrality - which involves objectively worse measurements.


 
   
  I'm with you 100% on the "amps that measure the same should sound the same", but that's just not my personal experience. I'm more than happy to admit that I'm an idiot, but does no one really want to just work together and figure this out?
   
  The only reason why I built the Obj2 in the first place, is to see how it sounds compared to the well regarded beta22. I really went out of my way to try and figure this out, but it does suck living in fear of being shot down by the sound science gang. 
	

	
	
		
		

		
		
	


	



   
  Until you actually get some first hand experience, it really seems like you have no idea what you are talking about. I don't mean that in a bad way, but come on man, as a scientist, put your balls against the wall and start doing something productive. You know what they say, if you aren't part of the solution, you're part of the problem.
   
  It's fine if you don't though, because at the end of the day, your opinion is just as worthless as mine. 
	

	
	
		
		

		
		
	


	



   
  You don't bother because you know it will lead you nowhere? Balls to it man, I've never heard of such a closed minded "scientist".


----------



## koolkat

So all that babble I recently saw in another subforum about DT880 600 Ohm having bad soundstage when underamped is baseless? ok.


----------



## mikeaj

koolkat said:


> So all that babble I recently saw in another subforum about DT880 600 Ohm having bad soundstage when underamped is baseless? ok.




It's quite possible for a worse amp to have worse channel separation (L and R channels leaking together) and significant phase shift across the frequency range. Those things should effect the perception of soundstage. Also, higher volumes tend to sound better, and it's easier to hear details if everything is louder, which a more powerful amp can accommodate--not to mention, if louder _and _less distorted. So I'd say "bad soundstage" is a subjective thing that you should listen for yourself about, but there are some things one amp could do differently than another, that may impact the sound in a real way. This may or may not result in a consistent perception of different soundstage.


----------



## Willakan

Quote: 





deadlylover said:


> You don't bother because you know it will lead you nowhere? Balls to it man, I've never heard of such a closed minded "scientist".


 
  Few things:
  1. I make no claim to being a scientist. Rationalist, quite possibly. I make decisions on the balance of evidence but lack the time and money to purchase monstrously expensive products to DBT them.
  2. The "I might be an idiot" bit is a bit of a misconception - please don't be amongst the many who take any suggestion of bias as an insult, rather than an inevitable part of being human.
  3. Audible differences to the Beta22 - aside from the unavoidable bias of it being a sighted test (again, don't take as insult/denigration) it is entirely possible that the Beta22 doesn't measure very well. The given crosstalk measurements are interesting - for all the wrong reasons.
  4. No idea what I'm talking about/Closed minded: As we seem to be coming at this with rather different approaches, let me lay down how I see it. Science in its present and undoubtedly imperfect state suggests that audible differences between 2 amplifiers which both measurably excel do not exist. Leaving DBTs and the like out of it (they are constantly misinterpreted as the cornerstone of the objectivist argument rather than simply an approach to try to win over the pseudo-objectivists whilst allowing them to still hold a fair chunk of their beliefs about the vital importance of human perception in every stage of design of anything in the audio chain) I have yet to see any compelling evidence that this is not the case, hence I believe it (belief not perhaps being the best choice of words). Any perceived differences can be adequately explained by current scientific ideas regarding unavoidable human bias.
  If someone presents any test with reproducible results that suggest such differences exist and are not due to bias, I will quite happily do a complete u-turn and not judge myself a fool for doing so. However, as it stands, there are more papers in the field of parapsychology claiming to prove the existence of telepathy than there are claiming to prove differences between practically identically measuring equipment. As it happens, the results from the tests in those papers proved impossible to repeat and their experimental design flawed. We don't even HAVE any study laying down a consistent set of "audiophile" beliefs - so what exactly am I meant to think?


----------



## kiteki

TL;DR someone made a headphone amp.


----------



## Maxvla

I'd like to know what the guy ringing the bell is standing on.


----------



## deadlylover

Quote: 





willakan said:


> Few things:


 
   
  Thanks for clarifying your position, I really have no problem with it at all, because you speak nothing but a large amount of sense.
   
  It just pains me a little that the rationalists such as yourself don't make any effort to confirm your beliefs(yeah, wrong word lol). I never really meant that the current science is incorrect or anything like that, because chances are, it isn't. It's not about being right or wrong, but don't you think that it's a little unfair that you are simply 'guessing' as to what an amp sounds like? The proper use for science IMO in this somewhat subjective hobby is to back up your findings, because let's be fair here, until you've heard something, you just have no idea what it sounds like.
   
  I'll have to apologise for coming off a little harsh. In hindsight, it's just not practical for everyone to do their own testing and what not, for reasons you've stated. For me, the sea of subjective impressions from all the different amps was enough to inspire me to do something about it and try figure things out for myself. Unfortunately, I've gotten nowhere of course, but hey, at least I now know which end of a soldering iron to hold =P.
   
  Quote: 





kiteki said:


> TL;DR someone made a headphone amp.


 
   
  No, someone made the best headphone amp ever, and anything that sounds better must be worse.


----------



## kiteki

Quote: 





maxvla said:


> I'd like to know what the guy ringing the bell is standing on.


 

 That's NwAvGuy, he doesn't need to be standing on anything.


----------



## Armaegis

Quote: 





maxvla said:


> I'd like to know what the guy ringing the bell is standing on.


 


  I thought he was a centaur at first.


----------



## Beefy

Quote: 





deadlylover said:


> No, someone made the best headphone amp ever, and anything that sounds better must be worse.


 

 Very astute.


----------



## Head Injury

Quote: 





deadlylover said:


> No, someone made the best headphone amp ever, and anything that sounds better must be worse.


 

 It's not the best headphone amp ever. It's the best headphone amp any listener would realistically need from an objective standpoint.
   
  There are amps that are more expensive and will be subjectively better because of it. There are amps with high amounts of distortion, coloration, and output impedance that will be subjectively better when paired with certain headphones. The O2 is objectively better than those amps. However, it is not objectively better than all amps. There are amps that measure better into certain loads. There are amps that output a lot more power. Neither of those things are really necessary though, because the O2 will drive almost all headphones to high volume and do so with distortion consistently below audibility.
   
  Someone will undoubtedly make something better, objectively or subjectively. There's not much reason to from a _playback_ perspective.


----------



## Armaegis

Quote: 





head injury said:


> It's the best headphone amp any listener would realistically need from an objective standpoint.


 


  Wait wait wait... are you saying we audiophiles have _realistic_ needs?


----------



## Willakan

Quote: 





deadlylover said:


> *...because let's be fair here, until you've heard something, you just have no idea what it sounds like.*


 
  I fear we are destined to disagree forever when it come to amplifiers and DACs
	

	
	
		
		

		
		
	


	




.
  Seriously, as we are approaching this from completely different and entirely opposed angles I doubt we're going to get beyond the level of polite appreciation of each other's opinions.
   
  I'm afraid that as the current balance of evidence stands, the second clause of your tongue-in-cheek final statement (unquoted) holds true for me (replacing "better" with different), at least as far as accurate audio production is concerned (with the average crapload of disclaimers regarding design limits to stop people going HA! IT SOUNDS DIFFERENT (into my 70db/mw headphones)). 
   
  As I said, different and wholly irreconcilable angles. (would put a smiley here, but I try to limit myself to one smiley per post)


----------



## deadlylover

Quote: 





armaegis said:


> Wait wait wait... are you saying we audiophiles have _realistic_ needs?


 
   
  Yeah, don't you listen to your headphones from across the hallway too? 
	

	
	
		
		

		
		
	


	



   
  Just wait a sec until I mod this thing to drive Stax. Then, and only then, will it be the best headphone amp ever.
  
  O2 driving an O2, I hope nothing bad happens to me.


----------



## Head Injury

Quote: 





armaegis said:


> Wait wait wait... are you saying we audiophiles have _realistic_ needs?


 

 Well, our ears do. Our brains might not, but I never trust my brain.
  
  Quote: 





deadlylover said:


> Yeah, don't you listen to your headphones from across the hallway too?
> 
> 
> 
> ...


 

 You're going to divide by zero, aren't you?


----------



## Armaegis

Quote: 





deadlylover said:


> O2 driving an O2, I hope nothing bad happens to me.


 

 Well it might cause a rift in the space-time continuum, or unleash the singularity upon humanity, or trash your headphones or something like that. No biggie.


----------



## Armaegis

Quote: 





deadlylover said:


> Yeah, don't you listen to your headphones from across the hallway too?


 

 My current ortho transplant using an SFI driver... actually, yes I do. It's kinda ridiculous that thing.


----------



## kiteki

Head Injury, Beefy and deadlylover have great avatars.
   
  p.s.


----------



## deadlylover

Quote: 





head injury said:


> You're going to divide by zero, aren't you?


 
   
  That sounds a lot more realistic compared to my current plan:
   
  Step 1: Build DIY T2
  Step 2: Strap DIY T2 to O2 with duct tape
  Step 3: ?????????
  Step 4: Profit
   
  Best dynamic amp ever + best stat amp ever = best headphone amp ever.
   
  That's so stupid it's smart.
   
  kiteki, looking goooood as always. ^^


----------



## Beefy

Quote: 





> Originally Posted by *deadlylover* /img/forum/go_quote.gif
> 
> Just wait a sec until I mod this thing to drive Stax. Then, and only then, will it be the best headphone amp ever.


 

 My M3 drives my Lambdas through an SRD7-SB to seriously earsplitting levels just fine. Sounds better than a t-amp while doing it too.


----------



## wink

Quote: 





> You're going to divide by zero, aren't you?


 
   
  Quote: 





> Well it might cause a rift in the space-time continuum, or unleash the singularity upon humanity, or trash your headphones or something like that. No biggie.


 
  Nothing will come of it.


----------



## wink

Quote: 





> That sounds a lot more realistic compared to my current plan:
> 
> Step 1: Build DIY T2
> Step 2: Strap DIY T2 to O2 with duct tape
> ...


 
  What about the new Stax SR009..???
  Seems to wipe the floor with the different O2's....


----------



## deadlylover

Quote: 





wink said:


> What about the new Stax SR009..???
> Seems to wipe the floor with the different O2's....


 
   
  I'll pick one up when I head to Japan for Christmas, it's a little expensive, heh, so I don't really want to buy it blind. I think it will pair nicely with the DIY T2.
   
  DIY T2 > SR-009, I can think of no better rig to use with my ~96kbps mp3's.
   
  It's gonna be fun trolling at the next years Sydney meet. 2x DIY T2, Blue Hawaii, 2x KGSSHV. Oh, I'll bring the Obj2 and the beta22 as well, ahahah.


----------



## Maxvla

Anyone who is making one of these going to be at RMAF? Love to give it a listen with IEMs. Thanks.


----------



## Willakan

Quote: 





deadlylover said:


> Oh, I'll bring the Obj2 and the beta22 as well, ahahah.


 

 Put them under a cloth, volume match and make people guess which is which


----------



## nattonrice

Quote: 





deadlylover said:


> I'll pick one up when I head to Japan for Christmas


 

 Do you know where you'll be and roughly when?
  IF I get this stupid thesis done in time I may head over in early Jan.


----------



## i_djoel2000

Quote: 





willakan said:


> Put them under a cloth, volume match and make people guess which is which


 

 i'm really looking forward to this. LOL


----------



## kiteki

Quote: 





willakan said:


> Put them under a cloth, volume match and make people guess which is which


 

 The best post you've made, right there.


----------



## kiteki

Except I think a shoebox with extension cables coming out of both is better.


----------



## tomjtx

Yes, but everyone will just say the shoebox degraded the sound of both amps so the comparison is invalid.


----------



## kiteki

What if it's a shoebox from santa claus workshop, that was once for sale at Harrods? and touched by Marilyn Monroe?


----------



## pocketrocket

Maybe someone could build a high quality shoebox that wouldn't smear the signal, and wouldn't have any nasty properties of the cognitive dissonance of a nasty and bad-sound-looking DIY box. Obviously it should be from a company that has ignorant zealots for fans too and it should be discussed about under the full supervision of the sponsorship-ran gestapo to gain the full benefits of having a nice looking box that does nothing.

 I'm not implying anything and neither is this sarcasm, I am 100% sincere it would actually improve the perceived audio quality of both products (and their sales) and nothing else matters.


----------



## kiteki

I can just imagine deadlylover 'trolling' everyone at a meet with his secret boxes.
   
  HAHA U NO LIE MY BOX LAI LAI LAI *meet catches on fire*


----------



## Armaegis

Quote: 





willakan said:


> Put them under a cloth, volume match and make people guess which is which


 

  
  And I'll bet if you put the O2 vs the e6 in the shoebox people might not be able to tell the difference there either.


----------



## Willakan

Cover the shoebox with LessLoss Blackbody quantum filter boxes to counteract the effect of the shoebox field. 6Moons says they work great!


----------



## kiteki

The Hifiman Express HM-101 has EM interference but I actually like it, it means I no longer miss calls to my mobile phone while I'm listening to music? 
	

	
	
		
		

		
		
	


	



   
  It picks up my phone signals from a good distance.
   
   
  Anyway the HM-101 is a great DAC/Amp and I'm curious how it stacks up against the objective2?


----------



## Head Injury

Quote: 





kiteki said:


> Anyway the HM-101 is a great DAC/Amp and I'm curious how it stacks up against the objective2?


 

 Definitely not as powerful, so no driving the HE-6 
	

	
	
		
		

		
		
	


	



   
  Unfortunately not much more can be said about it because the measurements on Head-Direct are too vague.


----------



## limpidglitch

Quote: 





head injury said:


> Definitely not as powerful, so no driving the HE-6
> 
> 
> 
> ...


 


  And suspiciously optimistic.
   
  That 96dB SNR seems very 'thoretical'


----------



## kiteki

Perhaps the measurements of the TDA1308 and PCM2702E would help?
   
  I haven't pried it open to look at what else is inside.
   
  I know the O2 will be be a better amp, was just thinking on price to performance ratio and such.
   
  Maybe Hifiman HM-101 DAC -> Objective2 Amp = win?


----------



## Willakan

In moderately exciting news, the DIYAudio GB has now closed at 750 boards. In a few short weeks, we will have more "impressions" of this amp than we know what to do with.
  I hope at least one person calls it "clinical" or "unmusical", so I can laugh at them.


----------



## Armaegis

I'm hoping for some negative reviews. It brings balance to the force.


----------



## kiteki

Quote: 





armaegis said:


> I'm hoping for some negative reviews. It brings balance to the force.


 

 That's why I feel automatically inclined to hate stuff like the RE0.


----------



## purrin

Quote: 





willakan said:


> In moderately exciting news, the DIYAudio GB has now closed at 750 boards. In a few short weeks, we will have more "impressions" of this amp than we know what to do with.
> I hope at least one person calls it "clinical" or "unmusical", so I can laugh at them.


 

 Doubt it, I built a prototype amp a few years ago with the same configuration of paralleled output NJM4556 chips. Those chips do sound nice in the output. It's was purely a subjective and accidental selection on my part though. I didn't set out to design it using objective measurements. I'm glad someone was able to partially validate my subjective impression with objective measurements.


----------



## maverickronin

Quote: 





armaegis said:


> I'm hoping for some negative reviews. It brings balance to the force.


 

 Well, its not perfect.  I'm sure some people will use some headphones it legitimately can't drive to decent levels and not like it as much because of that.
   
  It handles most 'phones just fine which I think is pretty cool for what the parts cost.  There has been talk about increasing the voltage of the power supply rails on the desktop version and/or using higher current buffer chips to get enough power to be able to cover everything but what it comes down to is that the necessary parts will raise the cost quite a bit for everyone and only benefit a small number of users so the idea runs counter to the O2's design goals.
   
  Its not for everyone's collection of 'phones, but it should be for most people's.


----------



## SpaceTimeMorph

^ I'm still waiting on the desktop flavor...


----------



## upstateguy

Quote: 





spacetimemorph said:


> ^ I'm still waiting on the desktop flavor...


 


  I'll take anything I can get..................


----------



## Hennyo

Quote: 





deadlylover said:


> I'll pick one up when I head to Japan for Christmas, it's a little expensive, heh, so I don't really want to buy it blind. I think it will pair nicely with the DIY T2.
> 
> DIY T2 > SR-009, I can think of no better rig to use with my ~96kbps mp3's.
> 
> It's gonna be fun trolling at the next years Sydney meet. 2x DIY T2, Blue Hawaii, 2x KGSSHV. Oh, I'll bring the Obj2 and the beta22 as well, ahahah.


 

 Sorry, I have read no longer through this thread... Let me just be the first to say, I'm buying a ticket to Sydney. 
	

	
	
		
		

		
		
	


	




 It'd be radical. When are you bringing these bad boys out to play again?!


----------



## deadlylover

Quote: 





nattonrice said:


> Do you know where you'll be and roughly when?
> IF I get this stupid thesis done in time I may head over in early Jan.


 
   
  I'll be in Tokyo from about 21st Dec to the 5th of Jan, it should be short and sweet ^^. Best of luck with the thesis =P (and the beast).
  
  Quote: 





willakan said:


> Put them under a cloth, volume match and make people guess which is which


 
   
  You are just full of good ideas, I'll remember to do that when the time comes ahahahah. I'll also throw together a desktop version one, bridged, for more power. You know, it has to be a fair comparison with a balanced b22. 
	

	
	
		
		

		
		
	


	



  
  Quote: 





hennyo said:


> Sorry, I have read no longer through this thread... Let me just be the first to say, I'm buying a ticket to Sydney.
> 
> 
> 
> ...


 
   
  Dunno, I hope the meet will be sometime mid-yearish, everything should be done by then. Hopefully, I can pull off a n3rdling and let the Stax blow people away. There probably won't be many people at the meet, so everyone should have heaps of head time with the Stax.


----------



## wink

Quote: 





> Dunno, I hope the meet will be sometime mid-yearish, everything should be done by then. Hopefully, I can pull off a n3rdling and let the Stax blow people away. *There probably won't be many people at the meet, *so everyone should have heaps of head time with the Stax.


 
  You talking about a normal meet or mini-meet?


----------



## deadlylover

Quote: 





wink said:


> You talking about a normal meet or mini-meet?


 
   
  Normal one, how many were there last time?
   
  I was kinda comparing it to the bay area meet a while back, that one had like a hundred or so?? (I MAY BE COMPLETELY OFF LOL)
   
  Fuzzy memory, I don't even know anymore......


----------



## kiteki

The looks of the Blue Hawaii are spinning me out.
   
  Does it have a sound to match?


----------



## deadlylover

Quote: 





kiteki said:


> The looks of the Blue Hawaii are spinning me out.
> 
> Does it have a sound to match?


 
   
  Well, some say it's the best commercial stat amp you can buy at the moment.
   
  Mine won't be anywhere as pretty though, =P.


----------



## kiteki

Deadlylover I used to use an SR-404 Signature with SRM-300, are the upper echelons of STAX much different than what I used?


----------



## deadlylover

Yep, they're completely different ^^.


----------



## kiteki

Curse you, audio satan.
   
  I just bought the Tesla, but I'll bit your apple, some other time!


----------



## Willakan

As wonderful at everything Stax doubtless are, can you stop discussing them in my thread? They're making me feel poor...


----------



## deadlylover

Quote: 





willakan said:


> As wonderful at everything Stax doubtless are, can you stop discussing them in my thread? They're making me feel poor...


 
   
  That's what happens when somebody takes up the name "O2" when an O2 has already walked the earth for over a decade. 
	

	
	
		
		

		
		
	


	



   
  Aahah don't worry, plenty of chatter will come when the boards run reaches people's hands.


----------



## khaos974

deadlylover said:


> That's what happens when somebody takes up the name "O2" when an O2 has already walked the earth for over a decade.
> 
> 
> 
> ...




Or even logner is you consider dioxygen


----------



## samsquanch

Does anyone know when the boards are supposed to ship?


----------



## MrSlim

The person running the group buy posted that the order was placed on the 19th with a 12 day delivery time to him, plus whatever time it takes to have them redistributed (1-2 weeks?) so probaby Mid October..
  He has people doing re-distribution for him on the various continents, to ease shipping costs..


----------



## dogears

You're all over the place my dear 
	

	
	
		
		

		
		
	


	



  
  Quote: 





kiteki said:


> The looks of the Blue Hawaii are spinning me out.
> 
> Does it have a sound to match?


----------



## alphaman

From Xin's site (SuperMacro IV):
   

   
  From Nw...Guy's site:
   


 [tr] [td] [size=10pt]*Measurement*[/size][/td] [td] *[size=10pt]Cmoy[/size] 13 dB Gain*[/td] [td] [size=10pt]*Cmoy 0 dB Gain*[/size][/td] [td] [size=10pt]*AMB Mini3*[/size][/td] [/tr] [tr] [td] [size=10pt]Frequency Response[/size][/td] [td] [size=10pt]+/- 0.1 dB Excellent[/size][/td] [td] [size=10pt]+/- 0.1 dB Excellent[/size][/td] [td] [size=10pt]+/- 0.1 dB Excellent[/size][/td] [/tr] [tr] [td] [size=10pt]THD 1 Khz 150 Ohms[/size][/td] [td] [size=10pt]0.002% Excellent[/size][/td] [td] [size=10pt]0.001% Excellent[/size][/td] [td] [size=10pt]0.002% Excellent[/size][/td] [/tr] [tr] [td] [size=10pt]THD 1 Khz 15 Ohms[/size][/td] [td] [size=10pt]0.030% Good[/size][/td] [td] [size=10pt]0.003% Excellent[/size][/td] [td] [size=10pt]0.017% Good[/size][/td] [/tr] [tr] [td] [size=10pt]THD 20 hz 15 Ohms[/size][/td] [td] [size=10pt]0.028% Good[/size][/td] [td] [size=10pt]0.005% Excellent[/size][/td] [td] [size=10pt]0.01% Very Good[/size][/td] [/tr] [tr] [td] [size=10pt]THD 20 Khz 15 Ohms[/size][/td] [td] [size=10pt]0.040% Very Good[/size][/td] [td] [size=10pt]0.02% Excellent[/size][/td] [td] [size=10pt]0.45% Poor[/size][/td] [/tr] [tr] [td] [size=10pt]IMD CCIF[/size][/td] [td] [size=10pt]0.010% Good[/size][/td] [td] [size=10pt]0.003% Excellent[/size][/td] [td] [size=10pt]0.043% Fair[/size][/td] [/tr] [tr] [td] [size=10pt]IMD SMPTE[/size][/td] [td] [size=10pt]0.012% Good[/size][/td] [td] [size=10pt]0.003% Excellent[/size][/td] [td] [size=10pt]0.009% Very Good[/size][/td] [/tr] [tr] [td] [size=10pt]Noise (ref 400 mV)[/size][/td] [td] [size=10pt]-89 dB Very Good[/size][/td] [td] [size=10pt]-96 dB Excellent[/size][/td] [td] [size=10pt]-94 dB Excellent[/size][/td] [/tr] [tr] [td] [size=10pt]Max Output 15 Ohms[/size][/td] [td] [size=10pt]100 mW Excellent[/size][/td] [td] [size=10pt]67 mW Very Good[/size][/td] [td] [size=10pt]104 mW Excellent[/size][/td] [/tr] [tr] [td] [size=10pt]Max Output 150 Ohms[/size][/td] [td] [size=10pt]180 mW Excellent[/size][/td] [td] [size=10pt]180 mW Excellent[/size][/td] [td] [size=10pt]38 mW Fair[/size][/td] [/tr] [tr] [td] [size=10pt]Output Impedance[/size][/td] [td] [size=10pt]0.67 Ohms Very Good[/size][/td] [td] [size=10pt]0.1 Ohms Excellent[/size][/td] [td] [size=10pt]0.9 Ohms Very Good[/size][/td] [/tr] [tr] [td] [size=10pt]Crosstalk 15 Ohms[/size][/td] [td] [size=10pt]65 dB Very Good[/size][/td] [td] [size=10pt]68 dB Very Good[/size][/td] [td] [size=10pt]40 dB Poor[/size][/td] [/tr] [tr] [td] [size=10pt]Channel Balance Error[/size][/td] [td] [size=10pt]1.1 dB Good[/size][/td] [td] [size=10pt]1.1 dB Good[/size][/td] [td] [size=10pt]1.14 dB Good[/size][/td] [/tr] [tr] [td] DC Offset[/td] [td] [size=10pt]21 mV Good[/size][/td] [td] [size=10pt]4.5 mV Excellent[/size][/td] [td] [size=10pt]4.1 mV Excellent[/size][/td] [/tr]    
   


 [tr] [td] *[size=x-small]Measurement[/size]*[/td] [td] *[size=x-small]O2[/size]*[/td] [td] *[size=x-small]QRV09[/size]*[/td] [td] *[size=x-small]FiiO E9[/size]*[/td] [/tr] [tr] [td] [size=x-small]Frequency Response[/size][/td] [td] [size=x-small]+/- 0.1 dB Excellent[/size][/td] [td] [size=x-small]+/- 0.1 dB Excellent[/size][/td] [td] [size=x-small]+/- 0.1 dB Excellent[/size][/td] [/tr] [tr] [td] [size=x-small]THD 1 Khz 150 Ohms[/size][/td] [td] [size=x-small]0.0016% Excellent[/size][/td] [td] [size=x-small]0.002% Excellent[/size][/td] [td] [size=x-small]0.005% Excellent[/size][/td] [/tr] [tr] [td] [size=x-small]THD 1 Khz 15 Ohms[/size][/td] [td] [size=x-small]0.0023% Excellent[/size][/td] [td] [size=x-small]0.022% Good[/size][/td] [td] [size=x-small]0.037% Good[/size][/td] [/tr] [tr] [td] [size=x-small]THD 20 hz 15 Ohms[/size][/td] [td] [size=x-small]0.0023% Excellent[/size][/td] [td] [size=x-small]0.07% Good[/size][/td] [td] [size=x-small]0.05% Good[/size][/td] [/tr] [tr] [td] [size=x-small]THD 20 Khz 15 Ohms[/size][/td] [td] [size=x-small]0.010% Excellent[/size][/td] [td] [size=x-small]0.02% Very Good[/size][/td] [td] [size=x-small]0.003% Excellent[/size][/td] [/tr] [tr] [td] [size=x-small]IMD CCIF 15 Ohms[/size][/td] [td] [size=x-small]0.001% Excellent[/size][/td] [td] [size=x-small]0.02% Good[/size][/td] [td] [size=x-small]0.05% Good[/size][/td] [/tr] [tr] [td] [size=x-small]IMD SMPTE[/size][/td] [td] [size=x-small]0.002% Excellent[/size][/td] [td] [size=x-small]0.0015% Excellent[/size][/td] [td] [size=x-small]0.002% Excellent[/size][/td] [/tr] [tr] [td] [size=x-small]Noise (ref 400 mV)[/size][/td] [td] [size=x-small]-105 dB Excellent[/size][/td] [td] [size=x-small]N/A (1)[/size][/td] [td] [size=x-small]-88 dB Fair[/size][/td] [/tr] [tr] [td] [size=x-small]Max Output 15 Ohms[/size][/td] [td] [size=x-small]337 mW Excellent[/size][/td] [td] [size=x-small]450 mW Excellent[/size][/td] [td] [size=x-small]1067 mW Excellent[/size][/td] [/tr] [tr] [td] [size=x-small]Max Output 33 Ohms[/size][/td] [td] [size=x-small]613 mW Excellent[/size][/td] [td] [size=x-small]640 mW Excellent[/size][/td] [td] [size=x-small]883 mW Excellent[/size][/td] [/tr] [tr] [td] [size=x-small]Max Output 150 Ohms[/size][/td] [td] [size=x-small]355 mW Excellent[/size][/td] [td] [size=x-small]345 mW Excellent[/size][/td] [td] [size=x-small]317 mW Excellent[/size][/td] [/tr] [tr] [td] [size=x-small]Output Impedance[/size][/td] [td] [size=x-small]0.54 Ohms Excellent[/size][/td] [td] [size=x-small]10 Ohms Fair[/size][/td] [td] [size=x-small]10 Ohms Fair[/size][/td] [/tr] [tr] [td] [size=x-small]Crosstalk 15 Ohms[/size][/td] [td] [size=x-small]65 dB Excellent[/size][/td] [td] [size=x-small]67 dB Excellent[/size][/td] [td] [size=x-small]63 dB Very Good[/size][/td] [/tr] [tr] [td] [size=x-small]Channel Balance[/size][/td] [td] [size=x-small]0.6 dB Excellent[/size][/td] [td] [size=x-small]N/A (1)[/size][/td] [td] [size=x-small]1.8 dB Fair[/size][/td] [/tr] [tr] [td] Battery Life[/td] [td] ~8 hours / ~30 hours[/td] [td] AC Only[/td] [td] AC Only[/td] [/tr]


----------



## Citan

alphaman, could you clarify why you posted that?


----------



## alphaman

Quote:


citan said:


> alphaman, could you clarify why you posted that?


 
  Collecting some 'facts'. 
  FWIW, I own a SuperMacro IV which -- if you can trust Xin's numbers -- measures "Excellent" for several marks ... uh ... RightMarks . I'm not that crazy about its sound -- and in retrospect, it is (was) WAY over-priced.


----------



## kiteki

Interesting, may I buy your Xin SuperMacro?


----------



## alphaman

Quote:


kiteki said:


> Interesting, may I buy your Xin SuperMacro?


 

 No   While its audio performance is sub-par (e.g., compared to a Pimeta 2), it's conveniently small, has a recharger circuit, functions as an effective op-amp test instrument, and provides crossfeed. Crossfeed is not common in portable amps (TTBOMK), and I find it a must for extended, non-fatiguing listening ... even for low-fi stuff like audiobooks and podcasts.
   
  You may want to try a PD XM4 ... no experience with this brand/model, but it *seems* very similar to -- if not nicer than -- the Xin SM-IV. Its base price (USD135) is also WAYYYYY lower than Xin's orig outrageous gouge ($350!!).


----------



## kiteki

Hmm nevermind I was thinking of the supermICro, I'm quite pessemistic about portable amps and was mainly attracted to the fact that it's discontinued. If anyone has a XIN superMICro I'll be more than happy to swap my Hifiman RE252 for it, (which is also discontinued, and not for sale)
   
   
  Anyone with a Buffalo DAC, please hit me up as well.
   
  I want to find a good USB DAC, DIY is fine just value for money you know and right now all I can see is the Buffalo and it's out of stock etc. :/ any more tips?
   
   
  Edit: Alphaman you edited your post, it said XM5 now it says XM4, anyway I'm not a portable amp junkie or anything like that I just wanted the XIN SuperMicro because it looks cool and it's discontinued, I'm highly skeptical of the sound quality performance of most portable amps in general just FYI.


----------



## Shike

Quote: 





kiteki said:


> I want to find a good USB DAC, DIY is fine just value for money you know and right now all I can see is the Buffalo and it's out of stock etc. :/ any more tips?


 

 If you just want USB HRT Streamers are great - if you want more functional you can't go wrong with a DacMagic (it's impossible going wrong with it IMO).  Of course this is assuming you're looking at empirical performance, since you are posting in the O2 thread.


----------



## kiteki

The DacMagic instantly turned me off since it's using dual WM8740 DAC chips which is exactly what my Teclast T51 is using.
   
  Same story with the Practical Devices XM5!... PCM2702E, exact same chip as the one in my $40 HM-101!
   
   
  I sortof want a nice reference amplifier and then churn through the more interesting/exotic DAC chips out there on a sound quality basis, preferrably on the affordable DIY level so I acquire some more skills and insight along the way, however my first high-end DAC might be the Fostex HP-A3 which I am leaning towards at the moment as it looks like both a very nice DAC along with an optical-in feature so I can use it as solely an Amp, or optical out so I can use it as solely a DAC.
   
  I'm posting in the O2 thread because the O2 is a cheap DIY high performance amplifier and I'm looking for a similiar project in the DAC field if any such projects exist out there at the moment? Please let your juices fill the sponge inside my head before I spend ~$450 on the Fostex as my first high-end unit TYVM <3


----------



## Shike

Quote: 





kiteki said:


> The DacMagic instantly turned me off since it's using dual WM8740 DAC chips which is exactly what my Teclast T51 is using.
> 
> *That tells you nothing - implementation means more than the chip.  Just look at the O2 for proof of this concept, other designs use more expensive chips and look how awful some perform.*
> 
> ...


 

 Responses in bold.


----------



## kiteki

If "all DAC's sound the same" at a certain level, and the O2 is providing everything an amplifier should empirically provide, would you say the HRT along with an O2 are providing 95% of the best sound quality you can possibly get?


----------



## anetode

Quote: 





kiteki said:


> The DacMagic instantly turned me off since it's using dual WM8740 DAC chips which is exactly what my Teclast T51 is using.


 

 The design and the price didn't mix. They went for a top of the heap DAC chip and grossly underutilized it. It would have made more sense to go with a cheaper Wolfson with lower voltage requirements and lower specs; they could have matched and possibly even exceeded the audio quality while maximizing battery life. And by the time you reach that high on the specs and electrical performance, it doesn't much matter whether it's a flagship Wolfson or AKM or AD or other company involved. As shike said, the implementation becomes the limiting factor.
   
  If you fall into the customer segment that demands top-notch desktop performance in a portable, then you'll have to shell out over 400$ for a beastly DAC that's at least twice the size of your portable music player and gets somewhere in the neighborhood of 6-12 hours on a charge. The O2 would not be in line with this approach.
  
  On the other hand, I'm kind of excited about the possibilities being discussed at the *bleep* website. A Violectric drop-in 24/96 DAC in an O2 chassis would be awesome.


----------



## kiteki

by the way, a guy with an Eastern Electric something or other DAC told me via PM that only Asahi Kasei and Sabre ESS DAC's are worth considering and other DAC's can't keep up with the texture and layering.
   
  I read a similiar comment about the Opus versus the Buffalo DIY projects saying the Sabre ESS in the Buffalo just took it to a new level, those comments along with listening to different DAC's (not Amps) have really inspired me to want to buy or build a high-end DAC! The difference from discman to sound-card to different DAPs' and so on just has me not believing that "All DAC's sound the same" !


----------



## Shike

Quote: 





kiteki said:


> If "all DAC's sound the same" at a certain level, and the O2 is providing everything an amplifier should empirically provide, would you say the HRT along with an O2 are providing 95% of the best sound quality you can possibly get?


 

 I said all DACs should sound the same at a certain level, unless they're made not to or generally have quality issues.  Just like amps, you may have a bunch that aren't designed properly.
   
  It's hard to quantify the percent of sound quality, because there's tons of tests.  I wouldn't say it's 100% because the HRT Streamer+ does have 1dB roll-off into 20khz that the DacMagic for example doesn't.  Beyond that it's above the law of diminishing returns in other respects.
   
   
  Quote: 





> I read a similiar comment about the Opus versus the Buffalo DIY projects saying the Sabre ESS in the Buffalo just took it to a new level, those comments along with listening to different DAC's (not Amps) have really inspired me to want to buy or build a high-end DAC! The difference from discman to sound-card to different DAPs' and so on just has me not believing that "All DAC's sound the same" !


 
   
  Did you control ANY of the variables?  For example, not every DAC has the same output voltage which would create level differences that are audible.  Some have early roll-off (look at Wadia for example).  Some have oddities in their output stages, perform odd filtering, etc.
   
  Let's look at your experience with the discman.  Was it line-level?  Was it put against something in a DBT level matched?  If not right there you have a volume difference.  Not to mention couldn't the volume control or other issues influence crosstalk?  Do we even know how it measured out of box?  Sound cards are hit and miss to, did you direct out or did you run them to an amp?  Were they doing sampling, or did you use WASAPI/ASIO?  They also have varying levels of performance, if you took a first generation SBL! I wouldn't be surprised to hear it performed awfully - under loaded measurements it tends to.  Heck, I know the HM801 as a DAP has a roll-off measured in the treble that IS audible applying the same curves to test samples for a proper DBT.
   
  This doesn't even take output impedance into account.  If you used headphone outs and they had impedance even above 5 ohms it could drastically modify the FR of some headphones.
   
   
  Randomly throwing money at products doesn't solve issues - knowing what the problems are solves issues.


----------



## kiteki

Quote: 





anetode said:


> 1. The design and the price didn't mix. They went for a top of the heap DAC chip and grossly underutilized it. It would have made more sense to go with a cheaper Wolfson with lower voltage requirements and lower specs; they could have matched and possibly even exceeded the audio quality while maximizing battery life. And by the time you reach that high on the specs and electrical performance, it doesn't much matter whether it's a flagship Wolfson or AKM or AD or other company involved. As shike said, the implementation becomes the limiting factor.
> 2. If you fall into the customer segment that demands top-notch desktop performance in a portable, then you'll have to shell out over 400$ for a beastly DAC that's at least twice the size of your portable music player and gets somewhere in the neighborhood of 6-12 hours on a charge. The O2 would not be in line with this approach.
> 
> On the other hand, I'm kind of excited about the possibilities being discussed at the *bleep* website. A Violectric drop-in 24/96 DAC in an O2 chassis would be awesome.


 

 1. Wow! So is _that_ why the T51 battery is huge and runs out in 8 hours?  
   
  2. No it doesn't have to be portable, that's just a bonus, I just want this "texturing and layering" and so on that only high-end DAC's can (apparently) provide, and I'd rather get there with DIY so I can acquire new skills and save money.
   
   
  Quote: 





> Originally Posted by *Shike* /img/forum/go_quote.gif
> 
> Did you control ANY of the variables? [...]


 

 Not really =p
   
  I'm just under this vague impression that DAC's offer more substantial improvements in SQ than amp's do.


----------



## dogears

I once heard a preamp that bettered a DAC in an audio chain. It was a jawdropping improvement over the (NOS) DAC. I wanted one but couldn't afford to buy and build it  But then again, it's just a preamp 
  Quote: 





kiteki said:


> I'm just under this vague impression that DAC's offer more substantial improvements in SQ than amp's do.


----------



## kiteki

To explain my "state of mind" a little bit further.
   
  Hypothesis 1 - The O2 is the "end all" of amplifiers, save for colouration and fake enhancement of SS.
   
  Observation 1 - People rave about different DAC's, for example just look at project86 on head-fi or Mike at headfonia.com. I just did a quick search and here's some comments I found in random forums from other ppl:
   
  "yes the Buffalo is very clear, clean and dynamic, but is also smooth neither sounding digital or analogue, instruments in 24/96 sound very real not just in tone but in space, sound is really spacious & envelopes you in a 3d way.
 Electronica, ambient, rock, orchestral the Buffalo is certainly an engaging musical experience and what I prefer, not to say it's bad with the others mentioned but prefer the Monica with those."
   
  another one:
   
  "ESS DAC impressed me a lot. The sound was so good that I was speechless. ABSOLUTELY FANTASTIC! So many details, so much wealth, background information, new instruments, new microphones at the recording venue, I sat and I felt like I was there at the recording. My room disappeared and turned into the real musical event, with all the vibrations, reverb, sound reflections, all nuances, background notes , and above all - the MUSIC.
 This DAC paints such beautiful picture it is beyond words. Immediately I knew I had a gem at home. I knew this DAC is the best one I know. The feeling of learning a well known recording as new - was sensational.
 Ladies and gentlemen, I declare a new King of CD players, even if I know there is a new strong contender coming up - the Sony CDP227ESD in NOS form."
   
   
  I mean What? His room disappeared and he can hear new microphones? It just looks like if I build a Buffalo and O2 I'm going to be in audio heaven or something?
   
  Edit: "In my very transparent and very revealing system this DAC shines like a diamond. The sensation I hear brings to my mind associations like : Mountain spring air in the morning, cool San Pellegrino water on a hot day in Milano, Ear cleanup with Q-tips while my wife is not watching, a glass of 100 dollar Seghesio Zinfandel in the evening by the fireplace with a piece of goat cheese. Only good associations with purity, clarity and pleasure. I cant even describe it properly. It is my favourite DAC with the Wolfson and TDA1541 being close second best."
   
  ..??? lol


----------



## qusp

kiteki, i think you are on shaky ground commenting on other people's prose


----------



## qusp

Quote: 





kiteki said:


> 1. Wow! So is _that_ why the T51 battery is huge and runs out in 8 hours?
> 
> 2. No it doesn't have to be portable, that's just a bonus, I just want this "texturing and layering" and so on that only high-end DAC's can (apparently) provide, and I'd rather get there with DIY so I can acquire new skills and save money.
> 
> ...


 


  if you are getting into diy to save money on high end kit, you will be rudely disappointed, certainly if you value your time and even if not if you want to case something properly, have to pay international shipping from more than 1 vendor etc etc it doesnt work out as cheap as you think and imo its the wrong motivation


----------



## kiteki

ok thanks for your input on the financial part.
   
  I wasn't commenting on his prose in a sarcastic way or anything, just pointing out that some people are exalted over DAC's, whilst others say "All DAC's sound the same", and awaiting input...
   
  you see, I'm quite new at this DAC game... that's all.


----------



## maverickronin

Quote: 





kiteki said:


> Hypothesis 1 - The O2 is the "end all" of amplifiers, save for colouration and fake enhancement of SS.


 

 Not really, but I think it can be close for many people.
   
  Ever if you discount the irrational lust for something with better specs even you can't tell the difference by yourself, there are a few practical concerns which would keep it from being as close to perfect as most anyone would need.  There are a few situations where some people could use more power and adding any more power to the O2 would probably require a complete redesign from scratch with much more expensive parts if you wanted to keep similar specs.


----------



## kiteki

Okay, well sorry about my interruption and newcomer thoughts, I just thought I could build an O2 and find it's DAC equivalent, save some money and acquire some new knowledge+skills along the way, and end result = 95% highest sound quality attainable (let's say for IEM use, at least).
   
  As it turns out it doesn't look quite so simple, and DIY DAC's cost more than normal DAC's? I just don't get it, why?
   
  Either way this thread has a curious "air" to it like it's the underworld of head-fi or something.


----------



## deadlylover

kiteki,
   
  The only way to find out, is to experiment for yourself.
   
  Grab life by the balls and go do whatever you want. All you need is a hot pan and some olive oil, and you can build anything you want. Well, there aren't so many DIY DACs around unfortunately. DIY is great value, but it is not cheap.
   
  The sound science gang make a fantastic argument, but you owe it to the subjectivists to at least try something for yourself before you hold an opinion, especially if it's going to be a strong one. 
	

	
	
		
		

		
			




   
  Personally, I don't believe in DACs, but I'm not going to force my opinion onto you until I cook up a delicious buffalo32 and do some comparisons for myself.
   
  All I'm saying is, I've been watching way too much iron chef and I don't know whats what anymore.
   
  Kino, it's been too long.


----------



## maverickronin

Quote: 





deadlylover said:


> Kino, it's been too long.


 

 I see a new addition to your sig...
    
  Quote:


> 2D for Life, and that's why I don't strive for reality/accuracy in audio, as I'd rather chase dreams.


 
   
  It makes an interesting contrast to mine.
   
  Quote: 





> Heaven's closed, Hell's sold out, so I walk on Earth.


 
   
  How cynically I interpret its meaning varies from day to day.  Funny we seem to agree on so much.
   
  Also, is Kino chasing dreams or running from nightmares?
   
  On Topic:  I'm still enjoying my O2 despite it merely being of this Earth.


----------



## deadlylover

Quote: 





maverickronin said:


> On Topic:  I'm still enjoying my O2 despite it merely being of this Earth.


 

 I'm going to build a balanced(maybe) desktop version, then I'm going to put it in an identical box to the balanced beta22, and then I'm going to have some epic lols at a headphone meet. I'm think going to name the desktop version "Kino".
   
  It's been about a month since I've had my O2 up and running, I still enjoy it as well, as it brings me the warm and fuzzies every time I look at it. I posted it elsewhere but I guess it deserves to be here as well:
   

   
   
  All those kids crying about finding a proper AC wall adapter for their country, look at how I roll.


----------



## maverickronin

Quote: 





deadlylover said:


> I'm going to build a balanced(maybe) desktop version, then I'm going to put it in an identical box to the balanced beta22, and then I'm going to have some epic lols at a headphone meet. I'm think going to name the desktop version "Kino".


 

 I'd be interested in seeing a balanced version for "MOAR POWER" on the cheap since EQ on top of high dynamic range movie soundtracks eats headroom like no there's tomorrow.
   
  I don't need it yet but if I get around to another modding spree on my planars they'll probably only get less efficient.


----------



## Willakan

Quote: 





deadlylover said:


> The sound science gang make a fantastic argument, but you owe it to the subjectivists to at least try something for yourself before you hold an opinion, especially if it's going to be a strong one.


 
  I have an excuse - absence of money/proximity to anywhere I could ever listen to this stuff. 
  Regarding the beta22 vs O2 blind comparison, it might be worth checking the beta22 doesn't do wrong by the test bench first - crosstalk at least is highly suspect. Also, you might have fun pretending the O2 is in fact a low-distortion tube amp and see how many people claim they can definitely hear the "tube warmth" of one of the listening test options.
  Admittedly, I am at this stage thinking of how to engineer the test to embarrass as many listeners as possible, but what fun is it being an objectivist if you can't make out everyone else is silly?
	

	
	
		
		

		
		
	


	



   
  EDIT: Also, da** (silly profanity filter) fine case.


----------



## Head Injury

Quote: 





willakan said:


> Admittedly, I am at this stage thinking of how to engineer the test to embarrass as many listeners as possible, but what fun is it being an objectivist if you can't make out everyone else is silly?


 

 Be gentle. This is the reason why no one likes social psychologists.


----------



## fishski13

Willakan,
  what version of a B22 are you talking about?  i've only seen measurements for a 3 channel configuration.  deadlylover has a balanced B22.


----------



## qusp

Quote: 





willakan said:


> I have an excuse - absence of money/proximity to anywhere I could ever listen to this stuff.
> Regarding the beta22 vs O2 blind comparison, it might be worth checking the beta22 doesn't do wrong by the test bench first - crosstalk at least is highly suspect. Also, you might have fun pretending the O2 is in fact a low-distortion tube amp and see how many people claim they can definitely hear the "tube warmth" of one of the listening test options.
> Admittedly, I am at this stage thinking of how to engineer the test to embarrass as many listeners as possible, but what fun is it being an objectivist if you can't make out everyone else is silly?
> 
> ...


 

 using the word objectivist is pretty silly imo since its literally impossible to be an objective human being, but hey play with your things that go beep all you like haha nah look i'ma mix of the 2, which can be confusing and conflicting at times, but what i dont enjoy is attempting to suck the fun and satisfaction out of other peoples hobby in situations that have no effect on you at all. 
   
  putting too much faith in science and yes that is what it is, its all we have, no different to religion, but things, even the big stuff can be proven in time to be fallacy, what happens to your 'objective' measurements if yesterday's craziness turns out to be true? i assume you know of what i speak, ripples are spreading all over the earth and its many fields of scientific endeavour. myself i wont believe it till its been chewed over, but wow.
   
  for those who dont, i'm talking about CERN and the OPERA group finding or at least claiming that neutrinos travel faster than light, a revelation that would turn Einstein's theory of relativity on its head and make time travel not so far fetched an idea after all


----------



## Head Injury

Quote: 





qusp said:


> using the word objectivist is pretty silly imo since its literally impossible to be an objective human being, but hey play with your things that go beep all you like haha nah look i'ma mix of the 2, which can be confusing and conflicting at times, but what i dont enjoy is attempting to suck the fun and satisfaction out of other peoples hobby in situations that have no effect on you at all


 

 But sucking the fun out of the hobby is what I do to fill the emotionless void in my soul.


----------



## kiteki

Oh noes it's impossible to be an objective sentient being, nothing can be observed to be perfect or true since our very nature of existence and non-linear vision can never be perfect or true?
   
  Just hold on a sec while I set fire to my local university and library and then sniff glue at the beach for the rest of the day.


----------



## Head Injury

Quote: 





kiteki said:


> Oh noes it's impossible to be an objective sentient being, nothing can be observed to be perfect or true since our very nature of existence and non-linear vision can never be perfect or true?
> 
> Just hold on a sec while I set fire to my local university and library and then sniff glue at the beach for the rest of the day.


 

 I calculate a 93.43974% probability that you will regret the stated actions.


----------



## deadlylover

Quote: 





willakan said:


> I have an excuse - absence of money/proximity to anywhere I could ever listen to this stuff.
> Regarding the beta22 vs O2 blind comparison, it might be worth checking the beta22 doesn't do wrong by the test bench first - crosstalk at least is highly suspect. Also, you might have fun pretending the O2 is in fact a low-distortion tube amp and see how many people claim they can definitely hear the "tube warmth" of one of the listening test options.
> Admittedly, I am at this stage thinking of how to engineer the test to embarrass as many listeners as possible, but what fun is it being an objectivist if you can't make out everyone else is silly?
> 
> ...


 
   
  I really really want to buy a dScope or whatever it was called, but bloody hell it's really really expensive. 
	

	
	
		
		

		
		
	


	




 You'd think if he had the dough for that kind of gear, Lord Voldemort would actually go and buy or build some "proper" desktop amps, and not meddle around with his stash of portable toys.
   
  But even if the crosstalk on the b22 is highly suspect, whats the point? I don't even remember Lord Voldemort being able to distinguish between his worse measuring amps with the Obj2 anyway, but it's been a while, and admittedly, I don't read his articles properly. 
	

	
	
		
		

		
		
	


	



  
  I suspect you guys just have a bone to pick with amb, and that's why you guys are burning him. So unless you were there when he made the measurements, and clearly saw him fudge them up, you should just let it go. His set of measurements are just that, a set of measurements. It's up to others to measure it as well, and it's not so much that his might be wrong, but as with any scientific experiment, you need a bunch of samples to see the whole story.
   
  For instance, look at the masses saying the most far fetched stupid things like "Einstein was wrong" due to the recent, but still unconfirmed discovery of neutrinos traveling faster than light. Did the world say the same thing to Newton when Einstein came out with his theories? Nope. They just said that Newton wasn't the whole story. Einstein's theory wasn't the whole story either, just take a look at quantum mechanics, and now, this discovery.


----------



## kiteki

Why are your posts so seasoned and intelligent, whilst you're listening to doof doof and little girls all day?


----------



## deadlylover

Quote: 





kiteki said:


> Why are your posts so seasoned and intelligent, whilst you're listening to doof doof and little girls all day?


 
   
  Because I am a mad scientist.
   
  MUAHAAHAHAHHHAAHAH.


----------



## kiteki

Aw man you stole post #777 I hate you.
   
  I like you because you're the polar opposite of people that ony listen to 24 bit classical and vomit on the internet all day.


----------



## Shike

Quote: 





deadlylover said:


> I suspect you guys just have a bone to pick with amb, and that's why you guys are burning him. So unless you were there when he made the measurements, and clearly saw him fudge them up, you should just let it go. His set of measurements are just that, a set of measurements. It's up to others to measure it as well, and it's not so much that his might be wrong, but as with any scientific experiment, you need a bunch of samples to see the whole story.


 

 The fact is that his measurements were done wrong and are physically impossible - this is mathematically proven (at least with the Mini^3).  I've done the measurements myself and confirmed that the crosstalk of the Mini^3 was grossly overstated getting roughly the same numbers NwAvGuy got.  He clearly pooched his dummy loads since there was a negligible difference for crosstalk into corresponding loads.  He also doesn't know what batteries he even used to measure the Mini^3 with, but doesn't go back to check to see if the numbers he's publishing are accurate based on the average build being both optimistic and misleading.
   
  Whether we were there when he made his measurements are irrelevant.  The fact is, he _refuses_ to fix his numbers when his mistakes have been brought to light and makes various cop-outs refusing to really discuss the matter at hand.  Rather than admit he made a (hopefully honest) mistake he tries to sweep dirt under the rug and continue.  So yes, I do have a bone to pick with him - but no one's burning him but himself.
   
  Anyway, let's do something else like drink Dr. Pepper since AMB really has 0 to do with this thread.


----------



## qusp

Quote: 





kiteki said:


> Oh noes it's impossible to be an objective sentient being, nothing can be observed to be perfect or true since our very nature of existence and non-linear vision can never be perfect or true?
> 
> Just hold on a sec while I set fire to my local university and library and then sniff glue at the beach for the rest of the day.


 

 you are a bit of a child arent you?
   
  yes sorry it IS impossible to be objective as a being that only has subjective experience/perspective, doesnt mean we cant pretend and we've come a long way doing so, but all i'm saying is its possible to be too confident in what amounts to belief, not objective fact. i dont yet believe yesterdays events are proven and they did the right thing opening it up to scrutiny, but if it is it will change things massively, does it mean our learning is a lie? no of course not, but does a thing that is at the heart of so much 'objective fact' create doubt about its accuracy and open up possibility to things previously though crazy talk? you bet it does.
   
  haha maybe you better go get another can of 'smart drink' maybe we should go through your reviews and check for objective accuracy?


----------



## deadlylover

Quote: 





shike said:


> Anyway, let's do something else like drink Dr. Pepper since AMB really has 0 to do with this thread.


 

 I'll let it go, just think about how much better the DIY community would have been if Lord Voldemort was a nice guy and chose to work with the community rather than try and take over the world.
   
  I miss Dr. Pepper, they used to make some here in Australia but it's long gone now. 
	

	
	
		
		

		
			





 They have some at the Costco here but I swear it's not quite the same as I remembered.


----------



## kiteki

Imho being obnoxious or over-confident is totally different to being objective.
   
  Imho claiming one has "found" an objective truth is obnoxious, the point is attempting to find it, or come as close as possible to it, as an attitude, or you know simply accepting that "it exists".
   
  I interpreted your comment that it does not exist, sorry it's just I keep seeing people imply that audio is super subjective and the only right thing to do is embrace that or something? I just don't get it it's a bit annoying.


----------



## kiteki

btw qusp if you think the name "objective2" is obnoxious or you have a problem with my prose you could just say so instead of making clever remarks about energy drinks?
   
  I don't really see what's wrong with the shoebox idea, I'd be happy to attend a meet with the shoebox idea, I can't really understand why your opposed to it so maybe if you explain again...


----------



## Shike

Quote: 





deadlylover said:


> I'll let it go, just think about how much better the DIY community would have been if Lord Voldemort was a nice guy and chose to work with the community rather than try and take over the world.


 

 He is working with the community - some have caught potential issues early on and had a great amount of input at the diyaudio forums.  What more do you want?


----------



## deadlylover

Quote: 





kiteki said:


> I don't really see what's wrong with the shoebox idea, I'd be happy to attend a meet with the shoebox idea, I can't really understand why your opposed to it so maybe if you explain again...


 
   
  The only thing I can think of is that it might offend some people who are really passionate or have an emotional attachment with their gear.
   
  When I do pull off the shoebox idea, I plan on being as nice as possible as I'm not one to look down on other peoples subjective experiences, even if they are different to mine.
   
  Not that anybody will care though, as I plan on blowing the place up with Stax anyway.
  
  Quote: 





shike said:


> He is working with the community - some have caught potential issues early on and had a great amount of input at the diyaudio forums.  What more do you want?


 
   
  This is what I would have done if I had access to such awesome measuring equipment:
   
  "Yo dawg, I've got some sweet boxes, let us measure lots of gear for the lols and the advancement of objective knowledge as a community"
   
  I would not have done this:
   
  "LOLOLOLOOL MINI3 MEASUREMENTS ARE IMPOSSIBLE AND WRONG, AMB IS FULL OF HORSE POO EVERYTHING HE DID WAS WRONG AND I AM THE SAVIOR OF THIS WORLD LOOK AT ALL MY 10,000 WORD ARTICLES AND AWESOME PROPER MEASURING GEAR AND ONLY I CAN LIVE FOREVER WHERE'D MY NOSE GO?"
  
  At the end of the day, the goal is the same but the way in which you proceed, matters so much IMO. But that is the past, and nothing can be done about it, you probably don't know the whole story as I'm guessing you are a somewhat new follower of nwavguy.
   
  I don't really have a problem in how he approached the Objective2 project except maybe calling it a $30 amp and comparing it to a $1600 DAC(lol) or a $2000+(lol) beta22. But that's mainly because I'm a cheapskate. 
	

	
	
		
		

		
		
	


	



   
  I know, it looks like I'm taking the piss out of him, but I kind of deserve to as I believe I'm still the only person here whose actually built an Obj2 by myself. And I did give it a glowing 'review', ahahah.
   
  I really do feel alone here as the subjective side feel strongly about their experiences, the objective side feel very strongly about their measurements, but where do I fit in? I don't care about anything, it's just gear. Why you guys so serious? or perhaps the better question is, why me no serious? Well, I guess you could say I'm only in this hobby for the lols, but apparently, this hobby is like a bushido for many. Have people forgotten what a hobby was supposed to be about?
   
  I'm getting sick of arguing over nothing.


----------



## Shike

I'll take my more lengthy reply to PM, and I'll say it once more:
   
  This thread is about the O2. 
  It's not about AMB.
  It has nothing to do with NwAvGuy's ego.
  The pot doesn't need more stirring.


----------



## deadlylover

Quote: 





shike said:


> I'll take my more lengthy reply to PM, and I'll say it once more:
> 
> This thread is about the O2.
> It's not about AMB.
> ...


 
   
  This thread is in the DIY section.
   
  I am still the only person on this forum who has built the amp, it would be quite boring if we couldn't talk about anything else, no? It's you guys who've brought up the beta22's 'measurements' anyway.


----------



## kiteki

Just to clarify about the 'objective' discussion before I don't equate objectivist to "measurement purist" in case there was some confusion there, to be honest I think the measurement purists for headphones are really annoying Lol.
   
   
  deadlylover Y are you "the only person on this forum that's built the obj2" ??
   
   
  p.s. not to go OT or anything, but can I get your guys quick opinions on NOS DAC's using really old chips on purpose? Just curious what your 'basic' thoughts are on NOS...


----------



## deadlylover

Quote: 





kiteki said:


> deadlylover Y are you "the only person on this forum that's built the obj2" ??


 
   
  I haven't been 'keeping tabs', but anyone else on this forum who has the obj2 either had some kind of review sample or had somebody else build it for them. Hardly DIY IMO.


----------



## Shike

Quote: 





deadlylover said:


> I haven't been 'keeping tabs', but anyone else on this forum who has the obj2 either had some kind of review sample or had somebody else build it for them. Hardly DIY IMO.


 

  
  Many "DIY" amps are sold commercially, so it really doesn't matter.  Besides, you didn't exactly build the "O2" exactly either - the designer was pretty sincere about using a PCB and not point to point.  Currently, you have something that resembles the O2 by topology in a box 
   
   
  Quote: 





kiteki said:


> p.s. not to go OT or anything, but can I get your guys quick opinions on NOS DAC's using really old chips on purpose? Just curious what your 'basic' thoughts are on NOS...


 

 They can sound fun, but they definitely have issues when it comes to reference accuracy.  I got one a long time ago and sold it off.  I think they're a novelty to have in a vintage CDP, but CDs aren't my main source anymore so I can sort-of justify it (plus, the CDPs were cheap).


----------



## deadlylover

Quote: 





shike said:


> Many "DIY" amps are sold commercially, so it really doesn't matter.  Besides, you didn't exactly build the "O2" exactly either - the designer was pretty sincere about using a PCB and not point to point.  Currently, you have something that resembles the O2 by topology in a box


 
   
  Heheheh, but an amp is it's schematic, not the final product. 
	

	
	
		
		

		
		
	


	



   
  By that logic, nobody is worthy of having the Obj2 until Lord Voldemort gives it his personal blessing.


----------



## kiteki

Thanks Shike... what do you guys think for my next Dac/Amp... Valab NOS DAC + obj2 - or - Fostex HP-A3?


----------



## deadlylover

Quote: 





kiteki said:


> Thanks Shike... what do you guys think for my next Dac/Amp... Valab NOS DAC + obj2 - or - Fostex HP-A3?


 
   
  I'd go for the former, I think it works out to be slightly cheaper and it's nice having a separate DAC and amp so you can change it up more easily when the time comes.


----------



## Willakan

Regarding objectivism, no-one is saying it is possible to be perfectly objective. It is, however, possible to try.
  And please, no more on the Mini3. This will not go anywhere. Let's just say from my correspondance with NwAvGuy I'm of the opinion he actually went rather easy on the criticism - there are things he could have highlighted strongly which he did not. Please save any further discussion on this for another thread.


----------



## Shike

Quote: 





kiteki said:


> Thanks Shike... what do you guys think for my next Dac/Amp... Valab NOS DAC + obj2 - or - Fostex HP-A3?


 


  Not a fan of NOS if you're looking for accuracy.  Once again, I stand by the DacMagic + 02 recommendation I made earlier.


----------



## kiteki

Haha, that post said "Not a fan of NOS" then you edited in "if you're looking for accuracy" 
	

	
	
		
		

		
			




   
   
  I think I may just start off with the NOS... I have to experience it at some point... with the money I save by not getting the DacMagic or Fostex I could actually buy a PS3 and hook it up to the NOS with optical and play a couple videogames in rich analog vinyl sound, what do you think?


----------



## Soaa-

what the heck just happened in the past few pages; last time you guys did this you destroyed a WHOOOOOOOLE kitchen!!
   
  Basically, NwAvGuy did serve the community and still does today. It's easy to say that he doesn't _here_, but that's just because he _can't_. _Obviously._
   
  He designed an amp with the goal of getting excellent measurements on his dScope analyzer. That goal has been achieved. You could argue that his dScope is flawed, but then you'd have Prism to deal with. Good luck. You could argue that his measurements were falsified/erroneous, but then the burden of proof is on you and without a dScope or equivalent piece of equipment yourself, good luck!
   
  I'll leave one word about AMB here: NwAvGuy accused him of providing false specs for his mini^3 amp and provided proof. The burden of proof is on AMB if he wants to prove NwAvGuy wrong, but he has done nothing of the sort. Instead, _he unleashed even more erroneous math in an attempt to discredit the O2._ Talk about contributing to the DIY community.
   
  About deadlylover's point to point O2: NwAvGuy said the O2 should be built on a PCB for best performance. Not _his_ PCB, just any PCB made to the specs that he's released. His personal blessing not required. A point to point build is prone to problems with grounding and other things that I'm not familiar with. Discuss where NwAvGuy can for more information on the subject.
   
  Jeez you guys drive me nuts.


----------



## Beefy

Quote: 





soaa- said:


> Basically, NwAvGuy did serve the community and still does today.


 

 He's a saint! 
	

	
	
		
		

		
		
	


	



   
  *
   
  What could have been interesting is instead getting very, very tedious. And the worst part is that the hard-core objectivists - who I would normally side with - have turned into bigger idiots than the subjectivists. Unsubscribe.


----------



## svyr

kiteki said:


> Thanks Shike... what do you guys think for my next Dac/Amp... Valab NOS DAC + obj2 - or - Fostex HP-A3?




 i suggest nos dac + tube amp + T5p... The combined THD+N/IMD figures will rival vinyl ... Why not see if you can hit 20% instead of 10% of T5p alone  ... (I'm sorry, I just couldn't help myself there)


any more info on commercial builds? I'd be curious enough to spend $100-200 on one depending on case and parts  My MD30/MD11 amps are quite bad.(esp in the high output impedance department)


----------



## Head Injury

Quote: 





beefy said:


> He's a saint!
> 
> 
> 
> ...


 

 Tell me, honestly, that a new quality DIY design and extensive third-party measurements of audiophile equipment isn't a benefit to the community?
   
  What was the last constructive thing you've added to the thread? If it could have been interesting, help make it interesting.
   
  Quote: 





svyr said:


> i suggest nos dac + tube amp + T5p... The combined THD+N/IMD figures will rival vinyl
> 
> 
> 
> ...


 

 Sold!


----------



## svyr

head injury said:


> Tell me, honestly, that a new quality DIY design and extensive third-party measurements of audiophile equipment isn't a benefit to the community?
> 
> What was the last constructive thing you've added to the thread? If it could have been interesting, help make it interesting.
> 
> ...




It does. Both in the sense of people making affordable amps, and hoping manufacturers will stop taking customers for fools and stop selling them poorly designed manure with high output impedance, stability issues, snakeoil marketing combined with horrible distortion specs and dubious safety (and other great things the audio industry can be sooo proud of). 

and he's trying to educate people about the design and measurements. He gets a + 10 on respect from me


----------



## Satellite_6

Quote: 





beefy said:


> He's a saint!
> 
> 
> 
> ...


 

 Well he designed his own amp that anyone can make, what is he, the devil?
   
   
  About objectivity - Once you start assigning numbers to things that are qualitative they can be come objective, i.e. "I think this amp has a lot of distortion." You go measure it. You get a high distortion value. Now you can say that the amp has a lot of distortion, and if if someone else reckons it has super clear sound and is the bestest amp evar, at least you have a quantitative value to back your opinion. 
   
  Science! No one said it was perfect, but theories are always changing, and that's what's great about it. If something that seems crazy can be proven, well. . . yay! It's not like religion where changes are blasphemous. 
	

	
	
		
		

		
		
	


	




 But the key is it has to be proven.
   
  i.e. the faster than light thing - still needs to be confirmed by others, it's not definitive yet.


----------



## Armaegis

Quote: 





deadlylover said:


> I'm going to build a balanced(maybe) desktop version, then I'm going to put it in an identical box to the balanced beta22, and then I'm going to have some epic lols at a headphone meet. I'm think going to name the desktop version "Kino".


 

  While you're at it, why not add a third box with something like a JDS Cmoy (or BSG, or Fred, etc). Heck, add a 4th box with an e6.
   
  People are going to such lengths to attempt to show superiority (or at least indistinguishability (is that even a word?)) over more expensive gear, for the sake of balance you should go the other way too.


----------



## kiteki

Quote: 





svyr said:


> Quote:
> 
> 
> 
> ...


 

 Very amusing 
   
  Let's not forget the TDA1543 chip is famous for it's [audible] high-end roll-off too, consider this along with the decidedly bass-light T5p, now all I need is some kind of high-end amplifier with weak mids, and I should have a nice [balanced?] trinity of.... amazingly expensive THD+N?


----------



## mikeaj

Silliness aside, the initial measurements published for an earlier PCB revision had worse performance and did not "pass" the 20kHz 15 ohms THD test (or was it something else?) according to his rule, and otherwise was worse than the E9 in the 15 ohms THD sweep across the higher frequencies. And who knows about revisions that were made prior to the design being published.

The point is that the PCB makes an appreciable difference, even comparing iterations of the same design by a guy who presumably has experience with boards relating to audio performance (and not just some dude laying out stuff where it looks pretty). So point-to-point would make an appreciable difference as well. So the PCB is a legitimate portion of the design and is a more important part than most of the components you put on top of it.


----------



## fishski13

Quote: 





beefy said:


> What could have been interesting is instead getting very, very tedious. And the worst part is that the hard-core objectivists - who I would normally side with - have turned into bigger idiots than the subjectivists. Unsubscribe.


 

 x2.  it's just kool-aid of a different flavor.
   
  i think by far and large seasoned DIYers fall on the side of measurements/objectivity, but correlate to what they hear, subjectively.  if it measures better and sounds better, then it is better etc.  
   
  the fact that this is a thread in the DIY forum that's largely void of DIYers speaks volumes.  i don't believe that this will change even after the PCBs hit the shores either.


----------



## deadlylover

Quote: 





armaegis said:


> While you're at it, why not add a third box with something like a JDS Cmoy (or BSG, or Fred, etc). Heck, add a 4th box with an e6.
> 
> People are going to such lengths to attempt to show superiority (or at least indistinguishability (is that even a word?)) over more expensive gear, for the sake of balance you should go the other way too.


 
   
  I'm all about balance, but is there much lower to go than the all mighty $30 amp? Hell, I just said I was doing the test for some lols, not to one up the subjectivists or anything like that. If you have a good recommendation, I'll be happy to build it for some three way action, but as I would have no use for it because I don't have any proper dynamics, keep it really cheap.
   
  Personally, I wouldn't bet my left nut on being able to tell my computer sound card from my beta22 or the obj2. Then again, I have the critical listening abilities akin to a bucket of rocks.
  
  Quote: 





kiteki said:


> Very amusing
> 
> Let's not forget the TDA1543 chip is famous for it's [audible] high-end roll-off too, consider this along with the decidedly bass-light T5p, now all I need is some kind of high-end amplifier with weak mids, and I should have a nice [balanced?] trinity of.... amazingly expensive THD+N?


 
   
  Aim for the stars buddy. Much lols will ensue if you get a nice tube amp =P.
  
  Quote: 





fishski13 said:


> x2.  it's just kool-aid of a different flavor.
> 
> i think by far and large seasoned DIYers fall on the side of measurements/objectivity, but correlate to what they hear, subjectively.  if it measures better and sounds better, then it is better etc.
> 
> the fact that this is a thread in the DIY forum that's largely void of DIYers speaks volumes.  i don't believe that this will change even after the PCBs hit the shores either.


 

 I agree, everybody who will need help building the amp won't be around here anyway, as the only people who currently have the Obj2 here have no clue about DIY.
   
  Nobody will be dumb enough to build a point to point or breadboard version as it goes against Lord Voldemort's will, but if anyone is, I'm happy to help. ^^
  
  Quote: 





soaa- said:


> what the heck just happened in the past few pages; last time you guys did this you destroyed a WHOOOOOOOLE kitchen!!
> snip
> About deadlylover's point to point O2: NwAvGuy said the O2 should be built on a PCB for best performance. Not _his_ PCB, just any PCB made to the specs that he's released. His personal blessing not required. A point to point build is prone to problems with grounding and other things that I'm not familiar with. Discuss where NwAvGuy can for more information on the subject.


 
   
  Ehh, stuff happens. 
	

	
	
		
		

		
		
	


	



  
  Neither my point to point or breadboard version exhibited and hiss or humming all throughout the pot. It wouldn't measure nearly as well as a PCB version, but you can hardly say I've ballsed it up so badly that I don't even have an Obj2. Don't worry, I was planning to build the desktop version with his personal blessing for use at the meet comparison.
   
  The whole point of me prototyping the amp was completely for the lols. It was "$30" and my balanced beta22 needed a good mate to play with. Honestly, I only read like 2% of the main article, I had no idea that he was against building it point to point or whatever. I also knew that anybody who was considering the Obj2 would most likely not have a well known high end amp such as the beta22 for comparison, so I kind of took one for the team to go find out how it they would compare, for personal curiosity.
   
  I am neither on the subjectivist side or the objectivist side(okay maybe a little bit objectivist as I am a scientist =P). I really am only here to have a laugh (it is a hobby after all), it's best that nobody takes my comments seriously, as you'll probably make a fool of yourself. maverickronin's old signature comes to mind, if anybody still remembers it.
  You guys have made my day, thanks.


----------



## Soaa-

Quote: 





fishski13 said:


> i don't believe that this will change even after the PCBs hit the shores either.


 
   
  Hard to say when barely anyone has even built one yet. With over 500 (or was it 700?) PCBs on order, it's not easy to not talk about it.


----------



## limpidglitch

Quote: 





soaa- said:


> Hard to say when barely anyone has even built one yet. With over 500 (or was it 700?) PCBs on order, it's not easy to not talk about it.


 


  800 


  Quote: 





fishski13 said:


> i think by far and large seasoned DIYers fall on the side of measurements/objectivity, but correlate to what they hear, subjectively.  if it measures better and sounds better, then it is better etc.


 


  I think you're perfecly right. Builders pride can be just as powerful as buyers pride.


----------



## kiteki

Quote: 





deadlylover said:


> Aim for the stars buddy. Much lols will ensue if you get a nice tube amp =P.


 

 I was just really close to selling my Hifiamn RE272 and picking up a NOS DAC on ebay, but the guy won't accept my $200 offer when it's mint condition and $249 RRP... then someone else turns up willing to trade a Hifiman HM-601 LOL so I ended up with a NOS DAP on the way now instead...

  
  Quote: 





soaa- said:


> Hard to say when barely anyone has even built one yet. With over 500 (or was it 700?) PCBs on order, it's not easy to not talk about it.


 

 I noticed there's a cheaper "battery only" option... are people going to be carrying these around as portable amplifiers..?


----------



## Head Injury

Quote: 





kiteki said:


> I noticed there's a cheaper "battery only" option... are people going to be carrying these around as portable amplifiers..?


 

 Considering the size, probably transportable more than portable. It packs some punch on battery power, too, so for those who don't have excessively hard-to-drive headphones, batteries work fine and can move with you.
   
  For me, because of the size, I'm just waiting for the desktop-only version.


----------



## Willakan

I fail to understand the objectivist hate. It's not KoolAid, it's rationality. We're just applying the same rules we apply to everyday life to audio.


----------



## Shike

It's funny how those that have contributed the_ least_ to this thread are some of the most vocal, and curiously have based their arguments not against the amp but the designer and taking personal swings at members.  Insecurity knows no bounds it seems.
   
  I'm still thoroughly enjoying my O2 to say the least. ^_^


----------



## Willakan

Oh, don't worry, we're all idiots taken in by NwAvGuy. How could I not see through his facade?


----------



## Armaegis

Quote: 





deadlylover said:


> I'm all about balance, but is there much lower to go than the all mighty $30 amp? Hell, I just said I was doing the test for some lols, not to one up the subjectivists or anything like that. If you have a good recommendation, I'll be happy to build it for some three way action, but as I would have no use for it because I don't have any proper dynamics, keep it really cheap.
> 
> Personally, I wouldn't bet my left nut on being able to tell my computer sound card from my beta22 or the obj2. Then again, I have the critical listening abilities akin to a bucket of rocks.


 

 *shrug* I thought ~$100 was the more realistic value. You could probably build a JDScmoy for around $30 too.


----------



## bcg27

Quote: 





shike said:


> It's funny how those that have contributed the_ least_ to this thread are some of the most vocal, and curiously have based their arguments not against the amp but the designer and taking personal swings at members.  Insecurity knows no bounds it seems.
> 
> I'm still thoroughly enjoying my O2 to say the least. ^_^


 

 Has anyone really contributed to this thread? As far as I can tell it has pretty much just been bickering so far, and probably will continue to be the same until people get boards in their hands. As far as I know deadlylover is the only one who has actually built one of these? This is the DIY forum, I think other discussion should be moved elsewhere or not had at all.


----------



## Soaa-

Quote: 





shike said:


> It's funny how those that have contributed the_ least_ to this thread are some of the most vocal, and curiously have based their arguments not against the amp but the designer and taking personal swings at members.


 

 Are voltage swings okay then? /shot


----------



## ujamerstand

I have never seen such a hostile DIY thread before. Can we stop the cheap shots against each other here? It does not benefit anyone.


----------



## wakibaki

The good thing about this thread (one good thing) and about many subjective/objective threads, is that while it's sometimes a bad-tempered argument more than a discussion or conversation, it is still a conversation to some degree. Many threads just die out because because of lack of steam. A bunch of people all going 'isn't so-and-so great' and congratulating each other on their good taste and judgement on buying it can get a bit boring. Being on the objectivist side myself, and not being able to afford $6000 worth of test gear, I sometimes find it a bit difficult to enthuse about my latest creation, because even though I may be well pleased with it, I don't necessarily find a great audible improvement over my last great creation, because  (apart from anything else) I generally think that they're all pretty much beyond the threshold of audible distinction. I'm not much given to hearing 'veils lifted', or 'increased texture and detail' or 'greater air and soundstaging'. Over the years I've heard some improvement in the intelligibility of vocals from, say, Mick Jagger or Van Morrison, but this pretty much reached a limit quite some few years ago.
   
  As far as point-to-point or perfboard builds of the O2 are concerned, I think the nwavguy may be being a bit oversensitive about their potential defects. I'm not criticising him in this, he has every right to be defensive about his creation and wish to see it set off only in the best light, but this may lead him to be overly prescriptive about the build.
   
  Some things about any build using his schematic are not going to suffer from the layout. The output current into a given load is pretty much governed by the two driver chips per channel, as is the output impedance, and obviously the peak-to-peak voltage can easily be matched or even exceeded. These are 3 of his main complaints about various marketed designs. The intrinsic noise and distortion due to the components are likewise not subject to any more variation than can be expected by any build on his design of PCB. The noise due to the topology remains the same. The feedback loops are local only, so there is no likelihood of pickup in a global feedback arrangement with a large physical loop area. Instability again is more likely where there are circuit loops with a large area, a neat build is all that is required to avoid these, the chips themselves do not have a huge slew rate and bandwidth, contributing to a reduced tendency to oscillate.
   
  This is not to say that THD + N might not be adversely affected by inductive or static pickup particularly from the power traces or because of a poorly implemented grounding scheme, but if you don't hear any hum, the chances are that there will be no audible difference between a build on his PCB and any other, the standards he has set for THD and noise performance almost certainly exceed the threshold of audibility by some margin. Many people have built cmoys and other headamps with evident satisfaction on perfboard, judging from the enthusiasm with which they defend their builds.
   
  w


----------



## kiteki

There's a lot of THD+N in this thread, but it's all in good measure. 
   
  The whole DIY conquest, it has it's plusses and it's minuses.


----------



## n3rdling

When are the PCBs scheduled to ship?


----------



## deadlylover

Quote: 





n3rdling said:


> When are the PCBs scheduled to ship?


 

 In about a week or two, I think they're currently halfway in production or something like that.


----------



## kingpage

The mention of O2, in another thread unrelated to amps here at Head-fi (it was about cheap sound cards), has helped me catch up with what's been happening in the last 6 months while I was absent from Head-fi. 

This is really eye-opening for me. I really liked head-fi until reading about these recent incidents. I think I'm liking my onboard laptop sound card and my new $4 CM119 USB sound card more and more. 

I look forward to a desktop (no batteries) version that can fit into my Edifier HA11 amp enclosure (79mm*61mm*36mm), so if I ever want to build it, I can use my existing cool-looking golden case rather than buying one. I wouldn't be surprised if NwAvGuy designs a DAC that will go well with the Objective 2 amp.


----------



## Satellite_6

I get flamed everytime I mention you know who. Anyway, I can't wait for the ODA. 
   
  "Getting back on topic, I'll be publishing some DAC tests soon and I'm still looking into an internal (single box) solution for the upcoming desktop version of the O2."
   
  (diyaudio thread)


----------



## Willakan

It is worth noting that NwAvGuy has absolutely no intention of designing a DAC himself, for reasons along the lines of the fact there are plenty of cheap, good ones and they're much harder to build and design.


----------



## alphaman

Quote:


willakan said:


> It is worth noting that NwAvGuy has absolutely no intention of designing a DAC himself, for reasons along the lines of the fact there are plenty of cheap, good ones and they're much harder to build and design.


 
  Despite the innate and PUTATIVE quality of the O2, the addition of an internal DAC section would not compel me to build/purchase. OTOH, if NwAvGuy were to also add _modern_ DAP features -- emulating QLS-QA350 or HiFi-Man 801, Colorfly C4, etc. -- *but w/o video/games/fancy LCD* ... _that_ would be a unique and worthwhile project.


----------



## Shike

alphaman said:


> AP features -- emulating QLS-QA350 or HiFi-Man 801, Colorfly C4, etc.




I fail to understand what you're getting at here - if you mean rolled-off treble he'd definitely want to avoid it.


----------



## Head Injury

I think he means turn the Objective2 into a portable player


----------



## alphaman

Quote:


head injury said:


> I think he means turn the Objective2 into a portable player


 
  Yup ... or creating ANOTHER "Objective n" device with MY requirements. The only ones that matter, of course


----------



## maverickronin

While we're at it why don't we ask him to replace the batteries with a portable fusion reactor which will power the amp for 5 straight years from the tritium in your wrist watch?
   
  Under $30 in parts from Mouser as well please.
   
  It shouldn't be that hard, but thanks for the effort anyway!


----------



## SpaceTimeMorph

Fusion's overrated, ... I think I could get this  to work in an O2.


----------



## Satellite_6

I have a 5v source so I need a redesigned version. 
	

	
	
		
		

		
		
	


	



   
  edited.


----------



## Willakan

You have a 5V source without a volume knob? The one in your profile isn't.
   
  EDIT: Bleh, missed the sarcasm (I did didn't I?)


----------



## maverickronin

Quote: 





spacetimemorph said:


> Fusion's overrated, ... I think I could get this  to work in an O2.


 
   
While we're at it...


----------



## mikeaj

satellite_6 said:


> I have a 5v source so I need a redesigned version.
> 
> 
> 
> ...




Pay me a reasonable sum (I accept payment in pure gold cables) and I will redesign the O2 to work with your 5V source! Since I'm so pro, I could get the new O2 approved with Lord Voldemort. But that would cost extra.

Oh crap I need to register as a sponsor first.


----------



## Head Injury

Quote: 





mikeaj said:


> Pay me a reasonable sum (I accept payment in pure gold cables) and I will redesign the O2 to work with your 5V source! Since I'm so pro, I could get the new O2 approved with Lord Voldemort. But that would cost extra.
> Oh crap I need to register as a sponsor first.


 

 Don't forget to upgrade the opamps, too! All the ones in this amp are too cheap to sound good.


----------



## alphaman

Quote: 





head injury said:


> Don't forget to upgrade the opamps, too! All the ones in this amp are too cheap to sound good.


 
  I assume you're being sarcastic. If not ... Huh?????! 
  NwAvGuy's "myth-busting" paradigm:
   
*Quote:*


> *MYTH: MOST OP AMPS SOUND DIFFERENT -There’s a general perception that op amps sound different. [...]*


 
  Whoa Nelly .... Aren't op-amps ... uh ... _amps?_


----------



## Willakan

He is indeed being sarcastic.


----------



## kiteki

Quote: 





alphaman said:


> Despite the innate and PUTATIVE quality of the O2, the addition of an internal DAC section would not compel me to build/purchase. OTOH, if NwAvGuy were to also add *modern* DAP features -- emulating QLS-QA350 or *HiFi-Man *801, Colorfly C4, etc. -- but w/o video/games/fancy LCD ... _that_ would be a unique and worthwhile project.


 


 Uh...... HiFiMAN and modern don't belong in the same sentence, HiFiMAN's favorite DAC is from 1979, and their products are about sound affectionism, not necessarily sound-quality/performance.


----------



## MrSlim

Flynhawaiian and I have just opened an "official" O2 Front Panel Group Buy Thread at DIY audio : http://www.diyaudio.com/forums/group-buys/197975-official-o2-headphone-amp-front-panel-group-buy.html#post2736247
   
  The previous interest thread was mainly to test the waters and finalize the design.


----------



## Questhate

Quote: 





mrslim said:


> Flynhawaiian and I have just opened an "official" O2 Front Panel Group Buy Thread at DIY audio : http://www.diyaudio.com/forums/group-buys/197975-official-o2-headphone-amp-front-panel-group-buy.html#post2736247
> 
> The previous interest thread was mainly to test the waters and finalize the design.


 
   
  Nice! I just put in an order for 2.


----------



## fubar3

Quote: 





deadlylover said:


> Yeah I'm sorry man, my bad. I just thought I was taking one for the team by cooking up another prototype,


 
  Hey wait.. since there is already a circuit board for the O2, it is long past the prototype stage.  Sounds like you have some DIY practice and can render a schematic into a working amp. But it is kind of tedious just doing an existing design. Why not do a Steve Jobs and invent something novel. I don't know what that would be since a headphone amp just needs a checklist. Power supply.. check, gain-stage.. check, buffer stage.. check. And the usual hardware fiddly bits.  A portable amp is more interesting since you have to trade-off battery life and performance.


----------



## deadlylover

Quote: 





fubar3 said:


> Hey wait.. since there is already a circuit board for the O2, it is long past the prototype stage.  Sounds like you have some DIY practice and can render a schematic into a working amp. But it is kind of tedious just doing an existing design. Why not do a Steve Jobs and invent something novel. I don't know what that would be since a headphone amp just needs a checklist. Power supply.. check, gain-stage.. check, buffer stage.. check. And the usual hardware fiddly bits.  A portable amp is more interesting since you have to trade-off battery life and performance.


 
   
  My comment on cooking up the prototype was to do with the extreme lack of sound impressions to do with the Obj2 at the time. Hell, it's been a few months now and you can count the number of impressions here on one hand.
   
  Dynamics bore me, and one does not simply surpass the DIY T2. People have thought long and hard about trying to improve the slew rate, distortion characteristics or whatever of the DIY T2, and we just don't see it happening at the moment. High voltage transistors have kinda left the world behind along with the death of CRT screens.
  
  A portable stat amp? Yeah right.


----------



## kiteki

So you use a CRT monitor dl?
   
  p.s. well done on 666 posts.


----------



## Willakan

Quote:


deadlylover said:


> Hell, it's been a few months now and you can count the number of impressions here on one hand.


   
  The thousand-board GB is flying over to the UK as we speak.


----------



## estreeter

@alphaman, Fang Bian makes no secret of the fact that the started the HM-801 project because he wanted to recapture the analog sound of old Walkmans from the 80s. Its hardly the basis for 'accuracy' or 'neutrality', as undeniably enjoyable as many here find the player's sound.


----------



## estreeter

Quote: 





alphaman said:


> Quote:
> Despite the innate and PUTATIVE quality of the O2, the addition of an internal DAC section would not compel me to build/purchase. OTOH, if NwAvGuy were to also add _modern_ DAP features -- emulating QLS-QA350 or HiFi-Man 801, Colorfly C4, etc. -- *but w/o video/games/fancy LCD* ... _that_ would be a unique and worthwhile project.


 
   
  As much as I admire the QA-350, if that resembles a 'modern' DAP I'd hate to see an old one. The devices you list are 'Portable Media Players', sure, but I cant see Cowon trying to buy up the patents anytime soon.


----------



## fubar3

Quote: 





deadlylover said:


> My comment on cooking up the prototype was to do with the extreme lack of sound impressions to do with the Obj2....


 
  Well, if you are doing a DIY investigation, I would be interested to know what difference does it make if an an amp is buffered or not. So if an amp has buffered and unbuffered outputs, or a method of switching, then one could investigate. For example, when doing opamp rolling, the variance of buffering might be significant.


----------



## deadlylover

Quote: 





kiteki said:


> So you use a CRT monitor dl?


 

 Nah, what is this, year 2003? 
	

	
	
		
		

		
		
	


	



   
  Quote: 





willakan said:


> The thousand-board GB is flying over to the UK as we speak.


 
   
  Nice, that should be interesting. I'm guessing a lot of people will enjoy the Obj2. I'm waiting for the desktop version at the moment, so I can prototype it quickly, stick some ponies on it, then laugh at people while they catch up a few months later. That, and run into every single avoidable problem/glitch that's discussed in the articles by pure skill/luck. 
	

	
	
		
		

		
		
	


	



  
  Quote: 





fubar3 said:


> Well, if you are doing a DIY investigation, I would be interested to know what difference does it make if an an amp is buffered or not. So if an amp has buffered and unbuffered outputs, or a method of switching, then one could investigate. For example, when doing opamp rolling, the variance of buffering might be significant.


 
   
  Nah I'm not doing a crime scene investigation, my Obj2 prototype was finished a few months ago, and I have no intention of molesting it as it's a piece of history/gives me warm and fuzzies. Build one and find out yourself, it's cheap and really easy to make. Where's all the DIY spirit around here =P.


----------



## firev1

I just stumbled on this not too long ago, been looking into DIY audio for a while but I did not know where to start and I guess this would be a good project to do. Pretty new to this but I have some experience with circuitry in school building clocks and stuff. Know any good places to prototype PCBs since I missed the GB and how to order them( layers etc)?


----------



## khaos974

Quote: 





firev1 said:


> I just stumbled on this not too long ago, been looking into DIY audio for a while but I did not know where to start and I guess this would be a good project to do. Pretty new to this but I have some experience with circuitry in school building clocks and stuff. Know any good places to prototype PCBs since I missed the GB and how to order them( layers etc)?


 

 The main thread is at http://www.diyaudio.com/forums/ under the"headphones systems" section.


----------



## Willakan

Olli1324 has a few left surplus boards from the GB. The UK orders are being put in the post (from the UK) on Monday, with the rest of the world following on either Wednesday or Tuesday. 
   
  After that, the surplus boards will be flogged off at £5 (plus postage, which is only about 60p). The only other alternative is to get your own run of boards done, which for most people will be a rather unattractively expensive option.


----------



## vizzle

Anyone know is european source of o2 is available at moment? and I mean fully assembled unit, I dont think I can handle kit


----------



## mikeaj

Quote: 





vizzle said:


> Anyone know is european source of o2 is available at moment? and I mean fully assembled unit, I dont think I can handle kit


 

 You can try buying from a DIY builder.
   
  Aside from that, you can pre-order now from Epiphany Acoustics in the UK.  Price is nominally 100 GBP, no payment until shipping.  Details here:
http://www.epiphany-acoustics.co.uk/7.html


----------



## brown5629

Just wanted to mention, my buddy is selling 8 of the O2 amps (assembled PCB) on diyaudio. 
   
http://www.diyaudio.com/forums/swap-meet/198536-fs-o2-headphone-amp-assembled-boards.html
   
  I built one myself, and so far I love it. Matches perfectly with my FrankenZero DAC that I modded.


----------



## i_djoel2000

Quote: 





brown5629 said:


> Just wanted to mention, my buddy is selling 8 of the O2 amps (assembled PCB) on diyaudio.
> 
> http://www.diyaudio.com/forums/swap-meet/198536-fs-o2-headphone-amp-assembled-boards.html
> 
> I built one myself, and so far I love it. Matches perfectly with my FrankenZero DAC that I modded.


 


  do you have any branded amp that you can compare to?


----------



## Willakan

I do believe I am the first person to get their hands on a board from the GB. Image hosting broken for me at the moment, so will link: http://i52.tinypic.com/29w0ld0.jpg


----------



## kiteki

Wow, nice looking board!


----------



## firev1

Quote: 





willakan said:


> I do believe I am the first person to get their hands on a board from the GB. Image hosting broken for me at the moment, so will link: http://i52.tinypic.com/29w0ld0.jpg


 


  Looking at the list, I will be getting my hands on a board once olli announces the spare boards for all. Looks great though  Can't wait for my panels too.


----------



## Willakan

I have started stuffing the board: regrettably, a lack of anything to hold the PCB or other suitable equipment(I do have a solder sucker thankfully) and abominably low levels of manual dexterity are making it slow going. I think I started using far too much solder (been a while/used to larger pads) so the quality of my joints is gradually improving, but it's still going to take a while - especially considering I opted to DIY the front panel.


----------



## deadlylover

Quote: 





willakan said:


> I have started stuffing the board: regrettably, a lack of anything to hold the PCB or other suitable equipment(I do have a solder sucker thankfully) and abominably low levels of manual dexterity are making it slow going. I think I started using far too much solder (been a while/used to larger pads) so the quality of my joints is gradually improving, but it's still going to take a while - especially considering I opted to DIY the front panel.


 

 I don't use anything to hold boards either when I DIY, are you stuffing the boards like 8 components at a time and then soldering those components in one go? I hope you aren't doing it one component at a time, the constant flipping will drive me insane 
	

	
	
		
		

		
		
	


	



   
  I hate using something to hold the boards because sometimes the parts wiggle while I'm soldering, and that just makes me mad.


----------



## estreeter

Looks great - cant wait to hear various impressions from those-not-easily-consumed-by-hype.


----------



## fubar3

Quote: 





deadlylover said:


> I hate using something to hold the boards because sometimes the parts wiggle while I'm soldering, and that just makes me mad.


 

 If reliability is important, then the parts should not wiggle.  Bending component leads slightly will cause them to press against the thru-hole. Then the solder is responsible only for the conductivity. It is not so good for mechanical support.


----------



## francisdemarte

Still haven't gotten my board yet...


----------



## BobSaysHi

Quote: 





francisdemarte said:


> Still haven't gotten my board yet...


 

 They just shipped from Europe, dude.


----------



## Pars

Interesting board layout...
   

   
  Not sure why the ground plane (green arrows) isn't filled in more. Also, there are a couple of traces connected on one end, but not the other (circles). Antenna?
   
  I grabbed the gerbers posted, and used a gerber viewer to produce the layer images. Apparently from the reviews, the amp is quiet, so it is probably doing its job somewhat.


----------



## fishski13

Quote: 





pars said:


> Interesting board layout...
> 
> 
> 
> ...


 

 i once cut my own ground plane for a guitar amp out of aluminum with a nice Freud circular saw blade 
	

	
	
		
		

		
		
	


	




.


----------



## LizardKing1

Guys sorry to bother, but I'm really considering this for christmas. I've been in wuv with the idea of a purely objective amp since I read about it. So right now my only choice, living in Portugal, is Epiphany? I just think paying 130€ + shipping for something that originally costed around 50$ is a bit much...


----------



## deadlylover

Quote: 





lizardking1 said:


> Guys sorry to bother, but I'm really considering this for christmas. I've been in wuv with the idea of a purely objective amp since I read about it. So right now my only choice, living in Portugal, is Epiphany? I just think paying 130€ + shipping for something that originally costed around 50$ is a bit much...


 

 Parts costs with shipping will run you about ~$100-$120 if you don't take advantage of any group buys and if you live overseas.
   
  So that's not a terrible price fully built, but yeah, kinda sucks not living in the states eh?


----------



## LizardKing1

Quote: 





deadlylover said:


> Parts costs with shipping will run you about ~$100-$120 if you don't take advantage of any group buys and if you live overseas.
> 
> So that's not a terrible price fully built, but yeah, kinda sucks not living in the states eh?


 

 Not really. Healtcare kind of pays off over here =)
  Just kidding. In terms of imports yes it sucks, since most of the things I want to buy in audio come from US sellers.
  Has anyone bought one from Epiphany Acoustics?


----------



## khaos974

Quote: 





lizardking1 said:


> Not really. Healtcare kind of pays off over here =)
> Just kidding. In terms of imports yes it sucks, since most of the things I want to buy in audio come from US sellers.
> Has anyone bought one from Epiphany Acoustics?


 

 I don't think Epiphany Audio is fully operational yet, but it's the same person running the 1000 PCB group buy on diyaudio.com and running Epiphany.


----------



## bcg27

Quote: 





lizardking1 said:


> Guys sorry to bother, but I'm really considering this for christmas. I've been in wuv with the idea of a purely objective amp since I read about it. So right now my only choice, living in Portugal, is Epiphany? I just think paying 130€ + shipping for something that originally costed around 50$ is a bit much...


 

 Do you really think it's any better for any of the commercial stuff people buy here? In fact there is probably a much bigger markup for most of the stuff. The difference is you never hear what parts costs actually are so you can't get offended. If only there was an iSuppli type thing for amps and dacs


----------



## mikeaj

They're running a stragglers / 2nd run group buy on diyaudio right now, at least for the PCB.  Maybe some of those participants in your region are also interested in a mini-parts group buy, which could help a lot.


----------



## svyr

deadlylover said:


> Parts costs with shipping will run you about ~$100-$120 if you don't take advantage of any group buys and if you live overseas.
> 
> So that's not a terrible price fully built, but yeah, kinda sucks not living in the states eh?




considering the time you'd spend ordering parts then soldering it and the case and testing it.. it seems pretty ok


----------



## LizardKing1

I tried that, I created the O2 thread on a Portuguese tech forum. It created some interest, but eventually people stopped posting and it was all talk. "I might be interested" well if no one does anything, interest is all you'll get. So I'm considering a more reliable source.


----------



## kiteki

Quote: 





deadlylover said:


> Parts costs with shipping will run you about* ~$100-$120* if you don't take advantage of any group buys and if you live overseas.


 

 Is that the portable version, including the steel enclosure?
   
   
  Quote: 





> Originally Posted by *LizardKing1* /img/forum/go_quote.gif
> 
> [...]
> Has anyone bought one from Epiphany Acoustics?


 

 Yes.


----------



## BobSaysHi

Quote: 





lizardking1 said:


> Guys sorry to bother, but I'm really considering this for christmas. I've been in *wuv* with the idea of a purely objective amp since I read about it. So right now my only choice, living in Portugal, is Epiphany? I just think paying 130€ + shipping for something that originally costed around 50$ is a bit much...


 

 Please don't do this again.


----------



## firev1

Quote: 





lizardking1 said:


> Guys sorry to bother, but I'm really considering this for christmas. I've been in wuv with the idea of a purely objective amp since I read about it. So right now my only choice, living in Portugal, is Epiphany? I just think paying 130€ + shipping for something that originally costed around 50$ is a bit much...


 


  Its not much considering 1. the time spent building it 2. the boards are not readily available 3.front panels are not readily available 4. They have a living to make. Alternatively you should at least try to secure a board first because those can cost a bomb to make individually.


----------



## kiteki

and 5. He is waiting for the preorder money, so he can afford to buy the enclosures and front panels.


----------



## firev1

So anyway, who is building a desktop version? I'm ordering the parts from the GB and will be placing orders for the electronics when I get my next pay.


----------



## Willakan

Word of warning: The 1/4 inch jack listed in the BOM is inappropriate. Not sure if they've been updated yet. You *could* use it, but it would require some first class botching - which I am currently enjoying.
   
  I am building a desktop version. Board was with me on Wednesday, so the soldering is finished, but haven't had time to test it yet. Come tomorrow, I should have a fully working O2, minus case front panel - will do a temp one out of card until I have the opportunity to drill and engrave a front panel myself in a few weeks time.


----------



## cheapskateaudio

Quote: 





willakan said:


> Word of warning: The 1/4 inch jack listed in the BOM is inappropriate. Not sure if they've been updated yet. You *could* use it, but it would require some first class botching - which I am currently enjoying.
> 
> I am building a desktop version. Board was with me on Wednesday, so the soldering is finished, but haven't had time to test it yet. Come tomorrow, I should have a fully working O2, minus case front panel - will do a temp one out of card until I have the opportunity to drill and engrave a front panel myself in a few weeks time.


 


  Any ideas on what the proper 1/4" jack is? What's the problem with the specified one?


----------



## firev1

Quote: 





willakan said:


> Word of warning: The 1/4 inch jack listed in the BOM is inappropriate. Not sure if they've been updated yet. You *could* use it, but it would require some first class botching - which I am currently enjoying.
> 
> I am building a desktop version. Board was with me on Wednesday, so the soldering is finished, but haven't had time to test it yet. Come tomorrow, I should have a fully working O2, minus case front panel - will do a temp one out of card until I have the opportunity to drill and engrave a front panel myself in a few weeks time.


 

  
  I know, I have to replace it with Neutrik NRJ3HF-1 and NRJ-NUT-B as stated by mrslim. Oh cheapskateaudio, you will have to use those stated and as a bonus, its cheaper too  As for first class botching, I do have the tools to reduce panel thickness at school(engineering).


----------



## cheapskateaudio

Quote: 





firev1 said:


> I know, I have to replace it with Neutrik NRJ3HF-1 and NRJ-NUT-B as stated by mrslim. Oh cheapskateaudio, you will have to use those stated and as a bonus, its cheaper too  As for first class botching, I do have the tools to reduce panel thickness at school(engineering).


 


  Thanks firev1!


----------



## LizardKing1

Quote: 





firev1 said:


> Its not much considering 1. the time spent building it 2. the boards are not readily available 3.front panels are not readily available 4. They have a living to make. Alternatively you should at least try to secure a board first because those can cost a bomb to make individually.


 

 I guess I'm used to bigger companies who mass-produce things and can cut costs. It's not that 130€ is a lot, I just mean it's a lot compared to what NwAvGuy's prediction of parts cost would be. But I guess you make a point.
   
  When you say "secure a board" do you mean with the PCO manufacturer or Epiphany?


----------



## estreeter

Quote: 





lizardking1 said:


> I guess I'm used to bigger companies who mass-produce things and can cut costs. It's not that 130€ is a lot, I just mean it's a lot compared to what NwAvGuy's prediction of parts cost would be. But I guess you make a point.
> 
> When you say "secure a board" do you mean with the PCO manufacturer or Epiphany?


 


  Look on the bright side - you are paying zero Euros for the time and effort nwavguy put into the design. Email Ray Samuels and ask him if he'd be prepared to do the same.


----------



## Head Injury

Quote: 





lizardking1 said:


> I guess I'm used to bigger companies who mass-produce things and can cut costs. It's not that 130€ is a lot, I just mean it's a lot compared to what NwAvGuy's prediction of parts cost would be. But I guess you make a point.


 

 They can mass produce things and cut costs, but that doesn't mean the prices they offer reflect that


----------



## Soaa-

Quote: 





lizardking1 said:


> I guess I'm used to bigger companies who mass-produce things and can cut costs. It's not that 130€ is a lot, I just mean it's a lot compared to what NwAvGuy's prediction of parts cost would be. But I guess you make a point.
> 
> When you say "secure a board" do you mean with the PCO manufacturer or Epiphany?


 

 Parts cost was $30 not including a case or batteries. Basically, at $30, your amp doesn't even have power yet. He estimated the cost to be a bit over $100 with a case, batteries and a power adapter. Factor in some profit and 130 EUR isn't that much for an amp that measures this well.


----------



## firev1

Quote: 





lizardking1 said:


> When you say "secure a board" do you mean with the PCO manufacturer or Epiphany?


 

  
  From the group buys going on.


----------



## brown5629

Quote: 





i_djoel2000 said:


> do you have any branded amp that you can compare to?


 

  
  I haven't tried too many amps.
  Another I have used regularly is the Xiang Sheng 708B, tube amp. Personally, I felt like this amp had very limited imaging/soundstage.
  That isn't really a fair comparison though - different kind of amp.
   
  I really prefer the accurate sound of the O2.


----------



## kiteki

Quote: 





soaa- said:


> Parts cost was $30 not including a case or batteries. Basically, at $30, your amp doesn't even have power yet. He estimated the cost to be a bit over $100 with a case, batteries and a power adapter. Factor in some profit and 130 EUR isn't that much for an amp that measures this well.


 

 x2


----------



## estreeter

Just to play Devil's Advocate, I've never heard the Benchmark DAC1, but it measures *extremely* well, right up to the point where most who have given their impressions here plugged a headphone into it. Just sayin.


----------



## Willakan

Quote:


estreeter said:


> Just to play Devil's Advocate, I've never heard the Benchmark DAC1, but it measures *extremely* well, right up to the point where most who have given their impressions here plugged a headphone into it. Just sayin.


   
  I am quite happy to entertain the possibility that most of the people who disparage the Benchmark's headphone amp either like colouration/are under the influence of unavoidable bias/are component snobs/ are experiencing a combination of the aforementioned conditions. Recently, I stumbled across an interview with a member of the Benchmark design team who expressed surprise that more people weren't using the headphone amp that comes with it, considering the objective quality of the output.
   
  Built-in headphone amps always get slated. It's the way of the audiophile world. Look at the amp in the Essence ST - essentially ideal for driving high-impedance 'phones, but why use that when you could plug them into some high-distortion monstrosity instead?
   
  I mean, like, the built in amp - it's in a computer, full of noise and stuff. And it's not separate in a giant metal box. And it doesn't come with a toroidal transformer the size of my head. 
   
  It would be funnier if I hadn't seen people make some of the above arguments seriously.


----------



## LizardKing1

Quote: 





estreeter said:


> Look on the bright side - you are paying zero Euros for the time and effort nwavguy put into the design. Email Ray Samuels and ask him if he'd be prepared to do the same.


 
   
  Don't get me wrong, I am more than thankful for what he created. From my very limited knowledge of amps, I understand it's something designed to sound transparent and adding no glamour value. I wish more people would use Creative Commons Licenses on stuff like this.

  
  Quote: 





soaa- said:


> Parts cost was $30 not including a case or batteries. Basically, at $30, your amp doesn't even have power yet. He estimated the cost to be a bit over $100 with a case, batteries and a power adapter. Factor in some profit and 130 EUR isn't that much for an amp that measures this well.


 

 Oh I see. 30$ included the board?


----------



## limpidglitch

$30 for a 'functional' amplifier, meaning the bare minimmum for it to make sound: A fully stuffed PCB.


----------



## deadlylover

Quote: 





limpidglitch said:


> $30 for a 'functional' amplifier, meaning the bare minimmum for it to make sound: A fully stuffed PCB.


 
   
  If by functional amplifier you mean paperweight, then yes. 
	

	
	
		
		

		
		
	


	



   
  Last I checked the $30 doesn't include the AC adapter or the batteries.


----------



## kiteki

Quote: 





deadlylover said:


> If by functional amplifier you mean paperweight, then yes.
> 
> 
> 
> ...


 

 I think $30 was the price for "meet DIY specialist Billy-Bob" who can walk into an electronics store in the USA.
   
  100 pounds + 17 pounds Xpress shipping is the price for X internet user in X part of the world, that wants X magical fully assembled unit in X smart black casing with 2 X NiMh batteries and X power adaptorz, so he can sign into X forum and say this X sounds XXX!!


----------



## limpidglitch

Quote: 





deadlylover said:


> If by functional amplifier you mean paperweight, then yes.
> 
> 
> 
> ...


 

  
  The transformer in the BOM is $5.55, so in that case it's $35.55 for a naked functional amplifier.
  But as Kiteki pointed out, there is no way in hell this will work out for anyone outside the US.


----------



## ohmer

JDS Labs has it for $9.75
  http://www.jdslabs.com/item.php?fetchitem=O2PCB


----------



## LizardKing1

Quote: 





ohmer said:


> JDS Labs has it for $9.75
> http://www.jdslabs.com/item.php?fetchitem=O2PCB


 

 Isn't that really cheap compared to what they cost normally? I'm getting 2 if I can o.o 1 for me to probably ruin with my lack of skills, and one for me to ask (pay) someone more experienced to do.


----------



## mikeaj

Quote: 





lizardking1 said:


> Isn't that really cheap compared to what they cost normally? I'm getting 2 if I can o.o 1 for me to probably ruin with my lack of skills, and one for me to ask (pay) someone more experienced to do.


 

 Hopefully I'm not misunderstanding what you mean, but what's being offered on JDSLabs is just the PCB, no other parts.  The technical docs specifying the layout of the PCB are freely available, but actual boards with all the right traces, holes, solder mask, etc. do not since that kind of stuff costs money to make, obviously.
   
  $10 is a reasonable price, and about what was expected, considering that the seller wants to make money.  I'm not sure if they have a "normal" cost since they're not really available elsewhere.  The ~900 PCB group buy came to something around 1 GBP per board plus shipping (a couple / few more GBP), because manufacturing those PCBs in bulk saves a lot of money per board.


----------



## ohmer

Quote: 





mikeaj said:


> Hopefully I'm not misunderstanding what you mean, but what's being offered on JDSLabs is just the PCB, no other parts.  The technical docs specifying the layout of the PCB are freely available, but actual boards with all the right traces, holes, solder mask, etc. do not since that kind of stuff costs money to make, obviously.
> 
> $10 is a reasonable price, and about what was expected, considering that the seller wants to make money.  I'm not sure if they have a "normal" cost since they're not really available elsewhere.  The ~900 PCB group buy came to something around 1 GBP per board plus shipping (a couple / few more GBP), because manufacturing those PCBs in bulk saves a lot of money per board.


 

 Now I'm confused. It has a solder mask, holes, and traces. You just don't get the diodes, caps, resistors, sockets, knob, etc...
  The group buy was about the same price per board but with shipping included. At JDS you have to pay additional for shipping. So you save a few bucks from the group buys but nothing crazy unless you buy more than a few. I was just providing this as an alternative if people can't get into the group buys on time and they can't wait for the next wave.
   
  United States Shipping Rates: 
   
*






 USPS First Class - $3.30 





 USPS Priority - $6.25 





 USPS Express Mail - $18.80 





 UPS Ground - $11.56 





 UPS 2nd Day Air - $23.10 





 UPS Next Day Saver - $39.65 *
  

International Shipping Rates: 
*





 International Economy (Uninsured) - $6.30 





 Standard International (Recommended) - $7.30 





 International Priority Air - $16.45 





 International Express - $29.80 





 Global Priority - $50.95 *


----------



## Willakan

The group buy was about £2.80 per board, so it is a bit more expensive, but nothing wholly unreasonable.


----------



## Paul Blythe

Very intrested in the O2 as a diy build, think I've spent as much as the rough cost of this build on 2 cmoy builds and  some extra opamps for rolling  ... at least I've gained some good basic building skills...
   
Question; though designed as a portable amp, can the pcb be used for destop implementation if mounted in a different case. Rear mounted RCA phono inputs would be preferable to the front jack input.
   
Quick search with my local parts supplier (RS Components) shows the spec'd NJM4556AD as a disontinued product!? ...


----------



## deadlylover

Quote: 





paul blythe said:


> Very intrested in the O2 as a diy build, think I've spent as much as the rough cost of this build on 2 cmoy builds and  some extra opamps for rolling  ... at least I've gained some good basic building skills...
> 
> Question; though designed as a portable amp, can the pcb be used for destop implementation if mounted in a different case. Rear mounted RCA phono inputs would be preferable to the front jack input.
> 
> Quick search with my local parts supplier (RS Components) shows the spec'd NJM4556AD as a disontinued product!? ...


 
   
  Yes you can toss RCA jacks on it, that's what I've done with mine, although, you might want to wait for the proper desktop version (I have no idea what the changes would be).
   
  Sour about that component availability =/, there's still plenty over at mouser.


----------



## Maverickmonk

Any word of whether it will power a 600ohm beast like beyer's or sextetts?


----------



## limpidglitch

Beyers: Yes; Sextetts: No


----------



## Paul Blythe

@ Deadlylover: thanks, just checked mouser & yes lots of the 4556AD's in stock, but €20 is very steep for duty/p&p ... I'll try finding some UK stock first.


----------



## LizardKing1

Quote: 





mikeaj said:


> Hopefully I'm not misunderstanding what you mean, but what's being offered on JDSLabs is just the PCB, no other parts.  The technical docs specifying the layout of the PCB are freely available, but actual boards with all the right traces, holes, solder mask, etc. do not since that kind of stuff costs money to make, obviously.
> 
> $10 is a reasonable price, and about what was expected, considering that the seller wants to make money.  I'm not sure if they have a "normal" cost since they're not really available elsewhere.  The ~900 PCB group buy came to something around 1 GBP per board plus shipping (a couple / few more GBP), because manufacturing those PCBs in bulk saves a lot of money per board.


 

 I understand it's just the board, no components. Still, the idea that it would cost around 30$ just for the board formed in my head. Good to know I was wrong 
	

	
	
		
		

		
		
	


	




 and the shipping isn't anything too extravagant either!
   
  Quote: 





deadlylover said:


> Yes you can toss RCA jacks on it, that's what I've done with mine, although, you might want to wait for the proper desktop version (I have no idea what the changes would be).
> 
> Sour about that component availability =/, there's still plenty over at mouser.


 

 I never read anything about a desktop version on his blog, but it's the second time I'm hearing of this. Any word of when it will come out?


----------



## deadlylover

Quote: 





lizardking1 said:


> I never read anything about a desktop version on his blog, but it's the second time I'm hearing of this. Any word of when it will come out?


 
   
  As a complete shot in the dark, sometime before the end of this year. And as far as I know, it's got a different power supply and relays for the output. I think he's doing something about the input stage clipping as well.


----------



## Questhate

Anyone finish building this yet? 
   
  I ordered the PCBs and front panels through the group buys on DIYaudio. All of the mouser parts were ordered, so those should be arriving mid-week. The volume knobs all seemed to be backordered (in every color), so my hand was forced to get the nicer metal knobs from Digi-Key (2 for about $10 incl. shipping). For me, the final price ended up being $76 including PCB, board parts, upgraded volume knob, front panel, casing, power supply and batteries.
   
  Good to see that JDS Labs is offering the PCBs. I bought a couple of the spares from Olli just to have around, but they ended up costing about the same as JDS Labs's price.


----------



## Magedark

Ok, I just ordered PCB, and the parts (Not enclosure or battery) I should order within the week. Looking forward to this...


----------



## estreeter

I'm paying (ahem..) _somewhat more_ for a 'turnkey' complete amp, but considering that it will be 'Made in the UK' (!), I still think getting an amp delivered to Oz for less than 200 USD all up is a bargain. I paid considerably more than 200 AUD for the uHA-120, also made in the UK, and it will make for an interesting comparison, albeit one without detailed measurements for Justin's amp. Also very keen to see the various housings/configurations DiYers come up with for this amp.


----------



## kiteki

Quote: 





paul blythe said:


> @ Deadlylover: thanks, just checked mouser & yes lots of the 4556AD's in stock, but €20 is very steep for duty/p&p ... I'll try finding some UK stock first.


 

http://www.ebay.com.au/itm/NJM4556AD-Integrated-Circuit-x-1-pieces-NJM4556-/160618319419


----------



## deadlylover

Quote: 





kiteki said:


> http://www.ebay.com.au/itm/NJM4556AD-Integrated-Circuit-x-1-pieces-NJM4556-/160618319419


 

 Five bucks for a part that only costs $0.77. 
	

	
	
		
		

		
			





 Keep in mind it's good DIY practice to buy spares just in case.
   
  Might as well just buy a bunch from mouser and build some extra amps for your mates.


----------



## Paul Blythe

Cheers 
   
  Double checked the p&p on mouser, the €20 is everything payed upfront (duty/vat/p&p etc.). Can't see €1.88 (4 units) of parts costing that much in extra charges if I use their normal delivery.
   
   
  updated: just run through the standard O2 BOM on mouser £16 plus £12 delivery (dosen't include the wall wart or enlosure) ... that's pretty good!


----------



## LizardKing1

Quote: 





limpidglitch said:


> Beyers: Yes; Sextetts: No


 

 Really? Would it be capable of powering the DT880 for example?


----------



## limpidglitch

Yes
  On battery power it will output about 5V or 42mW into 600Ω before clipping, on AC it is about 7V or 82mW. Both should be plenty loud with f.ex the T1.


----------



## Satellite_6

I asked this of you know who specifically and he explained it with math - yes it can drive the Beyers to ear damaging levels.


----------



## Maverickmonk

Quote: 





limpidglitch said:


> Beyers: Yes; Sextetts: No


 


  Bah, figures. I guess it was too much to hope for an affordable, small amp that would drive the Sextetts. Maybe the desktop version will suffice, I hope.


----------



## Paul Blythe

Ordered two O2 pcb's through the GB on diyAudio  ¦:O) 
   
Not sure on the enclosure yet, but 1st build will be a desktop version with 1/4" jack to the front, with (hopfully) the power & rca phono inputs wired up to the rear.
   
Err... wall power supply ... this needs to be AC to AC right, not AC to DC ... would this UK ac/ac multi-voltage 500mA power suply do the job? (Linky - http://www.maplin.co.uk/ac-ac-multi-voltage-500ma-power-supply-35927)


----------



## mikeaj

Quote: 





maverickmonk said:


> Bah, figures. I guess it was too much to hope for an affordable, small amp that would drive the Sextetts. Maybe the desktop version will suffice, I hope.


 

 Well, as always, it depends on how loud you want to go.  O2 can do about 6.8V (rms) into 600 ohms with very low distortion, before it starts to clip.  600 ohms DT 880 needs 0.514 V (0.43 mW) for 90 dB SPL according to InnerFidelity, so 6.8V would give you 112.4 dB SPL, which is probably enough.
   
  Anybody know the sensitivity of the Sextetts?  Is it 88 dB SPL / 1 mW like the intermediate models?
   
  But I wouldn't hold my breath of the desktop version sufficing.  I think it is intended to be mostly the same design and will probably use the same NJM4556 on the output, so don't expect much more output power.  Unfortunately, cheap op amps are usually unable to handle the really high voltages necessary to drive really insensitive headphones to high levels.


----------



## limpidglitch

Quote: 





paul blythe said:


> Ordered two O2 pcb's through the GB on diyAudio  ¦:O)
> 
> Not sure on the enclosure yet, but 1st build will be a desktop version with 1/4" jack to the front, with (hopfully) the power & rca phono inputs wired up to the rear.
> 
> Err... wall power supply ... this needs to be AC to AC right, not AC to DC ... would this UK ac/ac multi-voltage 500mA power suply do the job? (Linky - http://www.maplin.co.uk/ac-ac-multi-voltage-500ma-power-supply-35927)


 


  Looking at the specs of the BOM unit, yes, at 15V it should do fine.
   
  From his blog (which I'm prohibited from linking to):
   
*AC Wall Transformer* – For countries with 220 – 240 volt power you need a transformer with a rated output of at least 14 VAC and at least 400 mA. The no load AC voltage must be at least 13.5 and less than 22 volts AC. There are several part numbers listed in the BOM.
   
   

  
  Quote: 





mikeaj said:


> Anybody know the sensitivity of the Sextetts?  Is it 88 dB SPL / 1 mW like the intermediate models?


 


  ~89dB/mW it seems. As expected, Tyll has had pair of Sextetts in his lab. Linky


----------



## BobSaysHi

edited


----------



## Maverickmonk

By "small" I just meant something smaller than a vintage receiver, without having to jump all the way to the $200 price range and purchasing an LD MKIII,
  
  Quote: 





mikeaj said:


> Well, as always, it depends on how loud you want to go.  O2 can do about 6.8V (rms) into 600 ohms with very low distortion, before it starts to clip.  600 ohms DT 880 needs 0.514 V (0.43 mW) for 90 dB SPL according to InnerFidelity, so 6.8V would give you 112.4 dB SPL, which is probably enough.
> 
> Anybody know the sensitivity of the Sextetts?  Is it 88 dB SPL / 1 mW like the intermediate models?
> 
> But I wouldn't hold my breath of the desktop version sufficing.  I think it is intended to be mostly the same design and will probably use the same NJM4556 on the output, so don't expect much more output power.  Unfortunately, cheap op amps are usually unable to handle the really high voltages necessary to drive really insensitive headphones to high levels.


----------



## wakibaki

Quote: 





mikeaj said:


> Unfortunately, cheap op amps are usually unable to handle the really high voltages necessary to drive really insensitive headphones to high levels.


 


  That's not the issue here. The output is limited by the power rails, +/-9V nominal, 8.4 using widely available NiMh PP3s. Subtract a volt or so because the opamp doesn't swing rail-to-rail and you have problems driving a very few phones. The opamp itself is good for +/-18V supply,  which will probably drive any phones in existence. OK, somebody quote me a pair so insensitive that it won't.


----------



## mikeaj

Quote: 





limpidglitch said:


> ~89dB/mW it seems. As expected, Tyll has had pair of Sextetts in his lab. Linky


 
   
  Thanks.  I don't know how I didn't check if Tyll ever ran across one in the lab.
   
   
  Quote: 





wakibaki said:


> That's not the issue here. The output is limited by the power rails, +/-9V nominal, 8.4 using widely available NiMh PP3s. Subtract a volt or so because the opamp doesn't swing rail-to-rail and you have problems driving a very few phones. The opamp itself is good for +/-18V supply,  which will probably drive any phones in existence. OK, somebody quote me a pair so insensitive that it won't.


 

 I meant on AC power, but I should have said "really really high levels" to go along with the "really insensitive."  The limitation on battery is more relevant for more realistic headphones.  With +-18V rails, data sheet says maybe 14V on the top and bottom for almost 10V rms?  I guess if you need above 112 dB SPL on vintage AKG 240 models or plan to use K1000 earspeakers or something like that, there could be an issue.  And K1000 doesn't really count in my books.  I'm not that familiar with headphones that are unusually insensitive.
   
  (edited above values)
   
  And many alternatives other than the NJM4556 doubtlessly swing much closer to the rails.


----------



## kiteki

What's the difference between DIP and DMP apart from size? I can't seem to find the DMP version of the NJM4556 anywhere...
   
http://semicon.njr.co.jp/njr/hp/productDetail.do?_isTopPage=false&_productId=113&_moveKbn=PRODUCT_DETAIL_MOVE_SPEC


----------



## Tyll Hertsens

Quote: 





mikeaj said:


> Thanks.  I don't know how I didn't check if Tyll ever ran across one in the lab.


 
   
  Yer welcome!


----------



## deadlylover

Quote: 





kiteki said:


> What's the difference between DIP and DMP apart from size? I can't seem to find the DMP version of the NJM4556 anywhere...
> 
> http://semicon.njr.co.jp/njr/hp/productDetail.do?_isTopPage=false&_productId=113&_moveKbn=PRODUCT_DETAIL_MOVE_SPEC


 

 The DMP version looks to be surface mount, you don't want that. The DIP ones are better as they just pop into the sockets for easy installation and replacement.


----------



## kiteki

I see... thanks... it's just I'm looking for some DMP's to roll the TDA1308 in the HM-101, and I was wondering if there's actually any difference apart from their size.
   
  Since the HM-101 has two TDA1308 chips, one on the HO and one on the LO section, it will be possible to directly A/B the new chip with the previous chip.
   
  I'm not sure what's so special about the NJM4556 but I thought it would be a nice candidate, yet I can't find any DMP versions and I don't know if it's possible to connect a DIP.
   
   
  Edit: I want to change this chip here:


----------



## deadlylover

Quote: 





kiteki said:


> I see... thanks... it's just I'm looking for some DMP's to roll the TDA1308 in the HM-101, and I was wondering if there's actually any difference apart from their size.
> 
> Since the HM-101 has two TDA1308 chips, one on the HO and one on the LO section, it will be possible to directly A/B the new chip with the previous chip.
> 
> I'm not sure what's so special about the NJM4556 but I thought it would be a nice candidate, yet I can't find any DMP versions and I don't know if it's possible to connect a DIP.


 
   
  Ah I see, it won't be possible to use a DIP package unless you are absolutely heroic at soldering.
   
  There should be no difference between the DIP and DMP packages, but I would double check the pinouts of the DMP version if you'd want to plop it right in to replace the TDA1308, it most likely wouldn't be a problem. I don't think there was anything special about the NJM4556, it just filled it's role in the Obj2, specifically. I remember nwavguy tested a bunch of opamps and the 4556 was one of the best for the task, remember, it's all about the implementation (or so he says =P).
   
  I wouldn't go out and about opamp rolling that thing unless it's just for laughs.


----------



## kiteki

Nah, deadly you should get the HM-101, roll the OPA627AU into it, and then add another test to your shoebox "which is the expensive DAC?" trick.
   
  I'm pretty sure someone on head-fi said it's better than his iBass something with his custom IEM's.


----------



## Willakan

I think the 4556 is a *bit* special. As NwAvGuy said, no other DIP-8 opamp can touch it in his circuit - it's a good audio opamp with a seriously (and an virtually uniquely) beefed-up output stage. He even speculated that it had been designed especially to drive headphones, so uniquely suited was it to the role!


----------



## Paul Blythe

Like Willakan said, looks like the 4556 was chosen as it did everything that was required of it (and more) at a cheaper price, plus it has nearly double the output of most other audio quility opamps. Reading through NwAvGuy's site, it seems like the 4556 first cought his eye in the $39 ebay CMoy.
   
  Was intrested to read on the data sheet for the OPA2227, that it's recomemded it's used in parallel (similar to the 4556's in the O2) to give a higher output for driving headphones.
   
  [-o-]
   
  All the bits for my O2 have been ordered, hoping to build my first this weekend  )


----------



## wakibaki

Quote: 





kiteki said:


> What's the difference between DIP and DMP apart from size? I can't seem to find the DMP version of the NJM4556 anywhere...


 

 Dissipation is 700mW in the DIP and S types, in the M & E types it is only 300mW. This is probably due to the overall larger size of the packages given that the smaller ones have no supplementary cooling pad to leach heat into the PCB copper, as in the AD8397 or TPA6120.
   
  w


----------



## kiteki

Quote: 





willakan said:


> I think the 4556 is a *bit* special. As NwAvGuy said, no other DIP-8 opamp can touch it in his circuit - it's a good audio opamp with a seriously beefed-up output stage. He even speculated that it had been designed especially to drive headphones, so uniquely suited was it to the role!


 

 Thanks, maybe I'll put it inside my DAP too then, more info here
   
  @wakibaki - Thanks.


----------



## Magedark

Just got my board. Smaller than I thought, but makes it easier for me to shop for an enclosure.


----------



## estreeter

I emailed Oliver at Epiphany Acoustics to confirm a couple of things, and he had no objections to me passing this on:
   
  I_ will be using the NJM2068D opamps and the NJM4556AD opamps, as per the original design.

 I am not able to offer individual specs on each unit, unfortunately. However, they will measure identically given that they are identical to the ones NwAvGuy tested, i.e. same PCB and same components. _
   
  All good - cant wait to receive my new amp


----------



## WhDemon

I should receive all parts by Next Week.


----------



## LizardKing1

Has anyone tried them against the models recommended usually? Schiit Valhalla, Woo Audio 2/6...


----------



## micmacmo

Quote:


lizardking1 said:


> Has anyone tried them against the models recommended usually? Schiit Valhalla, Woo Audio 2/6...


 

Here's the first complete PCB build I've seen reported on head-fi. The article compares the O2 to another popular portable amp.


----------



## LizardKing1

Quote: 





micmacmo said:


> Quote:
> 
> Here's the first complete PCB build I've seen reported on head-fi. The article compares the O2 to another popular portable amp.


 

 Thank you, it was helpful.


----------



## svyr

any idea how suitable the amp is to driving fostex t50rp?


----------



## Willakan

They have a sensitivity of 98 db/mw (and a 50ohm impedance), so the O2 should drive them very easily with tonnes of headroom for any ridiculously quiet tracks.


----------



## Magedark

I'm almost done with my O2, except the low gain has a problem where it's playing very softly in the right channel. However, both channels work in high gain, so I know something's off.


----------



## limpidglitch

I'd probably look for a short in the gain stage feedback loop, it could just be that one channel is accidentally set to unity gain.


----------



## Magedark

limpidglitch said:


> I'd probably look for a short in the gain stage feedback loop, it could just be that one channel is accidentally set to unity gain.




Thanks for the help, but after I posted my problem, I actually went and bought isopropyl, and did what has fixed, as of now, 100% of my projects: I cleaned the board. Tests are going well, I'm going to run my AKG K501 a bit later. 

EDIT: Apparently the switch is broken, so the amp is always in high gain. In low gain, one channel is using the high gain resister, and the other is using the the low gain resister, so volume difference. Or there's something I horribly missed. But messing with the switch apparently triggers the low gain, but doesn't stay that way.

EDIT AGAIN: Ok, it works again. Fully....I hope.


----------



## Paul Blythe

Hi, did the initial build & mods on mine yesterday. A custom built desktop enclosure is next but I'm still waiting on some parts to arrive.
   

   
  face plate, as well as back, base and top will be brushed aluminium, the left/right sides will be mahogany (hopfully).


----------



## Willakan

@Magedark:
   
  Cleaning the board with the switch on is not a good idea. Gunk gets swept into the switch, which could explain its intermittent behaviour.
   
  @Paul:
   
  Nice, what did you use for wiring? I cut open an ethernet cable for some 24-gauge copper, but yours looks somewhat better!


----------



## Paul Blythe

Hi & thanks, I was being quite meticulous with the wiring, which is why it took just under 5 hrs to build & do the initial testing 
   
  output, ground & power - 16/0.2 equipment wire, <£3 for 10 meters, think it's 22 awg (from Maplin)
  left/right input - 16/0.2 single core braided shielded copper wire, £0.99 per meter, again 22 awg (from Maplin)
  volume pot - 28/0.1 up-ofc core wire from Van Damme Blue Series studio cable, <£5 per meter, 22/24 awg (from e-bay)


----------



## Magedark

willakan said:


> @Magedark:
> 
> Cleaning the board with the switch on is not a good idea. Gunk gets swept into the switch, which could explain its intermittent behaviour.
> 
> ...




It got working after one last pass for some reason.

Anyways, my build just needs a case, so that's probably something to do for this weekend. Paul, which mods have you done to yours?


----------



## Paul Blythe

Nothing major, just off-board input, output, power sockets and volume pot... be nice to see what changes are made to the proper destop O2 once it arrives.
   
  Had a good long listening session this evening... Muse, Bring Me the Horizon, The XX, Cinematic Orchestra, Goldfrap, Tchaikovsky's 1812, Coldplay... With my re-cabled HD-650's the amp sounds to be well balanced between low/mid/high frequencies. Nice solid, impactfull bass, clear mid's and upper range, very good levels of detailing... doesn't feel like I'm missing anything from the recordings and everything sounds controlled and well defined. The amp has some warmth thanks to the 650's, but I would like to hear how it sounds with some 702's connected.
   
  Very pleased with the O2 after my initial sitting, already hearing new details within much played & loved music, so all's good.
   
  Question: with using some wiring on the build, can I expect a small bedding in period? The two CMoy's built prior to this appeared to settle after about 20 - 30 hrs of usage.


----------



## limpidglitch

Quote: 





paul blythe said:


> Question: with using some wiring on the build, can I expect a small bedding in period? The two CMoy's built prior to this appeared to settle after about 20 - 30 hrs of usage.


 


  Objectively, no.


----------



## dogears

Someone has used it with the t50rp already and its highly recommended... At least that's what I remember. Preordered mine already 


svyr said:


> any idea how suitable the amp is to driving fostex t50rp?


----------



## Willakan

Quote:


paul blythe said:


> ...but I would like to hear how it sounds with some 702's connected.


   
  You'll never guess what my O2 is driving!
   
  I set the gain at 3.1, which has proved to be incredibly excessive, as I can't get the volume knob past 9 o'clock without blowing my ears off - and this with quietly mastered stuff! As for the amplifier's sound, it balances out my AKG's with the amount of bass they should have when given enough power and an amplifier with a low output impedance. I can't really say much else about liquid mids or airy highs without feeling incredibly stupid, so I'll just say it sounds nice. Like my Clip+, but with more bass and without the soft clipping.


----------



## Paul Blythe

Quote: 





limpidglitch said:


> Objectively, no.


 


 lol... thanks.
   
  For me the O2 feels transparent, dosen't appear to add or remove anything from the music, plus the tonal signiture is very much that of the headphones.


----------



## LizardKing1

So this could pretty much be used as someone's go-to amp for most hard-to-drive cans? It's just that amps don't have as much appeal to me as headphone - and often cost a lot more than what they're driving, and I wanted to get that out of the way.
   
  I especially like how this has no synergy. It's not a warm amp to pair with bright cans, or a relaxed amp to pair with detailed cans. It's an amp, and it just amplifies the god damned signal.


----------



## Magedark

Of course, some people may want flavor in their amp as well :wink_face:.

I'm liking my O2 though. Really brings power to the K501s, and allows me to actually listen to it efficiently. Now as to the fact the K501s reveal every bad recording on my setup, that's another issue .


----------



## estreeter

Quote: 





willakan said:


> I set the gain at 3.1, which has proved to be incredibly excessive, as I can't get the volume knob past 9 o'clock without blowing my ears off - and this with quietly mastered stuff! As for the amplifier's sound, it balances out my AKG's with the amount of bass they should have when given enough power and an amplifier with a low output impedance. I can't really say much else about liquid mids or airy highs without feeling incredibly stupid, so I'll just say it sounds nice. Like my Clip+, but with more bass and without the soft clipping.


 

 This. Damn it, I am going to email Oliver and ask if he will reconsider lowering the gain setting for low gain. The problem you describe is very similar to what I have atm with my uHA-120 : Justin had the gain too high on the initial batch, and only fixed it after a few IEM owners complained. Live and learn, I guess, and so many here seem to want to be able to drive big cans from small(ish) amps.


----------



## bcg27

Quote: 





estreeter said:


> This. Damn it, I am going to email Oliver and ask if he will reconsider lowering the gain setting for low gain. The problem you describe is very similar to what I have atm with my uHA-120 : Justin had the gain too high on the initial batch, and only fixed it after a few IEM owners complained. Live and learn, I guess, and so many here seem to want to be able to drive big cans from small(ish) amps.


 


  Your volume depends a lot on your source so unless you have the same source output voltage you may or may not be ok. Honestly I don't understand why people are always so confused about volume/power requirements, it is really a straightforward calculation. I think nwavguy may even have a blog post detailing it.


----------



## Satellite_6

Quote: 





bcg27 said:


> Your volume depends a lot on your source so unless you have the same source output voltage you may or may not be ok. Honestly I don't understand why people are always so confused about volume/power requirements, it is really a straightforward calculation. I think nwavguy may even have a blog post detailing it.


 

 I'm still confused. THE MATH IT BURNS.


----------



## mikeaj

I think I mentioned this earlier, but if you want 1x gain, all you need to do is read the instructions, find a couple of resistors on the board, and do a snip snip to remove them.  Channel tracking seems to be okay with the volume pot turned down, at least as far as analog volume controls go.  It should be okay.
   
  But Oliver probably has not gotten any of the amps made, so it's probably a good idea to message him about it anyway.


----------



## limpidglitch

Quote: 





satellite_6 said:


> I'm still confused. THE MATH IT BURNS.


 

  
  Fortuneately, someone has done the math already (not me, although I've done some amendments).
   
Linky
   
  But remember that on AC power the Maximum Gain = 7 / Vin(max) and on (low) batteries it’s 4.5 / Vin(max).


----------



## bcg27

All you need to know to calculate maximum volume are your headphones sensitivity and impedance, the RMS voltage output of your source, and the gain of your amplifier. Sensitivities are generally quoted in dB @ 1mW of power. To go from 1 mW of power for your headphone to volts use Power=Volts^2/Impedance. Solving for volts yields volts=sqrt(power*impedance). So, now take the voltage output of your source and multiply it by the gain of your amplifier. This yields the RMS voltage output from your amp. The maximum loudness your headphones will reach is then the quoted sensitivity of your headphones added to 20*log(voltage out of amp/volts), where the volts is what you calculated from the headphone sensitivity and impedance.
   
  Here is an example using some of my gear. My source is a gamma 2 which has an output of 1.4 Vrms. My amp is a beta 22 with a gain of 5, and my headphones are lcd2s with sensitivity of 91 dB @ 1 mW and impedance of 60 ohms. Using the steps from above I want to find out how many volts put 1 mW of power into the headphones, so 1 mW=Volts^2/60, Volts=.245. The output of my beta 22 with input of 1.4 Vrms and gain of 5 is 1.4*5=7 volts. Thus the maximum volume I can get is 91 dB + 20*log(7/.245)=91+29=120 dB. 
   
  The steps above can be repeated with any headphone/amp/source combination as long as the specs I mention are available. And if they aren't I would probably stay away from those products.


----------



## svyr

ordered one from oliver. looks like I might even use it as a portable amp, depending on the size  

rechargeables included, right ?


----------



## Magedark

As for size, don't think portable, think transportable.


----------



## svyr

magedark said:


> As for size, don't think portable, think transportable.




109X30X80MM; for 'B2-080 portable case' ... is that the right one? (*tries to suss out the dimensions considering the battery(ies?)


----------



## cheapskateaudio

Wow, the O2 has made me hate the uDac 2 with a passion. I think I understand the unnamed one's vitriol a little better. The uDac 2 is probably a purposefully hobbled component that sounds pretty nice until you put it in a proper system such as O2 + HD650. uDac 2 is not just bad with the O2, it's pain inducing. Preferring low volume I tend to respond to fatigue by dumping volume to the point my laptop fan sounds loud next to the music, but even whisper quiet levels are fatigue inducing over time with the uDac 2...


----------



## Willakan

Just to fill in the details of my previous comment, the source I'm using (DACMagic) has a 2.1V output.
  Channel balance seems O.K. even at low volumes, so I'll probably leave it as it is.


----------



## upstateguy

Quote: 





willakan said:


> You'll never guess what my O2 is driving!
> 
> I set the gain at 3.1, which has proved to be incredibly excessive, as I can't get the volume knob past 9 o'clock without blowing my ears off - and this with quietly mastered stuff! As for the amplifier's sound, it balances out my AKG's with the amount of bass they should have when given enough power and an amplifier with a low output impedance. I can't really say much else about liquid mids or airy highs without feeling incredibly stupid, so I'll just say it sounds nice. *Like my Clip+, but with more bass and without the soft clipping.*


 

  
  That it sounds like a Clip + is not very impressive.


----------



## cheapskateaudio

Quote: 





upstateguy said:


> That it sounds like a Clip + is not very impressive.


 


  It sounds pretty good overall. I haven't heard the Clip+ but it's a clear as day improvement over the uDac 2's headphone out which I found decent despite all the rage it inspired.
   
  It's not without faults. It's analytical to the bone. There is no turd polishing here. If the source is the bottleneck the amp will sound like everything else, ie the source. 
   
  What I'm hearing right now is that the sound is a little bass light and a little dry/analytical sounding as a result. EQ'ing fixes that, I'm not a big fan of doing that though. Since I'm using the computer line out which is a little thin compared to the uDac 2, I have to reserve judgment on that quality for the time being. I should probably try it with my DVD player...
   
  Overall it's good, great detail, lots of inner detail in instruments, still a fairly smooth sounding amp though. I'd love to do a side by side with a top notch SS amp like the ß22.


----------



## cheapskateaudio

Ok, I checked the sound with the DVD player, right off the bat the sound is a lot more full. The DVD player actually sounds pretty good which is amazing considering how cheap it is. The computer line out is simply flat sounding. Again, I'm feeling that the amp is completely transparent to the source. It's not so much dry sounding as extremely revealing. I think thats a good quality in an amp.
   
  It's probably just this DVD player, but the O2's gain is way too high with it, basically it's almost too loud at the 7 oclock position on the volume control.


----------



## Willakan

upstateguy said:


> That it sounds like a Clip + is not very impressive.


  My final comment there was slightly tongue in cheek, although in hindsight that doesn't really come across very clearly. The problem is, I have no real point of reference as nothing else I own can come close to meeting the AKG's power requirements, which whilst not that onerous are certainly beyond my cheap sound card and Clip. I would experiment with my Grados, but I can't find the 1/4 inch adaptor that came with them (I did a desktop build.)


----------



## estreeter

Kudos to Oliver for being so quick to respond to emails, btw.


----------



## svyr

estreeter said:


> Kudos to Oliver for being so quick to respond to emails, btw.




hehe, yea I complimented him on it as well. Usually takes < 12h (a lot less  )


----------



## Head Injury

Quote: 





cheapskateaudio said:


> Ok, I checked the sound with the DVD player, right off the bat the sound is a lot more full. The DVD player actually sounds pretty good which is amazing considering how cheap it is. The computer line out is simply flat sounding. Again, I'm feeling that the amp is completely transparent to the source. It's not so much dry sounding as extremely revealing. I think thats a good quality in an amp.
> 
> It's probably just this DVD player, but the O2's gain is way too high with it, basically it's almost too loud at the 7 oclock position on the volume control.


 

 See if you can find the DVD player's line out voltage.


----------



## mikeaj

It's alive! (good lord I hadn't soldered anything in years, my $8 Walmart soldering iron wasn't helping, so it took twice as long as it should have)
   
  Some stuff not done yet like clipping some thicker leads, so it can hopefully fit in the enclosure...it's not a huge deal though since I don't plan on using it as a portable.


----------



## estreeter

Quote: 





svyr said:


> hehe, yea I complimented him on it as well. Usually takes < 12h (a lot less
> 
> 
> 
> ...


 

 I suspect that he has orders up the Wazoo - will make it harder to get his pet project, the EPH-01, up and running, but I'm sure its a situation he can live with. How many hobbyists actually get to make money from something they enjoy ? Of course, that might mean he's still soldering at 3am, but hopefully that will be YOUR amp and not mine !


----------



## leeperry

cheapskateaudio said:


> the O2 has made me hate the uDac 2


 

 even a realtek sounds better than a uDAC2 tbh...so anyone compared the O2 to the big boys -subjectively speaking- ? I might consider building one w/ a nice stepped attenuator and some audiophool opamps


----------



## Shike

Quote: 





leeperry said:


> even a realtek sounds better than a uDAC2 tbh...so anyone compared the O2 to the big boys -subjectively speaking- ? I might consider building one w/ a nice stepped attenuator and some audiophool opamps


 


  I've compared it to a few, but mostly the Benchmark which you already don't like.  It sounds good compared to most solid state I've demoed off-hand in general, but I don't bother with tube stuff so no comparison there.
   
  As for using other opamps - it's really recommended you don't.  The developer tested a good many and everything created worse performance.  He picked these because they were the best performing regardless of price.  Stepped attenuator probably wouldn't hurt though, especially for a sub-desktop build if you don't want to wait till the desktop version.


----------



## Willakan

A stepped attenuator would indeed be nice, as long as it's not a crappy one off Ebay, which will measurably and significantly degrade performance (incredibly cheap resistors, that sort of thing). Having said that, such decent attenuators probably cost more than the parts cost of the amp!


----------



## Soaa-

Quote: 





leeperry said:


> audiophool opamps


 

 NwAvGuy recommends against using the opamps he selected because they provided best measured performance. Switching opamps would make it measure worse, but who knows, it might be a pleasant distortion. Think tubes and stuff.
   
  I really hope this thread doesn't get derailed into an opamp rolling thread though...


----------



## i_djoel2000

Quote: 





soaa- said:


> NwAvGuy recommends against using the opamps he selected because they provided best measured performance. Switching opamps would make it measure worse, but who knows, it might be a pleasant distortion. Think tubes and stuff.
> 
> I really hope this thread doesn't get derailed into an opamp rolling thread though...


 


  if i'm not mistaken nwavguy does recommend LME49720 in particular to replace the NJM4556. he said lme49720 gives slight better measurement than NJM4556. can't quote you on that though, i already forgot where he posted that comment


----------



## DingoSmuggler

Quote: 





i_djoel2000 said:


> if i'm not mistaken nwavguy does recommend LME49720 in particular to replace the NJM4556. he said lme49720 gives slight better measurement than NJM4556. can't quote you on that though, i already forgot where he posted that comment


 

 I think you're mistaken. The LME49720 has much lower current output and doesn't drive low impedance loads well, and would be a poor replacement for the NJM4556 in the O2.


----------



## Willakan

He has actually said that no other opamp he has measured can touch the 4556 in his amp, so opamp "rolling" is even worse of an idea than normal.


----------



## cheapskateaudio

Quote: 





soaa- said:


> NwAvGuy recommends against using the opamps he selected because they provided best measured performance. Switching opamps would make it measure worse, but who knows, it might be a pleasant distortion. Think tubes and stuff.
> 
> I really hope this thread doesn't get derailed into an opamp rolling thread though...


 


  Just ordered some! OPA2134, OPA2227, & NJM4562. As well as the beefier power supply (WAU16-400), which, really should just be the standard power supply for the build based on nwavguy's info about the different supplies.
   
  I also got some caps for various points in the circuit that according to traditional audiophile mythology, may have an affect on the sound.


----------



## Yoga Flame

Did he try any SOIC opamps?


----------



## mikeaj

Quote: 





yoga flame said:


> Did he try any SOIC opamps?


 

 I think not.  Also he was looking for options with reasonable power draw, since it's supposed to work on batteries too.  The potential swap that was recommended was gain stage NJM2068 -> NE5532 (higher noise, higher cost, higher power consumption, but better performance with higher gain).  As for the output stage: "For the output stage, the NJM4556 was untouchable among compatible DIP8 dual op amps."
   
  Then again, some emphasis is placed on driving low impedance loads.  Maybe it would be different if all you cared about was high impedance headphones, and particularly if there are some better (ignoring cost) SOIC options.


----------



## deadlylover

Quote: 





cheapskateaudio said:


> I also got some caps for various points in the circuit that according to traditional audiophile mythology, may have an affect on the sound.


 

 Blackgates? 
	

	
	
		
		

		
		
	


	



   
  Ya need some PRP resistors too, red makes everything faster, including sound. Might as well throw in a Khozmo or a DACT in there while you're at it.
   
  The delicious irony in making the most expensive Obj2. I'd do it if it weren't going to be such an expensive joke.


----------



## cheapskateaudio

Quote: 





deadlylover said:


> Blackgates?
> 
> 
> 
> ...


 


  Alright, you got me... 
	

	
	
		
		

		
		
	


	




 
   
  I was fairly reasonable, choosing all my parts from what was available at Mouser, I got a few WIMA & Panasonic Polypropylene caps and some Vishay/Dale RN series resistors ($1 each  
	

	
	
		
		

		
		
	


	




).


----------



## maverickronin

You'd probably be able to get better measured performance by replacing the gain stage opamp with an appropriate surface mount only part placed on an adapter or something but only DIP8 chips were tested in the design process because being easy to build and using only easily obtainable parts was given a higher priority than absolute maximum performance.


----------



## estreeter

Is this the part where someone puts together *a non-standard build*, posts atrocious measurements then finds themselves in a cyber-brawl with several defenders-of-the-faith ? Oh, wait ....


----------



## cheapskateaudio

Quote: 





maverickronin said:


> You'd probably be able to get better measured performance by replacing the gain stage opamp with an appropriate surface mount only part placed on an adapter or something but only DIP8 chips were tested in the design process because being easy to build and using only easily obtainable parts was given a higher priority than absolute maximum performance.


 


  Do you mean I should use the exact same op amp in a surface mount configuration?
   
  Or do you mean to find another higher end op amp with similar specs that is surface mount?
   
  If the latter, how important is supply current, can I go higher, +/- a mA or two, any ideas? Basically all that exists at the 8ma rating is the op amp that is already in it. The NJM2068.


----------



## Head Injury

Quote: 





estreeter said:


> Is this the part where someone puts together *a non-standard build*, posts atrocious measurements then finds themselves in a cyber-brawl with several defenders-of-the-faith ? Oh, wait ....


 

 "It sounded pretty good in stock configuration. I switched all the opamps for $10 audiophile brand Xs and it really opened up the soundstage. But I'm measuring 0.5% THD! Terrible design, I'm going back to my uDAC."


----------



## maverickronin

Quote: 





cheapskateaudio said:


> Do you mean I should use the exact same op amp in a surface mount configuration?
> 
> Or do you mean to find another higher end op amp with similar specs that is surface mount?
> 
> If the latter, how important is supply current, can I go higher, +/- a mA or two, any ideas? Basically all that exists at the 8ma rating is the op amp that is already in it. The NJM2068.


 

 I meant a different model of opamp that would work with the same voltage requirements.  I can't remember the names off the top of my head since I was looking this stuff up a while ago, but there are opamps that should measure better than the NJM2068 or the NE5532 which IIRC are only available as surface mount and thus weren't considered for the O2 as I was explaining earlier.  The differences in power draw might affect battery life, but they shouldn't be enough to mess anything else up.


----------



## cheapskateaudio

Quote: 





maverickronin said:


> I meant a different model of opamp that would work with the same voltage requirements.  I can't remember the names off the top of my head since I was looking this stuff up a while ago, but there are opamps that should measure better than the NJM2068 or the NE5532 which IIRC are only available as surface mount and thus weren't considered for the O2 as I was explaining earlier.  The differences in power draw might affect battery life, but they shouldn't be enough to mess anything else up.


 


  Any of these look good? I sorted them by voltage gain:
   
http://www.mouser.com/Semiconductors/Amplifier-ICs/Op-Amps/_/N-4h00gZscv7?P=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&FS=True&Ns=Voltage%20Gain%20dB|1


----------



## maverickronin

Quote: 





cheapskateaudio said:


> Any of these look good? I sorted them by voltage gain:


 

 I'm too dyslexic to remember the model numbers and I don't have the time to dig though the data sheets right now so I couldn't really give you a recommendation.  I just remember that neither of gain opamps are the absolute pinnacle of measured performance from when I looked into it several months ago.  There's a huge pdf here with some opamp measurements which would probably be a good place to start looking.
   
  Even if you pick out one of the better measuring ones I doubt the difference would show up on anything but an audio analyzer but if you're in it for the tweaking and building it might be fun.


----------



## joydivisi0n

Is there any word on when the desktop model is being released?  I'm interested in buying this amp, but not for the portability.  Trying to decide if it's worth the wait for the next amp design that will possibly better suit my needs since I don't use my headphones on the go.


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## Satellite_6

Winter.


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## mikeaj

Quote: 





cheapskateaudio said:


> Any of these look good? I sorted them by voltage gain:


 
   
  Yeah, you're not looking for most voltage gain but rather the most superior performance at typical headphones gain levels (3-12 maybe?), into normal line-level impedances.  So extremely low noise, low THD, low IMD, etc. for frequencies in the audio band (ignore super-duper DC specs and stuff into the MHz range), when configured in the circuit the way it is.  If you're hardcore, you can try messing around with the capacitor value for the dominant pole compensation, while you're at it.

  
  Quote: 





joydivisi0n said:


> Is there any word on when the desktop model is being released?  I'm interested in buying this amp, but not for the portability.  Trying to decide if it's worth the wait for the next amp design that will possibly better suit my needs since I don't use my headphones on the go.


 

 When it's done, it's done.  Nobody knows.  (You've maybe heard this before, but it's not really a new amp design, just the old design minus batteries, plus a larger enclosure and jack options, and maybe with a few usability tweaks.  Performance should be similar.)  Last I heard was:  hopefully done by the end of the year.


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## joydivisi0n

Quote: 





mikeaj said:


> When it's done, it's done.  Nobody knows.  (You've maybe heard this before, but it's not really a new amp design, just the old design minus batteries, plus a larger enclosure and jack options, and maybe with a few usability tweaks.  Performance should be similar.)  Last I heard was:  hopefully done by the end of the year.


 

 You know, I just found this comment the creator made in response to someone asking if the desktop model would be smaller since batteries take up 1/3 of the space in the current O2: "Because the upcoming desktop amp has several upgrades, and is not designed to be portable, the board will be at least as large as the O2 (100mm x 80mm) and might be larger."
   
  I sure hope it's out before the end of the year!  I think I will wait it out for now.


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## agdr

Quote: 





cheapskateaudio said:


> Any of these look good? I sorted them by voltage gain:


 


  The LM4562 and LME49720 are the same part and both have slightly better specs on paper
   
http://www.mouser.com/ProductDetail/National-Semiconductor-TI/LME49720NA-NOPB/?qs=sGAEpiMZZMtCHixnSjNA6M%252bbBaCn4IWbp9Mxv9qzvug%3d
   
  I made a similar suggestion over on DIYA to someone who is op amp rolling for fun.  But it is unlikely to improve anything since the output stage numbers would predominate, as the designer mentioned somewhere along the way.  Also - this is just for the gain stage op-amp (the NJM2068).  I'm not aware of anything that would effectively replace the output stage NJM4556 op amp in DIP8 format.  That one is kind of a unique beast given the current capability.
   
  FWIW the LME49860 is also the same part as the 4652/49720 but with slightly higher +/-22V max rails.


----------



## cheapskateaudio

Quote: 





agdr said:


> The LM4562 and LME49720 are the same part and both have slightly better specs on paper
> 
> http://www.mouser.com/ProductDetail/National-Semiconductor-TI/LME49720NA-NOPB/?qs=sGAEpiMZZMtCHixnSjNA6M%252bbBaCn4IWbp9Mxv9qzvug%3d
> 
> ...


 


  Thanks for the response. I also ordered up some SOIC-8 to DIP-8 adapters so if there is something better that is not DIP-8, I'll try it. I'll try anything, I'll even do what NwAvGuy says NOT to do, (largely because he said not to) cuz I'm craaaaaazy.
   
  DIY, learning lifes lessons the hard way, one exploded op amp at a time!


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## The Monkey

So what's the next version after the desktop and what upgrades will it have?


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## estreeter

Quote: 





the monkey said:


> So what's the next version after the desktop and what upgrades will it have?


 

 Monkey, I'm must be out of the loop, but I thought one of the main concepts behind this amp was the KISS principle - that doesn't tie in too well with multiple 'versions' (as opposed to DiYer 'variations'). I believe nwavguy originally told those who wanted a 'desktop' version to simply omit the battery enclosure  - that seems to have changed, but I havent seen any reference to a 'Super-Deluxe Limited Edition O2' - happy to hear otherwise.


----------



## The Monkey

Quote: 





estreeter said:


> Monkey, I'm must be out of the loop, but I thought one of the main concepts behind this amp was the KISS principle - that doesn't tie in too well with multiple 'versions' (as opposed to DiYer 'variations'). I believe nwavguy originally told those who wanted a 'desktop' version to simply omit the battery enclosure  - that seems to have changed, but I havent seen any reference to a 'Super-Deluxe Limited Edition O2' - happy to hear otherwise.


 


  Yes, we share the same understanding.  But with each mention of the "desktop" version, it seems to get a little bit "better."


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## limpidglitch

Quote: 





the monkey said:


> Yes, we share the same understanding.  But with each mention of the "desktop" version, it seems to get a little bit "better."


 


  Could have something to do with there only being second hand information on here. One feather becoming five hens and all that.
  As for getting the information first hand, I haven't seen him much on diyA the last few weeks. Wonder what he's up to?


----------



## deadlylover

From my dodgy memory, the overloading input stage will be fixed, and he's shoving some relays in to protect the headphones from the harmless dc offset. The board layout should be a little better as well, possibly leading to better measurements.


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## cheapskateaudio

I ordered the WAU16-400 PSU and yes, there are major improvements when driving high impedance phones like HD650. The sound is more to the 650's typical sound signature now, a little more bass, fuller midrange, more cohesive in the mids, big improvements on rock/pop types of music.


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## francisdemarte

Why are unregulated wall warts being recommended for the build? Wouldn't a regulated power supply be better?


----------



## cheapskateaudio

Quote: 





francisdemarte said:


> Why are unregulated wall warts being recommended for the build? Wouldn't a regulated power supply be better?


 

 I think it's purely a price thing, taken to an extreme.


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## Satellite_6

Because it doesn't matter. (don't ask me why though, go ask him)


----------



## Soaa-

From what my basic understanding of circuits can gather, the wallwart outputs AC current that gets turned into + and - DC voltage rails anyway, through a bunch of caps and smooth out the voltage already. Regulated power supplies seem to output direct current, which isn't what the O2 uses.


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## francisdemarte

ah! I didn't even take notice that it is a AC/AC power supply.


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## limpidglitch

Quote: 





cheapskateaudio said:


> I think it's purely a price thing, taken to an extreme.


 


  The powersupply _is_ regulated, it would have been a catastrophy if it wasn't.
   
  Please don't post as if you have a clue when you obviously don't.


----------



## cheapskateaudio

Quote: 





limpidglitch said:


> The powersupply _is_ regulated, it would have been a catastrophy if it wasn't.
> 
> Please don't post as if you have a clue when you obviously don't.


 


   
   
  Admittedly, I don't know anything about it. But I think your brain is glitching there bud, I didn't say it had a regulated or unregulated power supply. ???


----------



## limpidglitch

Quote: 





cheapskateaudio said:


> Admittedly, I don't know anything about it. But I think your brain is glitching there bud, I didn't say it had a regulated or unregulated power supply. ???


 


   
  Quote: 





> Quote:
> 
> 
> 
> ...


 
   
  I don't see how else to understad it.


----------



## mikeaj

The thing that plugs into the wall is just a simple AC/AC transformer, as opposed to some kind of AC/DC regulated power supply.  There are parts in the board for a dual half-wave rectification:  it uses the positive side of the AC cycle to create the positive DC rail, and the negative side of the AC cycle to create the negative DC rail.  Voltage regulators (7912 and 7812), filter caps, etc. all are on the board.
   
  With the parts as specified (unless with low line voltage from wall, using the recommended cheapest option wall wart with the relatively low output, and maxing out the output power into low impedance loads), the ripple into the regulators will be small enough that they can take care of most everything.


----------



## cheapskateaudio

C13 and C14 are coupling capacitors right? I replaced those with Panasonic 2.2uf polypropylene capacitors and I swear it sounds a little better. Midrange details come through more clearly, and bass notes seem a bit more musical and punchy. For instance, on Jimi Hendrix's live performance of "Purple Haze" it's very easy to hear the electrical hum in the background when he stops playing to sing "that girl put a spell on me"..
   
  After all the mods song beats seem less driven by the *&@^#% snare drums, thank god. I can't stand loud snare drums, it's like being stabbed in the eardrum 120 times a minute.


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## fubar3

Quote: 





francisdemarte said:


> Why are unregulated wall warts being recommended for the build? Wouldn't a regulated power supply be better?


 

 It is possible to use an external DC supply. However, the wires, jacks, and plugs impose a resistance between the regulator and the load which degrades performance. Computers are often designed like that to use an external DC power-pak but they are noisy beasts with additional switching supplies and digital circuits.


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## deadlylover

Quote: 





fubar3 said:


> It is possible to use an external DC supply. However, the wires, jacks, and plugs impose a resistance between the regulator and the load which degrades performance. Computers are often designed like that to use an external DC power-pak but they are noisy beasts with additional switching supplies and digital circuits.


 
   
  If by possible you mean 'having to tweak the entire power supply rectifier section and use two DC wallwarts for the dual rails' then yes, it's possible.


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## estreeter

Man, I'm glad Oliver is taking care of all this minutiae for me. All power to the DiYers, but it would really do my head in if I was halfway through a build and stumbled into this thread.


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## limpidglitch

Quote: 





estreeter said:


> Man, I'm glad Oliver is taking care of all this minutiae for me. All power to the DiYers, but it would really do my head in if I was halfway through a build and stumbled into this thread.


 


  The build is as straight forward as a build can be, but even the simplest of tasks can be made complicated if you just try hard enough.


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## Willakan

The irony of subjectively modifying an O2 is almost unendurable


----------



## mikeaj

Quote: 





willakan said:


> The irony of subjectively modifying an O2 is almost unendurable


 

 Modded Objective2 -> Objective1.  It has lost some of its objectivity.  Also it is now an O1...which we recall from basic chemistry principles, is unstable and does not exist in nature (O2 being normal diatomic oxygen form and O3 being ozone).


----------



## francisdemarte

Quote: 





fubar3 said:


> It is possible to use an external DC supply. However, the wires, jacks, and plugs impose a resistance between the regulator and the load which degrades performance. Computers are often designed like that to use an external DC power-pak but they are noisy beasts with additional switching supplies and digital circuits.


 

 Thanks for clearing that up. I'm going to start my build this weekend but I haven't looked at any of the parts in detail. I just cut and pasted the BOM into Mouser's project manager and checked out  I have a ton of power supply parts in my parts bin to experiment with.


----------



## estreeter

Quote: 





limpidglitch said:


> The build is as straight forward as a build can be, but even the simplest of tasks can be made complicated if you just try hard enough.


 

 And I would argue that several in this thread are trying very hard indeed. I know thats the DiY way - start with the basics and 'improve on it' - but I wonder how many are now looking at their wallwart and thinking 'man, I really need something better than this !' ..................


----------



## kiteki

Quote: 





mikeaj said:


> Modded Objective2 -> Objective1.  It has lost some of its objectivity.  Also it is now an O1...which we recall from basic chemistry principles, is unstable and does not exist in nature (O2 being normal diatomic oxygen form and O3 being ozone).


 

 Clever!
   
  If I make a DAC, remind me to call it the liquid helium-4.


----------



## Pars

One look at the schematic would show that it is using a half-wave rectified DC power section with 7812/7912 regulators. Input is max. 20Vac, min. of 200mA, so the Mouser AC-AC wallwart listed above would be a good fit at 16Vac, 400mA. This looks approximately equivalent to what you would find inside an Elpac regulated DC wallwart, such as the one used on a Gilmore Lite, etc. Sure, you could use a DC regulated wallwart, but you would lose ~0.7V across the rectifier diodes, etc. By not populating the DC power components other than the last set of diodes, you could wire any dual +/-12V DC power supply you wanted to (Amb Sigma 22 :devil.


----------



## Willakan

True, but the power supply is not the limiting factor in the amplifier's performance (I doubt it is a limiting factor for the majority of well-designed amplifiers TBH), so it would be a total waste of time.


----------



## svyr

willakan said:


> True, but the power supply is not the limiting factor in the amplifier's performance (I doubt it is a limiting factor for the majority of well-designed amplifiers TBH), so it would be a total waste of time.




yea,i really don't understand the purpose of people discussing it, when as you said the designer states black on white (uugh well, the blog is white on black ), that the psu noise is not a limiting factor at all, and that's reflected in the measurements.


----------



## Pars

IME, PSU quality is paramount, even in well designed amps. A well designed PSU like the sigma can probably outdo batteries in terms of the noise performance. I would think there is someone around here who has a sigma22 or equivalent PSU that could reconfigure it for 12V output and try it out with an O2. Maybe even let someone measure it?


----------



## cheapskateaudio

Quote: 





estreeter said:


> OK - when your ranting begins to sound like it really is coming from your avatar, perhaps its time for a cup of tea, a Bex and a damned good lie down. Its just pixels on a page, guys - random thoughts from the far reaches of cyberspace.


 


  NO, it's entertainment. After all you got the chance to pop in at just the right moment and pipe up with some rather practical words of wisdom, jolly good fun wasn't it?


----------



## Kibble Fat

Time to get this thread back on topic before it gets shut down... keep your personal issues out of the DIY section please!
   
  I've built two with 1x and 2.5x gains and everything went very smoothly.  3.5hrs with labeling and resistor matching for the first one, 1.5hrs for the second.  I've used the o2 for 3 hours with HiFiMAN IEMs and I'm really loving the 1x gain to keep the pot tracking in check.  I do use an impedance adapter anyway, 75ohm I think.  The noise floor is barely audible on 2.5x gain at full volume.  IMPRESSIVE!
   
  One of the main reasons I wanted to build one was because they use the same aluminum case as the AMB gamma2 which I built last year.  I'm looking forward to having a very capable, cheap, AND compact audiophile brick that I can bring to meets!  
   
  Cheers all!


----------



## cheapskateaudio

Quote: 





kibble fat said:


> Time to get this thread back on topic before it gets shut down... keep your personal issues out of the DIY section please!
> 
> I've built two with 1x and 2.5x gains and everything went very smoothly.  3.5hrs with labeling and resistor matching for the first one, 1.5hrs for the second.  I've used the o2 for 3 hours with HiFiMAN IEMs and I'm really loving the 1x gain to keep the pot tracking in check.  I do use an impedance adapter anyway, 75ohm I think.  The noise floor is barely audible on 2.5x gain at full volume.  IMPRESSIVE!
> 
> ...


 

 I hope you're not talking to me, lol!
   
   
  And yeah all the low impedance phones I've tried sound the best I've heard them.
   
  I heard noise at first because in my excitement I momentarily forgot about grounding electrical things. Now, I don't hear any noise with mine and it's the normal gain version.
   
  Kudos on building 2, now I don't feel excessive building another one.


----------



## Kibble Fat

one was for a co-worker -- 2 for yourself is definitely excessive lol


----------



## samsquanch

Quote: 





kibble fat said:


> one was for a co-worker -- 2 for yourself is definitely excessive lol


 


  you say that like it's a bad thing...  I have one built in stock form, and one board sitting aside to be modified, that way I have a base line to compare to, or so I tell myself.


----------



## kiteki

Kibble Fat... it took you 3 1/2 hours to build it, which walkthrough were you using? Linky?


----------



## cheapskateaudio

Quote: 





kibble fat said:


> one was for a co-worker -- 2 for yourself is definitely excessive lol


 


  But, they're cheap, right? You know, objectively, 2 is really not a lot more than 1, I mean, when you consider that there are so many numbers of amps I could have possibly built (1000 trillion billion comes to mind) choosing 2 seems relatively restrained actually. 
   
  Seriously though, I have an excuse, a valid one, I gave my GF my old ATH900's and so she's been slightly exposed to good audio and is jealous of my amp so I'm making her one.
   
  I'm TWO LEGIT baby...


----------

