[cishida]

 
And the Fulla2 is good with IEM's? Maybe you are just deaf.
I guess if "good" means that you have 0 volume control and that you cannot use IEM's with 3 tip plugs then sure.

Perhaps this goes without saying, but some IEMs are more sensitive than others.
 
I get adequate range with the hifiman RE-400. By adequate, I mean I can control the volume to my tastes and not blow my ears out (I think I have pretty sensitive ears).
 
 
BTW, don't have the channel imbalance problem with the RE-400. And no scratchy pot that I can detect.

 

[Jimster480]

  Perhaps this goes without saying, but some IEMs are more sensitive than others.
 
I get adequate range with the hifiman RE-400. By adequate, I mean I can control the volume to my tastes and not blow my ears out (I think I have pretty sensitive ears).
 
 
BTW, don't have the channel imbalance problem with the RE-400. And no scratchy pot that I can detect.

Those are even more sensitive than the triple drivers or my RP-HD10!
 
What is the max volume you go to on the POT?

 

[Jimster480]

   
Sounding poor, mostly. Crushed dynamics, prone to clipping etc.. It doesn't offend me, it's just not good. A shame, given all the hype at the time- I was hoping for something that sounded clean and didn't harm the sound. Having heard a few off the shelf pre-built ones, as well as one built by a very competent DIYer, I've probably heard more O2s now than are healthy- due to hoping that the first one wasn't representative. 
 
The Fulla 2 is a lot easier on the ears. It uses nicely-chosen op-amps on the output, the device achieves remarkable efficiency and manage to kick out most of that paltry 500mA that the device is allowed to draw. Don't expect it to sound like a Krell or somesuch, but for something that you can throw in a pocket and costs $99, its pretty slick.
 
As to the "how", the Fulla 2 doesn't fall into the same category as it has been designed by a skilled and experienced amp designer- Jason Stoddard. He carefully finessed the BOM and power budget to hit a target. It's not his first rodeo, and he knows the tradeoffs. His designs tend to maximise quality at a given pricepoint. He's not perfect, he screws up sometimes, but he's a smart cookie, and his stuff works.
 
The O2, on the other hand, is a poor design from an inexperienced amp designer, in an attempt to rig a very specific set of measurements with no care given to how the device actually sounds. That doesn't mean that being objective can't give you solid, decent sounding amps, of course. For example, Tom Christiansen is an almost obsessively objective engineer who has designed some decent amps that also measure beautifully, but he does so with his eyes open.
 
Simply, the O2 isn't very good, there are better choices for the price. Simply, if the answer is "an O2 amp", you may wish to rephrase the question. I'd stick with the headphone outs of my phone/laptop/whatever in preference to using an 02. Hell, even a little CMOY would sound better.

Sorry but the circuit design of the O2 is perfectly fine.
Its measurably flat and reference like.
If you like Amps that instead mess with the sound then it means that its not your cup of tea.
But that doesn't at all mean that the O2 is bad.
If you run into clipping then your gain is set too high or your headphones require too much power (protip, it has more power than the Fulla2 so you would run into the same issues).
 
The Fulla2 is bright sounding and doesn't have any special selected components, the components selected are indeed good ones but not "better" than what is put in the O2.

At this point you have no credit and are simply a hater who doesn't like a flat sound signature.

   
As a current owner of both the O2 and the Fulla 2, I'll like to offer a counter opinion. The O2 is my current oldest gear still in use (be it headphones, earphones, amps or DACs) and the Fulla 2 is my 2nd newest audio acquisition. I still frequently bring out my O2 amp to audio meets and stores when demoing earphones and headphones and it was because of its pairing with a Dita Answer that causes me to pay for one, at that time my most expensive earphones, and right now, my oldest earphones still in regular rotation.
 
So I have to respectfully disagree with your comment that the O2 doesn't sound good. You're right that the O2 is designed to measure extremely well rather than how it sounds, resulting it in being a very flat amp, and most definitely not for most people. I have no knowledge in circuit design of any kind, so I cannot comment on whether it's a good or bad design, but I did read before that it's a standard by-the-book Lin design. I've used mine for many years with no incident or issue, it didn't blow up any of my earphones, there is no hiss, and the only criticism that I can give is the channel imbalance that occurs at low volumes, which is a problem if your earphones is extremely sensitive.
 
The Fulla 2 is a different animal altogether. Similar to the O2 amp, I plan to bring it out with me for demo sessions in the future. It may or may not be able to be powered from my dap but I can always hook a power bank up to it.
 
I see an use case for both O2 and Fulla 2 in my gear selection and I should caution if you treat them as an "either or" recommendation.

 
I agree, the O2 is a flat sounding reference like Amp. It doesn't sound "bad" by any means.

 

[cishida]

 
Those are even more sensitive than the triple drivers or my RP-HD10!
 
What is the max volume you go to on the POT?

On my Fulla 2 the pot starts at about 6:45. I'm usually listening around 8:15-8:30 with the RE-400. It helps that the volume knob is large (compared the magni or vali) and is relatively good at small adjustments.
 
Based on my experience using the Fulla 2 with a particular IEM (the RE-400), I don't agree with the following assertions:
 
1. That there is no conceivable IEM that can be enjoyed with the Fulla 2 unless one is "deaf".
2. That Fulla 2 has "0 volume control" with any conceivable IEM.

 

[veloblur]

   
I'm wondering if the number has grown since he said that, because I didn't have any issue early on, it only appeared over time. The proportion of bad units could have grown significantly since he responded to the discussion before. It is obviously hard to judge based on a forum discussion because the bad reports will be amplified, but it does seem to be a good number. 

 
I have the same scratchy issue with the right channel of my Fulla 2 that comes and goes, and mine also has a slightly slanted pot. But these issues don't bother me because when I am listening to an album, I don't mess with the volume all the time. When I do adjust the volume, the scratchiness happens only during the adjustment and goes away after. And I'm not listening critically when I am adjusting the volume. I'm more interested in the music and as far as I can tell, the scratchiness during adjustment doesn't affect the sound quality when the pot is stationary. This was confirmed by Nick from Schiit that I posed the question to. That's good enough for me.
 
I was actually more concerned that the scratchiness was a result of corrosion or a sign that the pot's resistance tracks could degrade over time but he assured me that it was not an indication of either .
 
As long as the channels sound balanced to me, the Fulla 2 seems to work well enough for my requirements.

 

[Jimster480]

 
On my Fulla 2 the pot starts at about 6:45. I'm usually listening around 8:15-8:30 with the RE-400. It helps that the volume knob is large (compared the magni or vali) and is relatively good at small adjustments.
 
Based on my experience using the Fulla 2 with a particular IEM (the RE-400), I don't agree with the following assertions:
 
1. That there is no conceivable IEM that can be enjoyed with the Fulla 2 unless one is "deaf".
2. That Fulla 2 has "0 volume control" with any conceivable IEM.

From 6:45 to 8:30 is very little in the way of volume control, I find that its closer to "too loud" or "too quiet" and I repeatedly move my volume control from song to song.
 
On my A30 I have from 6:30 to 3:00 and thats alot of volume control.

 

[SomeTechNoob]

On my Fulla 2 the pot starts at about 6:45. I'm usually listening around 8:15-8:30 with the RE-400. It helps that the volume knob is large (compared the magni or vali) and is relatively good at small adjustments.

Based on my experience using the Fulla 2 with a particular IEM (the RE-400), I don't agree with the following assertions:

1. That there is no conceivable IEM that can be enjoyed with the Fulla 2 unless one is "deaf".
2. That Fulla 2 has "0 volume control" with any conceivable IEM.

Haha, try again with something ~18ohm or with an ba driver and come back to me again. I have to lower windows volume to 10% to get any sort of volume control without channel imbalance.

 

[Jimster480]

Haha, try again with something ~18ohm or with an ba driver and come back to me again. I have to lower windows volume to 10% to get any sort of volume control without channel imbalance.

Maybe its because his IEM's dont have BA's.
My triples, Quads, and 18Ohm RP-HD10's are really LOUD by 8:30 and honestly 7:15 is the minimum I can go before channel imbalance.

 

[SomeTechNoob]

 
Maybe its because his IEM's dont have BA's.
My triples, Quads, and 18Ohm RP-HD10's are really LOUD by 8:30 and honestly 7:15 is the minimum I can go before channel imbalance.

Well considering I just got my first IEM with an armature driver 2 days ago, I think any low-impedance IEM qualifies.  ZS3 needs windows volume pulled back as well.  At 50% I just exit channel imbalance range when I hit my regular listening level.
 
tbh I understand if efficient IEMs have trouble with channel imbalance, but it's not okay for me if full-size headphones have channel imbalance at regular listening levels.

 

[cishida]

 
On my Fulla 2 the pot starts at about 6:45. I'm usually listening around 8:15-8:30 with the RE-400. It helps that the volume knob is large (compared the magni or vali) and is relatively good at small adjustments.
 
Based on my experience using the Fulla 2 with a particular IEM (the RE-400), I don't agree with the following assertions:
 
1. That there is no conceivable IEM that can be enjoyed with the Fulla 2 unless one is "deaf".
2. That Fulla 2 has "0 volume control" with any conceivable IEM.

 
I should add that, wrt sound, I think this combo (the Fulla 2 and RE-400) is quite good. For me "quite good" means that while I'm listening to it I'm enjoying the music and not thinking about how much better it would sound on my other headphones or speakers. Occasionally, I actually like the sound more than my other setups.
 
The knob and pot allow for small adjustments (the knob is quite big and there is good resistance) and adequately allow me to control volume.
 
But I agree that it is not a good combo if you want / need volume knob range of motion. If you need to be able to turn the knob 20 degrees without blowing your ears out then you will want a different combo.

 

[Ancipital]

 
I agree, the O2 is a flat sounding reference like Amp. It doesn't sound "bad" by any means.

 
If "reference" is clippy, rolled-off, prone to distortion and with crummy voltage swing, sure. It's probably not the word that I'd prefer, mind. I think I'd be happier with an entry-level Magni, or even a competently constructed CMOY, at a pinch- and would certainly not accuse either of those of being "reference"-like, either.
 
Fulla 2 is slightly coloured, but a lot of that is the 4490 "Velvet Sound" processing, rather than the amp section. Yes, the highs are a little hot and the stage a little flat in a traditional solid-state manner, and it won't slew hard or fast enough to get the best out of HD650 either in transients or resolving power, but for $99 for a DAC and amp, it's pretty clever stuff. It's perfectly nice for casual listening or people who don't have terribly demanding requirements (the lucky sods).

 

[Jimster480]

If "reference" is clippy, rolled-off, prone to distortion and with crummy voltage swing, sure. It's probably not the word that I'd prefer, mind. I think I'd be happier with an entry-level Magni, or even a competently constructed CMOY, at a pinch- and would certainly not accuse either of those of being "reference"-like, either.

Fulla 2 is slightly coloured, but a lot of that is the 4490 "Velvet Sound" processing, rather than the amp section. Yes, the highs are a little hot and the stage a little flat in a traditional solid-state manner, and it won't slew hard or fast enough to get the best out of HD650 either in transients or resolving power, but for $99 for a DAC and amp, it's pretty clever stuff. It's perfectly nice for casual listening or people who don't have terribly demanding requirements (the lucky sods).

Sorry but that's just not the case. Sounds like you have the gain up too high and have some problem with your headphones or something like that.

You won't get clipping from an amp that is stronger and not get clipping from a nap that is weaker. It just doesn't work that way due to how electricity works.

 

[Jimster480]

Well considering I just got my first IEM with an armature driver 2 days ago, I think any low-impedance IEM qualifies.  ZS3 needs windows volume pulled back as well.  At 50% I just exit channel imbalance range when I hit my regular listening level.

tbh I understand if efficient IEMs have trouble with channel imbalance, but it's not okay for me if full-size headphones have channel imbalance at regular listening levels.

My RP-HD10 are headphones though and it's no better.

 

[JohnnyOps]

For what it's worth, my Fulla 2 unit displays absolutely no noise on my ancient ThinkPad X40 with Linux, and absolutely terrible scratchy noise with my Dell XPS13 and Win7. Now, the XPS13 doesn't have ASIO - my workplace has it locked town tighter than ____, - but I can't imagine that ASIO changes the power characteristics of the USB port, does it?

So my question is whether the difference is due to the change in OS / drivers, or the change in hardware. I unfortunately can't do a real A/B test because I can't switch the drivers that I have installed on the 2 machines. Where is the bad power management coming from on my Dell/Windows machine?

In the mid-term, it doesn't really matter to me, because I listen on my Ubuntu Thinkpad nearly exclusively, and it's sole purpose is music. And with the Fulla 2 that machine is buttery smooth, silent knob, etc. But I think a LOT of the problems being reported are source machine, not Fulla unit.

 

[K1030]

I'll have to tap out on this one, I just bought a monoprice 11567 instead. I know it works and the aux input is on the back panel too. That way I can throw a Dac on top and it won't look like a spaghetti monster.