[Mad Lust Envy]

I'll most likely be getting this amp for now, and keeping an eye on future products. I like the gusto this guy has, and backs it up with some pretty good info.

edit: Scratch that, I'm gonna wait for the desktop version as well as the DAC.

 

[tekdemon]

 

I've had the O2 for a while now.
 
I don't believe in solid state burn in but a curious thing has occurred. 
 
My O2 seems to have improved from it's initial sound, to one that is better than my M^3 or Woo3 and is on a Par with my GS-1.  With careful volume balancing, it becomes hard to tell the O2 (low gain and 9:00 volume setting) from the GS-1.  Not so against the M^3 and the Woo3 which seem to have more, but less articulated bass and not as much HF resolution or clarity.
 

 
I don't believe in solid state burnin either but it's somewhat possible in hand-soldered units like this that heat generated from actually using the unit helps stabilize (or destabilize) less than optimal solder joints.  That said, it's probably in your head.

 

[Willakan]

@Upstateguy:
 
I'm not sure about the Fuze's output level, but if clipping is occurring on high gain it will occur at any setting of the volume pot. The problem isn't in the output stage, it's the input stage that clips: by the time the signal reaches the pot the clipping has already occurred.  This can only be fixed with either switching from batteries to AC if you are using the former (which I don't believe you are) or by swapping the gain resistors for a lower amount of gain on the high-gain setting. Apologies if you have already said, but high gain is 6.5X presumably for your amp?
 
I'm not sure where this deterioration with higher volume settings could come from: the only explanation would be if you are using a borderline voltage (12VAC under load) AC adaptor. This can cause the power rails to drop out of regulation at higher volume settings, which increases distortion, albeit not by much (opamps having a stupidly high PSRR).
 
The limitation is a compromise for price and size reasons, as I understand it. However, the first problem at least (the second problem not existing AFAIK with a decent AC/AC adaptor) will be fixed in the forthcoming desktop version.
 

 

[arirug]

re upstateguy
 
My O2 is not clipping. headphones I use are Sennheiser HD650 and AKG K601.

 

[stv014]

Quote:

Originally Posted by upstateguy /img/forum/go_quote.gif
 
and I certainly know how to a-b something... <shrug>

 
Do you mean it was a blind test ?
 

 

[limpidglitch]

 
Quote:

re upstateguy
 
My O2 is not clipping. headphones I use are Sennheiser HD650 and AKG K601.

What headphones you use will not in a direct manner affect the amplifiers susceptibility to clip in this case.
 
The kind of clipping we're talking about here is an effect of the relationship between input vultage, supplied voltage, and voltage gain.

 

[MacedonianHero]

Quote:

 


 
I don't believe in solid state burnin either but it's somewhat possible in hand-soldered units like this that heat generated from actually using the unit helps stabilize (or destabilize) less than optimal solder joints.  That said, it's probably in your head.

Eutectic Tin-Lead reflows (melts) at 183'C, I seriously doubt that the components are getting to that temperature. The O2 would most likely use lead-free solder....reflows at a higher temperature.
 

 

[Reticuli2]

Meh.  O2 and Emu 0204 works much better.  The DAC on the E7 is pretty average, and you'd be going from a headphone jack into the O2... and not a great headphone jack into line-out loads like on the Emu.

 
Quote:

 
 
 
Well I can only get one atm so which should I get first?

 

 

[Mad Lust Envy]

Umm you can buy an L7 LOD for the E7 to have a direct line out. The headphone jack issue unused.

 

[upstateguy]

Quote:

@Upstateguy:
 
I'm not sure about the Fuze's output level, but if clipping is occurring on high gain it will occur at any setting of the volume pot. The problem isn't in the output stage, it's the input stage that clips: by the time the signal reaches the pot the clipping has already occurred.  This can only be fixed with either switching from batteries to AC if you are using the former (which I don't believe you are) or by swapping the gain resistors for a lower amount of gain on the high-gain setting. Apologies if you have already said, but high gain is 6.5X presumably for your amp?
 
I'm not sure where this deterioration with higher volume settings could come from: the only explanation would be if you are using a borderline voltage (12VAC under load) AC adaptor. This can cause the power rails to drop out of regulation at higher volume settings, which increases distortion, albeit not by much (opamps having a stupidly high PSRR).
 
The limitation is a compromise for price and size reasons, as I understand it. However, the first problem at least (the second problem not existing AFAIK with a decent AC/AC adaptor) will be fixed in the forthcoming desktop version.
 

Hi W
 
We'll have to discuss this further....
 
I'm using the AC adapter that came with the amp... what ever nwav spec'd out I guess.... and the high gain is the default 6.5
 
Not sure why there's distortion at very high volumes.  It almost seems like there is a maximum volume, past which, it distorts regardless of which gain is used.
 


Quote:

re upstateguy
 
My O2 is not clipping. headphones I use are Sennheiser HD650 and AKG K601.

You don't get any distortion or clipping with high gain? 
What is your source?
 


Quote:

 
Do you mean it was a blind test ?
 

No, not a blind test, just an a-b comparison.  Been doing them for years with all my equipment.  Certainly not scientific by any means, but it gives me an idea about how the various components sound.

 

[maverickronin]

Quote:

I'm using the AC adapter that came with the amp... what ever nwav spec'd out I guess.... and the high gain is the default 6.5
 
Not sure why there's distortion at very high volumes.  It almost seems like there is a maximum volume, past which, it distorts regardless of which gain is used.

You don't get any distortion or clipping with high gain? 
What is your source?
 
No, not a blind test, just an a-b comparison.  Been doing them for years with all my equipment.  Certainly not scientific by any means, but it gives me an idea about how the various components sound.

In to loads above 50 ohms or so where the JRC4556s in the output stage don't have to worry about running out of current the O2 should never be driven into clipping by changing the volume control.  With higher impedance loads it should always clip or never clip regardless of the volume pot's setting.  The pot is in between the gain and output stages so turning down the volume will have no effect on whether the input voltage is to high for the gain stage to amplify without clipping.  The only thing that should change whether or not it clips into those loads is changing the gain or increasing the input voltage.
 
None of the 'phones in your profile are low enough impedance to reach the 4556's current limit like that so if it really is clipping at one volume setting and not another then it may be broken or something.
 
 

 

[Draygonn]

I'm using the AC adapter that came with the amp... what ever nwav spec'd out I guess.... and the high gain is the default 6.5

I remember MrSlim mentioning something about wanting to upgrade the AC adapter for users with power hungry cans. I went with the upgraded adapter and I'm having no problems running High Gain(6.5) with my T50RPs. I don't know if this could cause your clipping but thought I'd toss it out in case its something to look into:

There was some discussion that the 12v 200ma adapter may be a little "under spec'd " for the job. Earlier, NwAVGuy had re-assured me that there should not be any issues with this adapter for anyone but those that have very power hungry headphones, and I decided to just keep things as they were. This is the adapter that I have been testing with, and I can confirm that anyone with reasonably efficient headphones, will not have any problem with using this adapter, at all. The reason I am bringing this discussion back up, is that since I'll have to place an order with Mouser anyway, I would like to offer any North American users who have more power hungry headphones( I know at least one person mentioned "Thunderpants" and/or Fostex TP-50's ) the opportunity to upgrade to a more powerful AC Adapter (either the 16V 400ma or 16V 1000ma units depending on availability) for the cost of the price difference

 

[maverickronin]

Quote:

I remember MrSlim mentioning something about wanting to upgrade the AC adapter for users with power hungry cans. I went with the upgraded adapter and I'm having no problems running High Gain(6.5) with my T50RPs. I don't know if this could cause your clipping but thought I'd toss it out in case its something to look into: Quote:

There was some discussion that the 12v 200ma adapter may be a little "under spec'd " for the job. Earlier, NwAVGuy had re-assured me that there should not be any issues with this adapter for anyone but those that have very power hungry headphones, and I decided to just keep things as they were. This is the adapter that I have been testing with, and I can confirm that anyone with reasonably efficient headphones, will not have any problem with using this adapter, at all. The reason I am bringing this discussion back up, is that since I'll have to place an order with Mouser anyway, I would like to offer any North American users who have more power hungry headphones( I know at least one person mentioned "Thunderpants" and/or Fostex TP-50's ) the opportunity to upgrade to a more powerful AC Adapter (either the 16V 400ma or 16V 1000ma units depending on availability) for the cost of the price difference

 
My modded T50RPs are at least a little more power hungry than the K701 which is USG's most power hungry 'phone and they're fine a 2.5x from a ~2.2V DAC on AC with the 12V adapter and at 6.5x from my Cowon D2+ on batteries.

 

[LizardKing1]

Quote:

 
My modded T50RPs are at least a little more power hungry than the K701 which is USG's most power hungry 'phone and they're fine a 2.5x from a ~2.2V DAC on AC with the 12V adapter and at 6.5x from my Cowon D2+ on batteries.

You're using the D1 DAC or the Maverick? Also what is the maximum input voltage the O2 needs without clipping? Is there a minimum treshold as well?

 

[maverickronin]

Using the Maverick D1's solid state output.
 
Max input before clipping is  7/gain on AC and 4.5/gain on battery.
 
I don't know why there would a threshold beyond whatever you could manage to hear.