[Sorensiim]

This thread made me change my signature. 
 
Just ordered an O2 pcb, I'm really curious to hear this thing.

 

[deadlylover]

Quote:

@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:

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:

 
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:

 
 
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:

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:

 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]

 


 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
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[Shike]

Quote:

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 ^_^