[ghuth]

Quote:

"Welcome to headfi! Sorry about your wallet"
Glad that you are enjoying it! I am using it as well, it is a good amp for the price but sometimes and for some other genres it's a bit TOO clean in my opinion. Either way, I get exactly what you are feeling!
Hope you stay on in this community Glenn! We would be pleased to have you here.

 
---Welcoming Post----

 
Thanks for the welcome!  Yeah my wallet has taken a hit but the ear-to-ear grin justifies it

 

[ghuth]

Quote:

I have a lot of much more expensive gear and it usually lives up to my expectations...it should, it is expensive.  I've had my O2 for a day and it is nice to have something exceed my expectations for once.  Listening to LCD-2 through the 02 right now.

 
I didn't even know what to expect... had I managed to destroy the CMOY (seems I must have fried something when the battery leads pulled away and I tried to re-solder them) I'd probably still be using that... knowing there was better out there but not knowing how much better....   The 02 seems to have brought sparkle and... spaciousness.
 
Does the expensive gear beat the 02?  Could you describe how?

 

[cce121]

OOH...nicely done..O.O
Some of the caps look different from standard parts,did you mod them?
 
 
Quote:

Pics of desktop variant O2:
 

 
the bottom is the NFB, the top is the TRIAD power adapter that I wanted to show.
 

 


 
 
Those are the parts used.
 
The cable is 0.8m Long, cable used is Denko 0.18mm^2 99.99% OFEC with braided shielding. (Read: Pro cable LOL). 
 

 

 

 
 
 
Weight: 480g
Size: 185mm x 165mm x 50mm
 
Positive Rail Voltage: 11.3V
Negative Rail Voltage: -11.4V
 
Output DC Offset:
R: 3.83mV
L: 3.92mV
 
Power-ON Transient at output:
400mV Peak, 0.5mS Duration (Loud Click)
Power-OFF Transient at output:
250mV Peak, 400mS Duration (Soft Thump)
 
Gain measurements:
Left-Low: 2.39x  Left-High: 5.69x
Right-Low: 2.37x  Right-High: 5.72x
 
Noise at output: 
L: 3.17mVrms
R: 3.32mVrms
 
 
 
Weight: 480g
Size: 185mm x 165mm x 50mm
 
Positive Rail Voltage: 11.3V (300mVrms Ripple)
Negative Rail Voltage: -11.4V (300mVrms Ripple)
 
Output DC Offset:
R: 3.83mV
L: 3.92mV
 
Power-ON Transient at output:
400mV Peak, 0.5mS Duration (Loud Click)

Power-OFF Transient at output:
250mV Peak, 400mS Duration (Soft Thump)

 
Gain measurements:
Left-Low: 2.39x  Left-High: 5.69x
Right-Low: 2.37x  Right-High: 5.72x
 
Noise at output: 
L: 3.17mVrms
R: 3.32mVrms
Approx.: 15mVp

 

 
  
 
 
 

 

 

 

 
 
CLOSEUP LINK:
https://www.dropbox.com/sh/wku3v79q79ctt32/GoCvJRJd8R?m

 

[bowei006]

Quote:

OOH...nicely done..O.O
Some of the caps look different from standard parts,did you mod them?
 
 

I believe my friend did.

 

[proton007]

@bowei006
Are you using the power adapter?
I think you have enough space for a power supply! 

 

[bowei006]

Quote:

@bowei006
Are you using the power adapter?
I think you have enough space for a power supply! 

The head fier that built it does use a power supply for his own. But I am not.

 

[billybob_jcv]

Quote:

That's why I have a custom built desktop variant with a Burr Brown op amp, 1/4 inch headphone out, and RCA input installed with 2.5x and 6x gain switches
 
 

 
bowei - why did you change the opamp?  I thought "He who cannot be named" made it very clear that he didn't think any other opamp would make the O2 better, and could make it worse?

 

[bowei006]

Quote:

 
bowei - why did you change the opamp?  I thought "He who cannot be named" made it very clear that he didn't think any other opamp would make the O2 better, and could make it worse?

Haha, I used his list. He who cannot be named provided a list of op amps that he thought worked best. There were the bargain one, high performance, and elite ones.
 
I have one of the high performance ones he had on the list. No worries of needless oscilation or pricing of the Elite opamps!
Also using the NJM4556 by JRC Some O2's use a cheaper "gain" amp but this is the one under the high performance section as well and also used quite often.
 
All in all, it is like I said A desktop only high performance variant....I got it because my friend was able to do it with spare parts , signifigantly dropping the price , I got it to learn off what the fricking hype on the O2 was. Good clean unit but for many songs, I prefer musicality. I will be selling it soon. 
Burr Brown op amp
JRC high performance gain amp
Triad recommended power supply
Large case
Desktop only purpose(no batteries)
Customizable if you know how.
 
That's basically why I got it right there. 

 

[mikeaj]

Quote:

Noise at output: 
L: 3.17mVrms
R: 3.32mVrms
 
[snippy snip]
 
Positive Rail Voltage: 11.3V (300mVrms Ripple)
Negative Rail Voltage: -11.4V (300mVrms Ripple)

 
 
Is it just me, or do all the above numbers look suspicious?  The rail voltages shouldn't be that low, and there definitely shouldn't be 300 mV rms ripple on them either...I mean, 7812 / 7912 regulators (outputting +12V and -12V, right?) plus a few caps shouldn't be doing that unless the AC input voltage is too low, or something else is amiss.
 
3.32 mV rms noise on the output?  That's like -50 dBV, a far cry from -112 dBV (unweighted) advertised.  

 

[stv014]

.

 

[mikeaj]

Quote:

 
The low power supply voltage is normal, because it is reduced by D1 and D5 (see here), and to a small extent by Q1 and Q2. On the other hand, the high output noise is strange, and from the picture below it looks like there may be a ground loop or some major problem with the power supply (which the 300 mVrms ripple does suggest).

 
Power supply voltages are reduced by D1 and D5 (1N5818), but not by 0.6-0.7V.  I could've sworn the supply rails were higher than that the last time I checked.
 

 
 
Forward current is much under 1A, I can assure you that.  Total amp power consumption is supposedly no more than 1.5W while maxing the output into a 15 ohm load, so we'd expect a drop more like 0.3V across the diode.  But how much is dropped across Q1 and Q2?  Anyway, it could be very possible I'm just remembering things wrong, like at which point (after regs, after diode, at the op amps?) I checked the voltage.
 
edit: wait a sec, the troubleshooting docs indicate that power supply voltage at the op amps should be more like +- 11.7V:
voltages

 

[stv014]

Quote:

Power supply voltages are reduced by D1 and D5 (1N5818), but not by 0.6-0.7V.

 
Correct, I should have checked the datasheet before replying, these diodes have lower than typical voltage drop.

 

[mikeaj]

Well, I forgot that the diodes were there in the first place, so I missed something too.  0.6-0.7V sounds like such a typical forward voltage drop too.

 

[billybob_jcv]

Quote:

Haha, I used his list. He who cannot be named provided a list of op amps that he thought worked best. There were the bargain one, high performance, and elite ones.
 
I have one of the high performance ones he had on the list. No worries of needless oscilation or pricing of the Elite opamps!
Also using the NJM4556 by JRC Some O2's use a cheaper "gain" amp but this is the one under the high performance section as well and also used quite often.
 
All in all, it is like I said A desktop only high performance variant....I got it because my friend was able to do it with spare parts , signifigantly dropping the price , I got it to learn off what the fricking hype on the O2 was. Good clean unit but for many songs, I prefer musicality. I will be selling it soon. 
Burr Brown op amp
JRC high performance gain amp
Triad recommended power supply
Large case
Desktop only purpose(no batteries)
Customizable if you know how.
 
That's basically why I got it right there. 

 
Ahh - gotcha - I really haven't read all the docs - I do remember one of the pages where he talked about measurements of different op amps and that some of the "Elite" ones were also harder to keep under control in the design.  I didn't really understand most of the technical details.

 

[bowei006]

Quote:

 
Ahh - gotcha - I really haven't read all the docs - I do remember one of the pages where he talked about measurements of different op amps and that some of the "Elite" ones were also harder to keep under control in the design.  I didn't really understand most of the technical details.

You have to google the op amps to learn more essentially.
 
The elite ones generally had many problems such as oscillation and other fixes that you need to accomadate to get them to work well. My friend didn't have one on him, nor did I want one and pay for more time in fixing it, unlike just buy and drop in of the amp he had.
 
I didn't do much research either. I only found out all this info, AFTER i told him I wanted it, the price he could build it at as he already had the parts was UNBELIEVABLE! SO I just said yes.