[cheapskateaudio]

 
Quote:

 
Or, the first version was dodgy, and you just fixed it.

Very well could have been, but I replaced all the op amps and mosfets on it at least once... Those are the only things to my knowledge that are fragile enough to get damaged in general handling. I also reflowed about half the joints, desoldering and resoldering each one... I'm going to continue to mess with that version to see what is "wrong" with it. It was improved by the changes made to it initially but it still has that pop and thump on power on/off as well as the generally inferior sound.
 
Clearly it should be possible to bring the first version in line with the current one given the same changes.

 

[Head Injury]

Build another in default configuration and DBT them.
 
Or measure the one you made to see if you butchered the THD or something.

 

[cheapskateaudio]

Quote:

Build another in default configuration and DBT them.
 
Or measure the one you made to see if you butchered the THD or something.

I guess I can try the second option, probably not going to build another one of these. I'll go ahead and measure both amps with a DMM according to NwAvGuys guide as well, that should at least show any major problems.
 
 

 

[Willakan]

Even if it does show variations from the expected values, how are you going to work out what effect they would have on the audio? A DMM doesn't provide much insight into audio performance.

 

[mikeaj]

Yes, the DMM testing is to catch potential anomalies that indicate circuit construction problems or malfunctioning components.  e.g. the power mangement not working properly, resulting in outputs that can potentially damage headphones.
 
Unless your idea of a "DMM" is much different than mine, I don't see how somebody who has used one before could possibly think that a DMM can be used to analyze audio performance (aside from max voltage output levels).

 

[cheapskateaudio]

 
Quote:

Yes, the DMM testing is to catch potential anomalies that indicate circuit construction problems or malfunctioning components.  e.g. the power mangement not working properly, resulting in outputs that can potentially damage headphones.
 
Unless your idea of a "DMM" is much different than mine, I don't see how somebody who has used one before could possibly think that a DMM can be used to analyze audio performance (aside from max voltage output levels).

I wasn't going to use a DMM to measure "audio performance". I was going to use a DMM to ensure that my first amp wasn't "dodgy". 
 
I have ears which are quite suitable for the analysis of "audio performance". For those of you who require colored lines to dictate your perception I will use REW and a microphone to measure the performance of the two amps. (Driving headphones of course)
 
 

 

[sphinxvc]

Quote:

Amazon may be a bit optimistic.  You're looking mostly at large electronics suppliers, which often have minimum order limits, significant shipping charges, etc.
 
You're looking for an AC/AC wall transformer with an output of around 14-20V.  Some "12V" transformers have a high enough actual level to be used.  In general, the cheapest option that works is the Triad WAU12-200, and it will be plenty except in some more fringe cases (say driving very insensitive low-impedance headphones or doing bench testing).  That's what I use for mine.
 
http://www.mouser.com/Search/ProductDetail.aspx?qs=gbLhNGEXPTb00xhB4fgq6w%3D%3D
 
Higher like WAU16-400, WAU20-200, etc. is okay.
 
 
Here is the snippet from the "place" which may not be linked:
 
"There has been some confusion over the wall transformer and it’s a critical component. Most wall transformers put out DC but the O2’s power supply requires at least 13.5 volts AC. The ideal transformer would be rated at 14 - 16 VAC and 400 mA or higher. In North America the Triad WAU12-200 from Mouser is rated at 12 volts but is really about 13.5 VAC with no load, and on normal 120 volt line voltage works fine for anything but full power sine wave testing or driving rare low impedance power hungry cans. If your line voltage is below 117 VAC  or 235 VAC, and/or you plan to drive difficult low impedance headpones (i.e. HiFiMan planars), I would suggest a 14+ VAC transformer at 400+ mA. The best Mouser transformers are the WAU16-400, 412-218054 or WAU16-1000 CUI. But those are more expensive than the WAU12-200. The WAU20-200 also works for higher impedance headphones. At least some European 230 volt input 12 VAC output transformers only measure around 11.5 to 12 volts on normal line voltage and won’t work (especially if designed for halogen lights). You can also change the power jack to a 5.5mm x 2.5mm version if needed to match the plug of different wall transformers."

Thx.
 
 

 

[LizardKing1]

Quote:

O2 GOLD EDITION
 
The sound:
 
In short, this version annihilates the first version.
 
That being said, I don't know what specifically made it so much better or if it's the totality of the upgrades. For the most part I just upgraded everything in the signal path. 

 
What did I do?
 
More precise resistors throughout, more precise caps, .22uf WIMA poly caps, higher precision ceramic caps throughout, 0.1% - 0.5% precision resistors throughout , high precision 170pf ceramic caps on the dominant poles of the op amps (vs 220pf).
 
The result is no smearing of the midrange, no audible clicks or thumps on power on or off, generally vastly improved sound.
 
I also used a higher spec'ed comparator and gain stage op amp.
 
Harshness is gone, HD650's sound really good, smooth, much more to expectations, HD448's sound superb also, amazingly good for $99.
 
I might post more details at some point. But I honestly think that all the "super designers" will just laugh at me as delusional, however, I know what my ears are telling me... PARTS MATTER.
 
 

Problem: an amp that smooths sound is supposedly a bad amp. The perfect amp would be harsh and cold, not at all warm and smooth. So of course it works with the HD650, because you're used to it being smooth, and since the original O2 is supposed to be very detailed it wouldn't work that well (unless you liked the sinergy). In any case, no one's trying to burst your bubble, I really think you made something good here: you took a good amp and changed it. Just stop calling it an improvement, since smooth IS NOT an improvement. Also, maybe contacting NwAvGuy and suggesting those changes, so that more people can know of this?

 

[redwarrior191]

Quote:

The FA-003 and the FA-002W sound fantastic with the O2. The High Editions do not.

LFF..I just noticed that you already had your O2 for awhile.. would you mind giving some impressions??? or do you also believe that it sounds like nothing??

 

[mikeaj]

Quote:

I wasn't going to use a DMM to measure "audio performance". I was going to use a DMM to ensure that my first amp wasn't "dodgy". 
 
I have ears which are quite suitable for the analysis of "audio performance". For those of you who require colored lines to dictate your perception I will use REW and a microphone to measure the performance of the two amps. (Driving headphones of course)

My apologies for being presumptuous then.  No offense, but I have read a number of (what I estimate to be) absurd postings from you and thought that was just another.  I do appreciate your willingness to question and try different things though.

 

[firev1]

cheapskateaudio, you need to prove your point to your naysayers! Get a dScope now!

 

[Willakan]

Heh, anyways...
Finally got around to taking a photo of my O2. As I mentioned on another thread, custom desktop build (so panel mounted jacks) with everything crammed onto a DIY front panel. Note the audio-grade Araldite used to secure the 1/4 inch jack and the strategic missing of the jack to...erm...improve absorption of standing waves.
Only flaw is that it turned out 3.1X gain (with a 2.1V RMS source - DACMagic) is ridiculously excessive for the K702s. Not much of the volume knob's range is usable - might clip the resistors on the high gain setting as I can't see myself using this with an MP3 player.
 

 

[deadlylover]

Quote:

Heh, anyways...
Finally got around to taking a photo of my O2. As I mentioned on another thread, custom desktop build (so panel mounted jacks) with everything crammed onto a DIY front panel. Note the audio-grade Araldite used to secure the 1/4 inch jack and the strategic missing of the jack to...erm...improve absorption of standing waves.

 
Nice!
 
It only looks....a little better than my robot-vomit in a cardboard box.
 
Quote:

Problem: an amp that smooths sound is supposedly a bad amp. The perfect amp would be harsh and cold, not at all warm and smooth. So of course it works with the HD650, because you're used to it being smooth, and since the original O2 is supposed to be very detailed it wouldn't work that well (unless you liked the sinergy).

The 'perfect' amp is neither harsh and cold, nor warm and smooth.

 

[DRUB]

Quote:

Problem: an amp that smooths sound is supposedly a bad amp. The perfect amp would be harsh and cold, not at all warm and smooth. So of course it works with the HD650, because you're used to it being smooth, and since the original O2 is supposed to be very detailed it wouldn't work that well (unless you liked the sinergy). In any case, no one's trying to burst your bubble, I really think you made something good here: you took a good amp and changed it. Just stop calling it an improvement, since smooth IS NOT an improvement. Also, maybe contacting NwAvGuy and suggesting those changes, so that more people can know of this?

The perfect amp will basically allow a headphone (with its own intrinsic limitations) to do its absolute best in recreating the source material. That's all there is to the holy grail; if the perfect amp sounds 'harsh or cold' it's because the recorded material has these characteristics or the headphones have a FR or other measurements that translate into this perceived sonic signature.
 

 

[Willakan]

That front panel is my eighth attempt:
 
Attempt 1: Drilling metal panel that comes with case with hand drill. 'Nuff said.
Attempt 2: Bought 2mm acrylic. Snap it in two when trying to cut it to size.
Attempt 3: Using first snapped half to try to make front panel with aforementioned hand drill. Snap it again.
Attempt 4: Using other snapped half. Going well until I try to drill the corner holes, at which point the corners snap off.
Attempt 5: Give up, decide to use laser cutter. Make various cardboard trial cuts (not included as not to inflate list massively). Manage to cut remainder of 2mm acrylic by giving the cutter a file with all the holes slightly off. Runs out of 2mm acrylic.
Attempt 6: I move on to 3mm acrylic. Set power settings incorrectly, resulting in the acrylic blackening and gushing green smoke. Still fails to cut through it.
Attempt 7: Find some yellow acrylic. Get holes in wrong places again when cutting.
Attempt 8:I finally cut a working front panel. Had to file the gain switch hole slightly and the bottom screw holes don't align, but it works and I'm past caring.
 
Luckily, the actual amp worked first time!