[b0ck3n]

Fortunately, since the designer has been so open about his design, criticism and concerns have been answered by others - everything, and I mean everything, is published for everyone to see on his blog.

I'm hoping that the thread can move on to providing information on how to get parts, kits or finished amps and later on, people's experiences using them.

 

[Currawong]

Quote:

I'm not complaining about that. I'm complaining about the fact that the design is being criticised, but any links that attempt to counter that criticism, even not to NwAvGuy's site, are being removed. Regardless of the vehemence or not with which the criticism is delivered, or indeed its prevalence, that is not a place I want my thread going (I know, technically not 'my' thread now, but hey)

I think you are missing the point of DIY. If you or I designed an amp and posted it here, the first thing that would happen is that people with knowledge would post critique of the design and suggest improvements. This is normal. However, because of the nonsense perpetuated about this design and Head-Fi, you see criticism not as part of the design process but as some kind of attack, even when the critique is given by engineers with no personal interest whatsoever in the design.  This thread will be good if, as I said in a previous post, you can stop with all the (totally incorrect and easily disproven) conspiracy theories and focus on getting it built well and overcoming any shortfalls in the design that may arise when using it with different gear.
 
 
 

 

[mikeaj]

Criticism and feedback is part of the DIY design process, which is why there's a gain switch now and then later on why the default lower gain setting is 2.5X and not 3X.
 
Anyhow, if the interest is in improving the design or helping the designer out, I'd think that the natural thing to do would be to post on one of the places where the designer can read and respond to potential concerns.  Serious accusations or differences in opinion are fine, but they seem small and petty if only posted here only and not in one of the other places.  (That is, unless people legitimately don't realize those places exist, since any mention of them is put on lockdown.)  Is one of the themes in this thread questioning other peoples' motives?

 

[deadlylover]

I just spent about 3 hours at a friend's place ping ponging back and forth in a level matched comparison between the Obj2 and beta22, using the LCD-2. I was unable to discern any large differences in sound between either amps, so any differences I heard were small, and may very well have been my imagination.
 
There was practically no difference tonality wise, but I felt that the beta22 sounded a little less congested, that's pretty much the best I can put it. Since I kind of tunnel vision the vocals when listening to music, the main difference for me was the vocal separation with the rest of the track.
 
Anyway, I don't claim to have a large amount of experience with the LCD-2, and I realise some differences may only show up after an extended audition, so that's why I left the Obj2 with my friend, so I can forward his impressions eventually. I'm no audiophile, I've never heard any real live music, I have tin ears and I don't particularly care how things sound as I am not nearly as passionate about music as most of you guys. I also loathe dynamics, so I was really trying to pick between the lesser of two evils here, so please take my impressions with a grain of sugar, spice and everything nice.
 
On the other hand, I may very well be a sucker for subjective bias, as the comparison was only volume matched, and not done blind. The beta22 was actually balanced, so it only had a 4pin xlr out, and I had to 'unbalance' it for this comparison. It was a pain having to switch the LCD-2's cable each time I went back and forth, which is why we couldn't be bothered to do a proper blind test. I would have liked to build a milosz style switcheroo box, but I was just too lazy.
 
Do keep in mind that my Objective2 was not done on the proper PCB, and I very well may have ballsed up the amp, so again, don't take my impressions too seriously.
 
Please don't hurt me.

 

[Currawong]

Thanks for the impressions. I tend to find the same thing, that better gear results in a more clear distinction between instruments and the vocals on recordings.
 
A couple of questions: How loud were you listening? Is the Beta 22 single-ended or balanced?

 

[deadlylover]

Quote:

Thanks for the impressions. I tend to find the same thing, that better gear results in a more clear distinction between instruments and the vocals on recordings.
 
A couple of questions: How loud were you listening? Is the Beta 22 single-ended or balanced?

 
About 70db or so, not terribly loud at all. The beta22 was configured for single ended operation (2ch) for a fair comparison, it's actually a balanced b22.

 

[b0ck3n]

Thanks for your straight up impressions, deadlylover. I find it extremely difficult to discern any difference between sources and amps when I can't make the switch instantly.

 

[Willakan]

The worldwide group buy over at DIYAudio has already got about 200 boards requested by various people. Many more impressions/reviews are looming on the horizon...
 
EDIT: Also, whilst I'm at it, for those worried about turn-on transients, NwAvGuy has measured them into various loads and found them pretty benign - it has a little turn on thump, but it is well within safe bounds for even the most sensitive 'phones.

 

[Costia]

can anyone explain how the current limiting works in the O2?
I understand how/why it  it will shutdown on low input voltage an the hysteresis, but i don't seem to figure out what actually limits the current.

 

[b0ck3n]

For anyone who's interested in the O2, but not quite ready to take the DIY plunge, MrSlim is offering a build service over at DIYaudio.
 
Short info: a complete basic build using the portable case and FPE front panel at $114 (shipping excluded), with the option to add batteries at a cost of $11. A "desktop" case with 1/4 headphone jack and RCA input jacks can be had at an added cost of $15.
 
 

 

[mikeaj]

Quote:

can anyone explain how the current limiting works in the O2?
I understand how/why it  it will shutdown on low input voltage an the hysteresis, but i don't seem to figure out what actually limits the current.

I think it's just the dual NJM4556 output stage.  They can't put out more than a certain amount of current, even though distortion into low impedances is pretty low just up until their limit.
 

 

[qusp]

better to leave the headphones plugged in if the thump is minimal is it not? i often wondered which would be more damaging, a small turn on thump, or shorting the outputs and headphones to to ground on the way in and out while the amp is on ie. hot plugging

 

[Willakan]

It is said to be more of a turn on click than thump, leave it plugged in.
If you're worried, wait for the desktop version, which will have proper board mounted RCA inputs, better gain stage structure and also will be completely silent on turn-on/off. 

 

[Kibble Fat]

subscribed.  Keep up the good work lads!

 

[Reticuli2]

Didn't two versions of a defective Cmoy and an E7 also blow your Mini3 away?

 
Quote:

 
 
The $30 figure is fallacious as has been mentioned in this thread.  It is also misleading for the designer to claim that a Mini³ is "more costly" than the O2, when the price figure for the Mini³ is a professionally-built unit with labor costs added.
 

Simple.  He had been abusive to me on my own forum and in several other forums, not to mention his blogs, repeatedly.  What makes you think it would be different now?  I don't see anything constructive in me engaging him directly.  His fanboys could do me the favor and spare me the grief.
 
Steve, that's the nature of this thread isn't it?  He can't respond to anyone's posts here.  Not just mine.  And when was it bad form to state the truth?  Do you not agree that my analysis about the O2's low input voltage overload margin is correct?  Kevin Gilmore also posted the same...
 
 
As an (already quoted) example, the γ1 DAC puts out 1.6Vrms @0dBFS.  It definitely qualifies as "portable" since it's less than half the size of the O2.  1.6Vrms (4.53Vp-p) into a battery-powered O2 set to a gain of anything higher than 2.6x will clip.