[amb]

No, I am not interested in discussing this directly with the designer.  If he is the brilliant engineer that he makes himself out to be, then he must know these limitations.  Must use a weak source, must use low gain, must use AC power... too many ifs, ands and buts.  None of the amps that he lists as "competition" have these problems.

 

[upstateguy]

Quote:

<snip>

 I'm sure you can find one of the many threads to discuss this directly with him if you're interested or shoot him an email.

 
+1

 

[Pyriel0]

Quote:

No, I am not interested in discussing this directly with the designer.  If he is the brilliant engineer that he makes himself out to be, then he must know these limitations.  Must use a weak source, must use low gain, must use AC power... too many ifs, ands and buts.  None of the amps that he lists as "competition" have these problems.

For $30 I can deal with a couple restrictions.
 

 

[upstateguy]

Quote:

No, I am not interested in discussing this directly with the designer.  If he is the brilliant engineer that he makes himself out to be, then he must know these limitations.  Must use a weak source, must use low gain, must use AC power... too many ifs, ands and buts.  None of the amps that he lists as "competition" have these problems.

Hi
 
I have 2 M^3s and have been recommending them to others for years, but I don't understand why you're making comments here and not where the designer can answer them?

 

[b0ck3n]

Any source likely paired with the O2 on batteries will put out ~1v, so it's unlikely an issue. Can you name one 2.5v output portable device, Ti?

 

[Steve Eddy]

Quote:

No, I am not interested in discussing this directly with the designer. 

But you are interested in discussing it on a forum where he can't respond to your criticisms.
 
Rather bad form if you ask me.
 
se

 

[sgrossklass]

One could argue that audiophiles are already used to taking care of all kinds of ifs and buts, so a few more for a good cause (namely, optimum noise and distortion performance) wouldn't matter all that much. Equip low gain resistors for a worst-case scenario and be done with it.
 
Any way of addressing this issue would involve increased complexity, and the board already is packed as-is (the price for all through-hole parts on a half-Eurocard sized board that also accomodates the batteries). Besides, while DC/DC generated supplies would be handy (I'm not a big fan of 9V blocks personally), switch-mode converters are a classic can of worms by themselves in the DIY realm.

 

[amb]

 
Quote:

Originally Posted by Pyriel0
 
For $30 I can deal with a couple restrictions.

 
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.
 
Quote:

 
I have 2 M^3s and have been recommending them to others for years, but I don't understand why you're making comments here and not where the designer can answer them?
 
Originally Posted by Steve Eddy
 
But you are interested in discussing it on a forum where he can't respond to your criticisms.
Rather bad form if you ask me.

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...
 
Quote:

Originally Posted by b0ck3n
 
Any source likely paired with the O2 on batteries will put out ~1v, so it's unlikely an issue. Can you name one 2.5v output portable device, Ti?

 
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.
 
 

 

[The Monkey]

I love the suggestions that criticisms of the design are inappropriate here. Pretty delicious irony.

 

[amb]

Yup.  Anyway, I've made my point, and to avoid stirring the pot any more, I'll refrain from further posts here and let others chime in.

 

[Beftus]

 
Quote:

Can you name one 2.5v output portable device, Ti?

A GrubDAC comes close: 2Vrms. My GrubDAC lives in a Hammond1455C801.
 

 

[purrin]

Quote:

But you are interested in discussing it on a forum where he can't respond to your criticisms.
 
Rather bad form if you ask me.
 
se

 
It seems you are taking this a little bit too personally. I don't think amb was trying to kick the designer while he was down or sucker punch him. What amb pointed out is completely fair and logical. If you've ever met the guy, carefully studied his project pages, or built his stuff, you would realize the kind of thought he puts into engineering things.
 
I however am quite astonished at the lack of understanding from some of you of basic engineering principles such as safety tolerances, especially for a project that is supposedly based on "objective" measurements. You can't design anything and assume "oh, people won't be doing that" or "that possibly won't happen" or "this is what people would typically do".
 
When I started out in this hobby, I ran a Headroom portable amp out of my DCX2496 XLR outputs. Now guess what would happen if I ran this amp that way? Probably only 3 of out 25 people would probably ever do something wierd like that. But it happens. Why not just improve upon the design instead of putting warning stickers on it: "DO NOT RUN OUT OF DESKTOP DAC" or "LIABLE TO CLIP IF BATTERIES AREN'T FULLY CHARGED"
 
Solving potential issues like this is what makes engineering fun, not putting your fingers in your ears and saying "la la la la la la la"
 
 
Quote:

Hi
 
I have 2 M^3s and have been recommending them to others for years, but I don't understand why you're making comments here and not where the designer can answer them?

 
Because he's addressing the general community here (and possibly the designer, who may be lurking around.) I know I certainly appreciate it. I've looked up the schematics to this amp and was intrigued by the design with the pot after the gain stage. I'm glad amb took the effort to look up the parts, analyze the design, and give us a "Danger, Will Robinson" warning. That's enough for me; I don't think amb should be expected nor responsible for finding the particular forums the designer hangs around or notifying him personally.
 

 

[Anonanimal]

Hold on a second here- I'm a bit confused at the overall tone from the vets here.  Bear with me, please.
 
So the limitations of the input stage are being touted as a "major problem" for the DIY crowd because it requires some forethought and building the amp such that the gain is correct for your gear?  From what I can gather, as long as you're paying attention when you build the thing, 99% of all situations are easily compensated for with some basic reasoning.  It's very clear in the design documentation that it was an intentional choice for performance reasons, with minimal tradeoffs as long as you know what you're doing (or read first).
 
What about the fact that the Beta22 boards allow you to install the trimpots backward, thus blowing parts up when power is first applied?  Even seasoned vets can make this mistake- and make no mistake that this is a design problem.
 
That being said, I'm a big fan of the Beta22 design and all of AMB's efforts in general.  I own one that I built myself (and no I did not make the backward trimpot error, though many have).  Don't take it personally- it's just a bit ironic.
 
I don't know about anyone else here, but I prefer to learn something from my DIY experiences and if that's the limitation I have to work around to produce performance results like I've seen this amp is capable of... well, okay then.
 
Don't be afraid! 

 

[purrin]

Quote:

 It's very clear in the design documentation that it was an intentional choice for performance reasons, with minimal tradeoffs as long as you know what you're doing (or read first).
 
What about the fact that the Beta22 boards allow you to install the trimpots backward, thus blowing parts up when power is first applied?  Even seasoned vets can make this mistake- and make no mistake that this is a design problem.

User error and builder error are two very different things.
 
In this case, it wouldn't even be user error unless there was a manual or warning sticker telling users to only use portable DACs with low output. Perhaps the manual should even provide a list of DACs that may possibly cause clipping, the Grub and the γ2 among them.
 
This is so wierd because didn't the designer of this amp "expose" some other manufacturer's gizmo to be prematurely clipping. 

 

[Anonanimal]

Quote:

User error and builder error are two very different things.

Fair enough.  I don't want to come across like I'm overreacting, was just trying to provide a parallel and it's a bit half-baked.