[Shamharoth]

@cheapskateaudio: I like how you carefully dodge any post asking for pictures of your board, list of your modifications and your measurements... IMHO that's clearly indicating something...

 

[kingpage]

Although I haven't read through the entire thread, I have read quite enough to see the correlation of the amount of hand waving and time.
 
"What if he's wrong a second time?" must be what everybody is thinking right now (at least I am).

 

[samsquanch]

Quote:

Calm down guys it's just a freakin amp.
 
I almost can't tell if you guys are just having a go at cheapskate, or whether you lot want to honestly crack down on what the hell is going on with his first amp.
 
cheapskate, I just think something is wrong with the first amp. Don't take it the wrong way, it's got nothing to do with your 1337 building skillz, but in DIY, stuff happens. I say this because I've compared my Obj2 with the beta22, and there was pretty much no difference in the bass at all (LCD-2 r1), and the b22 is a very well regarded amp. (go away willikan

)
 
Dodgy parts happen all the time man, I've once had regulators that refused to regulate, and a multi turn pot with a mind of it's own.

Do you notice any difference in the upper lowrange / lower midrange between your beta22 and O2?  I have a suspicion that the O2 has some phase distortion around 100Hz.  I need to find a way to test this, suggestions anyone?
 
Sorry I know this was off topic, back to arguing with a troll 

 

[cheapskateaudio]

 
Quote:

@cheapskateaudio: I like how you carefully dodge any post asking for pictures of your board, list of your modifications and your measurements... IMHO that's clearly indicating something...

I'll get around to it, unfortunately I do have more pressing matters at the moment.
 
I also want to look over the mods being posted on diy audio and try some that I think may affect sound quality (in my totally unprofessional opinion).
 
Once I've completed my modded amp to my satisfaction, I will certainly post pictures galore as well as measurements galore. 
 
It may be some time before I get around to that unfortunately, perhaps 2-3 weeks... Need to order parts etc.
 
 
 
 

 

[wakibaki]

One thing I will say:-
 
In common with many other controversial threads (I mean those that become out-and-out arguments), it does keep getting posts, which is something in its favour. We may be arguing, but we are communicating with each other, which in some way is better than sitting in our respective shells with nothing to say.
 
Kind of like children prefer to get scolded rather than be ignored.
 
Hmm.
 
w 

 

[estreeter]

Quote:

As a side note, I always thought his second choice of name was clever, since we could refer to him as "He Who Must Not Be Named."

I just call him 'Voldemort' - haven't had a problem thus far. I think it would be any reference to the original furore that might invoke a touch of mod rage. I expect that both sides might have approached it differently if given a second chance, but thats showbiz. My old boss used to tell us 'Never type angry, even if it means getting up and making a coffee'. Wise words, but he was as guilty as any of us when it came to breaking that little guideline. 

 

[upstateguy]

Quote:

@cheapskateaudio: I like how you carefully dodge any post asking for pictures of your board, list of your modifications and your measurements... IMHO that's clearly indicating something..

+1
Quote:

I'll get around to it, unfortunately I do have more pressing matters at the moment.
 
I also want to look over the mods being posted on diy audio and try some that I think may affect sound quality (in my totally unprofessional opinion).
 
Once I've completed my modded amp to my satisfaction, I will certainly post pictures galore as well as measurements galore. 
 
It may be some time before I get around to that unfortunately, perhaps 2-3 weeks... Need to order parts etc.
 

I see that you have a nice Canon S100. 
 
We'd love to see the boards side by side. 
 
Some of the more experienced DIYers might be able to spot what the problem is just by looking.
 
Edit:  you might want to man up and post your findings on diyAudio where nwav can respond directly to you. 
 
Certainly he knows more about this amp than anyone else and would be able to address your mods as well as why your amp isn't performing.

 

[mikeaj]

Quote:

Do you notice any difference in the upper lowrange / lower midrange between your beta22 and O2?  I have a suspicion that the O2 has some phase distortion around 100Hz.  I need to find a way to test this, suggestions anyone?

I didn't do any analysis of this to see if it made sense, but intuitively...
 
Generate a 100 Hz + 200 Hz tone, equal amplitude for both but that may not really matter.  Play it and record it using some type of sound card (line out -> line in), as a reference.  An accurate scope would be better.  Then hook up line out -> O2 -> line in and play it and record it again.
 
If there's a phase shift at 100 Hz, then the shape of the waveform through the O2 should be shifted.  Sound cards are no good at high resolution for amplitude data, but the time resolution may be good enough.  For example, check the number of samples (time) between 0 crossings (when the amplitude passes through 0).  There should be four 0 crossings (2 upwards, 2 downwards) per 100 Hz cycle.
 
At 48 kHz sampling rate, with no phase error, it should be 48000 / 200 = 240 samples between upwards 0 crossings.  It may be irregular like maybe 242 and 238 (two numbers that sum to 480) if there were phase error.
 
You can do all the above in something like Audacity, which is free.  Anybody is also free to tell me if this idea needs an extra bake cycle.
 
 
To be honest, Voldemort measured phase across the range and found only +- 0.8 degrees error between 100 Hz and 10 kHz, so I don't think you'll find much issue.

 

[SobbingWallet]

Quote:

Do you notice any difference in the upper lowrange / lower midrange between your beta22 and O2?  I have a suspicion that the O2 has some phase distortion around 100Hz.  I need to find a way to test this, suggestions anyone?
 
Sorry I know this was off topic, back to arguing with a troll 

 
Do you have any other amps to blind test 100Hz tones against, or have you already tried that?  Barring expensive equipment, blind testing between the O2 and other amps known to measure well should help substantiate whether there's an issue or not.  Since you seem to think there might be something there, I'd also be interested in you, deadlylover, or others doing preliminary blind testing for phase shifts.  I'm not hearing anything out of sorts, but I don't have anywhere near enough experience to easily detect or pinpoint a phase shift, and I don't have a reference to test against either.
 
The designer included phase response measurements using the dScope Series III (which showed the phase to deviate by +/- 2 degrees at most except for the very extreme ends of the spectrum).  That said, we ultimately need to get some reliable third party measurements to corroborate (or challenge) the ones he published.  cheapskateaudio's frequency response bashing may not be credible, but it's more believable that the designer might have made a mistake with something more subtle like phase response.
 
Do you know if anyone else on the board owns a dScope or anything close to its caliber?  It might be helpful to start another thread seeking takers, since I'm sure someone around these parts has something suitable.  In the meantime, does anyone know of any problems using RMAA for phase shift testing?  I've read that there are all sorts of problems, but I'm not sure if certain tests might be exempt from them.
 
EDIT:  mikeaj's ghetto test sounds like a good one to try too.  I don't know how reliable it would be or what might go wrong (might have false positives/negatives), but at least it's something!

 

[tomb]

 
Quote:

A properly built GrubDAC sounds fine. I own one (or two) and I plan on putting using one with my O2.
 
The 2707 chip is regarded pretty highly as far as diy USB DACs go. AMB uses one for the USB section of the y1/y2. You can also contact Tomb and ask him some questions since he sells the kit to make them, although I'm unsure if he designed the circuit.
 
http://www.diyforums.org/GrubDAC/GrubDACtechhigh.php

Cobaltmute designed the grubDAC, but thanks to his generosity, I sell it.
 
I hate to comment in this thread, because there are so many things bandied back and forth that are wrong, wrong.  The "real" DIY-er's on Head-Fi abandoned the original O2 thread a long time ago and have probably stayed away from this one as well.  I basically read this one from time to time for entertainment.

 
A few comments about the last few pages of posts, but first - BobSaysHi is a good guy and none of these are necessarily directed at him, although I think he may have missed the essential point about the GrubDAC, too:

1. The TI PCM2706/7 chip is used as a USB interface, only.  The actual DAC chip on the GrubDAC is the Wolfson WM8524.  So, you can see that any of these comments realtive to sound quality of the PCM2706/7 chip on the GrubDAC miss the point entirely.  This is the same for AMB's Gamma's - his PCM chips are for the USB interface, only.
2. Data sheets for chips/active devices/etc. almost always display the minimum, least expensive configurations to ensure the performance of the chip.  The difference between that and high performance audio often end up in a lot of added components.
3. Unless a data sheet is about a power supply chip (LM317 or the VR's that cheapskateaudio is complaining about), other data sheets for opamps and DAC chips almost invariably omit any discussion of power supplies whatsoever - they only specify the voltage needed.  Power supplies are everything when it comes to the quality of an amp's output.
4. The same can be said of a DAC chip - power supplies are always omitted in application schematics from the mfr.  This leaves a huge range of designs that may result from the very simple to the very complex.  One DAC might use USB power, another USB regulated power (on the DAC PCB), or another might use a completely independent power supply.  Still others may regulate the analog output, the digital supply voltage or both.  then there's regulation for the output buffer, I2S, whatever.  Very often the overall quality of the DAC - regardless of the chip - will be dictated by the quality of these power supply voltages.  (There are many other components that can be added to improve the sound besides power supply components, too.) 
5. You cannot judge the quality of a DAC chip or opamp without considering the overall circuit that's used.  If you start swapping opamps or DACs in the same or very similar circuits, then OK - you have a valid point of reference, but otherwise, no.  
6. Many of you are complaining about cheapskateaudio's failure to show any pics of his work.  Seems to me that khaos974 just posted them in plain sight for everyone to see.  Other than a lack of wicking to the top side of the PCB solder joints (it's obvious plated holes exist on the PCB), nothing seems untoward from this perspective.
7. Still - deadlylover made some decent points.  It's just another amp design.  There are amps that are worse and there are amps that are better.  In DIY, stuff happens.
8. There are not "God-like" powers granted to degreed Electrical Engineers around here.  I've been a Professional Engineer for over 30 years - as a Mechanical.  Yet, I can't tell any of you how to replace a toilet or design a gear drive.  A couple of the finest designers we've ever had at Head-Fi are computer engineers, not EE's.  Another is a mechanical type like me (not saying I design, but I do build).  Still another has no technical degree at all (he's a PhD, though) - and he is among the best.  There's nothing that says any one of you can't read and learn and eventually become as much of an authority on such matters as anyone else.   

 

[kingpage]

Quote:

1. There are not "God-like" powers granted to degreed Electrical Engineers around here.  I've been a Professional Engineer for over 30 years - as a Mechanical.  Yet, I can't tell any of you how to replace a toilet or design a gear drive.  A couple of the finest designers we've ever had at Head-Fi are computer engineers, not EE's.  Another is a mechanical type like me (not saying I design, but I do build).  Still another has no technical degree at all (he's a PhD, though) - and he is among the best.  There's nothing that says any one of you can't read and learn and eventually become as much of an authority on such matters as anyone else.   

I see this comment must be directed at me. If I'm not mistaken, I read OP admitted himself that he's not an engineer at all and is new to audio designs. As someone who's trained in the area of statistics, I know what the most likely thing being conditional on the information I have gotten so far. What you are saying is not the rule, but the exception. Not to mention, going from one engineering descipline to another is different. But this doesn't mean that he won't educate himself enough in a few months with some extreme dedication so that he will be able to design an amp from the ground up that outperforms O2 for a fraction of the cost. I welcome that idea. However, at this point, all that is just pure wishful thinking.

 

[mikeaj]

Quote:

1. There are not "God-like" powers granted to degreed Electrical Engineers around here.  I've been a Professional Engineer for over 30 years - as a Mechanical.  Yet, I can't tell any of you how to replace a toilet or design a gear drive.  A couple of the finest designers we've ever had at Head-Fi are computer engineers, not EE's.  Another is a mechanical type like me (not saying I design, but I do build).  Still another has no technical degree at all (he's a PhD, though) - and he is among the best.  There's nothing that says any one of you can't read and learn and eventually become as much of an authority on such matters as anyone else.   

I can corroborate on this for sure.  I have a degree in EE and passed Ph.D. qualifying exams in EE, and I have no idea about most technical concepts regarding audio.  Many dedicated hobbyists without a related degree know much much more.  It's possible I learned more relevant information from music classes and lessons, than from anything to do with engineering.
 
Pretty much anybody can learn something with enough time and interest.  A degree just gives you some background analytical tools, small experience and intuition, and hopefully training on how to think--all these are things you can pick up on your own.  You're probably not going to get specialized knowledge on a fringe application unless you study it yourself.
 
 
On a side note, I'd question "Power supplies are everything when it comes to the quality of an amp's output."  That depends on the design of the amp of course, and how good of a power supply we're talking about, but in regards to designs using chips with high PSRR, I think people are probably overstating the importance or going overkill for the power supply design.  That's just a guess by me though.  With regards to the power supplies not being mentioned on most data sheets, I would assume that the specs in the data sheet are given for relatively favorable conditions like a sufficiently good power supply, not too much EMI, etc...however, "sufficiently good" for the power supply may be pretty ordinary.

 

[Anaxilus]

Quote:
 
I was just about to quit this thread till I read your well reasoned, insightful and logical post.  I may just still till I get my O2 in hand and give it a listen.  You're on follow sir.  

 

[DRUB]

Quote:

1. Many of you are complaining about cheapskateaudio's failure to show any pics of his work.  Seems to me that khaos974 just posted them in plain sight for everyone to see.  Other than a lack of wicking to the top side of the PCB solder joints (it's obvious plated holes exist on the PCB), nothing seems untoward from this perspective.

I think the real issue is that there's a proper methodology by which you go about making claims regarding frequency response and various other solid measurements in an amplifier or a DAC. His assertion that the FR of the stock O2 design is all over the place under 50hz is provably, categorically incorrect and his disgusting attitude toward others on this forum is also far from laudable. 
 
Aside from that, largely agree with your post. I do however think Voldemort is one of those engineers who *does* in fact know a hell of a lot about audio.

 

[deadlylover]

Quote:

 
Aside from that, largely agree with your post. I do however think Voldemort is one of those engineers who *does* in fact know a hell of a lot about audio.

Nahh, it's mostly due to his possession of the Elder Wand. (dscope

)
 
Those things don't grow on trees, and if those bad boys were more accessible(cheap), I can't help but feel that the entire objective side of audio would make a nice leap forward.