The ENOBs depends on the bandwidth. So by filtering (read averaging, adding samples together) hard enough a fast enough ADC potentially can deliver that level of noise performance, just its only going to be useful in a digital multimeter, nothing that varies too fast. For an example, see this ADI device:
http://www.analog.com/static/imported-files/data_sheets/AD7191.pdf
Page 13 shows it just reaches 24 effective bits (although there's still some noise) at a sample rate of 10Hz. Not too shabby for a $4 chip
Yeah, I was (hopefully obviously) talking about audio use out to at least 20 Khz. High-End DMMs, like my Agilent 34410A, have user configurable filtering for the ADC that trades off resolution for speed. But you can't listen to music on your DMM or scope. Let's try to return to our regularly scheduled programming and get this back on topic here.
I've NEVER said don't build this amp. Never, ever, not once.
I've said modify it.
Nobody is saying this amp is a bad value. It's a good value, not quite a giant killer in my view, but a solid value, and a fun and easy project. (The not fun part is dealing with Willakan,
)All that being said, why not spend 10 cents more and get a little insurance for the v-regs? Nowhere in the datasheets does it state that you will gain a performance benefit by leaving them out, and every single example circuit in the PDF's has the input bypass cap in it. AND there are other brands of 7912/7812 that do require the input bypass. So in the interest of practicality it makes sense to include the input cap just to broaden the range of possibilities.
@cheapskateaudio, From the datasheet: "Cin is required if regulator is located an appreciable distance from power supply filter."
The O2 regulators are right on top of the power supply filter caps so no extra cap is required. And the circuit has been tested for stability, and noise rejection, with three different brands of regulators. And at least several hundred O2 users are not having any problems whatsoever. And thousands of bulletproof commercial products use the LM78XX and LM79XX in the O2's configuration without a special high frequency cap on the input. You're literally trying to invent problems where they don't exist.
It's clear to those who have commented on your posts here, and elsewhere, you clearly messed up your amp with a bad build and/or your mods, and now you're trying to irrationally, and erroneously, blame your mistakes on the design--despite the fact nobody else has reported the collection of problems you have. You have refused to post current pics of your amp and you have refused to address the technical errors in your posts and measurements.
As others have suggested, I would strongly suggest you give your pointless tirade up. As more and more people build O2s and report similar happy results to the great many who already have, your views are going to look increasingly like you're just making this stuff up. If you want to believe the earth is flat, that's your choice, but stop trying to tell everyone else it is without providing all the evidence.
As for adding parts that serve no useful purpose whatsoever, there's not much extra room to do so, and there are plenty of other designs full of excess parts. Perhaps you'd be happier with one of those? The whole point of the O2 was a minimalist amp centered around maximum performance. Extra parts that have no benefit just degrade the design.
The O2 regulators are right on top of the power supply filter caps so no extra cap is required. And the circuit has been tested for stability, and noise rejection, with three different brands of regulators. And at least several hundred O2 users are not having any problems whatsoever. And thousands of bulletproof commercial products use the LM78XX and LM79XX in the O2's configuration without a special high frequency cap on the input. You're literally trying to invent problems where they don't exist.
It's clear to those who have commented on your posts here, and elsewhere, you clearly messed up your amp with a bad build and/or your mods, and now you're trying to irrationally, and erroneously, blame your mistakes on the design--despite the fact nobody else has reported the collection of problems you have. You have refused to post current pics of your amp and you have refused to address the technical errors in your posts and measurements.
As others have suggested, I would strongly suggest you give your pointless tirade up. As more and more people build O2s and report similar happy results to the great many who already have, your views are going to look increasingly like you're just making this stuff up. If you want to believe the earth is flat, that's your choice, but stop trying to tell everyone else it is without providing all the evidence.
As for adding parts that serve no useful purpose whatsoever, there's not much extra room to do so, and there are plenty of other designs full of excess parts. Perhaps you'd be happier with one of those? The whole point of the O2 was a minimalist amp centered around maximum performance. Extra parts that have no benefit just degrade the design.
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Oh, he's a uDAC owner! That explains a lot (for those not aware I found some significant problems with the uDAC-2 a long time ago which didn't go over very well with many of the NuForce Faithful). Anyway... hopefully we can all get back to more constructive topics here. Let's not let one person try to turn diyAudio into H-F.
See:
Important Details
And:
Circuit Board Construction
And the latest PDF and XLS files at:
O2 Resources
I've been updating the above 3 sections regularly as issues come up.
I am not a big uDac/nuforce fan, I just found it to be reasonable given the cost and features. From a purely subjective standpoint I like how it sounds with certain types of music. Even the O2 with absolutely bottom barrel parts is more than either uDac 1 or 2 and obviously doesn't include a DAC.
I found your uDac rant kind of weird RS because in another article you claimed that the uDac's sound was second only to the Benchmark dac in a blind test... Kind of makes your resulting tear down of the uDac look redundant. I mean, is the point to satisfy the measurements or to be second in subjective performance only to the Benchmark DAC?
Alexium, the only "bug" I'm aware of is that with the September BOM resistor values, the power management might not latch into shutdown mode and will toggle off and on. I suppose a person could as easily say this is a problem with the batteries, not the amp. The newer BOM adjusts the values in an attempt to overcome the issue. Using either set of values, it will be time to recharge the batteries.
@ CSA: 50€'s say you are making stuff up!
I just recently assembled my first own O2 after sending out all the kits for people in the GB.
It was built using a cheap, unregulated soldering station built BEFORE the last war (and I live in Germany, we don't have many wars around here) by someone (me) with mediocre (at best) soldering skills.
I have successfully used it to drive a Medusa headset (more power hungry than HD650), a few HDXXX series headphones, my Shure SE530 cIEM's and a few others, all without problems.
But I am prepared to put my money where my mouth is.
I am offering you 50€ (which is more than the parts cost) for your bad sounding O2.
And when I get it, I will put it up and measure it against a few of my own O2s I will have built by then.
And I will publish the results here and on Head-Fi ( -.- ) to show what was really wrong with your O2.
Your turn!
Do you fold and give up?
I just recently assembled my first own O2 after sending out all the kits for people in the GB.
It was built using a cheap, unregulated soldering station built BEFORE the last war (and I live in Germany, we don't have many wars around here) by someone (me) with mediocre (at best) soldering skills.
I have successfully used it to drive a Medusa headset (more power hungry than HD650), a few HDXXX series headphones, my Shure SE530 cIEM's and a few others, all without problems.
But I am prepared to put my money where my mouth is.
I am offering you 50€ (which is more than the parts cost) for your bad sounding O2.
And when I get it, I will put it up and measure it against a few of my own O2s I will have built by then.
And I will publish the results here and on Head-Fi ( -.- ) to show what was really wrong with your O2.
Your turn!
Do you fold and give up?
How can both statements be true? Clearly you lack the ability to understand subtle phrasing of meaning. "Required" != "recommended".
he changes his story, changes his thoughts, changes his words; all in an effort to gain a reactionMoving on from cheapskate (I think bothering with what he has addressed to me, what he has addressed to NwAvGuy and what he has said regarding the amplifier design is no longer worth anyone's time) I have enjoyed listening to my O2, which incorporates RCA jacks and a PCB-mount headphone jack (secured below with the finest audio-grade glue after I realised it wasn't going to go in any other way) into the front panel.
The only thing I would draw from this build is that you shouldn't make the same mistake I did and not do the maths for the gain settings you want! I simply assumed that 3X gain would be appropriate for the K702s and now have an amp which requires very careful volume knob usage! Channel balance seems fine though, so I'm not overly fussed.
An externally hosted image should be here but it was not working when we last tested it.
The only thing I would draw from this build is that you shouldn't make the same mistake I did and not do the maths for the gain settings you want! I simply assumed that 3X gain would be appropriate for the K702s and now have an amp which requires very careful volume knob usage! Channel balance seems fine though, so I'm not overly fussed.
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