If you don't have the op amps installed, it's pretty hard to kill the circuit. And a typical anti-static mat shouldn't short that much current. I wouldn't completely rule it out.
You've checked for bridges, so now check that the capacitors C2 to C5, diodes D3 & D4, and regulators are installed and oriented correctly. If they are, measure the AC output of the transformer, the DC input to the regulators, and the DC output of the regulators. If the caps bulge kill the power immediately.
You've checked for bridges, so now check that the capacitors C2 to C5, diodes D3 & D4, and regulators are installed and oriented correctly. If they are, measure the AC output of the transformer, the DC input to the regulators, and the DC output of the regulators. If the caps bulge kill the power immediately.
I´m by far be the most qualified O2 builder around here but I will give you some things to consider.
Did you test the AC wall transformer output? I assume yes since you problem began on the next step.
Do NOT use an electrostatic bag as "base" yes, as you already figured out is could cause a short. I work on a wooden surface or mouse pad (neoprene I guess)
Did you matched the corresponding polarities of the electrolytic Caps with the ones of the board? Remember the have a + and - side.
Same as above for the diodes around.
Last but not least...solder bridges.
My suggestion would be to do the above visual checks and replace the "almost popped" caps and start over with test form step one.
HTH
Thanks for the help, guys. It seems it was the capacitors after all. I could have sworn I had correctly followed RS's instructions. Unfortunately I interpreted this :
"Note the electrolytic capacitors “face” different directions. The large strip is negative and should match up with the mark on the circle on the board. The large caps have the negative stripe on the right and the small caps (C8, C9) on the left."
...as meaning the length of the longer wire coming out of the bottom of the capacitors; since they consistently have one wire longer. I should have read that sentence more carefully; though it was 4 o'clock in the morning. I've assumed all the electrolytics are dead and replaced them and marvellously my newbie (ie. no prior experience of soldering and near zero knowledge of electronics) O2 passes all the tests and works and is now driving my current-hungry T50rp Orthodynamics to satisfactory volume levels. I'm jolly glad I didn't decide on the confidence I had in my build and simply plug in the opamps and go for it without testing first; I was tempted.
Reading people's comments I had expected to need to drive my T50rp's on the lower gain setting. However it seems that that may be true of ipods but the Sansa clip has so little voltage in the first place that I can actually wear the headphones with the o2 set to maximum gain and max volume on both O2 and clip; though it is too loud. Certainly, I have to use the 6.5x gain setting to get satisfactory volume. That was a surprise. I should add that I have no (known) hearing problems.
Right now I'm at a friends place but I can't wait to get home to stroke my new baby.
Thanks again to all those who help us (probably quite irritating) clueless newbies.
As for replacing the dead capacitors (in order to complete two more builds), does anyone have any suggestions? For example, must I return to Mouser to get the right quality or specs, or is there somewhere cheaper that will do just fine (I'm in the UK)? I've noted RS's warning about substandard rejects being sold on on ebay, and my experience is that Amazon is often a dumping ground also. In the meantime Mouser and Farnell's postage is a bit on the high side for just 4 small capacitors.
"Note the electrolytic capacitors “face” different directions. The large strip is negative and should match up with the mark on the circle on the board. The large caps have the negative stripe on the right and the small caps (C8, C9) on the left."
...as meaning the length of the longer wire coming out of the bottom of the capacitors; since they consistently have one wire longer. I should have read that sentence more carefully; though it was 4 o'clock in the morning. I've assumed all the electrolytics are dead and replaced them and marvellously my newbie (ie. no prior experience of soldering and near zero knowledge of electronics) O2 passes all the tests and works and is now driving my current-hungry T50rp Orthodynamics to satisfactory volume levels. I'm jolly glad I didn't decide on the confidence I had in my build and simply plug in the opamps and go for it without testing first; I was tempted.
Reading people's comments I had expected to need to drive my T50rp's on the lower gain setting. However it seems that that may be true of ipods but the Sansa clip has so little voltage in the first place that I can actually wear the headphones with the o2 set to maximum gain and max volume on both O2 and clip; though it is too loud. Certainly, I have to use the 6.5x gain setting to get satisfactory volume. That was a surprise. I should add that I have no (known) hearing problems.
Right now I'm at a friends place but I can't wait to get home to stroke my new baby.
Thanks again to all those who help us (probably quite irritating) clueless newbies.
As for replacing the dead capacitors (in order to complete two more builds), does anyone have any suggestions? For example, must I return to Mouser to get the right quality or specs, or is there somewhere cheaper that will do just fine (I'm in the UK)? I've noted RS's warning about substandard rejects being sold on on ebay, and my experience is that Amazon is often a dumping ground also. In the meantime Mouser and Farnell's postage is a bit on the high side for just 4 small capacitors.
Glad to hear of your success. Testing is virtually mandatory. We all make mistakes; newbies just make more than others.
I have no suggestions for where to get the components you need since I'm too far away. Because of the layout, you'll want to find caps that have the same lead spacing and the same or smaller dimensions. A higher value and voltage rating is OK.
I have no suggestions for where to get the components you need since I'm too far away. Because of the layout, you'll want to find caps that have the same lead spacing and the same or smaller dimensions. A higher value and voltage rating is OK.CE Marking
There's a regulation that all electronic apparatus sold in the European Union has to pass compliance testing to ensure that it meets all EU standards and be CE marked. I became aware of this when the much-publicised Raspberry Pi microcomputer suffered yet another distribution delay after the suppliers discovered that it would have to be CE certified, despite being an uncased device aimed at the hobbyist and education markets.
I have a suspicion that this legislation may apply to anyone selling batches of completed O2 units, and also to the upcoming ODAC, as it's a complete board, not a kit.
There's a regulation that all electronic apparatus sold in the European Union has to pass compliance testing to ensure that it meets all EU standards and be CE marked. I became aware of this when the much-publicised Raspberry Pi microcomputer suffered yet another distribution delay after the suppliers discovered that it would have to be CE certified, despite being an uncased device aimed at the hobbyist and education markets.
I have a suspicion that this legislation may apply to anyone selling batches of completed O2 units, and also to the upcoming ODAC, as it's a complete board, not a kit.
Hi greenalien,
interesting thought, and worth to look up. I had a look at the EU directives and the only one that would apply to O2 and ODAC is DIRECTIVE 2006/95/EC - relating to electrical equipment designed for use within certain voltage limits. This directive states in article one:
"Article 1
For the purposes of this Directive, ‘electrical equipment’ means
any equipment designed for use with a voltage rating of between
50 and 1 000 V for alternating current and between 75 and
1 500 V for direct current, other than the equipment and
phenomena listed in Annex II."
where Annex II reads:
"ANNEX II
Equipment and Phenomena outside the Scope of this Directive
Electrical equipment for use in an explosive atmosphere
Electrical equipment for radiology and medical purposes
Electrical parts for goods and passenger lifts
Electricity meters
Plugs and socket outlets for domestic use
Electric fence controllers
Radio-electrical interference"
none of above applies for O2 or ODAC, so I assume they would not need the CE Conformity Marking nor the EC Declaration of Conformity. The only part this would apply to is the power supply for the O2, and the once I sell are certified
I will double check the same with the producer of the ODAC though...
Stefan
I may be wrong (and I have been before) but I believe that since the power supply plugs into your completed unit, the entire assembly must be CE qualified. For example, if you look on you laptop you will see that there is a whole string of certifications including CE that are on the label.
Look at it another way... HP/Dell would sell there laptops without power adapters if they thought they could get away with not having to have compliance standards. It's cheaper.
This is not just about safety but also EMC compliance. There are hobbyist exemptions but I believe that a fully assembled unit does not fall into that category. So I believe that it must also be EMC compliant.
Anyway... That is just my $US0.02 worth the advice.
Tony
Look at it another way... HP/Dell would sell there laptops without power adapters if they thought they could get away with not having to have compliance standards. It's cheaper.
This is not just about safety but also EMC compliance. There are hobbyist exemptions but I believe that a fully assembled unit does not fall into that category. So I believe that it must also be EMC compliant.
Anyway... That is just my $US0.02 worth the advice.
Tony
I'm a bit rusty on CE marking but I believe the O2 would be exempt from EMC emissions because it has no clock oscillator(s) on board. The route with it would be to self-certify. The ODAC's another matter entirely because its a digital product so almost certainly would be subject to emissions regs if sold as a completed board.
Just as an update I tried the AD712 and even though its a higher end IC it does not sound better than the original one. I assume that is because the circuit is tuned up (brilliantly) for that specific IC. In other words if someone (not me) dares to change it will have to go through the process of revising the rest to squeeze all the juice out of a different chip.
Hats off for RS for the overall design and and clear tests done to develop this baby.
Hats off for RS for the overall design and and clear tests done to develop this baby.
As soon as you hook up an AC power supply, there's the potential for creating EMC emissions right there - think of it as a 50 or 60 Hz oscillator. No telling what frequencies of harmonics may be created in the circuit. This does imply that CE certification may be needed.
I agree, don't see any way around this.
I find the O2 itself more objective than the review. Which is quite alright.
If I were to give advice to the reviewers, I would say don't write things like, "...its transparancy [sic]. There is no coloration what so ever, it is very neutral sounding..." and follow that with, "...the bass... is missing some punch and impact. But the bass isn’t the only thing bothering me actually, there also is something bothering me with the mids . They sound a bit thin."
Or
"A good feedback from a pair of good ears to further improve the design and the tuning would definitely help." Whose ears?? And of course this implies that either a) the designer hasn't good ears, or b) he didn't listen to his own amp.
If I were to give advice to the reviewers, I would say don't write things like, "...its transparancy [sic]. There is no coloration what so ever, it is very neutral sounding..." and follow that with, "...the bass... is missing some punch and impact. But the bass isn’t the only thing bothering me actually, there also is something bothering me with the mids . They sound a bit thin."
Or
"A good feedback from a pair of good ears to further improve the design and the tuning would definitely help." Whose ears?? And of course this implies that either a) the designer hasn't good ears, or b) he didn't listen to his own amp.
Agree with your earlier points - the review in parts sounds self-contradictory. But yeah its most probable that a) is true - anyone who hears clear differences between components is hardly likely to be an 'objectivist' are they?
But 'hasn't good ears' is rather too simplistic - its more about paying attention to the right things, which isn't so much about ears, more about attitude.
