Does turning the O2 volume control have any effect?
Check that C8 and C9 are in the right way. The (-) side should go towards the input jack.
No, the volume control doesn't have any effect on that. It's all very weird, really. I don't think I've got the caps reversed or I'd have smoked them a long time ago
Anyway, even if I did, how would that couple the signal to the output all of a sudden?
I intend to give full credit for the AMP, i would have only put it together, the thing is if I aim for a high end market for the cases I would expect people will also want me to match the internals to the case. In other words , the best case I can build coupled to the best amp I can afford / can buy.
No, the volume control doesn't have any effect on that. It's all very weird, really. I don't think I've got the caps reversed or I'd have smoked them a long time ago
For the input signal to make it through to the output without power, given the common ground, it would pretty much have to either punch through the signal path, or out to the power supply rails via the internal circuitry of the op amp(s).
No change from the volume control should rule out the signal path. The power supply bypass capacitors C8 and C9 should also do an effective job at bypassing any signal current on the supply rails, leaving just whatever voltage results from signal current x capacitor series resistance.
Well that is an interesting one! I don't have any ideas.
And it's not like we intend to rip anybody off.
(I can really only speak for myself, but you get the point.)
If someone offers a service and performs according to the agreement, then this is not ethically questionable.
My hourly wage at work is FAR higher than what I make from the GB.
And I put nearly all of it back in, buying components before they are ordered (like the 500 PCBs).
And this holds true for most people in this community.
When Mr Slim offered the build-service, there were lots of people very happy to have him assemble their O2s.
He charged something for the services rendered, but again, it was a very reasonable amount.
For someone who doesn't own a soldering iron, his service was likely cheaper than a semi-decent iron.
So some people saved money using his service, just like 'my' buyers save money.
And as long as we propagate a good and productive spirit throughout this community, we provide it with a very strong incentive for others to join.
I know of several people that joined DIYaudio specifically for my GB and then stayed and participated in a variety of other discussions.
This is a good thing. At least in my book. And I have absolutely no problem with anybody that begs to differ.
I am paraphrasing: We are free citizens. We can do what and when we please. And we don't even have to do THAT!
Best regards,
Jokener
P.S.: I had lengthy conversations with RocketScientis on many topics.
He explicitly told me that he would be pleased to see me make a 'nice little profit' from my GB's.
And even though this was about my GB, his attitude towards any good-spirited person offering a service for and around the O2 will most certainly be identical.
P.P.S.: I would also very much like to see a 'donation box' for RS.
That way anybody could buy him a pint for his great work and spirit.
Wait, scrap that. With that amount of beer, he would end up an alcoholic.
(I can really only speak for myself, but you get the point.)
If someone offers a service and performs according to the agreement, then this is not ethically questionable.
My hourly wage at work is FAR higher than what I make from the GB.
And I put nearly all of it back in, buying components before they are ordered (like the 500 PCBs).
And this holds true for most people in this community.
When Mr Slim offered the build-service, there were lots of people very happy to have him assemble their O2s.
He charged something for the services rendered, but again, it was a very reasonable amount.
For someone who doesn't own a soldering iron, his service was likely cheaper than a semi-decent iron.
So some people saved money using his service, just like 'my' buyers save money.
And as long as we propagate a good and productive spirit throughout this community, we provide it with a very strong incentive for others to join.
I know of several people that joined DIYaudio specifically for my GB and then stayed and participated in a variety of other discussions.
This is a good thing. At least in my book. And I have absolutely no problem with anybody that begs to differ.
I am paraphrasing: We are free citizens. We can do what and when we please. And we don't even have to do THAT!
Best regards,
Jokener
P.S.: I had lengthy conversations with RocketScientis on many topics.
He explicitly told me that he would be pleased to see me make a 'nice little profit' from my GB's.
And even though this was about my GB, his attitude towards any good-spirited person offering a service for and around the O2 will most certainly be identical.
P.P.S.: I would also very much like to see a 'donation box' for RS.
That way anybody could buy him a pint for his great work and spirit.
Wait, scrap that. With that amount of beer, he would end up an alcoholic.
RS clearly made a deliberate decision when he chose the Creative Commons License. That means he specifically released the amp "into the wild" with a few clearly stated caveats (for example attribution, and don't distribute a derived work while calling it an O2). There is nothing immoral nor illegal about selling O2's in any state from bare PCB to complete product, as long as the conditions of the License are adhered to (including informing down-stream users of their rights and responsibilities).
Read the License, understand what it says, and you will have no problems.
Read the License, understand what it says, and you will have no problems.
You guys are right about this, I just hope the cases are the focal point as we all know that soon there will be O2 clones from china , doubt someone is going to hold a sustainable business soldering O2's. I heard they have a smaller version PCB with two 18650 Li-ion batteries 2500mah each (so 9V for much longer time) dc adapter, no AC and a desktop version with higher rails dip heatsinking and one of Ti's 32 bit DAC's. There is always seems to be a market for quality custom cases, the market for headamps especial low parts cost ones like is so competative, keep it fun , I don't mix business with pleasure. And each day the O2 becomes more pleasureable , hate to say it but until real headphone output transformers are available tubes are losing interest for me thanks to the O2. I never realized what I was missing below 30 hz, the distortion and level below 40hz from the O2 is really going to be tough to even come close to with tubes. The O2 is like a splash of cold water in the face in a way, but listening to electric bass and drums with this clarity is quite amazing.
Still strange volume control
I am hoping to pin down the problems before I order components (I would be fun to have $5 shipping for one .16 piece).
Resistance checks all seem proper.
Voltage checks are another matter.
pin 4 and pin 8 of U4 do not drop below 1v with one battery removed. Does this surely indicate broken a MOSFET (q1 or q2).
U2 AC only
p1=11.6 , p2=11.5, p3=-10, p4= -11.4, p5=-9.9, p6=-11.7, p7=11.5, p8=11.75
U2 AC w/ battery
Same as AC only
U2 battery only
p1=8.6, p2=8.4, p3=-6.8, p4=-8.6, p5=-6.8, p6=-8.6, p7=8.4, p8=8.6
(I am pretty sure I measured these values with u1, u3, u4 removed, u2 installed power on). Are the above U2 readings correct? If not, what do they indicate is damaged or improper?
Still having weird volume control (full volume, no control, on one channel and proper volume control on the other). I will try removing the pot and resoldering. Would this be due to damaged U2, Q2, Q1, U4, U3, or U1? Or is it almost certainly a solder bridge or some other non-component short?
Are there any empty holes that must be soldered (under C9 or otherwise?)
Thanks for the help and fun project.
I am hoping to pin down the problems before I order components (I would be fun to have $5 shipping for one .16 piece).
Resistance checks all seem proper.
Voltage checks are another matter.
pin 4 and pin 8 of U4 do not drop below 1v with one battery removed. Does this surely indicate broken a MOSFET (q1 or q2).
U2 AC only
p1=11.6 , p2=11.5, p3=-10, p4= -11.4, p5=-9.9, p6=-11.7, p7=11.5, p8=11.75
U2 AC w/ battery
Same as AC only
U2 battery only
p1=8.6, p2=8.4, p3=-6.8, p4=-8.6, p5=-6.8, p6=-8.6, p7=8.4, p8=8.6
(I am pretty sure I measured these values with u1, u3, u4 removed, u2 installed power on). Are the above U2 readings correct? If not, what do they indicate is damaged or improper?
Still having weird volume control (full volume, no control, on one channel and proper volume control on the other). I will try removing the pot and resoldering. Would this be due to damaged U2, Q2, Q1, U4, U3, or U1? Or is it almost certainly a solder bridge or some other non-component short?
Are there any empty holes that must be soldered (under C9 or otherwise?)
Thanks for the help and fun project.
That would not be caused by power supply issues (U2 etc). That indicates a solder bridge between wiper and input side of the pot on one channel. You should be able to track that down pretty quickly with resistance measurements. One channel will show varying resistance between the wiper (center pin) and both outside pins as the shaft turns. The other side will show constant near-zero resistance to one of the side pins (on the right facing the pot from the front, full clockwise position). I hope the bridge is on the bottom of the board so you don't have to remove the pot.
Good work on making the voltage measurements.
Pull U2 out also, so that ALL the chips are out, and with your headphones unplugged for all of these tests, power it up again on AC and repeat those U2 DC voltage measurements. Since U2 is out it will be easy - just measure right from the socket pins on the top of the U2 IC socket to ground (metal shell of the gain switch).Your voltage readings on P4 and P8 say that your power supply is working OK. Those are fairly good values for the positive and negative power supply rails (a little low, but that should work itself out when the real problem is found). Same with your P4 and P8 readings on battery.
But P2... not so much. That is way off. Please double check that you are measuring a positive +11.5Vdc on P2 with respect to ground, and not a negative value (-11.5Vdc). In your previous post you listed the U2 measurement as -11.8Vdc. With U2 out you should measure somewhere around -8.7Vdc or so to ground on P2. If you still get +11.5Vdc (or -11.5Vdc), that is one of your problems. If you get that check that R5, R9 and R25 are the right values. Try reheating their solder connections even if they look OK and take a resistance reading (with the O2 AC power unplugged now) from P2 of the U2 socket to ground. Also take a look with a magnifying glass to make sure P1 and P2 are not solder bridged to each other.
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I built my second o2 and having problems getting the power to the opamps. All the measurements checks up until q1 and q2. Also I have a short on pin 4 and pin 7 of U2 - drain and source of q2. I've replaced the mosfets but the problem is still there.
Any ideas where to check first? I'll re check the resistances again and see if I can find something unusual.
Any ideas where to check first? I'll re check the resistances again and see if I can find something unusual.
Remove U2 from the socket, and with the batteries out and the AC unplugged, measure the resistance between pins 4 to 7 of the U2 socket again and see if you get close to zero ohms (shorted).
If you were measuring voltages, in circuit, rather than resistances then pins 4 and 7 will look like a short when that part of U2 is "on". There is a pulldown transistor in there between those pins. If you were measuring resistances (with U2 installed) when you found the 4-7 short, and you had the batteries out and the AC unplugged, and that short goes away when you measure again with U2 out, then your U2 chip is bad.
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I was using the continuity buzzer. just checked it with resistance and without the u2 installed. I get 0 ohms..
Since you have already replaced Q2 that just leaves C21. Try unsoldering it and see if the short goes away. That would be fairly rare for the cap to be shorted, but it does happen.
Luckily the traces from pin 7 of U2 don't go very many places. With the battery part of the board at the bottom, one trace on the bottom of the PCB from pin 7 goes to the bottom of R25, to the left of the U2 socket. Measure across R25. That one is a huge 1.5 megohm resistor. As long as you read something large like that it is OK and that one isn't the short.
Next the other trace from pin 7 on the PCB bottom goes out the right side of the socket to C21 and R8. Same thing with R8 - that one is a 270K and should measure something up there across it rather than short. If that one is also OK that just leaves the mosfet (again) or a solder bridge to one of those two traces on the bottom of the PCB.
If neither R25 or R8 read a short, then just brute force it.
There are only those 4 things on that trace hooked to U2 pin 7. You already have C21 out. Unsolder the bottom of R25 and the bottom leg of R8. Then you are down to just the mosfet or a solder bridge if 4 and 7 still read shorted.One more thing to double check is that the mosfet is turned the right way, with the metal back toward the top of the board.
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