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Old 28th November 2011, 12:02 AM   #901
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So I built my first O2 amp last thursday, and all the checks came up positive and it started up with no issues.

But today I built my second O2 and it failed the first check. Using a Wallwart that supplies 13.5vAC, I measured from the + terminal of BT1 and the – terminal of BT2 and got 13.5v. I've gone over the back and corrected any sketchy-looking solder joints with little success.

Now, from about 30 minutes of part checking, and I'll look back into it tomorrow, all the parts are in the correct positions and orientations. Is there a way I can test for ESD damage/heat damage on the mofsets and on U5/U6, because I had some issues soldering them in and applied more heat than I would've liked, and ESD is always a possibility.

Thanks for your time, I'm really happy with how my working O2 turned out :P
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Old 28th November 2011, 12:11 AM   #902
Jokener is offline Jokener  Germany
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And in case anybody still needs parts: The new and improved GB thread is up and running.
It is almost the same as before, just better.

Order batches are limited to 40 kits, after that I will order.
(The idea is to make it continuous, so after the first batch, I will still accept orders for the second batch.)
I will always order some parts with my own money, so I can ship even faster.
The transformers will be available again, manufactured specifically for us.
The cases will also be up for sale, all colors and both heights are good to go.
NEW PCB's will be made, so there will be no more shortage of these (I got tons of mail asking for them).
The "Extras" are back, so people can still order solder/wick/goodness from Mouser & Farnell.
Shipping to all destinations worldwide (customs may apply for non-EU residents).

I upgraded my order processing for this by buying a database software for my computer and my iPad and my iPhone.
-> Less hassle for me and quicker updates for you through the PDF.

Only one limitation: Payments are only accepted via PayPal.
Sorry to the guys that would prefer a wire transfer, but it is fairly time-consuming.
Setting up a PayPal account is not too much work, alternatively, you can always ask friends/family to help you send the funds.

Thanks for everybody that participated in the first round.
May the second round be just as successful in helping this community build excellent equipment!

Best regards,
Jokener
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Old 28th November 2011, 01:19 AM   #903
agdr is offline agdr  United States
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Quote:
Originally Posted by BobSaysHi View Post
So I built my first O2 amp last thursday, and all the checks came up positive and it started up with no issues.

But today I built my second O2 and it failed the first check. Using a Wallwart that supplies 13.5vAC, I measured from the + terminal of BT1 and the terminal of BT2 and got 13.5v. I've gone over the back and corrected any sketchy-looking solder joints with little success.

Now, from about 30 minutes of part checking, and I'll look back into it tomorrow, all the parts are in the correct positions and orientations. Is there a way I can test for ESD damage/heat damage on the mofsets and on U5/U6, because I had some issues soldering them in and applied more heat than I would've liked, and ESD is always a possibility.

Thanks for your time, I'm really happy with how my working O2 turned out :P
Check again that the diodes D1 - D6 match up with the silkscreens on the PC board, so that the cathode is in the right way. And double check that the regulators are in the right place (7912 negative closest to the edge of the board), turned the right way, and the capacitors C2 - C5 are in the right way.

Then make sure the batteries are not installed and the power switch is off ("out" position). With the power switch "off" the mosfets don't matter - they are downstream from the power switch. Did you make that 13.5Vdc measurement with the batteries installed by chance? If so then 13.5Vdc is just an indication the batteries are out of juice and are charging. Measuring between BT1 and BT2 is *after* the charging resistors so you will get a voltage drop if the batteries are charging a lot.

What DC voltage do you measure between ground (the metal shell of the gain switch) and the BT1 "+" terminal? How about between ground and the BT2 "-" terminal? (batteries not installed of course)
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Old 28th November 2011, 01:42 AM   #904
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Check again that the diodes D1 - D6 match up with the silkscreens on the PC board, so that the cathode is in the right way. And double check that the regulators are in the right place (7912 negative closest to the edge of the board), turned the right way, and the capacitors C2 - C5 are in the right way.

They are in their correct positions.

Then make sure the batteries are not installed and the power switch is off ("out" position). With the power switch "off" the mosfets don't matter - they are downstream from the power switch. Did you make that 13.5Vdc measurement with the batteries installed by chance? If so then 13.5Vdc is just an indication the batteries are out of juice and are charging. Measuring between BT1 and BT2 is *after* the charging resistors so you will get a voltage drop if the batteries are charging a lot.

No batteries installed.

What DC voltage do you measure between ground (the metal shell of the gain switch) and the BT1 "+" terminal?

5.1 mV

How about between ground and the BT2 "-" terminal? (batteries not installed of course)
11 Volts


I think that narrows it down, huh.
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Old 28th November 2011, 01:59 AM   #905
agdr is offline agdr  United States
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Quote:
Originally Posted by BobSaysHi View Post
What DC voltage do you measure between ground (the metal shell of the gain switch) and the BT1 "+" terminal?

5.1 mV

How about between ground and the BT2 "-" terminal? (batteries not installed of course)
11 Volts


I think that narrows it down, huh.
Yep. Try replacing that positive 7812 regulator. It would also be worth removing one end of D3 and checking it with the DMM diode check function.

Also - a tip on getting the voltage regulator out. With the board upside down put a piece of solder braid across all three regulator terminals, then lay the soldering iron tip flat on the braid. It spreads the heat to all 3 pins at once and the thing just falls right out of the holes with gravity. I had to remove a couple of the regulator chips.

Last edited by agdr; 28th November 2011 at 02:07 AM.
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Old 28th November 2011, 02:35 AM   #906
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Yeah, I had probably applied too much heat to the 7812 regulator. I accidentally bridged the solder joints on the bottom and couldn't get it out without a lot of heat.

I don't have another one on hand, so I'll have to order it.
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Old 28th November 2011, 03:58 AM   #907
agdr is offline agdr  United States
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Quote:
Originally Posted by BobSaysHi View Post
Yeah, I had probably applied too much heat to the 7812 regulator. I accidentally bridged the solder joints on the bottom and couldn't get it out without a lot of heat.

I don't have another one on hand, so I'll have to order it.
I found a neat trick for soldering those larger pads on the mosfets and regulators without bridging. I apply solder to just one side of the lead and pad, esssentially soldering just the half-oval. Then I solder the other side of the same lead and the other half of the oval. About the time the solder starts to flow on that second half it also flows around the edges of the lead, mates with and re-flows the solder on the first side in about 1/2 second, then I stay on an additional 1/2 second to make sure all the solder on both sides is re-flowed. Then the whole thing cools together.

For some reason the solder seems to be able to make it around the edges of the lead enough to mate up with solder already on the other side, but not enough can get around the edges in the first place, just soldering one side, to get the other side soldered without it "jumping" to an adjacent pad some of the time. I'm using fairly fine 0.022" solder and a small 1/64" conical tip, too.

I bridged two mosfet leads on my first build until I figured this method out. Then no more bridges on 3 additional boards! I found that tapping the edge of the board lightly on a table right after heating was helpful in clearing the bridges. Would definitely be worth testing those two input rectifiers too, D3 and D5.

Also - given that the regulators are cheap compared to shipping I would really recommend getting another negative 7912 to have on hand, too. That negative reading should be closer to -12.0Vdc rather than -11.0Vdc. I was initially thinking the positive regulator would drag the secondary down if shorted and hence the slightly lower negative rail, but it can't do that since both are fed from different half cycles. Would definitely be worth checking those two input rectifiers too, D3 and D4. Once you have the 7812 out you could measure the negative rail again, with the power switch off, and it should be within +/- 0.1Vdc of -12.0Vdc.

Last edited by agdr; 28th November 2011 at 04:21 AM.
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Old 28th November 2011, 09:04 AM   #908
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@timjthomas

Getting good sound out of a PC does have a few problems, not least because internally, a PC is a very electronically noisy environment. For this reason, an external sound card that does all the analogue processing outside of the main PC case is recommended - this is the solution adopted by professional recording studios.

I use an Echo Layla, and it sounds as good as anyone could want - probably overkill for most home users, but I got mine, second hand, for a very reasonable price, and it certainly does the job very well - in fact, it was the search for a comparable headphone amp that would give me a similar level and quality of sound - but in a portable version - that initially drew me to the O2 project.

If you are after something simpler and cheaper, and have a sound card with SPDIF output, there's always Browse for Products | CPC
which should make a great input source for an O2.
  • Optical/Coaxial to Stereo L/R audio Converter
  • Converts digital Coaxial or Optical (TOSLink) to left/right analogue stereo audio (2x Phono) outputs
  • Inputs: 1x Phono (Coaxial) & 1x Optical (TOSLink)
  • Outputs: 2x Phono (RCA)
  • Simple plug & play, no settings required
  • 32, 44.1, 48 & 96kHz Sampling rate
  • 24bit S/PDIF Incoming bit stream on L/R channels
  • Metal body for better EMI elimination & gold plated contacts
  • Supplied with power adaptor
  • Dimensions (WxHxD): 41x51x26mm
  • Weight: 78g
Not bad for 22.40 plus VAT!

Last edited by greenalien; 28th November 2011 at 09:08 AM.
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Old 28th November 2011, 01:19 PM   #909
qusp is offline qusp  Australia
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too much of a generalisation. protools, EMU and RME just to name a few professional solutions that have perfectly good internal cards as well as external. just because its external does not mean its somehow isolated, the USB or firewire bus still connects to ground in the PC, so the same level of care is needed
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Old 28th November 2011, 01:25 PM   #910
Jokener is offline Jokener  Germany
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Also, as RocketScientists blog proves, price is not by definition related to quality or results.
And pretty much any spec is, in and of itself, useless.
I don't say any of the aforementioned products are good or bad, just that you got to be careful whom to trust with their numbers.

I am currently using an (internal) Asus Xonar HDAV 1.3 on my multimedia computer.
The entire computer was designed with EMI shielding in mind (CNCed my own case) and the Xonar passes the signal to second card via I2S.
The second card has its own power supply and sits in an even better shielded box.
-> There is no noise to speak of and signal quality is great.
(This solution may not be the end-all of PC based audio, but it cost 400€ for the computer and another 400€ for the case. You could spend more on a DAC, or even cables :-) ...)

Best regards,
Jokener
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