I recently finished my O2 + ODAC build and i'm loving it! I initially had some issues with buzzing/noise that got worse when I touched the case, but after closer inspection I found that the outer pin on J2 was shorting to the case and I had neglected to ground the chassis. The tolerances are really tight here. Snipped it off and added the ground wire and it's much improved - but not perfect...I want total darkness. With my uber-sensitive IEM's, and 100% volume (@ 2.5x gain) I can hear a quiet, but entirely audible, white noise.
Has there been any direct comparisons done between the NJM4556AD and the NJM4556ADD? When I placed my parts order, Mouser was out of stock on the DD part for the 4556 so I just ordered what was available. Since this is the final output stage, it might be significant.
Cheers!
Has there been any direct comparisons done between the NJM4556AD and the NJM4556ADD? When I placed my parts order, Mouser was out of stock on the DD part for the 4556 so I just ordered what was available. Since this is the final output stage, it might be significant.
Cheers!
A couple of posts back, a member had reported O2 + ODAC in same case resulted in somewhat higher level of noise (analog+digital ckts. too close for comfort?) on some high sensitivity h/p as compared to just single stand alone O2. Also to see if your O2 is "dead quiet" you need to disconnect 3.5mm i/p connector (so the sockets short i/p pin to gnd) & then chk. for any noise, provided you have shorted i/p socket gnd. pin to case properly.
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Hi guys I am having a problem with my O2. I have it hooked up to the ODAC and it was working fine until I plugged it into a powered USB hub. Then the sound went very distorted. However, it works fine on battery power. I need some help diagnosing the problem.
First of all R14 and R20 are reading beyond 1 on the 2k resistance on my meter.
With only U2 installed, I'm getting -8.73 instead of -11.8 on pin 4. So I'm guessing somewhere in the power supply theres a short?
First of all R14 and R20 are reading beyond 1 on the 2k resistance on my meter.
With only U2 installed, I'm getting -8.73 instead of -11.8 on pin 4. So I'm guessing somewhere in the power supply theres a short?
This wouldn't be feasible unless you made a new PCB since the board itself would be unchanged and the same size, and there are certain components that take up a non-trivial amount of height (jacks, pot, etc.).
This is all confusing to me.
You plugged the O2 into a USB hub?
R14 & R20 are 10k. Beyond 1?
The -8.73V seems more in line with battery voltage, not the regulated output. If it is the latter, you've got an unwanted voltage drop somewhere, not a short.
Yeah because I thought it would work through a hub (comes up in windows at least).
R14 and R20 if you follow nwavguys blog in the initial DIY tests section, it says to measure resistance. With all ICs out except U2 you're supposed to get between 100 and 300 ohms for those four resistors
Here is kind of what you would get:
http://www.diyaudio.com/forums/head...-smaller-smd-rs-o2-headphone-amp-version.html
Like ybz90 says, the pot, batteries, jacks, etc. take up a lot more room than the chips and resistors. I stayed with 1206 SMD parts just to make it easy to solder, but electrically a lot of those could be 0805 or 0603.
I kind of ran out of motivation to build it once I learned about the JDS Labs C5:
http://www.jdslabs.com/item.php?fetchitem=70
If you do build a SMD O2, please post some pictures!
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I want to make combo (o2+wm8740+wm8804) everything will be powered by 4 li on cells (+7,4v and -7,4v)
I have already designed bigger part of pcb, some of capacitors will be leaded but I can't find replacement for this transistors, can someone help me?
P.S dimensions of the pcb 15x100x60mm (similar to ibasso db2 but with very good amp)
I have already designed bigger part of pcb, some of capacitors will be leaded but I can't find replacement for this transistors, can someone help me?
P.S dimensions of the pcb 15x100x60mm (similar to ibasso db2 but with very good amp)
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So I tested this a bit more: the noise disappears completely with the DAC unpowered, confirming once more that the DAC does cause noise. I have not ye tried removing the ODAC from the case to see if the noise is reduced. I'll try that later tonight. If this turns out to be the case, I wonder if additional shielding might work to isolate the noise, assuming it is radiated and not getting in on the LOD.
The On Semiconductor NTZD3155CT1G might be an interesting part for your application. It has both the n-channel and p-channel mosfet in the same part, so they will be well matched for similar switching times.
http://www.onsemi.com/pub/Collateral/NTZD3155C-D.PDF (opens PDF)
20Vds which is enough for your +/-14Vdc rails. Rds = 0.5R, which is 10x larger than the O2 mosfets but still just 0.125V drop at 250mA. They have low threshold voltages, turning on hard at just 1.8Vdc. I see "single and dual cell lithium battery operated systems" listed as one of the applications. One problem, Vgs (max) is just 6V - logic level - so you would have to use a resistive divider on the gate of each with the O2 circuit.
Mouser #863-NTZD3155CT1G. Farnell has them in stock, #2101817.
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Yeah I typo'ed that. You have +/-7.5Vdc rails and 15Vdc rail-to-rail, which is what the mosfet gates see.
Here is an even better part that has +/-20Vgs. No resistive divider needed. You could use it in the O2 circuit just the way it is. Smaller Rds (on) too, around 0.1R. Fairchild FDS4559:
http://www.fairchildsemi.com/ds/FD/FDS4559.pdf (opens PDF)
Mouser #512-FDS4559, Farnell #1471052, RS Components #6710523.
Hey, this sounds like a quite nice idea. I'm currently thinking about a SMD-O2 version powered by li-ion cells with an integrated dac (probably the odac). Because i only want to drive iems, the 2V rms from the odac would be totally fine so i can left out the gain part to same more room. Is there any easier way for the low voltage protection part than nwavguy's solution? None of the li-ion protection chips i found so far, are suited for a bipolar design. Greetings
