tag:blogger.com,1999:blog-6890046273025265768.post4591053537676353922..comments2024-03-18T03:10:30.572-07:00Comments on NwAvGuy: O2 SummaryNwAvGuyhttp://www.blogger.com/profile/00309644608738074125noreply@blogger.comBlogger157125tag:blogger.com,1999:blog-6890046273025265768.post-2092471298424962862012-08-23T16:06:54.987-07:002012-08-23T16:06:54.987-07:00Ok my first O2 amp passed all the checks and volta...Ok my first O2 amp passed all the checks and voltages....and it works wonderfully. This little amp is so simple and easy to build...pay attention and be careful handling the parts, Q1, Q2 etc...now to figure out a case and maybe an integrated ODAC with RCA's and 1/4 phone jack.<br />Thanks again for such a wonderfully honest design!<br /><br />All the best<br />Alexlost33https://www.blogger.com/profile/08954109482039273818noreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-32561081450276552142012-08-20T11:20:25.032-07:002012-08-20T11:20:25.032-07:00It should be fine unless you have unusually low AC...It should be fine unless you have unusually low AC line voltage. Ideally about 14 volts is ideal and 15-16 volts is also OK but the O2's regulators will run a bit hotter. Because the audio circuitry in the O2 has such high power supply rejection even some noise on the power supply (such as the ripple you get if the AC voltage is too low) barely changes the audio performance in a measurable NwAvGuyhttps://www.blogger.com/profile/00309644608738074125noreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-52337316829735353702012-08-18T13:22:25.851-07:002012-08-18T13:22:25.851-07:00The Jaycar MP3020 is rated at 12V this seems a lit...The Jaycar MP3020 is rated at 12V this seems a little close to the minimum?Danielhttps://www.blogger.com/profile/03579451127151648932noreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-31194904024903625782012-08-08T16:02:48.942-07:002012-08-08T16:02:48.942-07:00Funny I got all the resistors in using the BOM and...Funny I got all the resistors in using the BOM and the 1/2 watt resistors fit in the board with no issues at all...so no need to order 1/8 for fear of not fitting on the board...lol...now have to wait for 3 backordered 40.2k's and the NJM2068D. These have been hard to find....Aug 20th due in at Mouser. Thanks for the response!!<br />AlexAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-59372620339969206642012-08-07T12:42:34.521-07:002012-08-07T12:42:34.521-07:00Those resistors can be anywhere from 1/8 watt to 1...Those resistors can be anywhere from 1/8 watt to 1/2 watt. The only issue is they be metal film and physically fit the board. The Mil Spec "upgraded" resistors in the parts list have a lower power rating so they can meet much tighter specifications. AFAIK, JDS is supply valid parts.NwAvGuyhttps://www.blogger.com/profile/00309644608738074125noreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-16466842842922416342012-08-07T11:30:01.092-07:002012-08-07T11:30:01.092-07:00Hello, I found the answer for the resistors i ment...Hello, I found the answer for the resistors i mentioned in the BOM, the ones that are 1/2 watt partnumbers instead of 1/8 watt...page 65 or so on the DIY forums Mr. Slim has a BOM that has the correct resistors that will fit etc..<br />Thanks Alex.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-25466222083402111582012-08-04T14:53:04.457-07:002012-08-04T14:53:04.457-07:00If your O2 is made with the official O2 PCB layout...If your O2 is made with the official O2 PCB layout, and uses the PC board mounted jacks, it's not possible for it to flip the channels from the input jack to output jack. Tip of the input jack goes to tip of the output jack. There's nothing hand wired to get wrong.NwAvGuyhttps://www.blogger.com/profile/00309644608738074125noreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-69343714241041254852012-08-04T02:33:53.139-07:002012-08-04T02:33:53.139-07:00It seems like my O2 has left and right channels fl...It seems like my O2 has left and right channels flipped. Did this happen to anyone else?Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-45759431051067592052012-08-03T07:05:03.744-07:002012-08-03T07:05:03.744-07:00Yes, a 100 volt input would give about 13.3 volts ...Yes, a 100 volt input would give about 13.3 volts output from the WAU16. That will work great. There are several European/Australian 220 volt wall transformers you could also use instead of the WAU16-400 and you wouldn't need a step down converter--like the Stontronics AC-1550EU, AC-1550BS, Maplin N57AT, N58AT, and Jaycar MP3020.NwAvGuyhttps://www.blogger.com/profile/00309644608738074125noreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-63064298029140156292012-07-31T05:54:48.277-07:002012-07-31T05:54:48.277-07:00Hi NwAvGuy
i have a qustion since its impossiable...Hi NwAvGuy<br /><br />i have a qustion since its impossiable to find as transformers here could i just get WAU16-400 with a 220V to 100V step down converter, the mains here are standered 230-240 i could only find a 220V to 100V<br /><br />Ps i live in hong kong<br /><br />regards sidsid123https://www.blogger.com/profile/00725127306058636970noreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-65055127489598542152012-07-26T07:50:57.287-07:002012-07-26T07:50:57.287-07:00If you don't mind changing 4 resistors, you ca...If you don't mind changing 4 resistors, you can increase R3 and R7 to around 2.2K, 3.3K or 4.7K and decrease R14 and R20 to 8.2K, 6.8K, or 4.7K respectively. That will reduce the O2's "gain" to around 0.75X, 0.67X or 0.5X respectively.<br /><br />And you should remove either R17/R21 or R19/R23 completely (use no resistor instead of the 10K resistors you're using now).NwAvGuyhttps://www.blogger.com/profile/00309644608738074125noreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-31892028758335034342012-07-23T12:23:08.612-07:002012-07-23T12:23:08.612-07:00Using 250 Ohms DT-150s with O2+ODAC I've notic...Using 250 Ohms DT-150s with O2+ODAC I've noticed that even in the car I am using only 1/3 of x2.5 gain. So I've changed gain resistors to 10k to get x1.15 gain. And find it also too high. so voltage wise ODAC is giving more then I need. <br />I am not sure if putting in-line resistors in ODAC->O2 connection is good idea?<br />Is there any reasonable way to get gain less then x1?Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-22036603984201836452012-07-23T11:49:09.903-07:002012-07-23T11:49:09.903-07:00Thanks for sharing. There's work already under...Thanks for sharing. There's work already underway on a USB powered O2+ODAC so I'm going to wait and see where that goes, and if it becomes a reality, I'll be measuring it and publishing results. the one caution the O2 can't manage the same maximum output with even a 2W DC-DC converter as it can on battery or AC power. But that doesn't matter for most popular headphones.NwAvGuyhttps://www.blogger.com/profile/00309644608738074125noreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-84368973513288792422012-07-21T20:47:03.888-07:002012-07-21T20:47:03.888-07:00Hi NwAvGuy, I've just tried DC-DC bipolar conv...Hi NwAvGuy, I've just tried DC-DC bipolar converter to power O2 from USB of ODAC, http://www.pbase.com/objective3/dcdc <br />however it is 1W, it works perfectly (no lack of power and noticeable noise). As it can be a nice power option for ODA-ODAC combo, It will be great if you can do the measurements for it with O2 and ODAC combo. I can Mail you ready assembled converter. pls send me the Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-36829642863004922082012-07-20T11:05:05.526-07:002012-07-20T11:05:05.526-07:00I suggest reading the Benchmark article about the ...I suggest reading the Benchmark article about the "sonic advantages of low impedance headphone amplifiers". With any amplifier that has non-zero (even if it is low) output impedance, some of the distortion from the dynamic headphone driver is fed back to the output of the amplifier. 2 Vrms into a 50 ohm HD595 is an extremely loud sound, and could easily result in distortion above 10% atAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-36789621282426355542012-07-20T10:59:32.718-07:002012-07-20T10:59:32.718-07:00Ground loop related noise will not be a problem in...Ground loop related noise will not be a problem in normal use. Headphones "float" and are not grounded, but when you connect the output of the O2 to a grounded ADC input, you create an artificial problem. Adding more grounds won't help (and will probably make it worse). The problem is you are coupling output ground signals back to the O2's input stage through your soundcard.<br NwAvGuyhttps://www.blogger.com/profile/00309644608738074125noreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-82923999689454898492012-07-19T07:41:09.991-07:002012-07-19T07:41:09.991-07:00To NwAvGuy,
Thanks for answer. Can I just add som...To NwAvGuy,<br /><br />Thanks for answer. Can I just add some additional ground to lower this THD? I know that I cant hear this distortions but its interesting thing. <br /><br />To Anonymous, <br /><br />I tested at very high level. About 2 Vrms. But I think mechanical distortions (that depend on signal level) dont affect electrical distortions that I measured.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-45317692406028798012012-07-17T04:14:13.058-07:002012-07-17T04:14:13.058-07:00Hi NwAvGuy,
I just wanted to take the opportunit...Hi NwAvGuy, <br /><br />I just wanted to take the opportunity to thank you for all the outstanding information you are sharing on your blog, and especially for designing something as brilliantly performing as the o2. While I had trouble trusting all those feature claims before, I now cannot help but praise your achievements after I just finished my own o2 build last night (got a parts kit from Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-8123195551400567202012-07-15T11:54:44.515-07:002012-07-15T11:54:44.515-07:00What level were you testing at ? At high volume, t...What level were you testing at ? At high volume, the distortion could easily have come from the HD595 through the output impedance of the O2. Even though the damping factor is about 100, the HD595 can have a few percents of distortion at 60 Hz already at 100 dB SPL (~0.2 Vrms), and is one of the most reactive full size dynamic headphones, so the -76 dB output impedance distortion is not Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-77024209688819546722012-07-15T09:07:49.837-07:002012-07-15T09:07:49.837-07:00First of all, all sorts of things can go wrong wit...First of all, all sorts of things can go wrong with RMAA. Please see my <a href="http://nwavguy.blogspot.com/2011/02/rightmark-audio-analyzer-rmaa.html" rel="nofollow">RMAA article</a> if you haven't already.<br /><br />Second, because you're using the same sound card for both source and measurement, you're likely creating a ground loop within the O2. The input and output grounds of NwAvGuyhttps://www.blogger.com/profile/00309644608738074125noreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-28056754301701186792012-07-15T08:18:08.281-07:002012-07-15T08:18:08.281-07:00See my Feb 2011 articles on impedance. The short a...See my Feb 2011 articles on impedance. The short answer is: It's complicated.<br /><br />A lot of headphone outputs have an output impedance that's too high for even some modestly priced headphones--especially balanced armature IEMs (like those from Shure, Etymotic, etc.). Those devices benefit from a good headphone amp with a lower output impedance.<br /><br />The lower-end Grados are NwAvGuyhttps://www.blogger.com/profile/00309644608738074125noreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-76091108337003154812012-07-14T12:55:22.093-07:002012-07-14T12:55:22.093-07:00This is very cool. Are headphone amps beneficial f...This is very cool. Are headphone amps beneficial for "normal" headphones or are they mainly for those high-end, high ohm headphones? I have a pair of $80 Grado SR60s, fwiw. <br />Thanks!<br />I might have a hard time proving I'm NOT a robot. For all I know, I could be like Daryl Hannah in Bladrunner! JRRRR CHIKA BINGBING ;PRustonnoreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-57546718511451011832012-07-13T08:46:58.812-07:002012-07-13T08:46:58.812-07:00Hi NwAvGuy! I need your help.
I just soldered the...Hi NwAvGuy! I need your help.<br /><br />I just soldered the O2 amp. And some measurments with RMAA dissapoint me. The strange thing is THD level at low frequencis (<100 Hz) with load of HD595 headphones. For 60 Hz tone is -76 dB at 2nd harmonic, -85 dB at 3rd and -106 dB at 4th. Distortions at 1 kHz is absolutley negligible. If I connect amp directly to input of my audio card low freq Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-88658125498846934522012-07-13T07:01:36.450-07:002012-07-13T07:01:36.450-07:00It could be shrunk as a commercial design, with so...It could be shrunk as a commercial design, with some tradeoffs, but it's not practical as a DIY design. The batteries are by far the limiting factor and, because of the power supply requirements, moving to Li-Ion batteries is not trivial (and potentially not safe for DIY). Also the SMT versions of the output stage op amps have much lower power dissipation creating thermal problems driving NwAvGuyhttps://www.blogger.com/profile/00309644608738074125noreply@blogger.comtag:blogger.com,1999:blog-6890046273025265768.post-46073010714429115722012-07-12T19:47:59.562-07:002012-07-12T19:47:59.562-07:00Just measured O2 consumption with my D150 250Ohm h...Just measured O2 consumption with my D150 250Ohm headphones <br />In DC side (at Power switch) on +23.5V DC it consumes around 23 mAmps idling and 26 mAmps on max volume (at x2.5 Gain) that is really so loud that can damage hearing. So we get 0.6W of max consumption...<br />BTW I just made another step to portable ODAC + O2 combo http://www.pbase.com/objective3/inboxAnonymousnoreply@blogger.com