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O2 Build Complete: Let the objective, subjective listening tests commence!

Discussion in 'Sound Science' started by cheapskateaudio, Oct 27, 2011.
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  1. Willakan
    I hope there is somebody over there reminding them of the evils of opamp rolling [​IMG]
  2. maverickronin
    Well, they allow animated GIFs for starters...

    It really seems to be catching on worldwide.  I think that's good for this hobby as a whole.
  3. mikeaj

    Off topic...but what happens?  Higher temperatures -> higher thermal noise power spectral density -> lower SNR -> higher BER?  Amplifier and/or gain control stages start to show nonlinear effects, degrading the signal component, so effective (matched) signal at receiver is less -> lower effective SNR -> higher BER?  Problems with acquisition or locking onto phase (if applicable)?  What burns out first?
    On a side note, my new  7812 / 7912 (only 7912 has problem) are probably coming in today.  I'll post back about how it goes.
  4. Questhate
    To anyone in on the Front Panel Group Buy on DIYaudio:
    Flynhawaiian stopped by earlier to test-fit the panels before sending them out to everyone. Fitment is cherry. Here's a preview:
    The group buy panel is the one on the left. 
  5. shadow419
    Sweet it looks awesome!  The black panel should contrast nicely with the silver box and knob I'm using .  [​IMG]
  6. Twinster
    Very nice! I'm waiting for a B2 & B3 panel. I like the alu knobs on your O2. Do you mind sharring the Mouser part #?

  7. Questhate
    Ahh yes. I should post pictures of the B3 panels too:
    I didn't have a B3 cased O2 built for test fitting, but all of the board-mounted component holes (power, source input, gain switch, etc) lined up exactly to the B2 panels, while the other ones are panel mounted anyway. It'd be safe to assume that those would line up as well. 
    For the knobs, I like those too. Kind of a stroke of luck that I ended up with those because the Mouser knobs were out of stock when I ordered my parts. I had to get them at Digikey (part number:  OEJL-63-3-7) and it cost a few bucks more, but I like the look of them way better. There are black ones and glossy ones as well: http://search.digikey.com/scripts/DkSearch/dksus.dll
  8. wakibaki

    The higher temperatures increase the likelihood of failure in just about every component. There are formulas which equate the effects of high temperature to lifetime in accelerated testing, although that's a slightly different subject from burn-in.
    Yes, the performance is degraded in general, but the BER is a good measure of the cumulative effects..
    These were synthesized frequency hopping spread spectrum secure digital radios with a low probability of intercept, the automatic BER exercised most functions of the radio, there was a maximum BER allowed before failure and of course if the radio stopped working it would be repaired and then enter the process again from scratch.
    Each individual who built a radio was responsible for getting it through a variety of tests dependent on model, everybody had a personalised QC stamp for traceability. They were mostly dual-conversion superhets so there were known problem frequencies caused by spurs. If those were OK, chances were the rest were OK too. Once the builder was satisfied the radio was passed on for release test. On arrival at the customer the radios went through a battery of acceptance tests. With 3k audio bandwidth + noise they still sounded terrible, you needed your 'radio ears' on to understand what the guy at the other end had said. My Yaesu VHF/UHF handheld has better sound quality.
    I spent my placement year doing release test, a great introduction to electronics and the use of scopes, spectrum analyzers, signal generators and all the rest and test automation in general. It was pre-Labview so I did GPIB control using HP BASIC. How we laughed and sang and lusted after the girls who did solder rework...
    ...OK, back to the mad world of subjective and objective audio.
  9. mikeaj
    Oh whoops I'm an idiot.  It wasn't the regulator.  I'm 95% sure it's just D4 (negative side 1N4002 diode) failed open.  When my cheapie DMM is set to DC measurement, the claimed voltage across the positive side D3 is like 18V, while the same across D4 is a little under 19V.  Sounds like a diode forward active voltage drop difference to me.
    This is about the time I wish I had some real instrumentation lying around, even if it's just a bottom-end budget scope with next to no features and triggering options...and somebody stop me before I get funny ideas about a voltage divider network and capturing via a sound card line in.  [​IMG]
  10. sphinxvc
    Been listening to my SM3s out of the O2s lo-gain for some time now: very nice. I think I may just get an LOD and start using this thing as a semi-portable amplifier.
  11. wakibaki


    I like this:- http://www.sillanumsoft.org/    ...Visual Analyser. OK, the bandwidth is limited, but when I needed to see the bit pattern of an IR remote and my scope trig packed in, it did the job. You can use a cheap USB ADC/DAC, I used my Behringer UCA202 rather than risk my soundcard, which anyway is not as accessible. I see this:- http://www.amazon.com/Syba-SD-CM-UAUD-Adapter-C-Media-Chipset/dp/B001MSS6CS for $8.54 and this:- http://www.amazon.com/External-Channel-Sound-Adapter-Notebook/dp/B000N35A0Y/ref=pd_bxgy_pc_text_b for $1.83!!! You do need to take care about the voltages though.
  12. digger945
    ^ Never tried the software you linked to, but I use True RTA sometimes, which recommends the UCA202 in the read-me files.... http://www.trueaudio.com/rta_abt1.htm (they have a free evaluation version)...
    I used the 0404usb briefly while testing a prototype earlier this year. Slightly more useful than some other software for visual real-time alterations/tuning to a circuit. A little trickier setting the input level.
  13. francisdemarte


    I'm also in the big idiot group now too. I also thought I had regulator issues too but after a complete re-flow of every joint the problem resolved itself, my O2 is working fine again and sounds great even over battery power. The only suspect part I had was a possible flakey 3.5mm jack, had some minor rattling or looseness. It's replace now and everythis is solid!
  14. Armaegis
    Will anyone be doing comparison tests with cheaper gear like the e5 or e6 or a well made cmoy (JDS, BSG, FredFred)?
    If people are trying to prove that there is no distinguishable difference (or "improvement", whatever floats your boat) between the O2 and more expensive gear, it's only fair we go the other way as well.
  15. cheapskateaudio


    I will be doing a comparison between the O2 and The Wire at least. 
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