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Posts by wakibaki

I'm used to using heat to shrink plastic film, the kinds used for covering airframes and wings of model aircraft. I used the heat gun a long way away from the mylar film to keep the temperature low and controllable. At first the film sagged, then tightened as I moved the heat closer VERY slowly. As soon as the wrinkles disappeared I removed the heat. I haven't been able to test the result yet tho. w
Why not make up a circuit board, or more than one if necessary, that will allow you to build a unity-gain buffer with each of these devices, then send a sample of music out of your soundcard, through the buffer, and record it back in through your soundcard. Then post the samples here without stating which is which opamp. Get people to vote for which they like best. w
I went to Malta for a week. I used to live there when I was 8~12 YO. Some things arrived by the time I got back:- These are the parts for the transformer-style amplifier I decided to take a flyer with. It's only ~8W into 8ohms, which is 8vrms, with a transformer ratio of 40, but I still think it should drive the phones. w
Yes, but not in this case, when it's only 75ohms. Amplifiers' input impedances are typically in the 1000s of ohms. When the output impedance starts to approach these values, then the output volume will fall. Since the amplifiers input impedance typically does not vary much with frequency, unlike phones, there should be no effect on the overall output quality except for the SNR, and no noticeable effect on that in this case.w
Some of the most productive engineers I have known had the most untidy desks. I work untidy, I can mostly lay my hands on anything. I think it's best not to try to adopt a working style that is not your own. w
Very nice. Pleased with it? w
You say you've got 40~50dB of attenuation in there, that sounds like a lot to me, so I ignored it, and offered a guesstimate of what I thought would be a good starting point, bearing in mind that I expect you to experiment. You obviously want to be operating closer to 10 on the output scale rather than 1, so you can achieve this by losing a fair chunk of signal voltage across a series resistor. The DAC O/P impedance is negligible, so a 220k resistor will reduce the...
2.5vrms/75ohms output will drive many phones without any amplifier. It will certainly drive virtually any amplifiers input impedance without issue. Not only that, it will drive many phones to unbearable volumes. The stock Crack has 120ohm output impedance, so it is a distinct dis-improvement on your DAC run stand-alone. I guess all this is complicating the task of composing a suitable reply. I'd just put a large value series resistor in each DAC channel's input to the...
I found these:- http://www.ebay.co.uk/itm/Toroidal-230V-Mains-Transformer-15VA-0-6V-0-6V-/300976618233?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item46139abaf9   In this case the primary and secondary swap roles, but this is dual both sides.   This is the bias supply:-       w
Doh! I picked a tx with a CT secondary, when what is required is a CT primary. I must be a bit distracted.   Here is the latest iteration of the depletion MOSFET design. I have carefully made these stacking boards 100mm square, this is the best value/size on sites such as seeedstudio.com and iteadstudio.com. 10 ea. of these cost ~U$75.     The bottom layer, the amplifier, has a largely unbroken copper plane on the upper surface, the upper 2 layers have largely...
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