Usually it is a mixture of various reasons; I don't know about the Cobalt (usually it is NI in this kind of solders), but that might be due to patent considerations.
Suprisingly even quite small percentages of additional elements can have a strong impact on the results; billshurv is right, Ge is used as it enhances the wetting of the surfaces, enhances the filling to lower the risc of microcracks in the solderjoint and enhances the look of the solderjoints (more looking alike lead solder joints) and reduces the oxididation of the melted solder by allegedly 40% which is a huge advantage when using wave soldering machines.(reduction of dross generation)
All that by adding 0.02 % +-0.002% of Ge to otherwise standard alloy (according to manufacturers specification sheets).
The patent situation is a bit strange, as some alloys are patented (even ranges of weight percentages for various metals) while others are not, but the resulting solderjoint might be patented as well; the nonpatented alloy gets enriched during the soldering process so that the resulting solder joint can be in the same range as one composed by a patented solder alloy.
So I'd guess that the incorporation of a metall not used in other patented alloys could help to avoid such situations.
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Samuel sent me privately a plot of an ESS9018 with the IMD hump. He simply removed the fundamental and showed the residual. It was very clear that it was pathological DAC behavior as the error residual did not even repeat on each cycle, not possibly caused by any op-amp. Anyone should realize that a sudden dramatic change in behavior with level would be unlikely to be caused by fairly simple analog post processing but more likely a change in state of the DAC internals. Most likely a similar effect to gain ranging in a test instrument.
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That warrants vision panels on the chassis and even mirrors under like they do in hot-rod conventions.
Very interesting data point. Would like to see how some others weigh in on the subject. The issue certainly continued for a long time after ES9018, with some dacs manufactured right around the same time showing the effect and some not. Maybe some manufacturers were supplied from, or used their own stocks of old chips?
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It is well known that it changes "strategy" at a certain level. Monotonicity should be precious. ESS also has the "funny" habit of coming up with ideas for tones now and then... Go figure... Every and anything for the benchmarks...
//
Around here we like to see 1,000 connectors done correctly at the bench before being allowed to solder in the field. At three joints per connector and three seconds per joint, that is really only 2.5 hours of soldering in roughly 100 hours total work. So to reach your goal of 10,000 hours should take 50 ish years without rest.
With very small bias (20mA), this is much less distortion with almost same harmonic profile: Pelatuk amplifier.
We always used to say there's two things you can never criticise in a person, their sexual prowess, and their soldering prowess...
Ok that went completely over your head. In my first job I had the pleasure of working with Space Qualified wiremen and realised that, if something just had to work best to get a professional to do it. Bob Pease had the same view.
I still have my NASA soldering standards book, along with my IPC standard. Still takes time and practice. Proper tools help.
The secret to good solder skills is good inspections! That accelerates the learning curve.
So I don't think it is so much time involved as knowing what the result should be.
I did know some vidiots (TV audio folks) who had the practice of when soldering cup style audio connectors would solder the connection and then before the solder cooled, push the wire into the cup until the insulation just touched the solder.
I just got in 100 of my microphone PCBs. One failed visual inspection. All passed electrical tests. It is taking 6 minutes to install them into their case and pack into the box with directions. Have 450 more in this batch and at least 1500 more after that.
Wave soldered surface mount parts were picture perfect. Hand soldered not so much.
They did send a picture of the first assembled board, so I was able to spot an error with one resistor value!
I am interested to hear what is so bad ("IMO Lead free solder is crap") about LF solder.
Dan.
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