John Curl's Blowtorch preamplifier part II

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#89,886
The trick is aiming the fan away from you. This means it can't be too far away, but the suction is gentle and doesn't change the soldering. Now if the fan is blowing in the direction of the solder it's a careful game to aim it above the solder joint and still have the benefit. Professional places have suction hoods that are also gentle, but move a fair bit of air.
 
#89,887
billshurv said:
you can get fume extractors that clip to the iron! How much closer do you want?
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This standard practice in most commercial (if not all) assembly facilities, health and safety requirements in this country make them mandatory... And they work, without any cooling of the solder joint. Though hand soldering is avoided where possible, selective soldering being the first choice. Wave soldering is rarely used unless the board is all PTH components, very rare these days, most being a mixture of SMD with a few PTH components, such as large caps. Inductors, connectors etc. The move where ever possible is to SMD rather than PTH if for no other reason the ease of assembly.
Breathing in rosin flux early in my career is what really triggered my asthma, the days before all the health and safety rules.
 
#89,888
I used to have one of these little guys. Worked well enough.
https://www.amazon.com/Aoyue-Benchtop-Solder-Smoke-Absorber/dp/B001RLZGKK
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#89,890
If I can get a clip on one for less than a kidney I probably would just to avoid the hassle of having to position a fan on the debris field that is my workbench.

https://www.youtube.com/watch?v=HpUbVgVsbyQ

Can you guys comment on what you think is a reasonable way to protect your hearing in the shop and elsewhere, based on current science? Not that I consider earplugs unreasonable, but I'd like to know what works best and try to avoid misleading or incorrect information.
 
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#89,891
I keep a dozen or so of the headset style scattered throughout my shop. They are 3M brand. Bought from McMaster Carr. I also have a dispenser box of foam plugs with silver powder in them. That reduces the risk of ear infections, which can leave you deaf in a day or two.
 
#89,892
Kean,
ultimately the hard shell over ear protection has the best protection but for just simple protection against lower level sound the foam plugs work well. I have used both and personally prefer to wear over ear protection than have the foam plugs in my ears. For high impact sounds such as guns I would never consider the foam plugs sufficient for protection. So it comes down to what type of sound and what spl level protection you need. For higher frequency sounds the foam plugs work well.
 
#89,898
1audio said:
The LF noise is very good. The open loop gain and distortion at audio frequencies is not good. I'm sure there are trade-offs they exploited for this device.
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I doubt it; I think they have a better (lower 1/f corner) process on which they can design/build pretty much anything they want. It's just that the product champion for this particular device, didn't want zoom-zoom specs for open loop gain or audio frequency distortion.

George Erdi's ISSCC paper on the super low noise LT1028 is instructive; they burned so much power (by IC opamp standards!) getting the noise down, that they didn't dare run the last few non-noise-contributing stages at high current. So the output is wimpier than we would have preferred. Output transistor bias current is 500 microamps, oh the humanity!

ISSCC 1986 p.14 "A Bipolar Opamp with a Noise Resistance of Less Than 50 Ohms".
 
#89,900
And I agree open lopp BW is very low,
But THD at 10kHz 3Vrms into 600R is still a respectable at -104dB.
Current consumption is 7mA.

And noise goes up 5x between 100kHz & 10MHz (DS P.7).

A nice chip to measure LF noise between 0.1Hz & 10Hz.
Probably also not bad for audio if the bandwidth is limited to 20kHz ?
EXpenive though.


Patrick
 
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