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Quad or Series/Parallel Resistors as an alternative to traditional power resistors
Quad or Series/Parallel Resistors as an alternative to traditional power resistors
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Old 31st March 2018, 03:09 PM   #31
lehmanhill is offline lehmanhill  United States
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Quote:
Originally Posted by Damon Hill View Post
How far do we have to go before hitting quantum noise? There's got to be a rock bottom somewhere!

--Damon
When I was learning about electronics from my father as a kid, he told me that -30 dB was something you could hear, but very quiet. -70 dB was a great noise floor. For years I believed that. Then I heard the difference that -90 or -100 could make and was shocked.

I don't know where the bottom is, but I keep trying to learn.
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Old 31st March 2018, 04:17 PM   #32
DF96 is offline DF96  England
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Quote:
Originally Posted by lehmanhill
As anti is saying, I wonder if we wouldn't be better off using soldier mounting (vertical) for axial power resistors. The inductance might be a little higher, but I would expect the heat transfer from a vertical cylinder to be better than a horizontal one.
Better convection may help with power dissipation, but will make very little difference to any thermal distortion because for that you need to consider the instantaneous temperature changes of the resistive element, and that is some distance in thermal terms from the surface temperature.

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Then I heard the difference that -90 or -100 could make and was shocked.
Some of us might be shocked if you can demonstrate that you can genuinely and reliably hear down there, especially when not in a specially prepared 'quiet room'.
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Old 31st March 2018, 04:31 PM   #33
EUVL is offline EUVL  Europe
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Inspired by Samuel, who uses Beyschlag MELF in series-parallel in his low-distortion oscillator design :
My version of the G = 1000 low noise measurement amp (for Ikoflexer).


Patrick
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Old 31st March 2018, 04:45 PM   #34
scott wurcer is offline scott wurcer  United States
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Quote:
Originally Posted by lehmanhill View Post

As anti is saying, I wonder if we wouldn't be better off using soldier mounting (vertical) for axial power resistors.
In modular DAC's vertical mounted standard resistors can exhibit a differential thermocouple effect due to the heat flowing preferentially out the board end. Many standard semiconductor manufacturing materials are not pure metals and you can get 10-100uV/C in some cases from even bond wire terminations.
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Old 31st March 2018, 06:17 PM   #35
lehmanhill is offline lehmanhill  United States
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Originally Posted by scott wurcer View Post
In modular DAC's vertical mounted standard resistors can exhibit a differential thermocouple effect due to the heat flowing preferentially out the board end. Many standard semiconductor manufacturing materials are not pure metals and you can get 10-100uV/C in some cases from even bond wire terminations.
Very interesting. I had not thought about that.
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Old 31st March 2018, 06:18 PM   #36
lehmanhill is offline lehmanhill  United States
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Quote:
Originally Posted by EUVL View Post
Inspired by Samuel, who uses Beyschlag MELF in series-parallel in his low-distortion oscillator design :
My version of the G = 1000 low noise measurement amp (for Ikoflexer).


Patrick
Patrick,

I should have given you credit for starting me on this configuration. A diyaudio friend pointed me to your posts and you pointed me to Groner. Thanks. It has been an interesting learning experience.

Jac
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Old 31st March 2018, 06:24 PM   #37
lehmanhill is offline lehmanhill  United States
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Quote:
Originally Posted by DF96 View Post
Some of us might be shocked if you can demonstrate that you can genuinely and reliably hear down there, especially when not in a specially prepared 'quiet room'.
I would be shocked as well. I am not claiming to be able to hear -90 dB sounds. But the first time I heard a modern amp, not knowing any of it's specs, I was amazed how clear and detailed the music sounded. One of the characteristics of that amp was a noise floor about -90 dB. Since then, I have found some level of correlation between a low noise floor (among other things) and sweet sounding music. That's all.
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Old 1st April 2018, 03:30 PM   #38
DF96 is offline DF96  England
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Low noise floor may mean that the designer knew what he was doing, which will have benefits in other aspects of performance. The connection is thus correlation rather than causal.
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Old 13th September 2018, 11:27 PM   #39
spaceistheplace is offline spaceistheplace
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Quad or Series/Parallel Resistors as an alternative to traditional power resistors
I believe the EAR 834p uses a quad for the plate resistors.

IMG_0928.JPG

Just an example of commercial use of this concept “in the wild”
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Old 14th September 2018, 08:51 AM   #40
trobbins is offline trobbins  Australia
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Originally Posted by spaceistheplace View Post
Just an example of commercial use of this concept “in the wild”
Perhaps.
A plate resistor typically has a circa 500V rating requirement, which often dictates a 2W resistor at least. Maybe a 0.6W or 1W resistor with 350V rating is just acceptable. That quad of resistors look a bit like 0.6W style - so maybe that quad is more about spreading heat-dissipation, and economics of manufacture by using a common part on the pcb.
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