I'm reading a microchip layout book that was given to me long before I would have been able to understand it. Every now and then I pick it up and try to figure out more.
It says that in a BJT very high current hot spots can occur because of "the formation of a stable hot spot". This is nothing new (secondary breakdown), but it was the "stable" part that got me thinking. Is there such a thing as "unstable" hot spots? At high stress do unstable hot spots ripple across the junction? Would this cause noise related to the thermal time constant of the die?
Kind of an obscure question, but... Curiosity.
It says that in a BJT very high current hot spots can occur because of "the formation of a stable hot spot". This is nothing new (secondary breakdown), but it was the "stable" part that got me thinking. Is there such a thing as "unstable" hot spots? At high stress do unstable hot spots ripple across the junction? Would this cause noise related to the thermal time constant of the die?
Kind of an obscure question, but... Curiosity.
FYI -- power conditioning (includes filtering) can make a difference IFyou have noisy gear like SMPS on the line and they are not PFC nor filtered AND if one or more of the connected gear in the system is susceptible to those freqs entering inside the amp/circuit.
Most of the complainst about if the ac line filtering helps or doesnt help depends on those conditions.
Then you have series filters and parallel filters to remove unwanted freqs.
High current music requirements often dont do well with the series type filters.
Where do you want to start? For SY --- noise/freq injected on the ac line side at specific freqs for the amp DUT has shown distortion to rise for that amp.... see D.Self as he did the tests which showed the distortion increased.
THx-RNMarsh
Most of the complainst about if the ac line filtering helps or doesnt help depends on those conditions.
Then you have series filters and parallel filters to remove unwanted freqs.
High current music requirements often dont do well with the series type filters.
Where do you want to start? For SY --- noise/freq injected on the ac line side at specific freqs for the amp DUT has shown distortion to rise for that amp.... see D.Self as he did the tests which showed the distortion increased.
THx-RNMarsh
Last edited:
Ask, and you shall be answered ...
First hit in Google, www.uta.edu/ronc/4345sp02/lectures/L16a_4345_Sp02.ppt
Well, my reading of that presentation is that the instability is of temperature, not movement - the hot spot gets hotter and hotter, and the thermal runaway causes the transistor to short. In the stable situation the hot spot "stabilises" at a temperature below this point - there's a negative feedback loop - but the transistor is not saved by this: it burns out during turn-off.
Also, came across this interesting tidbit while looking around: https://www.fairchildsemi.com/application-notes/AN/AN-9067.pdf - MOSFETs can self-destruct because a parasitic BJT element forms in the device under certain conditions, and the classic hot spot behaviour kills it.
Also, came across this interesting tidbit while looking around: https://www.fairchildsemi.com/application-notes/AN/AN-9067.pdf - MOSFETs can self-destruct because a parasitic BJT element forms in the device under certain conditions, and the classic hot spot behaviour kills it.
It doesn't do PFC: there is no rectification or energy storage, or anything, it simply subtracts everything that differs from a pure sinewave, and the input current it draws is that of the load under ideal sine conditions, which is probably not sinusoidal unless it incorporates a PFC.
Also, the current draw will be governed by the load and the sine voltage it sees, and (generally) won't be correlated to the distortion of the raw incoming mains
It does not generate noise of its own, except for the noise floor of a typical class AB amplifier, which is very low.
In the version I built, there is a light passive filter upstream, to remove the highest frequencies and also to protect the circuit against high voltage transients.
I haven't included common mode filtering, because it is a stand-alone class 2 device, but it would be perfectly doable for other applications. .
Active PFC circuits are a powerful source of EMI/RFI, just like any switching circuit
Two points...
One, why don't the promoters of this Scam, deceit, fraud whatever you want to call it provide some evidence to back it up.
Secondly, promoting this kind of magic and similar joke products does more disservice to Audio than good, it is a cause of much ridicule from the mainstream world of electronics.
As an added bonus now, you can also wax lyrical about magic crystals embedded in resin....That just have to be placed near equipment to combat noise, whereas on of the accepted methods in other electronics for this (the evil ferrite bead or clamp) is denounced as making things sound bad, I sometimes think I have fallen through the looking glass...
That's fine, Doug does actual engineering rather than handwaving and provided some actual relevant data. But if one wants to discuss the effect of actual line conditioners on audio devices, it would be kinda nice to measure the effects of the actual line conditioners on audio devices. Especially if one is promoting or selling such gadgets and has a pile of test equipment to characterize the output of the audio devices.
Hi Frank I.
I bought the Belkin box from a bloke in a nearby suburb via the local Trading Post classified type online site after reading a few positive online reviews.
I think I paid $30.00 or so, just for the experience of trying out such a commercial product.
It looks flash, and has useful functions and facilities like display of AC supply voltage and load currents/wattages and ability to switch on/off individually filtered outputs.
It does filter/work as advertised, however it adds that ferrite annoying (to me) subtle distortion/veiling.
Ultimately, for me, it's a fail, and no great expense for the experience.
Ok, so what do you define/regard as a good transformer ?.A good power supply starts with a good power transformer to my ears. Trouble is you almost invariable have to have it custom made.
Cheers,
Dan.
We're not in court. Nobody is required to provide anything to anyone! Period.
Same goes for SY's requests to show data, measurements etc.
Life's just too short to back-up every move with evidence to every naysayer in the world.
Don't like what stories other people tell? Fine, don't listen to them.
Suspicious of some product? Also fine - don't buy it!
Peace!
Hi Frank II.
Thanks for the compliments, but the experiment was not as complete as could be.
Like I said, this was just a quick'n'dirty exploration of only adding a specific noise to a random music track.
Like I said also, it was not (able to be) an exploration of including dynamic modulation effects such as dynamically modulated resistor/capacitor/conductor noise, dynamically modulated transistor noise and dynamically modulated transistor characteristics as would be found in typical amplification stages.
So within these limitations, the experiment does go some way to illustrating the damage done by simple addition of out of band VLF noise.
The next step is to measure/characterise the collateral modulation effects of out of band 1/f noise on typical audio gear.
This one ain't going away, trust me.........one Powerball
Dan.
Last edited:
That's correct. And people are also free to point out that nonsensical-seeming claims without any backup data (especially where commercial interests are at stake) are at best suspicious and at worst dishonest.
There are many forums where even the mention of the need for evidence is against their rules. There are forums where nothing may be posted without backup evidence. This forum is neither, but allows any technical discussion in an open manner.
- Status
- Not open for further replies.