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Author Topic: Watt-zit-do?  (Read 1955 times)

phatt

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Watt-zit-do?
« on: March 01, 2015, 06:21:56 AM »

Anyone wanna have a go at explaining this odd ball circuit?

Judging by the lamp I figure it's a limiter for the tweeter of some sort
but the diodes and transistor have got me stumped. Head,scratch?

Also I'm not fluent in Glockenspiel type languages so I can't even read it.   xP

I have been experimenting with even more limiting ideas for my Cruize Control concept and dug this up from one of my very first hunting trips on the net, which I saved. While cleaning out the bottom draw I found it again and I would like to at least understand how it works as it might hold some ideas for my quest to limit,sag or compress the signal in some way.
Thanks, Phil.

J M Fahey

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Re: Watt-zit-do?
« Reply #1 on: March 01, 2015, 10:25:00 AM »
It's an "amplified diode" , same as what's used in bias circuits, where the transistor turns on when its base reaches around 0.7V .
Because of the voltage divider (100r/10r in the single 2N3055 example) the transistor will turn on with 7.7V CE , so the whole shebang will work as two 9V zeners in reverse parallel protecting the tweeter.

Easy and cheap to make, probably cheaper and definitely easier to find than a pair of 9V 15A 50W TO3 cased Zeners ;)  ... if they happen to exist at all.

Clamping action is brutal and unmusical, but better than hunting for and replacing that very expensive and unobtainable spare diaohragm for your priceless horn driver.

Added advantage is that it's safer against 5 thumbed, 1 neurone PA operators (or DJs, same thing).

The more complex one is more musical, allows *narrow*  pulses reaching the tweeter so it can reproduce that acoustic guitar attack, or cymbals, but any sustained onslaught such as mic feedback or an over enthusiastic synthesizer player gets the axe.
« Last Edit: March 01, 2015, 10:30:02 AM by J M Fahey »

Roly

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Re: Watt-zit-do?
« Reply #2 on: March 01, 2015, 01:51:40 PM »
It's Polish (or possibly Bosnian).

zgw1.jpg

Zabezpieczenie glosnikow wysokotonowych

w tym ukladzie posiom znieksztalcen moze dochoczic do 10%

Quote
Speaker tweeter protection

In this arrangement, the IMD can posiom dochoczic to 10%


Now if we don't want to posiom dochoczic to 10% we can...


zgw2.jpg

Zabezpieczenie glosnikow wysokotonowych

Uklad ulepszony,w ktorym przy takim samym napieciu poziom znieksztalcen osiaga zaledwie 0.2%.

Stala czasowa C1-R1 umozliwia pojedynczym silnym impulsom niezaklocone przejscie przez uklad.

Wartosc C1 moze wynosic od 1uF do 470uF.

Ponadto niwielkie zmiany R2 i R3 umozliwiaja tranzystora T2 do indywidualnych potrzeb.

* Transzystor 2N3055 na niewielkim radiatorze.


Quote
Speaker tweeter protection

Improved layout, in which at the same voltage level of distortion reaches only 0.2%.

Time constant C1-R1 allows a single strong impulses smooth transition through the layout.

The value of C1 can be up from 1uF to 470uF.

In addition, changes niwielkie R2 and R3 allow the transistor T2 to individual needs.

* Transzystor 2N3055 on a small heatsink.


As JMF said, the transistor part is effectively an adjustable power zener, and the bridge makes it back-to-back zeners or a bipolar zener (both useful tricks for your bag).
If you say theory and practice don't agree you haven't applied enough theory.

phatt

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Re: Watt-zit-do?
« Reply #3 on: March 02, 2015, 06:23:52 AM »
Thanks heaps, I'd be lost without you chaps. :dbtu:
Just wanted to rule in or out another option that might have been worth testing.
Hum,,,, "Unmusical" was mentioned so maybe that idea will be put back in the bottom draw. An adjustable bipolar Zener you say, that could get complicated fast and maybe perform no better than what I've already got.

I might just stop testing and start building. New Cruize Control circuit coming. 8)
Phil.