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Old 7th May 2009, 11:22 PM   #1
athos56 is offline athos56  United States
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Default Gyrator Question

I wired up a gyrator and put in my 40v supply, it ended up with 4 volts at the output, I assume I miss wired it, however just to be sure I'm going to ask a quick question. I used this schematic
http://www.loetstelle.net/projekte/gyrator/gyrator.php
Do I hook this up between B+ and ground, or along the B+ rail like a normal choke?
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Old 7th May 2009, 11:48 PM   #2
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Not speaking Dutch my guess is it's an in-line device. It's polarity sensitive so you gotta connect it the right way X1-1 to the +ve rail X1-2 to the load.

Also. it needs a current through it to work. Were you testing open circuit?

As you pull current through it, the cap charges up and "programs" the current source Q1-R3. The MOSFET regulates it's Rds to maintain said current.
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Old 7th May 2009, 11:53 PM   #3
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Right. And a voltage drop on it will be about 5V plus voltage drop on the resistor in source.
There was a thread recently about gyrators.

Here it is: http://www.diyaudio.com/forums/showt...15#post1778215
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Old 7th May 2009, 11:54 PM   #4
athos56 is offline athos56  United States
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Ok, I read something that led me to believe it went the other way, I'll try it again, hopefully I didn't fry it
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Old 8th May 2009, 03:49 AM   #5
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Quote:
There was a thread recently about gyrators.
Hi Wavebourn,
Why does the term Gyrator apply to your circuit? It's your original idea, why not give it an original name?
Thanks
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Old 8th May 2009, 09:07 AM   #6
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Hi Athos56

It is indeed a directional device: you should connect X1-1 to the B+, and X1-2 to the following cap in the PS circuit. In other words, X1-1 should be more positive (higher voltage) than X1-2.

The text is German, actually!

Erik
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Old 8th May 2009, 03:37 PM   #7
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I tried to build that gyrator myself and promptly smoked it. I haven't tried to repair it yet, but I believe my mistake was to work exclusively from the schematic. I'd suggest using the PCB layout as a wiring guide.

My test was done on a 300v +180ma circuit. Indeed X1-1 in your "In" and X1-2 is your "Out". The next test I'll do will be on a lower voltage/current circuit with a resistor load. Won't get a chance to play until after I get into my next house.

Pictures? I'm curious how you've done yours.
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Old 8th May 2009, 05:41 PM   #8
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I have seen someone else complaining about the circuit, in that it oscillated wildly...maybe that also happened to Whitelabrat's circuit?

I have made a layout to build this unit on protoboard, but was not able to put it together, yet. I included space for a small resistor (couple R) in series with the drain as well as space for a gate stopper resistor (around 1k). I think that at least the gate-stopper is very important!

Let's see if I can put it together in the weekend and test it.
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Old 8th May 2009, 05:52 PM   #9
athos56 is offline athos56  United States
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Default Failure

Well, so I tested my amp for the first time and got distorted output of music, removing the Gyrator will be my first troubleshooting measure.
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Old 8th May 2009, 07:07 PM   #10
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Could be that I didn't smoke it at all. I didn't think about oscillation. It sure sounded like that is what it was doing. It was almost as if it were amplifying the B+ noise instead of filtering it.
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