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Old 9th December 2007, 07:01 AM   #31
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Default 180 Kilograms..... something alike 1/5 of a Ton..... may be more than 350 pounds


I think..... and i use to walk, to climb stairs and i have a new girl friend...i am 56 and she has 29....ahahahahhah.

This picture was in 99....only 320 pounds here.... today i am bigger.

Big magic my friend!

Yes... the girl is crazy...but for sure i am not.... i know how to evaluate advantages to myself.

regards,

Carlos
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Power supply; ripple, filter, noise, stability and the use of capacitance multiplier... Portuguese and English; https://www.youtube.com/watch?v=sSm0ku1eIgg
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Old 11th December 2007, 12:41 AM   #32
CBS240 is offline CBS240  United States
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Hi

As I suspected, lowering the gate resistors on the output Mosfets increased the speed and helped some with that crossover notch. I had to re-install the input wire, and twist it with a ground wire to help with the RF. The input wire was acting as an antennae and receiving RF interference from the output wire, which was in relative close proximity.
The first set of waveforms is a 100 KHz square wave, input on top, positive output on bottom. 10V @ 2A RMS, per phase. In the second set, I cranked the frequency up to 200 KHz.
Man! this circuit's fast....and very quiet too.
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Old 11th December 2007, 12:45 AM   #33
CBS240 is offline CBS240  United States
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Lowering the gate resistors didn't quite compleatly get rid of the crossover problem. You can still see it in this 500KHz sine wave, but only if it is under load. Top is input, bottom is positive output phase. The negative phase looks exactly alike.

The bottom set is a 100KHz triangle wave, under load, 10Vp per phase.
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Old 11th December 2007, 05:58 PM   #34
xocoatl is offline xocoatl  Poland
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Nice and fast circuit you have.
Did you try to measure it's THD? Maybe with good soundcard and some free software?
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Old 11th December 2007, 10:30 PM   #35
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Default Very good to 100 Kilohertz


really fast and precise.

regards,

Carlos
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Power supply; ripple, filter, noise, stability and the use of capacitance multiplier... Portuguese and English; https://www.youtube.com/watch?v=sSm0ku1eIgg
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Old 14th January 2008, 07:35 PM   #36
CBS240 is offline CBS240  United States
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Hi

An update on my quest to build the “ultimate amp”…I have had a chance to throw a few hours off at re-construction of this crazy vero-board amp prototype just to make sure that it works and was not just a fluke of physics. I have found that it works better with a slightly more compact layout, even on vero-board. This version has even less noise (better input filtering), and is faster with a bit wider bandwidth. The beauty of this latest circuit is that it can be driven with a single line input OR a balanced input. All that needs done is to change the position of a simple jumper, just like you would set a HD to either slave or master, and the output to the speaker will always be balanced from either input type. Bit of an unexpected and beneficial side effect of the way the circuit works.
I’m thinking of naming this amp the NSSKA as in Not So Simple Killer Amp. It turns out that I don’t even need an output relay for this circuit. Apparently, the bridge circuit balances strait away so there is no output to the speaker until the common mode bias balance is achieved, which takes about 2 sec. Both outputs will fluctuate positive then negative with respect to ground for that 2 seconds that it takes to settle, but the speaker is bridged between the outputs and not to ground, so both speaker terminals fluctuate positive and negative for those 2 seconds together. There is simply no output until the common mode FB and DC servos bias the circuit, then there is only signal. I found this out by accident by forgetting to remove the speaker before powering it up. My first thought was ‘crap’, rather a different 4 letter word, but to my surprise, nothing happened. I sat there and turned the power on and off several times with the speaker connected without any faults. After the first second from power up, one output measures +6mVDC and the other measures +4mVDC with respect to GND. That leaves 2mVDC on the speaker. Good enough I suppose, eh? So far, this right on target with the original goals for this circuit and it might be the version I make a PCB for. Surly if I can build this thing on vero-board, a proper PCB isn’t out of the question. Ecstatic isn’t quite the word to describe my emotions right now.

It seems I have failed to drum up much interest in non-GNFB amp designs or even symmetrical topologies. If there is one thing about this circuit, it is symmetrical, in more than one way. Really it is just separate multiple cascade symmetrical amplifiers, designed to be direct coupled with each other and to the speaker, built entirely with discrete devices, no IC’s. Talk about a trapeze balancing act. BUT it seems I have pulled it off. If there is any interest, I can try to explain how this circuit works with a bit more detail. In the mean time, here is some pictures of the construction….

This is the start of the VAS circuit board "IC". Notice the two SOIC 14 THAT 340 matched arrays.
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Old 14th January 2008, 07:47 PM   #37
CBS240 is offline CBS240  United States
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This is the finished VAS "IC".

I labeled the pins as if this circuit is a "black box"
Pin 1== -40V

Pin 2== -15V

Pin 3== +Phase output, negative bias.

Pin 4== +Phase output, positive bias.

Pin 5== +Phase input

Pin 6== GND

Pin 7== -Phase input

Pin 8== -Phase output, negative bias

Pin 9== -Phase output, positeve bias

Pin 10== +15V

Pin 11== +40V

Notice how symmetrical it looks. It is relatively easy to vero-board a symmetrical SMD circuit because the traces and wire connections are exactly alike except each complementary transistor is flipped upside down. Works great for prototyping if you can do a little solder sculpting.
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Old 14th January 2008, 08:34 PM   #38
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This is the completed circuit. Another version for the Ugly Amp thread.
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Old 14th January 2008, 08:35 PM   #39
CBS240 is offline CBS240  United States
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No if THIS ain't getto, I don't know what is....
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Old 14th January 2008, 08:43 PM   #40
CBS240 is offline CBS240  United States
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One thing is for sure though, it sure doesn't sound like it looks. Notice the 2N3904/2N3906 pair. They are the only TO-92 transistors in the circuit. I used them as the pass transistors for the voltage regulator. The entire circuit requires only 30mA from a +/- 45 to 50V supply. The output Mosfet channels are powered by a +/- 25V higher current supply. I need to dissipate up to 200mW of heat and a SOT 23 just can't quite reliably pull that off so I had to upgrade to TO-92, with some old junk parts that I refuse to throw away. See, their still good for something!
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