Since it's very similar to Cubie, its worth noting Nelson's response in that thread (post #2): "I tamed the top end response with input resistor (meaning input JFETs' gate stopper) values larger than 1K."
With lab power supply it looks like this.
With CRC power supply (below) some reduction/improvement in overshoot is observed.
With CRC power supply (below) some reduction/improvement in overshoot is observed.
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Should have checked this earlier. The bloody crappy signal generator also has some overshoot.
I'll need to retest with better waveform generator.
I suspect it will still have overshoot, but no point making changes till it's properly tested.
I'll need to retest with better waveform generator.
I suspect it will still have overshoot, but no point making changes till it's properly tested.
Just discovered something.
This may seem counterintuitive but reducing the resistance at the input/gate of the jfets (2sk170/2sj74) reduces the overshoot and shorting out the 1k input resistor eliminates overshoot all together.
Papa is it ok to eliminate the 1k input resistor on the jfets or does it need to be there?
This may seem counterintuitive but reducing the resistance at the input/gate of the jfets (2sk170/2sj74) reduces the overshoot and shorting out the 1k input resistor eliminates overshoot all together.
Papa is it ok to eliminate the 1k input resistor on the jfets or does it need to be there?
With 100 Ohms at input it looks like this. That is with lab power supply, hopefully after installing crc supply it will improve further as previously observed.
I noticed something similar some time ago in SPICE, but figured it was a lie told to me by a computer program...
Yeah that is how I first discovered it too.
I was doing square wave testing in spice with increased resistance values at the input (which was actually making things worse), then all of a sudden I hit the jackpot when I put 10k at input.
I was super happy.
Then I discovered I made a mistake and instead of labeling the resistor 10k I labelled it 10 Ohms.
Some times it pays to be dumb and fearless. Hahahahaha. ABFAB baby, yeah. 😀
So I went and tested this result out straight away on the amp, with various values at input. It seems below 200 Ohms the overshoot virtually disappears on the amp.
Very happy. 😀
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Hooked it up to speakers.
Turned on amp a few times. Absolute silent operation (dead silent) with no turn-on or turn-off thump.
Put some music through it (Weather Report). Pretty bloody nice, that's Australian for "seriously frigin good". (intentionally miss spelt frigin to escape censorship-nazibot)
Hahahahaha
Edit: My son freaked out when I turned it on for first time. He now thinks I am a magician. Hahahahaha
Turned on amp a few times. Absolute silent operation (dead silent) with no turn-on or turn-off thump.
Put some music through it (Weather Report). Pretty bloody nice, that's Australian for "seriously frigin good". (intentionally miss spelt frigin to escape censorship-nazibot)
Hahahahaha
Edit: My son freaked out when I turned it on for first time. He now thinks I am a magician. Hahahahaha
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Why is the 200kHz square wave passing with so many high harmonics present?
The first squarewave harmonic of 200kHz is 600kHz !
Did you forget to fit an effective RF filter to the input?
The first squarewave harmonic of 200kHz is 600kHz !
Did you forget to fit an effective RF filter to the input?
Edit: My son freaked out when I turned it on for first time. He now thinks I am a magician. Hahahahaha[/QUOTE]
Congratulations ! You are a magician ( of a sort) when you can get magical music from a circuit!
Nice work.
Congratulations ! You are a magician ( of a sort) when you can get magical music from a circuit!
Nice work.
Thank you.
I'll give a proper impression of this amp sound-wise later, when I can compare it with my other amps.
I'm not into long winded wordy reviews though. It'll be short and sweet
I'll give a proper impression of this amp sound-wise later, when I can compare it with my other amps.
I'm not into long winded wordy reviews though. It'll be short and sweet
Just some specs of the amp. Gain is certainly adjustable but I prefer low gain amps with my efficient speakers
Bias 2A
Open Loop Gain is 40dB
Closed Loop Gain is 12dB (adjustable to what ever you want)
Damping Factor 50
THD at 1 Watt less than 0.001% (not measurable with my equipment)
Frequency response: DC to over 1MHz
So very similar specs to original F5 but with better performance into low impedance loads (due to increased bias), and with lateral mosfets making a simpler circuit possible, that was the goal for this amp.
Another thing worth mentioning is, there is virtually no warm up time as the amp biases up to 2A immediately at turn on.
Bias 2A
Open Loop Gain is 40dB
Closed Loop Gain is 12dB (adjustable to what ever you want)
Damping Factor 50
THD at 1 Watt less than 0.001% (not measurable with my equipment)
Frequency response: DC to over 1MHz
So very similar specs to original F5 but with better performance into low impedance loads (due to increased bias), and with lateral mosfets making a simpler circuit possible, that was the goal for this amp.
Another thing worth mentioning is, there is virtually no warm up time as the amp biases up to 2A immediately at turn on.
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And last but not least this version of the amp is dominant 2nd harmonic as opposed to dominant 3rd harmonic of original F5
There is a famous quote ( don't know from whom ) that says sufficiently advanced technology is indistinguishable from magic. I believe there is truth in that statement. I think Papa's design genius qualifies for that. Without his explanations of how his designs work ( and sometimes even with ) I marvel at the way they do what they do. It often seems like magic to me. Always the term genius applies. Pico your new creation is quite impressive. I admire your capabilities. Thanks for letting us ride along with you on this journey.
Arthur C Clarke
Clarke's first law
When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.
Clarke's second law
The only way of discovering the limits of the possible is to venture a little way past them into the impossible.
Clarke's third law
Any sufficiently advanced technology is indistinguishable from magic
Clarke's first law
When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.
Clarke's second law
The only way of discovering the limits of the possible is to venture a little way past them into the impossible.
Clarke's third law
Any sufficiently advanced technology is indistinguishable from magic
Thanks Pico.
I feel silly for not remembering who said it. Clarke was my favorite author as a young lad. I read everything I could get my hands on from him from the time I first saw 2001 A Space Odyssey. A truly brilliant man. Thank you for remembering and for reminding me. I wonder what kind of sound system he had at home? I think perhaps Papa might be a fan of his also.....
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