> Need to look into that, but they are obsolete.
National Semiconductor Lot of 20 LH0033G-SH64103 High Speed Buffer Amp **NEW** | eBay
I still have more than 10 from the 20 I bought.
In addition, I have also made them myself successfully.
http://www.diyaudio.com/forums/head...portable-headphone-amplifier.html#post4676680
Patrick
National Semiconductor Lot of 20 LH0033G-SH64103 High Speed Buffer Amp **NEW** | eBay
I still have more than 10 from the 20 I bought.
In addition, I have also made them myself successfully.
http://www.diyaudio.com/forums/head...portable-headphone-amplifier.html#post4676680
Patrick
input parasitic C is always to some other pins on the chip, but it doesn't have to split equally between +/- ps pins
that assumption could give fortutious cancellation of ps common mode noise
bootstrapping the ps pins has possible complex consequences (a EE joke)
the bootstrapping will have to have some eventual roll-off, the details of the parasitic input Z and the bootstrapping frequency response transforms the input parasitic Z
bootstrapping rolloff may even give a region of negative input Z
so bootstrapping has only a limited frequency range of effectiveness, may require added parts to keep stability with any or no input beyond that frequency range
that assumption could give fortutious cancellation of ps common mode noise
bootstrapping the ps pins has possible complex consequences (a EE joke)
the bootstrapping will have to have some eventual roll-off, the details of the parasitic input Z and the bootstrapping frequency response transforms the input parasitic Z
bootstrapping rolloff may even give a region of negative input Z
so bootstrapping has only a limited frequency range of effectiveness, may require added parts to keep stability with any or no input beyond that frequency range
I think the Bode is not the right instrument for that. Its low Z and measuring small cap is only possible at high frequencies near the top of its range. I have access to one and have used it a lot but not for small C's and large R's. It looks like you should be in the gigaohms at low frequencies with that type of input.
The best way to see input cap is to measure response with low source Z and then with a source Z high enough to get like 3 dB of attenuation.
If the chip has any bypassing its C to + and C to - should be identical. However if you have one of the Tek capacitance meters 130 - TekWiki you can use it to measre between nodes and guard the nodes you don't want to measure.
A larger insight into what your attempting would be helpful.
Yup.
Filtering incoming mains at the facia board power entry point changes sound of my audio system, audible from outside the house, subtle but not subtle.
Same deal in other houses too.
I see what Fostec are doing, some of what they say in pdfs is correct, some is not.
Dan.
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I am discovering that too. I tried with the external coupler (attached) but it is still noisy and I don't trust it. Of course it never has been designed for this but I thought I'd give it a shot.
I'll try this weekend to use my audio analyser the classical way, measuring input current, dump data to Excel and calculate Zin. Watch this space.
What I am attempting is to drive a power follower with a 1500V RMS Vas, and a critical issue is the Vas loading, thus my interest in the output follower Zin.
Jan
I have done a Bode plot of the bootstrapped supplies (don't have access to it right now) and it is fairly flat with a mild (6dB) bump at 3MHz IIRC.
So for the extended audio range (say 100kHz) it should be ideal for practical purposes.
BTW When you say capacitance to ps pins do you mean external only or also internal capacitance to the power pins? External only would just be a pF or so I think.
Jan
They talk about Tachyons... the maximus site is amazing, electrosmog, I would probably be better reading this stuff after a good dose of LSD... But for those that believe in the power of resistors wrapped fabric...
We truly live in a post-fact world now. So many people believe and espouse all kinds of batshit crazy stuff like this. Is it a failure of our education system?
EMR Electrosmog is perfectly real, the problems with typical emrs are in the extra information encoded/piggybacking and there are ways to deal with that.
Better get some blotters and pull up a comfy chair for a Youtube session to get with the tripping these old school physicists are on...... John Archibald Wheeler's crazy ideas for a crazy world
The first 30 seconds is true, "it's not just a matter of nice simple formulas", after that the question is can the walls talk, perhaps they can.
My usb cable experiments maybe indicate that there really is deeper information that can be revealed/modified at will.
Keeps them safe, warm and snug.
Dan.
electrosmog!, having been involved with eMC since 1982ish and intensively dealing with it on a real practical level for many years I prefer the proven measurable methods rather than flooby products and beliefs...
As to USB cables and digital data, there is nothing hidden that we don't understand, no dark bits hiding in there, as any USB data is buffered at either end the data is effectively re-created so it just is bits and nothing more... There are many arguments regarding noise and many silly products to address the noise issue, again though no measurements and they are all a universal fix, many of which are not laid out correctly to stop noise. But digital noise (often termed simultaneous switching noise) is well studied, measurable and solvable with some basic engineering practices, no need for voodoo or other forms of magic ( maybe illusion is a better term or even better delusion).
🙂
As to USB cables and digital data, there is nothing hidden that we don't understand, no dark bits hiding in there, as any USB data is buffered at either end the data is effectively re-created so it just is bits and nothing more... There are many arguments regarding noise and many silly products to address the noise issue, again though no measurements and they are all a universal fix, many of which are not laid out correctly to stop noise. But digital noise (often termed simultaneous switching noise) is well studied, measurable and solvable with some basic engineering practices, no need for voodoo or other forms of magic ( maybe illusion is a better term or even better delusion).
🙂
Oh Henry Ott and Ralph Morrison to name but two have some very good books on dealing with "electrosmog"...
Marce,
You just might be watching the magician's right hand while he is really using his left hand.
Looking at the effect of the interconnect on the digital data is the right hand. While the left is how much EMI is spraying into the rest of the circuitry.
Not a big issue in properly designed equipment but we are talking audio products here.
Inside a CD player rolling an opamp can actually have an effect. Changing to an FET input device with poorer distortion specifications may actually lower the output noise level. As once you drop below the perceptable THD level other issues may be the limit.
You just might be watching the magician's right hand while he is really using his left hand.
Looking at the effect of the interconnect on the digital data is the right hand. While the left is how much EMI is spraying into the rest of the circuitry.
Not a big issue in properly designed equipment but we are talking audio products here.
Inside a CD player rolling an opamp can actually have an effect. Changing to an FET input device with poorer distortion specifications may actually lower the output noise level. As once you drop below the perceptable THD level other issues may be the limit.
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Ain't that the truth!
I've seen this many times as well. What is done in the audio section often determines how a CD player sounds, not the DAC section. Not always true, but you can sink a good product by handling the audio signal less well than the competition.
-Chris
IIRC Walt Jung was one of the first op-amp rollers doing just that. I had some theories but the 5532 posse drove me out of town. It had to do with the rising output impedance and residual glitch/clock energy at the input, bi-polars don't like that a lot more than FET's. This was all easy to demonstrate with a wide band spectrum analyser and an 1862 eval card (which I sent to someone here).
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5534 also suffers from asymmetric output stage which in DAC I/V application shows up very clearly with the feedtrhu zero on the output - no subtle instrumentation needed - just a 'scope and a current step input
basically the DAC I step edge shorts to the ouitput thru the low pass feedback cap - and initially moves the output opposite the wanted response as the fast rise current edge flows in the open loop op amp output stage Z - which is nonlinear - way diferent for positive and negative edges
more modern vertically isolated, better symmetry output stages will reduce the nonlinearity
faster, better ouputs should reduce the magnitude of the feedthru zero response too - again a place for composite circuits with a CFA ADSL driver op amp output making for a lower output Z both inherent from device capability and from speed, local feedback
basically the DAC I step edge shorts to the ouitput thru the low pass feedback cap - and initially moves the output opposite the wanted response as the fast rise current edge flows in the open loop op amp output stage Z - which is nonlinear - way diferent for positive and negative edges
more modern vertically isolated, better symmetry output stages will reduce the nonlinearity
faster, better ouputs should reduce the magnitude of the feedthru zero response too - again a place for composite circuits with a CFA ADSL driver op amp output making for a lower output Z both inherent from device capability and from speed, local feedback
I have mentioned noise on digital lines, I am very aware of what noise you can get on digital interfaces, how to limit it and how much effect is has on audio signals, all this is measurable and solvable, Max in getting into a different flooby area, similar to discussions that were had with SandyK many years ago... As I have said many many times, signal integrity and EMC are the two faces of the same coin. Signal integrity is the effect of local EMI issues, EMC is the effect in the wider environment.
I will concur that many (especially earlier) CD players had horrible looking layouts with minimum number of layers, even now for cost factors the number of layers are limited, this does not help keep simultaneous switching noise under control...
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I wonder where JC is ?
JC if you are still alive... call me after the 16th... I am coming back from 3 month vacation in Asia.
🙂
-RNM
JC if you are still alive... call me after the 16th... I am coming back from 3 month vacation in Asia.
🙂
-RNM
Not flooby Marce, just exploring some deeper levels.
What did SandtyK have to say.
How compatible is EMI/EMC/EMR to life forms..there are interesting questions, interesting answers and interesting solutions.
Most consumer audio has always had rotten layout, cdp in particular.
Dan.
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