Whoa, that must have been difficult. Just reading the TI datasheet on that chip makes me nervous with all the warnings about triple bypassing on each power supply pin, etc.
Hmmm sounds like an intriging possibility. We should try it as that problem was a major hold-back to making it work like it ought to.
-RNM
The originally considered in this thread is a phase-shifting type of oscillator, detailed analysis of its circuitry is now available at the website http://www.vkaudiotest.co.uk .
I represent there my VK-1 audio oscillator which was designed and built fifteen years ago and since then, along with the VK-2 distortion meter, has become an indispensable assistant in creating my original low-distortion (<0,001%) audio components.
Their comprehensive descriptions are placed at the above website too and I hope the material may be interested for both electronics amateurs and professionals.
I represent there my VK-1 audio oscillator which was designed and built fifteen years ago and since then, along with the VK-2 distortion meter, has become an indispensable assistant in creating my original low-distortion (<0,001%) audio components.
Their comprehensive descriptions are placed at the above website too and I hope the material may be interested for both electronics amateurs and professionals.
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Is the information available for these links:VK-4 LOW-VOLTAGE AUDIO SYSTEM, VK-6 LIVE-SOUND AUDIO SYSTEM, AUDIO UNIVERSAL METER, VK-8 RMS CONVERTER ?
@vkaudiotest --
Very nice presentation and very useful designs -- thanks for posting your site. It certainly is new to me.
I noted in the design of the distortion analyzer that you take the input signal and use a phase-shifter to develop the quadrature tuning signals. Is there a particular reason that you didn't pick-off the signals from the midpoints of each T section, which are innately in quadrature?
Very nice presentation and very useful designs -- thanks for posting your site. It certainly is new to me.
I noted in the design of the distortion analyzer that you take the input signal and use a phase-shifter to develop the quadrature tuning signals. Is there a particular reason that you didn't pick-off the signals from the midpoints of each T section, which are innately in quadrature?
We are looking for all such test equipment options and designs in order to be able to design and test our own amplifiers. How close are you (weeks, months, years?) to make available your finished product for DIY building?
And .... have you also made any FFT hardware ? Or recommend a DIY design for an existing ADC/FFT system?
Thx-RNMarsh
Hi DDB, richiem and RNMarsh,
Thanks for your kind responses, I'm very glad to communicate with you as specialists highly competent just in low-distortion measurements and generation.
Sooner or later, all my designs will be available for DIY building, I promise that. But now there is also a commercial interest in some of them and at the moment I negotiate with a German company about launching the production of my VK-1,2 instruments.
I don't like copying existing projects and prefer to do my developments from scratch, clearly setting the ultimate goal and going my own way to its realization, relying only on accurate calculations and correct experiments. Digital signal processing isn't my specialization and fifteen years ago I solved the problem of spectrum analysis by building a pure analogue device operating in a 20Hz-200kHz bandwidth and based on my original automatically tunable selective filter. One of its applications was extracting the required harmonic (n=2-9) from the distortion meter THD+N output that allowed to confidently measure the separate harmonics of distortion down to -140dB at the noise background of, say, -110dB, just what I do now with the help of SpectraLab software.
Now I am preparing a HTML version of my article on the VK-8 RMS converter being one more unit of my Universal Meter project which, alas, hasn't been realized as a complete device.
By the way, the image of the converter's operating breadboard construction can be seen on the title page of my site.
Vladimir.
Thanks for your kind responses, I'm very glad to communicate with you as specialists highly competent just in low-distortion measurements and generation.
Sooner or later, all my designs will be available for DIY building, I promise that. But now there is also a commercial interest in some of them and at the moment I negotiate with a German company about launching the production of my VK-1,2 instruments.
I don't like copying existing projects and prefer to do my developments from scratch, clearly setting the ultimate goal and going my own way to its realization, relying only on accurate calculations and correct experiments. Digital signal processing isn't my specialization and fifteen years ago I solved the problem of spectrum analysis by building a pure analogue device operating in a 20Hz-200kHz bandwidth and based on my original automatically tunable selective filter. One of its applications was extracting the required harmonic (n=2-9) from the distortion meter THD+N output that allowed to confidently measure the separate harmonics of distortion down to -140dB at the noise background of, say, -110dB, just what I do now with the help of SpectraLab software.
Now I am preparing a HTML version of my article on the VK-8 RMS converter being one more unit of my Universal Meter project which, alas, hasn't been realized as a complete device.
By the way, the image of the converter's operating breadboard construction can be seen on the title page of my site.
Vladimir.
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I am looking forward to your original concepts and design... can you give an estimated time when they will all be available to DIY? is it in weeks, months or years or ?? Is it variable or selected fixed freq?
The most interesting part for myself would be the analyzer as we have tried several available means to measure accurately, very low levels.
One such analyzer maker has been able to specify the accuracy of its measured 2H as +/- 1dB. That is important to me.... accurate harmonic measurement at level below -100dB re 1v. Will you be able to show your accuracy of harmonic measurement?
Have you designed any amplifiers using a CFA topology??
Thx-RNMarsh
The most interesting part for myself would be the analyzer as we have tried several available means to measure accurately, very low levels.
One such analyzer maker has been able to specify the accuracy of its measured 2H as +/- 1dB. That is important to me.... accurate harmonic measurement at level below -100dB re 1v. Will you be able to show your accuracy of harmonic measurement?
Have you designed any amplifiers using a CFA topology??
Thx-RNMarsh
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The VK-2 distortion meter uses the active twin-T notch network which is automatically tunable at any audio frequency, its Q-factor is chosen Q=2 that means a -0,5dB attenuation of the second harmonic of distortion and only -0,2dB attenuation of the third (see table 1 of the VK-2 description). This value is optimum both in terms of measurement accuracy and circuit stability.
Greater Q-factor values bring more trouble than benefit, they are particularly harmful for smooth operation of the system of automatic tuning, causing notable chaotic fluctuations of the tuned filter output.
I used CFA circuitry in my measurement equipment, but not in my audio.
Greater Q-factor values bring more trouble than benefit, they are particularly harmful for smooth operation of the system of automatic tuning, causing notable chaotic fluctuations of the tuned filter output.
I used CFA circuitry in my measurement equipment, but not in my audio.
Hi Vladimire,
If you don't already, I highly recommend you get into micro controllers and programming.
One 28 pin dip can replace all that discrete digital circuitry you have in you analyzer. I only suggest this because I think you could do amazing things with them. It would only take a few weeks of you spare time to get over the learning curve. After that things come easily.
The Microchip PIC stuff is great to start with and there's a ton of stuff on the net for that.
It would also cut you cost way down. I don't often tell anyone what they ought to do on this forum but for you......
Team work --
Dave -- maybe if you and/or others reading this thread already have the PIC knowledge... lets all work to our knowledge/strengths and help get it done. we can help and/or do parts of it together. I would love to see a cost effective, high performance test equip come out of this in a timely manner. Myself, I have about 4-5 months before leaving the country for awhile and will be only able to monitor, ask questions etc after that. But when back, I can test and measure and compare against the commercial models I have here and help in any other ways.
Thx-RNMarsh
Dave -- maybe if you and/or others reading this thread already have the PIC knowledge... lets all work to our knowledge/strengths and help get it done. we can help and/or do parts of it together. I would love to see a cost effective, high performance test equip come out of this in a timely manner. Myself, I have about 4-5 months before leaving the country for awhile and will be only able to monitor, ask questions etc after that. But when back, I can test and measure and compare against the commercial models I have here and help in any other ways.
Thx-RNMarsh
I think this is what the manufacturer (Panasonic brand -- made by Matsushita Communications) does and so your numbers would also fall under a guaranteed spec of +/-1dB also.
Thx-RNMarsh
Been looking for a way to do this -
This is of great importance to me and will make its operation by others much more flexible and useful and convenient. Been looking for a way to do this ---
-Thx-RNMarsh
This is of great importance to me and will make its operation by others much more flexible and useful and convenient. Been looking for a way to do this ---
-Thx-RNMarsh
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PICs are easy to get into. C programming for hardware isn't so simple. Or at least that's what i have found
Hi David,
Thank you for the remark, my German friend tells me the same.
But I built my distortion meter fifteen years ago and now, with micro controllers and programming, it would be quite another design. I would left to do this part of work to future DIY enthusiasts.
At least, the filter tuning algorithm is explained clearly and comprehensively in the device's description and the Multisim simulation has confirmed its validity.
Vladimir.
Thank you for the remark, my German friend tells me the same.
But I built my distortion meter fifteen years ago and now, with micro controllers and programming, it would be quite another design. I would left to do this part of work to future DIY enthusiasts.
At least, the filter tuning algorithm is explained clearly and comprehensively in the device's description and the Multisim simulation has confirmed its validity.
Vladimir.
Well C itself is not difficult if you've programmed in any other language. What I have trouble with is understanding other peoples code. The PICs and other controllers have a million registers and a million acronyms for them or least it seems. That's where I get hung up.
The data sheets are not a very good description of how to use the modules but each module has it's own documentation and if I RTFM I can usually get a better grasp on things.
What's your difficulty with C?