The latest Zen is Zen ver 7, common inductance loading. Mr. Pass said that this amp cannot be trimmed by matching voltage or matching current, it has to be done with distortion analyzer.
He said that we can also built (if cannot buy one), like the IM analyzer (Audio Express).
Does anyone has copy of that article? Or have other DIY distortion meter that can be used for trimming this amp?
He said that we can also built (if cannot buy one), like the IM analyzer (Audio Express).
Does anyone has copy of that article? Or have other DIY distortion meter that can be used for trimming this amp?
Mr. Pass said something about notch filter. What is notch filter, and how can it be used to tune ZV7?
A notch filter is tuned to filter out the fundamental frequency of interest so that what you're left with is harmonic distortion and noise. You could observe the filtered signal on an oscilloscope or use an audio voltmeter.
You can construct a notch filter of your own.
Try:
www.sound.westhost.com
You can construct a notch filter of your own.
Try:
www.sound.westhost.com
OK Fred, here's your opportunity to play educator. I know you
can do it for us. 😎
Lacking that, build one - there's enough information out there,
and it doesn't have to be particularly good. 1% scale will serve.
can do it for us. 😎
Lacking that, build one - there's enough information out there,
and it doesn't have to be particularly good. 1% scale will serve.
NP, Fred: I hope my desciption was accurate. I'm working on a "Poor Guy's" Audio Precision test rig. It's a hardware / software design. Would you guys be willing to critique the design of a fledgling like me? Maybe even compare it to the real thing? (NP - I know you keep one at you bedside!)😎
Thanks
Mike
Thanks
Mike
How about RMAA?
Rightmark Audio Analyzer
Have been playing with it recently. It's free and it's interesting.
It has been suggested in this forum before. But I still would like to hear more commend about it. Any more RMAA users here?
Rightmark Audio Analyzer
Have been playing with it recently. It's free and it's interesting.
It has been suggested in this forum before. But I still would like to hear more commend about it. Any more RMAA users here?
Still from the same paper, what is IM analyzer (featuring in Audio Express)? Is this a device to display harmonics?
How do Mr. Pass get this picture? I've always wanted to see harmonics (more than measuring it). Many people in this website can view 2nd, 3rd,even, odd, etc harmonic. How can I do that?
How do Mr. Pass get this picture? I've always wanted to see harmonics (more than measuring it). Many people in this website can view 2nd, 3rd,even, odd, etc harmonic. How can I do that?
Attachments
You can still find some analog audio test equipment from Leader. They have a model with signal generator and distortion analyzer. I have to find the model number.
To first familiarize yourself with the equipment and methods you may want to pick up a copy of "Audio Measurement Handbook"
An externally hosted image should be here but it was not working when we last tested it.
I'm sorry. Yes, the book is published by Audio Precision and can be ordered from their website.
Try here:
Audio Precision Book
Try here:
Audio Precision Book
FFT
FFT stands for Fast Fourier Transform. It is a means of implementing Fourier transforms using Digital Signal Processing hardware.
A DIYer with experience in programming DSP chips could conceivably do it. I don't expect it would be an inexpensive project, but then I haven't looked at DSPs since using Motorola's 56001, about 12 years ago. Perhaps prices have come down on the older models?
Erik
FFT stands for Fast Fourier Transform. It is a means of implementing Fourier transforms using Digital Signal Processing hardware.
A DIYer with experience in programming DSP chips could conceivably do it. I don't expect it would be an inexpensive project, but then I haven't looked at DSPs since using Motorola's 56001, about 12 years ago. Perhaps prices have come down on the older models?
Erik
We all have a set of decent DSP in our sound card.
Just dowdload RMAA for free and let the software do all the Math. Everything like Freq resp, THD, noise, IMD etc are done by a click. Of course, the measurement accuracy is limited by the performance of your soundcard. But remember, it's free.
There should be more people trying it out.
Just dowdload RMAA for free and let the software do all the Math. Everything like Freq resp, THD, noise, IMD etc are done by a click. Of course, the measurement accuracy is limited by the performance of your soundcard. But remember, it's free.
There should be more people trying it out.
An externally hosted image should be here but it was not working when we last tested it.
About RMAA:
When you run a measurement, do you simply measure the device on the input, or measure the soundcard in "loopback" mode and substract this result from the device's measurement?
When you run a measurement, do you simply measure the device on the input, or measure the soundcard in "loopback" mode and substract this result from the device's measurement?
lumanauw said:
A scope displays the signal in the time domain, how the intensity change as a function of time. This is a fairly useless way to gain any visual info about the frequency content of the signal since the small harmonic components are hidden under the huge fundamental freq (your 1kHz test signal or whatever). FT is a linear transformation from the time domain to the frequency domain. Although there is an analytical formula to get the FT (fourier didn't have a computer back then), we are lazy, short on time and much prefer to use computers to get it done. The signal is digitized (the analog waveform is represented by a table of intensity of equally spaced points along the curve) and transformed into a series of peaks at various frequencies.
Ideally with no distortion one would get a single peak at the fundamental frequency. Unfortunately there are harmonic components that appear at integer multiples of the fundamental freq. luckly this are generally small 1% or so of the real signal and so you need to display the intensity of the peaks using a dB scale. (see Banana's post)
Hope that helps.
Sorry, could have sent you to the web but I felt like writing. 😉
I was doing a "direct loopback" measurement, soundcard line-out to soundcard Line-in. So the graph is showing the performance of my cheapo on-board soundcard.
I'm still new to this RMAA stuff. As far as I've learned, it has a function to record the test tone onto a wav file or onto a CDR, so that we can perform the test using our CDP or external DAC. But I'm not sure whether the intrinsic distortion of the soundcard can be "subtracted" away or not.
lumanauw said:
According to (Joseph??) Fourier, all 2 dimensional signals(amplitude - time) can be split into simple sinusoidal signals. FFT is basically a DFT (Discrete Fourier Transform), but with the optimized DFT algorithm to speed up the calculation process.
So, if you run an FFT on a signal, you will know the contents of frequency in the signal. A real FFT analyzer is really expensive, and I have only used it in a fully equipped lab durring my college year. You could use the simple software like banana's suggestion. Don't forget to use an appropriate low pass filter to avoid aliasing problem, and also don't forget to select an appropriate FFT windows.