OK, I found what I remember. Are you referring to the test procedure found on pages 7 and 8 of the OPA604 datasheet ?
It uses the DUT to boost the amplitude of the distortion to make the result easier to measure.
mlloyd1
It uses the DUT to boost the amplitude of the distortion to make the result easier to measure.
mlloyd1
Yes,- I think I remember this circuit. This approach could be married to a soundcard type analyzer....
I do have the original copy stashed away somewhere, but because of a rebuild of my basement section I don't have complete tracking of all my stuff!
The idea of using a sound card for spectral and distrtion measurements is great, but I think most of us do want "a little extra" if terms of freq. range and probably sensitivity. I have been looking for 96kHz soundcards and software for some time, so this thread is very useful.
Hope it continues for a while with a lot more tips and links.
I do have the original copy stashed away somewhere, but because of a rebuild of my basement section I don't have complete tracking of all my stuff!
The idea of using a sound card for spectral and distrtion measurements is great, but I think most of us do want "a little extra" if terms of freq. range and probably sensitivity. I have been looking for 96kHz soundcards and software for some time, so this thread is very useful.
Hope it continues for a while with a lot more tips and links.
For the folks that recommended PC sounds cards, I just wanted to point out some interesting discussion taking place in this thread
mrothacher said:
I measured a SBlive at around 0.05% THD at the output, both from internally generated tones and through the line-in jack. (the plot is shown in another thread somewhere). The distortion is mostly 2nd order.
I currently use a Clio system by Audiomatica to do FFT/freq. response/THD measurements. It is a custom ADC/DAC PC card based system with a really nice software package. It measures capacitance/inductance, plots impedance curves and derives TS paramaters of any driver (without a box!). Other cool features are an arbitrary function generator and scope. It will also do power VS thd and TIM of amplifiers.
It'll also score your car stereo with an official IASCA score sheet =)
Don't know how much it costs, since someone gave it to me... I am assuming it is quite expensive.
AudioFreak said:
Please elaborate! Have you done this successfully?
I already had the line input signal maxed out at one point (tried with and without a preamp). The SBlive exhibits at least 0.05% or worse at any input level I have tried. Also tried tones generated internally using a tone generator program without better results.
S&N ratio is in the mid 70's so noise measurements are a joke.
Distortion Analyzer
Folks, In response to a posting about a design that was in Audio some time ago, it was in the July/August/September issues, written by Bob Cordell. The design and article were nothing short of phenominal. A friend and I have built several of them. It has full automatic phase/frequency tracking and overall measurement floor of .001%, and typically .0003% through much of the audio band. It stands up well to the best and most expensive alternatives. No,it does not use TL071s, it uses 5534s. There may be better op amps now, but you'd be hard pressed to surpass this design. I use mine often, along with an audio spectrum anayzer for IM distortion measurements.
If there is a sufficient clamoring, I can copy or .pdf or photgraph and .jpg the articles. They are a landmark in audio engineering and disclosure for the DYIers.
Folks, In response to a posting about a design that was in Audio some time ago, it was in the July/August/September issues, written by Bob Cordell. The design and article were nothing short of phenominal. A friend and I have built several of them. It has full automatic phase/frequency tracking and overall measurement floor of .001%, and typically .0003% through much of the audio band. It stands up well to the best and most expensive alternatives. No,it does not use TL071s, it uses 5534s. There may be better op amps now, but you'd be hard pressed to surpass this design. I use mine often, along with an audio spectrum anayzer for IM distortion measurements.
If there is a sufficient clamoring, I can copy or .pdf or photgraph and .jpg the articles. They are a landmark in audio engineering and disclosure for the DYIers.
rmetz:
It's funny you mention this; I very recently acquired the boards for this project from a friend who got them from an ad in Audio before they vanished. It seems the company that made the boards for Bob was looking to get rid of some leftovers.
I'd like to see the articles also. I think I'd like to try building this thing myself, but all I have are the boards
.
mlloyd1
It's funny you mention this; I very recently acquired the boards for this project from a friend who got them from an ad in Audio before they vanished. It seems the company that made the boards for Bob was looking to get rid of some leftovers.
I'd like to see the articles also. I think I'd like to try building this thing myself, but all I have are the boards
.mlloyd1