Most scopes won't do that. You'd need one that can do Fourier transforms. And you'd need a very clean sine input to your amplifier.
Assuming you have a sine generator with adjustable frequency connected to the amplifier input, just sweep the frequency and observed the amplitude change to determine the frequency limits at the output of your device.
Read the amplitude of the test signal on the screen of your scope. Some scopes also provide measuremens of RMS, peak, and peak-to-peak levels.
DI? Dispersion Index? That's a loudspeaker thing, so I guess I don't know what you're referring to.
Thank you for your immediate response.
I have a Picoscope Oscilloscope which has many measurements including THD, Signal to Noise Ratio etc. and also signal generator.
So I will try it with this one to see.
As for the DI, I mean Direct Injection Box which convert the unbalanced signal to balanced.
I think with the same way as measuring preamp I will take the measurements also for the DI.
I have a Picoscope Oscilloscope which has many measurements including THD, Signal to Noise Ratio etc. and also signal generator.
So I will try it with this one to see.
As for the DI, I mean Direct Injection Box which convert the unbalanced signal to balanced.
I think with the same way as measuring preamp I will take the measurements also for the DI.
Budget friendly distortion analyzer:
https://www.diyaudio.com/community/threads/how-to-distortion-measurements-with-rew.338511/
https://www.diyaudio.com/community/threads/how-to-distortion-measurements-with-rew.338511/
Hi George,
What bandwidth are you hoping to cover, and how low of distortion are you hoping to measure?
The higher the signal level, the greater SNR that can be characterized, as it allows you to stay above your source/sig gen’s noise floor longer. An audio interface can meet many goals of the DIYer both for signal source and measurement inputs. The QA401 measurement system also takes it further. It uses BNC terminals for low capacitance coaxial probes, and has inputs protected from overload.
You are correct.
@kouiky
The bandwidth that I would like to have is from 20Hz until 30kHz.
I have the Picoscope 2204 which can go until 10MHz. It has 8 bit Resolution but can be enhanced until 12 bit.
Do you think that it's ok to use it or to go in a better solution as QA401 that you suggest me.
Thank you guys!
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Sadly
Sadly, I’ve never got to use Pico-scope. A $150 audio interface however can easily do 2Hz-50kHz with 18 bits effective resolution using their onboard 24-bit ADCs and DACs.
@kouiky Thank you very much!
I have a good audio interface, the SSL2+
https://solidstatelogic.com/products/ssl2-plus?tab=features
With which software do you suggest me to take measurments? With TrueRTA?
I have a good audio interface, the SSL2+
https://solidstatelogic.com/products/ssl2-plus?tab=features
With which software do you suggest me to take measurments? With TrueRTA?
I use ARTA and REW for all audio measurements.
ARTA will not be supported any more by its creator but in its current status, it is an excellent program.
REW is very good for loudspeakers and room measurements, but will do the job, and it is free.
With a good soundcard you could have excellent results with these programs.
ARTA will not be supported any more by its creator but in its current status, it is an excellent program.
REW is very good for loudspeakers and room measurements, but will do the job, and it is free.
With a good soundcard you could have excellent results with these programs.
These days its the QA403, from QuantAsylum, though this is not cheap (but it is cheaper than "professional" audio measurement units...
Hello,
My apologies for not replied you earlier, I was ill.
@gdan thank you for your suggestions.
I tried the REW and it's very good, I took some measurements and please I would like to ask you how to measure the dynamic response of an audio unit, etc the sound card or a preamp?
Here are the measurement of my SSL sound card. The -110.5 dBr is the dynamic range?
@Mark Tillotson thank you, I will check it. Yes It's not cheap, I agree with you.
Thank you guys and sorry again for my late response.
My apologies for not replied you earlier, I was ill.
@gdan thank you for your suggestions.
I tried the REW and it's very good, I took some measurements and please I would like to ask you how to measure the dynamic response of an audio unit, etc the sound card or a preamp?
Here are the measurement of my SSL sound card. The -110.5 dBr is the dynamic range?
@Mark Tillotson thank you, I will check it. Yes It's not cheap, I agree with you.
Thank you guys and sorry again for my late response.
Attachments
For a number of years the 2204a was my only scope. It works great for testing and trouble-shooting most audio circuits and has enough bandwidth to observe loop stability problems with many amps (my 2204a bandwidth is more like 25 MHz). That includes square-wave testing.
Your 2204 can also do automated frequency-response measurements up to 100 kHz using FRA4Picsocope:
https://bitbucket.org/hexamer/fra4picoscope/wiki/Home
But it isn't useful for measuring THD much below something like 1%.
I concur with the REW+soundcard/audio interface approach for budget distortion measurements. Your soundcard seems to be pretty good - certainly suitable for assessing distortion of many DIY audio projects. You probably want to plot more harmonics, though. There is no guarantee that H2 is the dominant distortion, and it is useful to see how fast the harmonics fall-off with frequency.
jason
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The dynamic range is defined as the ratio of the amplitude of the maximum possible signal (without distortion) of the device to the noise floor of the device.
So, first find the maximum signal that can output the device without distortion (for example +15 dB with a distortion of 0.1%).
Then find the noise floor, for example -110 dB.
The dynamic range is then, 125 dB (+15 - (-110) = 125dB).
So, first find the maximum signal that can output the device without distortion (for example +15 dB with a distortion of 0.1%).
Then find the noise floor, for example -110 dB.
The dynamic range is then, 125 dB (+15 - (-110) = 125dB).
Hello Jason,
Thank you very much for your post.
2204 is a very nice tool, I'm using it to measure the output of amps but I will give it a try with the FRA4 Picoscope. Until now I'm using the standard Picoscope.
But as I checked with REW I have very good results.
I didn't expect it to be honest but the engineers of it surprised me! Very nice software!
@gdan thank you very much.
Very helpful your advice about REW software!
I will check it next days.
Can I take measurements both unweighted and weighted?