I'm not sure if you really appreciate how a soundcard and software package can make amp testing so much more automated and with so much better performance in many testing aspects.
Frequency response sweeps of bandwidth and distortion are all automated, along with stepping through amplitude levels, which can be a real timesaver if the amp includes tone controls or other adjustments like volume that may change such a characteristic. Also specific distortion tests like the various IMD setups are all programmed in. Hum and noisefloor performance standout due to the 24bit resolution of a reasonable soundcard. This is all achievable because the soundcard and software align the signal generator with the signal input processing, right down to using specific frequencies aligned with FFT processes.
A reasonable soundcard will achieve valid processing from circa 2Hz to 96kHz. The need to go below or above that range would imho only arise for diving deep in to specific and detailed stability aspects of certain amplifiers.
And by the way, the software typically includes an oscilloscope display to ease in the early days of use before one appreciates how much more information a frequency spectrum tells about the amp.
If you are keen to spend some money, then I'd suggest a modern laptop would be the biggest cost item to aim for, as it allows the measurement system to be completely battery powered (and portable) and so avoid any hum loop related measurement quirks that may arise from mains power equipment.
Frequency response sweeps of bandwidth and distortion are all automated, along with stepping through amplitude levels, which can be a real timesaver if the amp includes tone controls or other adjustments like volume that may change such a characteristic. Also specific distortion tests like the various IMD setups are all programmed in. Hum and noisefloor performance standout due to the 24bit resolution of a reasonable soundcard. This is all achievable because the soundcard and software align the signal generator with the signal input processing, right down to using specific frequencies aligned with FFT processes.
A reasonable soundcard will achieve valid processing from circa 2Hz to 96kHz. The need to go below or above that range would imho only arise for diving deep in to specific and detailed stability aspects of certain amplifiers.
And by the way, the software typically includes an oscilloscope display to ease in the early days of use before one appreciates how much more information a frequency spectrum tells about the amp.
If you are keen to spend some money, then I'd suggest a modern laptop would be the biggest cost item to aim for, as it allows the measurement system to be completely battery powered (and portable) and so avoid any hum loop related measurement quirks that may arise from mains power equipment.
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Software capability is pretty agile, so the ability to do certain extreme FFT scans with averaging is now available but can require a similarly modern computer processor and memory.
And the soundcard is imho preferably a standalone USB connected and powered device, with input and output level adjustments and automated input of unbalanced and balanced signals. The main note is that a separate voltmeter is required to benchmark the output level if reporting is to be done at a specific output power level in to a known resistor load - although that can be done with say a 1kHz tone where even a cheap voltmeter can be very accurate.
And the soundcard is imho preferably a standalone USB connected and powered device, with input and output level adjustments and automated input of unbalanced and balanced signals. The main note is that a separate voltmeter is required to benchmark the output level if reporting is to be done at a specific output power level in to a known resistor load - although that can be done with say a 1kHz tone where even a cheap voltmeter can be very accurate.
Hi,
You might also have a look at the AD2, Analog Discovery by Digilent.
It might appear like a toy at first glance, but it is a very capable multi-purpose tool, that also allows for reasonable THD measurements due to its 14Bit ADCs and DACs.
Its Bandwidth suffices for audio and above, but might be too low to capture HF oscillations.
jauu
Calvin
...and btw. You can't do wrong with a Siglent SDS1x04E
You might also have a look at the AD2, Analog Discovery by Digilent.
It might appear like a toy at first glance, but it is a very capable multi-purpose tool, that also allows for reasonable THD measurements due to its 14Bit ADCs and DACs.
Its Bandwidth suffices for audio and above, but might be too low to capture HF oscillations.
jauu
Calvin
...and btw. You can't do wrong with a Siglent SDS1x04E
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Joined 2008
Thanks for your reply trobbins!
Can you please suggest a few soundcards and software packages suitable for this purpose? (we do have a nice win10 laptop as we work on cad/cam software, but i would prefer to use an external sound card connected with it)
Looking forward for your reply - many thanks for your time!
P.S found this article :
7 best oscilloscope software for Windows
which one would you prefer?
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Joined 2008
Diyaudio has quite a few threads on people using specific soundcards and specific software for this type of tool - it is well worth appreciating what has been done. Perhaps the most prolific USB soundcard range over recent years has been the Focusrite Scarlett range, as they are not too expensive new and a lot have been sold (and tested in threads) and they have been through a few revisions so can be relatively cheap to get started with. There was also a range of E-MU USB soundcard interfaces (now over a decade old) that had excellent specs and performance (I have the 0404 USB), but it would be luck if you found one on ebay nowadays, and they need their own external battery power setup for least noise. If you can afford a lot more dollars then Focusrite have a better range, as do RME ADI and Steinberg AXR4 and others - perhaps google for comparisons to pick up interfaces that may suit, and to get a feel for what features some have or don't have, and whether that is a concern to you.
Similarly there are many threads on different software being used. I can only really suggest REW as I have used that over the last few years - as a software product it has a lot more range of applications than most other software, as it has a main application related to speaker and sound system assessment. There is a website and user forum, and it is freeware so no cost if you decide to use something else or don't want to donate. But given its wide functionality, it is a detailed technical tool, so there are help descriptions and starter tutorials/threads etc to get you through the initial shock of having a lot of functions and options, just as much as I still keep learning ways to tweak it sometimes to set up and eek out high-end performance, plus it has a very active improvement program based a lot on user feedback. It seems to have a fan base here based on reading a few threads (which can provide the quickest way to appreciate how people are using it for amplifier assessment).
There are also a few vintage distortion analysers that are getting restored and tweaked, if you are in to analog electronics - many threads on helping get those instruments working again, but in general they are manual and so may not suit depending on what you want to test and display, and what lower level of noise floor and distortion you want to test down to.
You could also by an AP test system.
Just my 2c.
Similarly there are many threads on different software being used. I can only really suggest REW as I have used that over the last few years - as a software product it has a lot more range of applications than most other software, as it has a main application related to speaker and sound system assessment. There is a website and user forum, and it is freeware so no cost if you decide to use something else or don't want to donate. But given its wide functionality, it is a detailed technical tool, so there are help descriptions and starter tutorials/threads etc to get you through the initial shock of having a lot of functions and options, just as much as I still keep learning ways to tweak it sometimes to set up and eek out high-end performance, plus it has a very active improvement program based a lot on user feedback. It seems to have a fan base here based on reading a few threads (which can provide the quickest way to appreciate how people are using it for amplifier assessment).
There are also a few vintage distortion analysers that are getting restored and tweaked, if you are in to analog electronics - many threads on helping get those instruments working again, but in general they are manual and so may not suit depending on what you want to test and display, and what lower level of noise floor and distortion you want to test down to.
You could also by an AP test system.
Just my 2c.
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Joined 2008
Thank you Trobbins,
we already use REW (along with Omnimic V2 for frequency response measurements and for measuring caps and coils etc)
Please add anything that might be helpful.
(please make it easier for me - i am working on cad , cam software, designing in 3d, also cnc milling mdf- thick plexi- corian- aircraft grade aluminum - i read a lot but i dont have a lot of time any day of the week and i want to check audio amplifiers' outputs before connecting them to speakers or buying them)
we already use REW (along with Omnimic V2 for frequency response measurements and for measuring caps and coils etc)
Please add anything that might be helpful.
(please make it easier for me - i am working on cad , cam software, designing in 3d, also cnc milling mdf- thick plexi- corian- aircraft grade aluminum - i read a lot but i dont have a lot of time any day of the week and i want to check audio amplifiers' outputs before connecting them to speakers or buying them)
The DDS signal generator at $20 is hard to pass up. I ordered one. However its distortion is not that low. The review I found indicated around 1%. Review: JOY-iT JDS6600 DDS Function Generator - page 2 - p 20478 | Elektor Magazine I have an HP generator that cost 100X as much new that's no better.
I have a 1013D and can recommend it.
RE using a sound card as an oscilloscope- It works but you need to protect the card inputs and they will get fried by an amp if you don't. You could get Jan's Autoranger to address the input limits. The Focusrite Scarlett seems to be a good value in USB sound interfaces that works well.
The go-to software for audio hobbyists are REW and ARTA.
While the PC option is good I would find even the cheap scope I recommended more useful for troubleshooting and basic testing. I would use a soundcard as a source. This P601PC Sound Card Oscilloscope Spectrum Analyzer Probe (audio) | eBay or this P601PPC Sound Card Oscilloscope Spectrum Analyzer Probe (audio) | eBay will work with a soundcard they say. (I have no experience but it looks like they did some good homework.)
I have a 1013D and can recommend it.
RE using a sound card as an oscilloscope- It works but you need to protect the card inputs and they will get fried by an amp if you don't. You could get Jan's Autoranger to address the input limits. The Focusrite Scarlett seems to be a good value in USB sound interfaces that works well.
The go-to software for audio hobbyists are REW and ARTA.
While the PC option is good I would find even the cheap scope I recommended more useful for troubleshooting and basic testing. I would use a soundcard as a source. This P601PC Sound Card Oscilloscope Spectrum Analyzer Probe (audio) | eBay or this P601PPC Sound Card Oscilloscope Spectrum Analyzer Probe (audio) | eBay will work with a soundcard they say. (I have no experience but it looks like they did some good homework.)
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Joined 2008
Analyze_it, perhaps you could clarify specifically what you know are the tests you want to be able to perform to be confident with the task at hand.
For example, if you are 'on the road' and get offered an amplifier to buy, then are you just aiming to buy eg. solid-state amps - in which case turning it on and checking each output for DC offset is perhaps the simplest first test, then you may have other first-in tests you want to perform likely crackly pots or inputs/channels that just don't pass signal at all, or .........
With respect to connecting an 'unknown' or 'just repaired' amp to a speaker then would you not just use a beefy guitar speaker as a test load, or do you have other concerns like unconditional stability, or do you have amp specs and want to confirm the performance against spec .....
For example, if you are 'on the road' and get offered an amplifier to buy, then are you just aiming to buy eg. solid-state amps - in which case turning it on and checking each output for DC offset is perhaps the simplest first test, then you may have other first-in tests you want to perform likely crackly pots or inputs/channels that just don't pass signal at all, or .........
With respect to connecting an 'unknown' or 'just repaired' amp to a speaker then would you not just use a beefy guitar speaker as a test load, or do you have other concerns like unconditional stability, or do you have amp specs and want to confirm the performance against spec .....
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Joined 2008
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Joined 2008
Trobins i would like to:
1. Be able to get a Harmonic distortion graph. Then i will be able to measure the volts from the output and know the output wattage for that specific distortion.
2. Be able to get a sine / square wave at various output voltages
3. Be able to compare left and right amplifier output channels (see a sine wave or square or thpd) at the same time and under exactly the same conditions on a screen.
please share links with the best vfm oscilloscope/sound card/anything else in your opinion.
Many thanks for your time!
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Joined 2008
If you want to look at THD at 20kHz, then you will need a 192kHz soundcard, to capture the harmonics. For example a Focusrite Starlett. I have not tried it but people seem to like it. If however a 24kHz or 48kHz bandwidth suits your needs, then you can get plenty of used 96k or 48k USB soundcards at very cheap prices, especially from musicians. The balanced inputs are a plus.
I used to use an E-MU 0202 USB, but it is very noisy, and the switching converter is next to the headphone/line output, which means it outputs a generous quantity of HF noise from the switcher.
You could use the motherboard audio, on laptops it is usually abominable but on desktops Intel HD audio is not too bad, but if there is a regrettable incident, it's much cheaper to fry a USB soundcard.
I used to use an E-MU 0202 USB, but it is very noisy, and the switching converter is next to the headphone/line output, which means it outputs a generous quantity of HF noise from the switcher.
You could use the motherboard audio, on laptops it is usually abominable but on desktops Intel HD audio is not too bad, but if there is a regrettable incident, it's much cheaper to fry a USB soundcard.