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How can I take (simpler) measurements like what Amir does?

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#1
Obviously, Amir has an incredible testing setup. I have no illusions of coming close to that level of accuracy. But, for my own enjoyment and experimentation, I would like to be able to take some general measurements of things like power draw, distortion, etc.

I'll take any advice or suggestions you may have. I'm willing to spend a bit of money, but not multiple hundreds of dollars.
 
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#2
Something like Picoscope will allow you to play with measurements and FFT. But don't expect anywhere near the accuracy of Amir. You won't be able to come anywhere near close to the -140dB he regularly measures.

https://www.picotech.com/oscillosco...J-fSLX0aw0MBNytG3ITIST2-bCQKcLlwaAi16EALw_wcB

EDIT - having just read the specs - 12 bits of resolution, and 4mv sensitivity means the noise of any decent kit is going to be unmeasureable with that.

I think anything capable of 16 bits or more, and 10uV (-100dB) is going to be outside your price range.
 
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Thread Starter #3
Something like Picoscope will allow you to play with measurements and FFT. But don't expect anywhere near the accuracy of Amir. You won't be able to come anywhere near close to the -140dB he regularly measures.

https://www.picotech.com/oscillosco...J-fSLX0aw0MBNytG3ITIST2-bCQKcLlwaAi16EALw_wcB
Thanks! I will explore that. Like I said, I don't expect to get anywhere near his readings. Ballpark figures, and especially being able to compare pieces of gear I have with the same relative accuracy would be plenty.
 
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#5
You have to be careful with power measurements unless you have a dummy load. You can fry a 100W speaker with a 100W amplifier and constant test-tones, especially the tweeter. Typically you measure voltage (across a dummy load) and then calculate power based on resistance. (Power = Voltage squared/Resistance.)

Distortion is pretty hard to measure unless it's terrible. You CAN see clipping on an oscilloscope.

You can probably measure noise but the random nature of noise may makes it difficult to measure in a meaningful way.

With most electronics frequency response is flat and you might not be able to measure it accurately enough to see a difference. Speakers have plenty of frequency response deviation to measure but of course room acoustics affect any measurements. (You can measure speakers outdoors.)
 
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#6

Doodski

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#7
One could purchase a multimeter that can do at least 10 Amps current draw, a good range of frequency response from the meter and then look for more test gear. For distortion and such you'll need electronics devices for that. Probably at least $300+ for anything decent for hobby'ish hardware and software. Secondly most peeps usually buy a O-scope before a FFT setup or sometimes both at the same time. I suppose you can skip the whole O-scope thingy but maybe you'll be missing things along the way.
 
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Thread Starter #8
One could purchase a multimeter that can do at least 10 Amps current draw, a good range of frequency response from the meter and then look for more test gear. For distortion and such you'll need electronics devices for that. Probably at least $300+ for anything decent for hobby'ish hardware and software. Secondly most peeps usually buy a O-scope before a FFT setup or sometimes both at the same time. I suppose you can skip the whole O-scope thingy but maybe you'll be missing things along the way.
I have an analog scope I picked up cheap to mess around with. Can I do anything useful with it, or do I need a digital unit capable of FFTs?
 
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Thread Starter #9
You have to be careful with power measurements unless you have a dummy load. You can fry a 100W speaker with a 100W amplifier and constant test-tones, especially the tweeter. Typically you measure voltage (across a dummy load) and then calculate power based on resistance. (Power = Voltage squared/Resistance.)

Distortion is pretty hard to measure unless it's terrible. You CAN see clipping on an oscilloscope.

You can probably measure noise but the random nature of noise may makes it difficult to measure in a meaningful way.

With most electronics frequency response is flat and you might not be able to measure it accurately enough to see a difference. Speakers have plenty of frequency response deviation to measure but of course room acoustics affect any measurements. (You can measure speakers outdoors.)
I've taken a voltage measurements out of my amplifier playing test tones, then used the impedance graphs available for my speaker to estimate the impedance at that frequency and calculate power.
 

Doodski

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#10
I have an analog scope I picked up cheap to mess around with. Can I do anything useful with it, or do I need a digital unit capable of FFTs?
The O-scope is handy for analogue and digital circuitry. If you want to measure like @amirm then you need FFT. The bright side is that you only need it for audio frequencies and maybe up to 100KHz. A quick look indicated to me that the bandwidth of the FFT measuring device is going to be critical. Some of the FFT units don't have low frequency bandwidth. I have no idea what kind of budget a FFT device will expense to you.
 
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Thread Starter #11
The O-scope is handy for analogue and digital circuitry. If you want to measure like @amirm then you need FFT. The bright side is that you only need it for audio frequencies and maybe up to 100KHz. A quick look indicated to me that the bandwidth of the FFT measuring device is going to be critical. Some of the FFT units don't have low frequency bandwidth. I have no idea what kind of budget a FFT device will expense to you.
I don’t know what they cost, so I don’t to sound like a rube, but realistically my budget for gear like this is a few hundred dollars.
 

Doodski

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#12
I don’t know what they cost, so I don’t to sound like a rube, but realistically my budget for gear like this is a few hundred dollars.
I would start viewing YouTube reviews and explanations of newer O-scopes with FFT stuff built in. Otherwise I'm guessing it'll be used gear at that price range.
 
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#13
So this is their high res version still with only 96db of dynamic range, and costing nearly £1000 (the low cost models only have 52dB)

https://www.picotech.com/oscilloscope/4262/picoscope-4262-specifications
Any decent oscilloscope is going to be expensive because it needs to handle high-frequency applications. This has a 5MHz bandwidth, but you only need 50kHz for audio.

If you want to do measurements on the cheap, get a good audio ADC (like the new E1DA Cosmos) and analyse stuff in REW or RMAA. As @DVDdoug said, the dummy load you use is important as well, a reliable 300W 4ohm resistor is going to cost you around £30.
 
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#14
I don’t know what they cost, so I don’t to sound like a rube, but realistically my budget for gear like this is a few hundred dollars.
Most of the cheap USB digital scopes (like the picos I've linked above will do FFT (because it is done by the software running on your PC). What is crititical is the sensitivity, accuracy, bandwidth of the analogue measurement system, and the ADC.

Though if you search you might find entry level audio analysers that do a better job of specific audio applications.
 
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#16
Any decent oscilloscope is going to be expensive because it needs to handle high-frequency applications. This has a 5MHz bandwidth, but you only need 50kHz for audio.

If you want to do measurements on the cheap, get a good audio ADC (like the new E1DA Cosmos) and analyse stuff in REW or RMAA. As @DVDdoug said, the dummy load you use is important as well, a reliable 300W 4ohm resistor is going to cost you around £30.
That is a good shout. $150 for an ADC, plus REW will provide a lot of interesting information. Plus I could use that to digitise my vinyl ;)
 

Rick Sykora

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#19
I was looking to do just what you want (actually a bit more) and @NTK suggested QuantAsylum a couple of years ago. I bought a QA401 and am very pleased. The advantage it has is an ecosystem built around doing audio measurements. The software and support make it much easier than buying more general equipment and figuring out how to do each measurement. Have had a few digital scopes in my Amazon watch list since then and have not found a reason to purchase one yet! :cool:

That said, it is a $500 price of entry and, unfortunately the QA402 software still appears to be playing catchup to the QA401. While I have not tried, another comparable product is TrueRTA from TrueAudio. It has a lower cost that might be a better fit for you too.
 
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Thread Starter #20
Thank you all, this is exactly what I was looking for! The ADC route seems promising.

I am a big fan of used gear, and have had much success on Craigslist. If I am looking at digital scopes, what is/are the key things I should look for to determine suitability?
 
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