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what do you think of this oscilloscope?
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author what do you think of this oscilloscope?
EATyourGUITAR
thinking about getting a 4 channel scope that also has a logic analyzer and an arbitrary waveform generator all in one unit. I wanted to know if anyone has one or has played with one. I am open to suggestions from other brands but nothing $4000 please. as you already know, I do audio so I only need 20Hz to 40KHz. I need a good FFT that works in audio range. I also need rs232 rise times and packet decode + storage for work related stuff. the logic analyzer is needed but I could get by on only 8 channels. the generator is nice but not absolutely needed. I can just use a different test oscillator I already have.

https://www.tequipment.net/Instek/MSO-2204EA/Mixed-Signal-Oscilloscope s-(MSO)/
JohnLRice
EATyourGUITAR wrote:
thinking about getting a 4 channel scope that also has a logic analyzer and an argitrary waveform generator all in one unit. I wanted to know if anyone has one or has played with one. I am open to suggestions from other brands but nothing $4000 please. as you already know, I do audio so I only need 20Hz to 40KHz. I need a good FFT that works in audio range. I also need rs232 rise times and packet decode + storage for work related stuff. the logic analyzer is needed but I could get by on only 8 channels. the generator is nice but not absolutely needed. I can just use a different test oscillator I already have.

https://www.tequipment.net/Instek/MSO-2204EA/Mixed-Signal-Oscilloscope s-(MSO)/
Fixed ^ I think the URL wrapper doesn't like the parenthesis? hmmm.....

Here's the manufacturer's site for that scope:
https://www.gwinstek.com/en-global/products/detail/GDS-2000E
Mungo
Its a competitive market place around that price, many good models to pick from:

GW Instek MSO-2204EA
Siglent SDS2204X
Rigol MSO-5104
Keysight MSOX2024A
Rohde & Schwarz RTB2K

Shop around, decide on the important characteristics for you and pick one. None of them are awful! they're all such a leap ahead of older products that its hard to recommend buying an older scope these days.
cackland
Perfect timing as I’m in the market for an osc and curious as to everyone’s suggestions.

I was comparing this siglent and keysight models
Mungo
cackland wrote:
Perfect timing as I’m in the market for an osc and curious as to everyone’s suggestions.

I was comparing this siglent and keysight models
Depends on your specific needs, there are really good models around $1000 but they don't have all the features the OP wants.
Synthiq
EATyourGUITAR wrote:
I need a good FFT that works in audio range.

With only an 8-bit ADC, you will never get a great dynamic range, maybe around 50dB. Some oscilloscopes have an enhanced resolution mode at lower sampling frequencies that can increase the resolution to 11-12 bits which might improve the situation. But you will still get better results if using a PC with a sound card. I have used the free Visual Analyzer with (for me) good results. At least my oscilloscope can only display the FFT with a linear frequency scale and not a logarithmic one as I would prefer in some situations.
EATyourGUITAR
Thank you for pointing that out. I just looked up the specs. How bad is 8 bit really? If I have a filter and I want to quickly see what the corner frequency is, I have a built in sine sweep and a built in gaussian noise. My idea was to have less stuff on the bench. Consolidating a logic, a awg/afg, a scope, a fft, a laptop seemed like a good idea at the time. I would still need a 5.5 digit voltmeter and a decade box to complete the whole set of bench tools. LCR is not that important to me right now. I guess what you are suggesting is that this 8bit FFT might not be good for selecting flat white noise diodes?
Synthiq
8 bits are good enough if you just want to check white noise or checking the -3dB corner frequency of a filter but with 50dB dynamic range you can barely check 0.3% distortion for instance. With repetitive signals you may be able to use the average function to reduce the noise floor but it will be slower than the enhanced resolution mode that use oversampling to improve the dynamic range in a single sweep.

[Edit] Below is a FFT of white noise on my scope and as you can see there is a lot of amplitude variations between the frequency bins. If this is too much, some sort of averaging over many FFTs is needed to smooth the curve, but it's not something my scope can do but PC program can.

Mungo
Synthiq wrote:
EATyourGUITAR wrote:
I need a good FFT that works in audio range.

With only an 8-bit ADC, you will never get a great dynamic range, maybe around 50dB. Some oscilloscopes have an enhanced resolution mode at lower sampling frequencies that can increase the resolution to 11-12 bits which might improve the situation.
Dynamic range is comparing the largest to smallest signal you can measure, when a scope has 60dB of gain available in the front end you can extend the dynamic range for many measurements. But if you want to limit the dynamic range to a single capture then you're still overestimating the noise.

Measuring the noise floor of the 64k point FFT compared to a 20V peak to peak signal I see 67dB dynamic range, or 90dB in high resolution mode (for a signal with a known and limited bandwidth such as audio its hard to see why you wouldn't use that). Taking a longer FFT window as some of the scopes suggested can do it reduces the noise further.
Synthiq
Mungo wrote:
Measuring the noise floor of the 64k point FFT compared to a 20V peak to peak signal I see 67dB dynamic range, or 90dB in high resolution mode (for a signal with a known and limited bandwidth such as audio its hard to see why you wouldn't use that). Taking a longer FFT window as some of the scopes suggested can do it reduces the noise further.

Every time the length of the FFT is doubled, the noise energy in each bin is reduced by a factor of 2 so the noise floor is reduced by 3dB so the noise floor is only limited by the maximum length of the FFT.

Another limiting issue is the non-linearity of the ADC. When the ADC error is of the same order as the error in the signal you want to measure you can no longer separate the two, no matter how low the noise floor is.
weasel79
Hey i am also in the market for a DSO, and i was looking at the cheaper 500 EUR ish siglent/rigol 1104 series. Do i need 200 MHz bandwith for audio applications though? since all the recommended models in here seem to be that... i thought with audio frequencies only up to 24k, 100MHz should be more than enough?
i can live without the signal generator and don't really see myself doing a whole lot of logic analysing either...
Synthiq
weasel79 wrote:
Hey i am also in the market for a DSO, and i was looking at the cheaper 500 EUR ish siglent/rigol 1104 series. Do i need 200 MHz bandwith for audio applications though? since all the recommended models in here seem to be that... i thought with audio frequencies only up to 24k, 100MHz should be more than enough?
i can live without the signal generator and don't really see myself doing a whole lot of logic analysing either...

For audio, even a 50MHz scope is fine. The higher bandwidths are still useful if looking at digital signals where you want the oscilloscope rise and fall times to be significantly lower than those of the signals you measure.
wsy
Add OWON to your "look at these" list.

I have one (broke one, they replaced it with a *NEW* unit) and they are really sweet.

- Bill
Mungo
weasel79 wrote:
Hey i am also in the market for a DSO, and i was looking at the cheaper 500 EUR ish siglent/rigol 1104 series. Do i need 200 MHz bandwith for audio applications though? since all the recommended models in here seem to be that... i thought with audio frequencies only up to 24k, 100MHz should be more than enough?
i can live without the signal generator and don't really see myself doing a whole lot of logic analysing either...
The OP made some quite specific requirements, so the suggestions were matched to those. If your requirements are different you are probably interested in other products!
weasel79
Mungo wrote:
The OP made some quite specific requirements, so the suggestions were matched to those. If your requirements are different you are probably interested in other products!

Yeah of course i was hoping someone could enlighten me why these sepcific requirements might or might not be needed for general audio circuit testing. i guess i overlooked the part asking for a logic analyzer and stuff.
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