oscilloscope for audio (mostly guitar pedals) analysis? - Page 1
Forum section: electronics / testgear

author: vns
author_rank: Contributor
timestamp: June 18, 2020, 05:58:52 pm
content: Hi,first message here but I have been reading the forum for some time now.I am starting to get interested in modifying and creating circuits to use in guitar pedals, maybe one day I'll jump into amps too or even synthesizers. My knowledge in electronics is pretty limited, last time I touched an oscilloscope was 20 years ago when I was at the university.I would like to buy an oscilloscope, I think it is really useful to have one to see what's going on with the "sound" when it passes through the different parts of a circuit. But I would like to ask to those of you that are in the audio world, maybe building pedals and amps too, for some advice.First of all, I am not familiar at all with 99% of the features packed in a scope nowadays, so I don't know what stuff is a must, what would be useful, etc. The main uses I can foresee are 1) seeing output signal shape and comparing it to the source, 2) analyzing harmonics to see how the circuit affects them, 3) signal to noise ratio and 4) it would be nice to be able to generate a signal to nothing fancy, e.g. sin, 400mv, 1KHz...I don't want to spend much because this won't be one of my main hobbies, and of course I am doing this just for fun.I have been reading a lot about entry level scopes this week, but to be honest I don't really know what specs are really important for what I am going to do. At least I would like to have a couple of channels, but I could use 4 channels.I don't know if I should go to something super cheap and buy one of those portable oscilloscopes, dso213, ds212 (I don't like the UI much in these two), 1013d (not sure if this is better in that regard), etc. or if I should spend more in a Hantek, Rigol, etc.These are the "proper" scopes I've been looking and their prices VAT and shipping included (btw, I am located in Spain/Europe, so brands availability is also a factor):Hantek DSO5102P - 282.95€ (or 204.09€ sent from Spain in Aliexpress, so I guess I would avoid customs...)Rigol DS1054Z - 419.52€ (in Amazon, the seller is Rigol EU)hantek DSO4204C - 389.64€ (sent from Spain in Aliexpress)Hantek DSO4102C - 225.04€ (sent from Spain in Aliexpress)One thing that caught my eye is the super small record length in the Hantek scopes, not sure if this matters for my usage or not, or if there is a workaround....I would appreciate any help.

author: bob91343
author_rank: Super Contributor
timestamp: June 18, 2020, 06:57:16 pm
content: You will get the most bang for the buck and simplicity of operation if you pick up an old Tektronix unit of almost any age. Often they are even free, and most are overkill for your needs, complete with voltage calibrators and multiple channels.The only thing you mention that caught my eye was the word harmonics. Perhaps you would want to have a spectrum analyzer for that.Audio signal generators are cheap and easy to use. I have several oscilloscopes and audio generators, far more than I can ever use, and I'm sure many other hobbyists are in a similar situation.

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: June 18, 2020, 07:39:02 pm
content: Buy a Rigol DS1054Z, it's perfect for your needs. You can buy one fromBatronix for 339 Eurosand you can get another 6-7% off for being a eevBlog forum member.A search for "Riglol" will reveal a site that can generate the codes for you to upgrade it to a DS1104Z with all features enabled.

author: vns
author_rank: Contributor
timestamp: June 18, 2020, 07:42:38 pm
content: Can't FFT be used to measure harmonics in an oscilloscope? I've heard FFT in the Rigol 1054Z is bad, but not sure why.

author: DaJMasta
author_rank: Super Contributor
timestamp: June 18, 2020, 08:03:02 pm
content: They can, but oscilloscope digitizers are limited in their dynamic range (typically 8 bits, more with eres but at a reduced effective sample rate), so they generally aren't good for detailed audio work (about the minimum they can see is still above what's audible in terms of harmonic distortion and their frontend is often not that linear). The 1054Z and Siglent's 1104X-E are my go-to recommendations for inexpensive entry level scopes, but there are others that will work fine. It's worth mentioning that when dealing with audio, you can get a lot better detail and analysis out of a basic PC based sound card (internal or external) and some software than with a scope. A scope is still great for a lot of stuff, it's nice to have the standalone unit, and the extra bandwidth and capability could come in handy when looking for sources of noise or other troubleshooting, but if you want actual characterization of audio band stuff, there really is no better budget option than a sound card, not only that, it will also have an output channel for test waveforms.This topic comes up every week or two here on the forums, do some searching and take a look at what else has been recommended for audio types looking for a first scope.

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: June 18, 2020, 08:10:30 pm
content: I've done some audio preamp and pedal designs recently and used my newly purchased Rigol MSO5074 to do Bode plots to map frequency response of the audio circuits. The MSO5074 is $1,000 but you don't really need one unless you're doing design work.

author: vns
author_rank: Contributor
timestamp: June 18, 2020, 08:22:51 pm
content: Quote from: DaJMasta on June 18, 2020, 08:03:02 pmI have a couple of dedicated sound cards for music recording, I will try that way before purchasing an oscilloscope.

author: nctnico
author_rank: Super Contributor
timestamp: June 18, 2020, 08:24:46 pm
content: Quote from: vns on June 18, 2020, 07:42:38 pmThe FFT in that oscilloscope is very short so you won't get much detail. Hantek scopes seem so suffer from poor firmware.A device you should consider is the analog discovery 2. This has 14 bit (IIRC) ADC and DACs and software to do all kinds of analysis. Where it comes to dynamic range no oscilloscope can touch it.If you insist on buying an oscilloscope anyway then look at the lower end ones from Siglent which have bode plotting which allows to make a frequency response graph quickly. A cheaper alternative without bode plotting would be the GW Instek GDS-1054B. This is in the same price range as the Rigol DS1054Z but it has much better (more performance, 1Mpts FFT).

author: vns
author_rank: Contributor
timestamp: June 18, 2020, 09:23:04 pm
content: @DaJMasta Thanks for the tip about using a sound card.It turns out that my DAW, Reaper, has some tools for this purpose: signal generation, basic oscilloscope, frequency spectrum analyzer...And there are third party plugins with more capabilities, for now all this is going to serve me well

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: June 18, 2020, 10:40:00 pm
content: Quote from: nctnico on June 18, 2020, 08:24:46 pmReality is that, for a beginner in audio pedals, FFT will be meaningless to you - all it really does is show you frequency spikes showing the make up of a given signal. While Siglents do have slightly better FFT performance than Rigols at the $300 price point, for some reason nctnico always seems to have a bias towards GW-Instek gear; I admit I'm biased towards Rigol but that's because of problems I've had with other brands, especially Siglent.

author: nctnico
author_rank: Super Contributor
timestamp: June 18, 2020, 11:06:15 pm
content: Just check the specs / facts. The GW Instek GDS1054B wins versus the Rigol DS1054Z in every aspect. And with the price difference between them being minimal you'd be crazy to buy a Rigol DS1054Z nowadays. All the Rigol DS1054Z has is a huge momentum but other than that it is a seriously outdated piece of equipment.And me recommending GW Instek every now and then is also because the brand is often overlooked while they do have good & useful equipment in their line-up for a decent price.