Need advice on Audio Electronics Lab Setup - Page 1
Forum section: electronics / beginners

author: GameProgrammer79
author_rank: Contributor
timestamp: March 12, 2016, 02:34:29 am
content: Hi All,Lately I have been watching a lot of eevblog videos on youtube.. precisely about 3-4 years now.. been a fan of Dave. I did my graduation in electronics engineering almost 13 years back but I have been working in banking finance as a expert programmer since graduation. I have lot of interest in electronics, have done a lot of small projects mostly Analogue / RF stuff, I quite enjoyed them as well as it was so involving I think I was and I am now very much interested in electronics.I have been thinking of setting up a small electronics lab lately to pursue my hobby as well as getting back to my electronics R&D roots. I want to research on digital audio amplifers, low noise and hi-fi amplifiers..I have following equipment in my list .. pls suggest some good models and brands for themElectronics Lab project==============================1. 2 Digital Multimeters2. Oscilloscope - MSO 50 Mhz or more 4 channel3. Spectrum analyzer4. Function generator5. Power Supply - DC6. Soldering workstation7. Data acquisition for doing wave form comparison8. FPGA evaluation boards - zync or so9. ARM Cortex evaluation boards - from mediatec or likes10. Adruino ?? Raspbery PIs ?? Hard Kernel ??11. Any thing extra like specialist measurement equipment for audio signalsI want to read Audio from inputs, spdif, toslink, usb, wifi, internet through a ARM processor. Run various DSPs on the digital signal - both software and hardware (FPGA), use FPGA for PWM and generate Analogue audio signals from PWM..Any suggestions will be welcome.. thanks

author: uncle_bob
author_rank: Unknown
timestamp: March 12, 2016, 03:08:26 am
content: HiOk, what you are looking for is way more than a audio setup.Start with the power supplies and DVM's (you will need multiples of each). Next for me would be a *good* soldering / rework setup. A scope should be next.I'd stop on the equipment at that point. Hopefully you would have:1) At least one hand held DVM that can be used for a whole lot of things (like fixing a light socket).2) A fairly good bench DVM, possibly surplus that has pretty good accuracy. Bopefully this has a data interface on it (serial / usb / ethernet / GPIB)3) Two or three variable supplies with full metering and adjustable current limiting. Somehow you need to be able to cover +/-12, +5 and 3.3 all at once. Those may not be the voltages, but the pattern is correct.4) An industrial grade soldering iron / station. It should last you >20 years so don't scrimp here. Get a good one.5) A scope with (probably) 100 to 200 MHz bandwidth and 2 to 4 channels. It should interface via USB and LAN.That's enough stuff to start playing with various boards and projects. I would wait on the rest until you have done some things. Items like programmer dongles should come before more test gear.What to buy and from who depends a lot on your local market. Here in the US, surplus is the way to go for power supplies. It's not as good a bet for a scope.Bob

author: jpb
author_rank: Super Contributor
timestamp: March 12, 2016, 10:01:55 am
content: I you're sticking to audio frequencies, a spectrum analyser is very expensive and probably overkill (also probably not optimised for low frequencies). I think a good quality sound card or an external one which will directly record A to D output combined with software would be cheaper and probably better.This might also fulfil some of the functions of the scope though a scope will be much better for probing circuits.I'm not an expert in this area but there have been several threads on the subject on this forum (you'll have to search for them as I can't locate them off hand).

author: EEVblog
author_rank: Unknown
timestamp: March 12, 2016, 12:03:39 pm
content: Quote from: GameProgrammer79 on March 12, 2016, 02:34:29 amAny audio lab is not complete without an Audio Precision Analyser

author: danadak
author_rank: Super Contributor
timestamp: March 12, 2016, 01:06:09 pm
content: A great scope for the price is the DS1054Z, Rigol. Can be hacked to 100 Mhz, see theforum for that info. Has FFT, Digital Filter, many more measurement capabilities, as wellas serial buss decode capabilities for embedded work. Use eevblog coupon.For FPGA, if you anticipate small FPGAs, consider Microsemi, Igloo series, small packages,low cost tools, low chip prices.Regards, Dana.

author: nowlan
author_rank: Frequent Contributor
timestamp: March 12, 2016, 01:55:20 pm
content: https://www.eevblog.com/forum/projects/analog-disovery-as-audio-analyzer/analog discovery maybe useful?

author: Richard Crowley
author_rank: Super Contributor
timestamp: March 12, 2016, 02:18:27 pm
content: Quote from: EEVblog on March 12, 2016, 12:03:39 pmIndeed. And an audio analyzer like an AP would seem an order of magnitude more import and more useful than a "spectrum analyzer" (which typically implies something for RF frequencies).But without a more focused objective it is not clear what your intent is?

author: GameProgrammer79
author_rank: Contributor
timestamp: March 12, 2016, 07:28:54 pm
content: Quote from: uncle_bob on March 12, 2016, 03:08:26 amHi Bob,Thanks for the replies.. yes I agree my small lab equipment list is a bit over kill for audio frequencies .. however it is always good to start with small number of equipment and see where I end up. My project has a lot to do with software / dsp space a well as electronics as audio amplifier electronics - mechanical (speakers) is a classical non linearproblem, solving those require a lot of computation. I will try to source auxiliary power supplies from ebay. That's a good suggestion to have 2-3 power supplies. Also DVMs I will try to get a bench top version.Sanjit

author: GameProgrammer79
author_rank: Contributor
timestamp: March 12, 2016, 07:37:04 pm
content: Quote from: EEVblog on March 12, 2016, 12:03:39 pmThanks for the information .. yes a AP is quite something I might require as well. I didn't know about APs.. I will check them out. Probably it will be a bit overkill at the moment if they are expensive however I have to go through features/functionalities of a AP.I was thinking of measuring sound response of a speaker using optical techniques - build my own audio response analyzer using a simple data acquisition device and my ownIdea is to measure how accurate the sound output is when compared the digitally sampled original audio file. Do you know of any such device which will measure vibrations in frequency time domain ?

author: GameProgrammer79
author_rank: Contributor
timestamp: March 12, 2016, 07:44:28 pm
content: Quote from: nowlan on March 12, 2016, 01:55:20 pmquite useful.. really it is some thing I would want.. thanks.

author: jpb
author_rank: Super Contributor
timestamp: March 13, 2016, 07:08:15 pm
content: Quote from: GameProgrammer79 on March 12, 2016, 07:37:04 pmIsn't this just a microphone (or rather microphones) and an A2D? Though what you measure will depend on the setup. What is really needed I guess is an Anechoic chamber :https://en.wikipedia.org/wiki/Anechoic_chamberOtherwise you can measure what drives the speakers as a signal but that is not the same as the sound produced.

author: Audioguru
author_rank: Super Contributor
timestamp: March 13, 2016, 07:19:04 pm
content: I used the outdoors as an anechoic chamber. The speaker was laying on the ground or on a small tall table pointing straight up to the microphone hanging above it in a tree. No echoes if the tree trunk is narrow and there is no building nearby.

author: jpb
author_rank: Super Contributor
timestamp: March 13, 2016, 07:47:11 pm
content: Quote from: Audioguru on March 13, 2016, 07:19:04 pmDidn't you have problems with wind noise? It is not an area I've ever worked in, but my experience of using a video camera is that microphones don't like even small amounts of air movement - though my kit was never very sophisticated.

author: GameProgrammer79
author_rank: Contributor
timestamp: March 13, 2016, 08:38:20 pm
content: Quote from: jpb on March 13, 2016, 07:08:15 pmMicrophones are not perfect i.e. if i record the sound using microphone and compare it with audio signal it will add another complex system (microphone) into the equation which I want to avoid.Below is an illustration of how many complex non linear systems are involved in audio (CS stands for Complex System)Digital Audio ----> Amplifier (CS1) ----> Speaker (CS2) ----> Room (CS3) ----> Human ear (CS4)Probably the best comparison can be done by removing CS3 and CS4, and introducing a new complex system Microphone (CS5) in anechoic chamber, or may be an altogether different way to measure output. The idea is that every electric or physical device has its unique frequency-time and amplitude-time response which is non linear and complex. In amplifiers we get harmonic, same we have in speakers as well, a resonant frequency and harmonics.

author: uncle_bob
author_rank: Unknown
timestamp: March 14, 2016, 01:31:33 am
content: Quote from: GameProgrammer79 on March 13, 2016, 08:38:20 pmHiWhich is why people sell calibrated microphones. They are surprisingly inexpensive.Bob

author: BobbyK
author_rank: Regular Contributor
timestamp: March 15, 2016, 02:55:50 pm
content: Quote from: GameProgrammer79 on March 12, 2016, 02:34:29 amI had a little bit of a DejaVu when I read this (EE -> Programmer -> 13 years later back to EE -> Audio!!!). I have been busy designing and building my own preamps, power amps, etc. in the last few years. I also build and test plenty designs from others, and I know a guy who knows a guy with an Audio Precision setup, so if I'm really curious about measurements I go to him, otherwise, I just enjoy the sound coming out of those circuits!So here is what I find extremely useful:1. 700 VA+ Variac, spend extra and get an isolated one (though those are harder to find). For any power amp work you will need one.2. Oscilloscope - the Rigols with big screens will do. Bear in mind, even though Audio frequencies are low, you will be doing Power supply debugging, digital debugging, etc. And you will be trying to catch plety spurious stuff once you get into circuits with lots of opamps, feedback loops, etc. So bear that in mind when choosing a scope.3. I have 4 multimeters, but I wish I had 10 sometimes! Setting circuit biases, nulling offsets, etc. becomes a joy when you have all the multimeters right in front of you. I'm a big fan of the Brymen BM867s.4. You will need a good low-noise function gen - I have a few Analog Wavetek's, and even though their frequency accuracy or THD isn't that good, they are pretty good when it comes to less noise and higher harmonics.5. I don't have a Spectrum Analyzer. A friend of mine who actually designs and sell audio amps, has one - and he only uses it to check EMI, never for any audio stuff, so that should not be neccessary for a hobbyist.6. DC power supply: Don't even try to get a bench supply that can feed big amps. Get a couple of dual tracking presision low-noise supplies with lower currents to drive your sensitive circuits. For the power stuff, you will need to build you own supplies, so set aside some money for enclosures and toroids and caps!7. FPGA's, DSP chips, etc. have a high barrier to entry. We used Alteras back in uni, but it's all getting so complex nowadays...I try to stay away from them, and they tend to be very pricey, so it's easy enough to stay away! On the other hand, manufacturers of DSP chips, Amp chips, etc. do have evaluation boards, and a lot of times, they give you the basics, so you can just go in there and hack their board to do what you want it to do. Look at the "development tools" and search for audio related stuff at mMouser.com e.g.8. Microcontrollers: I love the Cortex F7 board (STM32F746G-DISCO). Has some good audio possibilities and a nice big touch LCD, drivers, and software too. Check out the specs. Comes to about 50 bucks on Mouser.9. Soldering station: I am very happy with my HAKKO FX888. Got a bunch of different tips back in the US (hard to find in europe, middle east,...) and it is serving me well.10. Don't forget to buy a good set of monitors/speakers, and possibly a good amp (if you are not planning to make one yourself. It will increase the joy you get out of your hobby by a whole lot! Any good brand that looks solid and weighs a lot should do (Don't laugh, I weigh amps and speakers before I even listen to them - so far it's been a better measure of quality)That was my 2 cents - hope it helps.

author: MrSlack
author_rank: Frequent Contributor
timestamp: March 15, 2016, 03:30:16 pm
content: Writing lists and collecting tools is fun but using them is more fun. All the audio stuff I've done, which has been a lot, has been on a shitty old analogue scope, dual rail bench supply, couple of DMMs and a sound card. The latter is a pretty good tool for signal generation and analysis I.e. THD measurement etc. Unless you're throwing money into building a product, forget all the fancy stuff.

author: Richard Crowley
author_rank: Super Contributor
timestamp: March 15, 2016, 05:32:08 pm
content: I completely concur with @MrSlack.Unless your interest is limited to assembling a nice-looking lab, start working on projects of interest and let genuine need motivate your equipment/tool acquisitions.