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Audio Tweaker's Wishlist - What do I need to build/maintain audio gear?

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Many makers and engineers got into engineering through audio. Whether it be building a guitar pedal or modding the power amp in your home theater, working with audio components is a fun way to use your engineering skills.

This wishlist presents some of the tools and parts you need for working with audio. Audio is a broad topic, so this wishlist is a general overview of analog audio components. We'll get specific in later articles.

Tools
For audio related building, here are some handy tools to have on your bench!

Oscilloscope
An oscilloscope is your best friend for audio work. They can be used to check frequency response, distortion characteristics, and everything other specification that is important to an audio signal.

Oscilloscope

Multicomp Pro Oscilloscope

Function Generator
Audio work is all about frequencies. A function generator sends different kinds of waves at different frequencies so you know if your build is responding the way you want it to.

 Function Generator

Multicomp Pro Function Generator

Multimeter
Multimeters are essential for every kind of electronics work; audio is no different.

Multimeter

Multicomp Pro Multimeter

Speaker Dummy Load
Since we can't use speakers for our testing, all that power needs someplace to go. A dummy load simulates a speaker in your circuit without blowing your head off with volume. A dummy load can be built with a high wattage resistor at the desired resistance, usually 4, 8, or 16 ohms for speakers.

Speaker Dummy Load

Vishay Dummy Load

Contact Cleaner
If you're repairing equipment that has scratchy pots, many times, a bottle of contact cleaner is all you need. Drip a little bit into the pot and exercise it; your noise issues will often disappear.

Contact Cleaner

Contact Cleaner  

Helping Hands
You've probably already got a nice soldering station, so we won't get into soldering equipment, but with any soldering project, because we don't have six arms ourselves, a set of helping hands is very valuable.

Helping Hands

Duratool Helping Hands

Components
Audio circuits use a wide variety of analog components to keep that audio sounding good.

Transistors
Transistors are typically used to amplify audio signals, and sometimes distort. Different types of transistors have different characteristics, whether they are BJT, MOSFET, JFET, or even silicon or germanium.

Transistor

Multicomp Pro Transistor

Potentiometers
If you're putting any kind of analog controls on your new creation, you'll likely need pots or faders.

Potentiometer

Bourns Potentiometer

Opamps
Opamps (operational amplifier) designed to amplify signals and there's a wide range, from large and discrete, like the vintage API 2520 (and its descendants), to surface mount. Opamp design has come a long way and newer opamps, like the AD797, boast near zero distortion and noise, although classic opamps like the TL072 and 5532 still offer great sounds in the right circuit.

Opamp

AD797 Opamp

Transformers
Transformers do a whole lot of things in an audio circuit; impedance matching, balancing, stepping up or down, etc. Because they only transmit audio signals, transformers also provide an important benefit: isolation.

Transformer

Hammond 119DA Transformer

Power Supply
Your opamps and transistors need to be powered, so chances are you'll need a good DC power supply. Op amps typically take somewhere in the range of +/-16V, while a discrete transistor based circuit might require a 24V supply. If you're making a microphone preamp that supplies phantom power, you'll need to supply 48V.

Power Supply

Delta 24V Power Supply

Connectors
To get your audio signal in and out of your circuit, you'll need connectors.

 

XLR Connector

Neutrik XLR Connector

Terminal connectors

Cliff 8-Way Spring Terminal

Speakers, Headphones, and Mic
Now the fun part! The most important tools for testing audio devices are your ears.  Speakers, speaker drivers, and headphones are the most important tools once you're ready to test your design. Fingers crossed that you don't get a blast of loud feedback when you flip the switch!

Trust powered speakers

Trust Speakers

Headphones

Koss UR20 Headphones


There are several different types of microphones – large diaphragm condensers, small diaphragm condensers, dynamics, ribbons, and more, all designed for specific purposes. We’ve selected a lavalier because it’s a tiny inexpensive mic that is convenient for testing on the bench.

Microphone

Pulse Lavalier Microphone

Parents

  • I've been interested in Audio for along time. My first real job was working for a company that made microphones, speakers and (for a short while) a HiFi amplifier and a tuner.

    I've still got a good collection of gear:

    Here are some of my favorites:

    There would have been some pictures but I've just encountered the image uploader  - is anyone able to tell me what the size boxes are for - the old one just took a jpg file and got on with it.

    No time to wrestle with it now Cry

    MK

  • in reply to michaelkellett

    This is a nice (and long since ceased manufacture)  general audio testing box. Pretty good low distortion perforamnce. (0.03% or better). The downside is that it doesn't talk to computers.

  • in reply to michaelkellett

    Picture didn't worK

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    sems to have worked this time !

    MK

  • in reply to michaelkellett

    I like this but haven't used it much since I got it.

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    It has GPIB so can talk to computers.

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    This is a nice simple and reasonably low noise and distorion audio oscillator.

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    This is the amplifier I worked on in the early 1970s. Probably not many of them left now. It would need a bit of work before using it.

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    I use these rather uncommon AR speakers for everyday listening. I bought them on Ebay for about £130 the pair. They still sound quite good, no idea how old they are.

    I have a home made very low distortion 2kHz oscillator (about -110db) that I use for checking ADCs

    I'd really like a nice low frequency spectrum analyser (1Hz - 100kHz)  but I think I'll need to make my own - very rarely see anything on the second hand market at a reasonable price.

    MK

  • in reply to michaelkellett

    Really nice seeing that HP Audio Analyzer, it brings back nice memories of my first job, for improving radio systems... I'd have to sit there all day tuning the radio to different channels (there were thousands - and repeat the tests whenever any modification is made, to see the impact) injecting audio tones and recording SINAD values (amongst other stuff). I also used the same instrument for testing audio handsets.. the competition had subjectively better speech sound, so we tried to look at the frequency response and see how it was different to our product. That instrument was quite fundamental for testing radio systems in general, since some tests can be framed as audio tests even though they are testing portions of RF functionality, for instance intermodulation distortion is easier to test by injecting audio, although the thing you're trying to measure is mainly the performance of the RF circuitry. Similarly SINAD, although an audio measurement, was really being used as a proxy to measure receiver sensitivity more than anything else.

  • in reply to shabaz

    No edit button : ( 

    I was also going to add, incidentally Matlab is also convenient for SINAD (reasonable to do SINAD with any sound card since typically that measurement is more used for speech and not audiophile-level).

  • in reply to shabaz

    Hello Shabaz,

    I powered up the the 8903 yesterday and initially i9t seemed to be working fine with loop tested 1kHz distorion at about -83dB. After a couple of hours I connected the Neutrik analyser and was amazed that it read about 0.3% distortion. I re-looped the HP and it agreed that the distortion had leapt up.

    This morning the looped THD was about 0.1% (-60dB) but  a bit unstable.

    Obviously something is wrong so I'll need to get inside the works - have other plans for this weekend so it will have to wait a while.

    MK

  • in reply to michaelkellett

    Oh, hopefully it's something trivial to fix. I've sometimes been lucky, and sometimes unlucky with ebay purchases. My unluckiest purchase so far was a mains power meter, which can't measure current : ( Whatever it's using (I think it's a sense resistor) is buried under a lot of metalwork and multiple board layout (and I think (can't recall precisely) a soldered screen that I'd need to remove around the ADC too) just to get to it, so it feels like a very major rainy weekend project : ( In the meantime the reason for getting it has reduced, so now I'm unlikely to ever fix it anytime soon : (

Comment
  • in reply to michaelkellett

    Oh, hopefully it's something trivial to fix. I've sometimes been lucky, and sometimes unlucky with ebay purchases. My unluckiest purchase so far was a mains power meter, which can't measure current : ( Whatever it's using (I think it's a sense resistor) is buried under a lot of metalwork and multiple board layout (and I think (can't recall precisely) a soldered screen that I'd need to remove around the ADC too) just to get to it, so it feels like a very major rainy weekend project : ( In the meantime the reason for getting it has reduced, so now I'm unlikely to ever fix it anytime soon : (

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