Everything You Always Wanted to Know About Audio Electronics (But Were Afraid to Ask) May 30, 2012 12:45 60 Comments

What do the different amplifier classes mean? Why is class-A supposed to be desirable?

-Matt from Texas

What parts are most/least to susceptible to heat damage from soldering?

What troubleshooting process do you recommend when your PCB-based project isn’t working?

Could I build a multichannel dropsnake with cat5 without having to do any programming?

I live in the shadow of FM and AM radio towers. What can I do to keep them out of my speakers, pre-amps, and audio interface?

What should we be using for power conditioning in our small home studios? Are there any good solutions that are cost effective?

Is there really a difference with NOS and Chinese transformers in terms of sound color, or is it just a myth?

I meant to say transistors ^

Well, if no question is too dumb to ask: Can you help me understand ground a little better? Why do parts of the circuit, in a guitar pedal for example, go to ground?

How should I ground and shield inside the box? (Preamp, compressor, eq)

The differences between LC and RC filters?! The theory behind how they work and what I can achieve with one or the other and what their typical applications are. Thanks!

What are the best ways to keep yourself safe when building or repairing tube equipment?

What is star grounding and what is the best way to reduce hum in a tube amplifier?

Can you recommend a good textbook/web resource for learning electricity & magnetism, preferably with practical applications to audio circuits, particularly tube amp design? It seems like most resources I find either assume deep knowledge, or they skip the physics all together and read like cookbooks. Thanks.

For cheap/home audio setup’s, Why today we need c.XX telephone’s patch to drive our old analog gear audiomatrix ?. Now Are there IC’s for this, that can be programmed and can work with analog audio without degrading the signal ?

What happeneds to the Q or bandwidth in a swinging input eq topology. How could one explain how that effects the coloration/sound/summing of the eq bands. In curious about swinging input eq in general.

Do some 51x modules use both the 24 and 16v rails? And if so does this count as ‘2 modules’ to the draw on a 51x power supply? What is a good way to test the totals draw of modules in a 51x rack?

Can you recommend any resources which discuss analogue circuit design with a view to audio? i.e, pairing resistors and capacitors to create filters, why that works, audio balancing, audio/electronic earthing, and so on.

how do you know if a device such as a mixer or preamp needs recapping?

Can you clarify and explain the correlation between audio frequencies & amplitude, and their electrical counterparts current, voltage, and resistance… In other words what does a change in resistance, current, or voltage do to sound waves.

What do you think about Discrete Electronic components like Forsells Opamps instead of a low-noise Chip OPA like 2406 from TI ?

Is that just a myth or maybe insignificant to use so expensive components ?

Beginner question: When I plug multiple outputs (headphone, speakers, etc.) into a single input (an iPod, for example), the levels all drop. Worse yet, if I turn one of those outputs off, it seems to ground the audio signal, causing severe degradation on all the other outputs. My question is: How can I distribute a single audio source to multiple outputs without degrading the audio?

Like Jesse and Loki, I am also looking for a resource for learning/teaching basic electronics. Specifically, I hope to find something that discusses the basics of electronics but also the basics of DIY electronics (tools, soldering, safety, ground, etc). Thanks, I look forward to hearing the podcast

What’s the simplest way to make a noise electronically?

What is a great mid range (price) stereo equalizer for all around use in a small music studio?

I’ve found I love my Vari-Mu and Chandler Limited TGII. They are worth every dime I spent however I am hoping not to cough up as much dough on an equalizer. Being that I have those goodies and more in the chain is it worth getting an EQ on the same level (2k+) or is there room the cheap out? And or can you recommend a non 500/500x kit I could build

When I have an oscillator set up, do I need to run that through an amplifier circuit or is it just good to go to make some sweet squarewave goodness through my nearest speaker/guitar amp?

Ive always wondered about the different reference levels in professional audio. How are they defined, how to they correlate? how do i best translate from one to the other? Im talking: Mic -> Instrument -> Line (-10) -> Line (+3) -> …
Where do consumer electronics headphones fit in?

Similarly, how to differentiate between the different decibel definitions as dbA, dbC, and so on.

What an easy/affordable DIY (or purchase if it’s cost-friendly) headphone amplifier?

@newman, check out Grado DIY headphone amp.. How can I find an entire home electronics video course? YouTube?

What do you think the top five safety rules are when building audio gear , whether tube or solid-state?

How close do you think it is possible for DIY’ers to come to replicating the sounds of vintage processors? Can the 1176’s, 1073’s, Pultec’s, etc, that can be built today really be sonically identical to the originals if built carefully? What components are most important in achieving this?

There is a website that has a bunch of super old but useful audio electronics books in PDF format. I am currently reading a 3 part book series called Basic Audio by Norman H. Crowhurst. None of the resources there are up to date, and I don’t feel any one of the books answers all question. However it is a good place to start. I THINK this might be the site I got them from… but am not 100% sure. http://www.tubebooks.org/technical_books_online.htm

Identical is near impossible but could be achieved for the most part. Most of the DIY for these projects are not exact clones but are based on the circuits. There are some “clone” projects. I know the LA2A projects are supposed to be pretty much an exact clone. The most crucial components to achieving the same sound are the transformers. However opamps, photocells (for la2a), and what not are also important. If you want to be faithful to vintage designs you could also use NOS tubes in tube projects. Also part of certain units sounds are the fact that they used resistors with large tolerances like 5%, where as most new resistors are rated anywhere from 2%-1%. Also over time a lot of the values shift as the components get old (from what I understand) adding unique coloring.

I don’t know a top 5, but I can give you a top 2. If you plug in the gear to test it… Wait a good half an hour or longer before you try and handle the tubes, or any large capacitors (especially the ones in the power section). Also another one might be to make sure everything is grounded before you try plugging anything in, and make sure there are no loose wire connections. I am sure there are more, but those few will helpfully save you from death by audio.

I can speak from personal experience. Transformers are probably the most important in terms of coloration of the sound. NOS isn’t as important as just a well made transformer. There are great transformers from Jensen, Cinemag, and Sowter. I did A/B tests when I did an Apex mod to both test the difference in the capsule and the transformer. I got a transformer from Peluso and it was wonderful. A BIG difference in the sound.

Someone else can probably answer this better than me. However I do know IC’s are pretty damn susceptible to heat damage. Resistors I have abused quite extensively along with capacitors, and they have always performed fine. I have removed, replaced, and reused resistors over and over again and they always worked.

Hey Henry. Do you mean either a relay cross-connect or a patch-bay. It’s a good question that shows a lot about a good signal path.

Grant: (and Roko)
Remember that these are for the Podcast coming out over the next few weeks. Also see that Roko corrected to Transistors for the NOS question.

From a technical point of view, Transistors age VERY VERY SLOWLY for the older ones (before about 2000) we’re talking centuries before you detect much gain or noise impact.

The difference is seen in the curves. There are very few Chinese doing the new parts. The biggies for new discrete transistors are Linear Systems and Central (who might actually source from China). Both are really great manufacturers. The real problem is that the huge variety available before the mid ‘90s made for lots of coloration due to the frequency response, very particular beta vs. op-point and a thousand variables. I personally always favor NOS over new parts because of the variety. a 2SK170 from Toshiba just doesn’t age. Coloration, though, is still for us to decide.

Try it and listen.

Cat5 is 4 twisted pairs, so you could get 4 channels if you have a balanced system. The balance (hum rejection) that a traditional snake gets is massive, as much as 120 dB at 60 Hz for a 30-60 meter run. Cat5 will not get you anywhere near this hum protection, but you might give it a try. It’s much less expensive cable than snake cable. Cat7 has individual shielding per pair, but it costs more. DO NOT put 8 channels on the 8 wires then use shield as the ground for a single-ended connection system. The twisted channels will cross-talk like nobody’d business.

But wait, there’s more:

This is not a snarky answer! If you mean a digital multichannel protocol, I’ve been slaving over this for quite a few years now. Sometimes for a paycheck, sometimes in IEEE committee, sometimes for love.

For a nominal service charge, I could do this for you. It’s about a $1,000,000, 5 man-year project to do it right. Can you fund me? This would be a hella DIY project.

If you’re up to the open-source, you might be able to get some AVB or RAVENNA to work. I don’t mean you write software, but you’d have to put your whole workflow into Linux. I think there are some MADI or other high-channel-count interfaces available. There might even be some AVB interfaces ready for Ardour, Rosegarden or Audacity.

So

First, you get a MADI or ADAT port on some rack or console.

Then you make a Synchronous-Ethernet transport converter. That will have the Cat-5 hole on the front side with the MADI or ADAT port on the other side. You’d have to go in the RSGMII side of a PHY chip without a MAC. This solution would not be switchable over routers and hubs, but that’s OK. Next we move to PTP (IEEE-1722 AVB) in the next release.

Google MADI or ADAT over Cat5 or Ethernet. Also, look for a firewire-over-ethernet box, but that would make for grotesque latency.

The details I outlined show why the big audio companies are mostly proprietary for gear hookup.

This is a really great question. Lots of the questions here are either directly about grounding or very closely related (radio stations, power conditioning and all that.) I’ll have a good discussion on grounding in the podcast that will start with basics like this and grow to things like shielding and case ground, etc.

This one’s a Ph. D. of circuits, functions and signals subject from start to finish. The swinging input EQ topology is (please, anyone out there correct me if I’m wrong) a so-called constant-Q configuration. I just checked out a classic, the API 553 and that’s a great example that is loved by all. So, this turns into the constant-Q vs. proportional-Q argument. I’ll spend a little time on this and other signal coloration issues in the podcast. The circuit topology question, however, will take a long off-line conversation that I’d love to start as a thread here if you’d like.

What audible impact does input/output impedance have on the connected equipment. The effect it has upon the amount of voltage transferred is clear, however a more comprehensive explanation on how impedance can alter the sound of interfaced equipment would be hugely appreciated.
Thanks!

Good one, we’ll cover that.

Noisyness, popping in particular. Also, you will sometimes see bias points off of normal.

This takes lots of living with numbers. I’ll go into this, because it’s really important for setting up a studio.

Subtle and grotesque, depends on the equipment and the cable. This is a good one. It comes along with levels as discussed above. I’ll spend some time on this.

I work for MOTU and am stuck on the assembly side of the building and want to get over to the engineering side of the building because I have so many great ideas for products and am extremely involved in the DIY community blogs and live on gearslutz and have gotten great suggestions for projects. My work is filled with every cap, resistor, diode, IC, AD/DA chip that we have ever used. What would you suggest for a beginner DIYer in designing a project. Is there a ‘go to’ book that you could suggest for designing analog circuitry? What should I be studying to get my foot in the door in engineering?

How can intermodulation frequencies problems be avoided with DSD 1-bit 5.6MHz audio signals for tube pre and amplification?

This is very general, but I would like to know more about ways that different components can get damaged so that I can take better precautions when building and have a bit more to go on when troubleshooting.

Super beginner.

Preamps and mixers. I’ve seen them on the ‘essentials’ list. But what does a preamp do that I can’t just post-edit in after I record with my mic? Why are they so expensive?

I record with my computer. Do I need to buy a specific type of soundcard; if so, what do you recommend? What type of mixer is optimal for computer recording?

How do I go about calculating a power supply needed for a DIY tube gear?
Or how to calculate what is needed for power supply?

Quick answer – amplifier classes are referring to the amount of the waveform that they amplify. ie class A is desirable because it amplifies 360 degrees of the waveform. class B is 180 degrees, and class AB is inbetween at about 181-200 degrees (plus push-pull operation) class C is only useful for radio freqs and not for audio due to its 100-150 degrees and class D is, i believe some type of digital using pulse-width modulation and is becoming quite powerful, i think Adams monitors utilizes class D amplification now even. ok ok, not the quickest answer

Why is there a photocell in te Sontec MEP250a??
is it wired for clipping? and does not use its photo-variable properties?
I am beyond new to this but can wrap circles around pros with my imagination
so don’t even try and stump me with your jimmy-jamber
and just give me the deets : :
Thank you : : aldeen – the ultra new uuu.fo et

Capacitors have been causing me headaches for a while now. In pedals for guitars, tone circuits for guitars, audio paths for pre’s, and so on, it always seems like folks go the extra mile to use film caps. Why? Isn’t a cap a cap a cap? Putting aside electrolytics for the moment, and voltage limits, why would anyone use one style (ceramic, mica, polyester, polypropylene) over another for audio purposes?

I love the cap, as a musical component, more than any other component (except maybe Ge transistors) There are differences for feelings reasons and for reliability reasons. I’ll cover this one when we get back to it soon. Check for the next Podcast.

It’s very hard to make a pop-free switch from EQ-in to EQ-out. The photo-resistor can be controlled to ramp its resistance up and down slowly and smoothly so it changes the contribution from the EQ without the hard pop of a mechanical switch.

It is in parallel with the mechanical switch and timed (the JFETs R/Cs and diodes driving the relay coil and lamp) against the relay. The relay is needed because photo-resistances can be noisy and can lead to gain inaccuracy because they aren’t precisely controllable values.

drop relay, Ramp in, re-connect relay … drop relay, ramp out, re-connect relay.
Do you hear two clicks from the box when you actuate the switch?

Hopefully neither jimmy nor jamber.

I’ve been away for a while, but I’m back now. Staying employed is tricky business sometimes.

Correction, there will only be one delayed click. The “open-circuit” is enforced by the photo-resistor (it can get up to more than 10 Meg when fully off) … sooo … going from off-to-on, there will be a delay in the relay to wait for the photo-res. In the on-to-off direction, the relay turns off immediately and lets the photo-res do the slow ramp to high resistance.

I have a USB Mixer (XenYX 302) and a solid state amp (Fender Princeton 65). I am wondering if this is possible: I would like to use the effects on the Princeton, without the Princeton outputting any sound. I would like the sound output to come from the mixer instead. Basically, I want to use my amp effects while listening on headphones or recording on a computer.

I heard on “The home recording show” podcast a episode on upgrading cheaper microphones to higher grade by changing components inside… can anyone point me to some current literature on the web on this issue? ….Oh damn… Im sorry, this is not a electronics question..

Attempting to hook up a older equalizer to an up to date ampreamp all in one. Havent the slightest clue as to how to get it done. There 3 components that will be running thru the amplifier. DVD player, 1980/90’s Pioneer eq, and a 50 inch Panasonic tv. Need help w/ getting the eq to work w/the rest of the components.