Transistor Equivalents – old equipment restoration

Where to find transistor equivalents?

Restoring old gear can be a nightmare when it comes to some of the more obscure transistor types, and a pretty expensive exercise as well. Transistor equivalents for substitution is often a necessity when repairing vintage gear. This applies equally well to silicon devices and not just Germanium.

Years back we were confined to telephonic conversations or writing letters to the supplier, the snail mail variety.  In South Africa we are fortunate enough to have proactive suppliers in the electronics industry, unlike in the motor or metal industries where staff are still learning how to send emails, except if they see a big sale pending. Continue reading “Transistor Equivalents – old equipment restoration”

Electronic Circuits for Beginners

Electronic Circuits for Beginners - Prototyping

What to look for when starting out – Electronic circuits for beginners

What is the attraction behind electronics?  This is a sore topic in many South African circles chiefly because the architects of education are failing the academia, the principals and the teachers.  This in turn fails the learners, our future. This article, “Electronic Circuits for beginners” was written for grade 8 learners and in subsequent articles will hopefully add some value and direction to your schooling.  Education does not stop when you leave the classroom.

Electronic Circuits for Beginners - IoT
Electronic Circuits for Beginners – IoT – the spares box

Anybody whom loves reading should get a copy of the book “Elon Musk – How the Billionaire CEO of SpaceX and Tesla is shaping our Future” by Ashlee Vance.  Musk has all the makings of not just a great scientist and entrepreneur but a great leader.  He is regarded somewhat as an opportunist. Ditto Bill Gates and the gone but never forgotten Steve Jobs.

Electronic circuits for beginners – making a career choice Continue reading “Electronic Circuits for Beginners”

Soldering and Rework Stations and other Kit

Magnum Rework Station 3005

The best soldering iron and rework stations for the job?

Of course this is a commonly asked question and the reply will always be to get the best one can afford.  Most home users are now spending a lot more money on getting better quality soldering and rework stations to complete projects. Cheaper irons, the home store DIY project types are not designed for intricate electronic circuitry.

Weller WSD81
Weller WSD81

There is no thermal control, the stupid tips wear away after ten minutes of use and after an hour one can hardly pick the thing up because it is radiating more heat than Koeberg. So bottom line, get one for an emergency – it will only last a day.  Do not use it on CMOS or static sensitive devices, just for simple home wiring.

Weller, Antex and Magnum Continue reading “Soldering and Rework Stations and other Kit”

VU Meters Vs Bargraph

Volume Units and Decibels

My first peek at a Nakamichi was in Japan.  Sparse in detail, no flashing lights, VU meters or fluorescent displays.  Just so damned gorgeous. OK, then you have the PA-7, industrial strength, industrial looks and what a beauty. But if you one needs to really capture beautiful looking amplifiers, then look no further than the McIntosh range. Black in finish, blue lit VU meters.

Mcintosh MC2300
Mcintosh MC2300 – wiki commons awgrasso

So what to do if you need that really cool look and have a budget of a few ZAR?  Unfortunately VU meters, really good VU meters are not cheap. The question about where to source comes up often on the web and besides eBay where you may not necessarily get exactly what you are looking for, Meter Sales or Instrument Meter Specialties in the USA may be your answer. In South Africa the Model 543 is going to land at about R1 800.00 ex duties and VAT.  So make sure your amplifier is worth it.

The bargraph, long being favourite for many enthusiasts is your economical solution in most cases.  Why have a VU anyway if a bargraph is a better solution in many ways?  It all comes down to vintage. In the 50s, 60s, 70s and 80s most equipment was still analogue where the outputs were designed to be fed into an analogue recording device.  Analogue recorders are a lot more resilient to input overloads, in some cases even done deliberately. Not so with digital devices where the results are painful to listen to.  VU meters are very slow and don’t necessarily slot in well high with speed transients but they are brilliant for monitoring the average output amplitude.

VU meters with peak overload, monitoring the 0VU perimeter and making sure the VU meter is correctly calibrated is all part of your sound engineering experience. Continue reading “VU Meters Vs Bargraph”

Audio and consumer electronics – trends in 2017

Curved HDTV, Bluetooth and Sound Bars

Love it or hate it, Bluetooth is making a big comeback in the world of audio. Although Bluetooth never really left our shores it’s only with the iPhone 7 that we gather a lot more emphasis is being placed by certain manufacturers on either Bluetooth or Wi-Fi or both. (here it would be for BT earphones). Or maybe inductive charging?

Crystal Radio - Arnold Reinhold
Crystal Receiver:  Wiki Commons – Arnold Reinhold – Own work

Bluetooth is treated as a proprietary protocol because of licensing requirements,  Wi-Fi more for internet usage.  Wireless on the other hand, like Bluetooth can also be used for components to communicate with each other albeit at longer distances and at higher speeds, bandwidth allowing better imaging as well (stereo, quad etc). Continue reading “Audio and consumer electronics – trends in 2017”

Analogue Routing – patchbays and cables

Samson S-Patch Plus

Patchbays – routing your signal

Note:  This is a preliminary article and will cover the construction of a basic Arduino controlled patch bay/audio signal router.  Users should be aware that manufacturing a patchbay as a DIY project can and will will be very expensive. The Samson S-Patch Plus retails for between R2000 and R2500.00 in South Africa.  A parts B.o.M places this project at about R5 000.00. However, careful consideration of B.o.M (input types) and digital control will be infinitely cheaper than an electronic audio signal router off the shelf.

The Samson S-Patch Plus is remarkable in that it tidies up your flow,  gets rid of unsightly cables, is quick and affordable.  If you are like me you prefer to purchase pro series audio because it’s modular and often cheaper than commercial consumer integrated audio.  So you can throw away the parts you don’t like and only add that which you deem necessary and very importantly, have some control from the PC or laptop.

This comes at a price of course, spaghetti!  And if you are like the mechanic whose car never runs properly this spills down to never being able to find that missing plug or socket. To be honest, pro audio can be a nightmare.

Samson S-Patch Plus
Samson S-Patch Plus

Continue reading “Analogue Routing – patchbays and cables”

The ubiquitous 555 IC

And now for the world’s most famous IC – the 555 Timer

This Signetics – Hans Camenzend IC was not just a best seller but for electronics specialists possibly the most versatile chips of it’s time.  Possibly still is. What was most intriguing was that for any youngster just starting out in electronics, this was an experimenter’s dream.  It was low cost and with just a handful of components one could learn one helluva lot about oscillators (astable or free-running), bistables and monostables.  Of course it could be used for a lot more than just a police siren.

555 Timer Chip
                        Inside the Beast!    The 555 Timer Chip

Continue reading “The ubiquitous 555 IC”

Light Control – the DMX system

From LED flashers to DMX Lighting

Programmers starts with “hell world”. Beginners in electronics start with light flashers.  Arduino does too! Although we boast about this being an analogue sight be mindful of the fact that digital is with us and won’t go away. It has made things smaller, faster and more accurate.  Audiophiles don’t like the nasty little bits (pun intended) added in between but high end ADC and DAC chips really make a difference.  So we have this great sound system and now we want to party. Ever party without lights?

For the younger generation

Amplifiers, loudspeaker and loud music has always been around,  but lighting was primitive. Lights were manually controlled, sometimes by servo but the local church hall definitely did not have this – we had the coffee can approach, lowering, tilting and panning all done manually by possibly using draw wires or some or other trick. Digital?  Bah, that was for sissy’s.  Along came the heady 80’s and of course this was also around the time that manufacturers realised that a computer could be used for other things besides arithmetic and nuclear tests. This also around the time that United States Institute for Theatre Technology (USITT) wised up and cracked the code.

Chauvet Helicopter Q6
The popular Chauvet Helicopter Q6 – DXM controlled lighting display.

Before moving on I suggest you have a look at the Grateful Dead’s “Wall of Sound”, a marvel at the time and boasting the best sound system in the world. Have a look at some of the image files and think of what this might have looked like at midnight without any stage lighting? Continue reading “Light Control – the DMX system”

Total Harmonic Distortion meter

Hantek DSO

THD Meters – how they work

Many years back the must haves for anyone building audio equipment would have been the multimeter (DVM), oscilloscope and a function generator. With specialised audio test equipment falling in price over the last twenty years two other pieces of equipment are now also found on the test bench, the THD meter and spectrum analyser.  Indeed your laptop or desktop could be used for many of these functions but it can be cumbersome and/or inaccurate because of sound-card bandwidth limitations.

Hantek DSO
Hantek DSO – 1202B

The THD Meter is definitely a must have, even something for impressing one’s audiophile friends.  Consisting of an oscillator, internal or external, a notch filter to attenuate the fundamental to as little as possible and a voltage / instrumentation amplifier to drive the resultant combination of harmonics and noise to the output meter or video graphics display.

Block Diagram of THD Meter using Wien Bridge Notch Filter
Block Diagram of THD Meter using Wien Bridge Notch Filter

Interesting DIY angle to THD metering from “Wensan” – DIY Audio – Simple THD Meter

Robert Cordell,  American (as in USA) electrical engineer and expert in the audio field kindly publishes his high end THD Analyzer circuit on his website, Cordell Audio.

Analysing the Waveform – skirting the FFT

The analysis of signal waveforms is rather mystical to most of us and becomes a highly complicated mathematical subject when breaking a signal or rather batch of frequencies down to a function of time. FT, or Fourier Transform converts the waveform data in the time domain into the frequency domain each containing individual signals of phase, amplitude (magnitude) and frequency.

Modern computer software makes this previously time consuming and highly mathematical task accessible to the home experimenter using what is now commonly known as FFT or Fast Fourier Transform.

Digital Signal Processing

Digital signal processing in the modern computer has made decomposition of signals in audio a common discussion point on the forums, possibly not always in our best interests because of the complexity and hence confusion.

FFT and Nyquist are of interest to the engineer, especially now in the DSP domain where bit rates and sampling frequencies have become an integral part of our lives.

Our modern (and even older) hardware can run software for analysing and changing the audio signal – and sometimes it’s free. See Audacity and it’s features.

Shit in Shit Out

Technically speaking it is not probable that an ill designed amplifier using inferior components will sound good. 🙂

It is probable that with the assistance of application notes, spec sheets and white papers from most manufacturers to build a quality product with the minimum of fuss.

Hantek  – USB oscilloscope, multi-function

I have four oscilloscopes, three of them analogue. I like the ease of triggering and set up. Coming from the analogue era certainly assists – the digital scopes don’t appeal from a GUI perspective until one needs to record an event or compare functionality to price. They become indispensible. Just look at the hand-helds.

The digital scope I use is the Hantek 3062. It has a logic and spectrum analyser, frequency counter and of course it’s a scope.  It cost about R4K five years back from Kmeasure, based in Pretoria. Very good service. I mention this as an aside, there are always sensible, cost effective solutions in our pinched South African market.

Lastly, of course we need a good quality function generator.  I find Instek to be of exceptional quality and reliability. Available at Mantech Electronics. (Cape Town, Johannesburg, Durban).

Further Reading:

Cordell Audio:  Robert Cordell Build your own THD Meter

KMeasure – Professional measurement systems (based in Pretoria)

Signal Lab – SigView Signal Analysis software

The VCF or Voltage Controlled Filter