Class D – The beginning of a new Era

Why Class D amplifiers are the way to go

As a young (or old) student it takes some time to get one’s head around the design idiosyncrasies of solid state amplifiers. Truth be told many of us found tube nomenclature and circuit design easier to comprehend than anything that followed “hole” theory.  Big bad things come to an end and eventually we found it easier to crib other designs.

Class D insides
Behringer 6000 4 channel Class D

Continue reading “Class D – The beginning of a new Era”

The importance of RIAA

Trichord Dino+

Why do we use RIAA?

To kick off, and this is a response to forum user “Roggies” request for a schematic for a budget quality tube pre-amp for MC cartridges.

Unfortunately MC never has a cheap solution and that’s the bottom line.  MM may be getting better but phono die-hards are still going to have to dig deep if they want to belong to the elite.

We won’t get into a debate about which is better, tube or SS but on a spec level there are some incredible op-amps around which do an incredible job to amplify low level signal from vinyl but of course we have the tube purists.   Continue reading “The importance of RIAA”

National Semiconductor – LME49811

LM4702 - Mouser

The LME49811 from National Semiconductor / TI


Class D amplifiers and drivers are becoming so popular that some of the largest IC manufacturers are no longer focusing on class AB or A driver chips.  This is certainly the case for TI and sub group National Semiconductor.  Of course some of us don’t like class D.  What about our firm favourites: LME49xxx series or the LM4702? Continue reading “National Semiconductor – LME49811”

Protecting your Amplifier

Transistor Junction Temp and Derating

Protection devices for Audio Amplifiers

There is a lot of theory put into amplifier design and when one looks at these complicated circuits often the protection circuits are more sophisticated than the gain stages.  Purists believe the only true amplifier is a piece of wire with gain.  Engineers often criticise the protect circuits of creating their own problems, along with causing inferior quality reproduction.

These are the major problems come across in the design of any amplifier:

  • Heat – is there sufficient cooling for heavy duty work?
  • Can the output transistors go out of their Safe Operating Area?  (known as SOA).
  • Can the amplifier drive a 2 Ohm load when minimum load spec is 4 Ohm?
  • The dangers of mains voltage boosting and sagging?
  • Oscillations and instability.
  • Over driving and distortion.
  • Loudspeaker protection – expensive lessons to be learnt.

These are just a few of the problem areas in the design of amplifiers. Continue reading “Protecting your Amplifier”

Practical examples Differentials and Current Mirrors (Part-II)

Functional Block Diagram of LM741

A quick glimpse into the lives of differential amplifiers and current mirrors.

Here again we bring out the tried and trusted LM741.

Functional Block Diagram of LM741
Schematic 1.  Functional Block Diagram of LM741

I doubt there is anyone in the electronics field that hasn’t worked with or come across one or more of the most popular op-amps of all time, the LM741.  We peer inside schematic 1 and lo and behold, differential amplifiers and current mirrors. Q9 and Q10 are the current source, Q10 and Q11 the current sink. Continue reading “Practical examples Differentials and Current Mirrors (Part-II)”

Current Mirrors and Long Tailed Pairs

Differential Amplifiers – what they do  (Part One)

Long tail pairs or differential amplifiers have one important purpose:  To amplify the difference between two inputs or act as a switch.

Differential or Long Tailed Pair amplifier
Differential Amplifier or Long Tailed Pair amplifier

In a perfect case the voltage gain of the differential amplifier is the product of the differential gain or Ad and (Vin+  subtract Vin-). Continue reading “Current Mirrors and Long Tailed Pairs”

Sziklai Pair and Quasi Complementary output stages

Who made this well-known Quasi Complimentary Amplifier

Sziklai versus Darlington

The Sziklai, like the Darlington is a very high current gain device.

After dabbling on a few pages about Darlington transistors, what about the pseudo Darlington, the compound feedback pair, the Super Transistor, the Sziklai stage.  (in some of the images Sziklai is spelt Ziklai – apologies for this)

One needs to go back a few steps to understand the significance of the Sziklai design (after George Sziklai).  Many years back the only transistors used in power amplifiers were Germanium types which had a few quirks, the most dodgy being thermal runaway. Continue reading “Sziklai Pair and Quasi Complementary output stages”

DMX – Making the whole thing work

What and how to connect – the mechanics of DMX

So now you have purchased or built your own desktop DMX lighting controller, what next?

Chauvet Geyser RGB
Chauvet Geyser RGB – Fof and Light

The 1970s glitz and glamour model

If one looks back to the 1970s and the disco scene there was a lot of glitz and glamour to spinning mirrors, strobe lights, colour organs and mood lighting in general – don’t forget the silver jackets. UV or black tube magic was very popular.  Don’t forget the gorgeous girl with dark underwear.  This was all just very kitch.  Nowadays “clubbers” wouldn’t be seen dead in a place that sported such grotesque lighting but do bear in mind this was just a phase mom and pop went through. Coming into the millennium there were some surprises in store:  3D laser – holograms,  motor driven lighting, pan, tilt, high powered strobes (we had that one before) – all controlled from one interface, either software driven from your computer or a free standing light mixing console.

Mechatron your idea

Along with the Arduino, Pi and Bone we have had some interesting changes in buyer focus – 3D modelling, CNC and drones. Why the importance? Continue reading “DMX – Making the whole thing work”

How DMX Intelligent Lighting works

Some real work for the Arduino and Pi – DMX Lighting

In a previous article we briefly touched on DMX lighting – Light Control – The DMX system .  Lighting control has been with us for eons and where there is sound there should always be light, right?  But first things first.

The DMX controller is very versatile, modern units have large memory reservoirs to control lighting automatically for almost every theme and scene.  Smaller units are available for the DJ scene and pack the power of old analogue lighting controls used for supergroups years back.

Chauvet Obey™ 40 D-Fi 2.4
Chauvet Obey™ 40 D-Fi 2.4

Most audio equipment at home draws very little current from the mains supply. As we go up the pecking order we have amplifiers which can draw in excess of 20A from 220V which usually attracts the neighbours and police and then we have the juggernauts, arrays being driven by over 100kW of power amplifiers.  Sound like a lot of power? Well, think of the light show. Continue reading “How DMX Intelligent Lighting works”

Top Links for the DIY Audio Nut

Learning about Audio

Although SEO is all about well written material sometimes we do need to veer off this patch of oasis and not re-invent the wheel.  Audio circuitry, your own equipment, testing, listening and boasting is all part of the job. Here we list some awesome websites which should get your own creative juices flowing.

Illustrated History of High End Audio V1 - Robert Harley
Illustrated History of High End Audio V1 – Robert Harley

But first, some words from Popular Mechanics and some home grown products…  (16 September 2013), which sort of sums it all up. Continue reading “Top Links for the DIY Audio Nut”