Part One
Pro Audio – buying something to last….
When one buys any budget power tool you’ll find that the warranty does not usually cover it being used in a professional environment, so if you are a carpenter, electrician or builder you need to pay that extra to get something for heavy duty use. Ditto with sound equipment. However I find it intriguing that the forums are full of complaints about gear falling apart within a very short time of ownership. Is this possibly just blatant abuse? Let’s have a look at the life cycle and life span of some tier one manufacturers then.
Top end brands of electronic products have all but moved their manufacturing facilities to China. Products such as notebooks were all plagued by poor craftsmanship, inferior components and a blatant disregard for Q.C. Professional monitors (PC/video) suffered the same fate. Of course the forums are full of a very well known brand of pro audio equipment as well. The group CEO became an ear for the gripes on a sound forum and he quickly quelled the flames. Hero or villain?
I don’t know but what I do know is that they put their money where their mouth is and now give all their components a three year warranty. Tier one brands seem to have a much better life span than they did five years back because of the positive changes in the Chinese work space. Of course now the Chinese workforce are earning top dollar as well, so where to next?
Life Cycle of professional audio
What I like about the pro audio life-cycle is that a product may become available and stay available for many years. You will see this in stomp boxes, audio amplifiers and even the trend for copycatting vintage audio equipment. As the Asians are very good at this and yes, certainly making better, I think the trend has mostly proven to be a positive one with top end quality been supplied at budget prices. We have, of course, many people still buying based on snob value, so have the entry level products being lambasted by the press, musicians and the well-heeled – are they the misinformed?
The interesting thing is, again, is that many of these entry level products are now outliving their more expensive rival sibs. We hear of how ruthless the CEOs of these companies are but yet has anyone given a thought to what lives they lead or don’t lead. If your entire life has been committed to either controlling the market in a specific domain or more so, committed to providing reliability at low cost then sorry mate, it’s not going to be controlled by Peter Pan. This field of electronics is no different. Professional musicians stick to one brand and whether it be quality, uniqueness or just plain sentimentality, the professional sound domain is full of equipment which has remained very much in vogue since the 60s.
Pro Audio and Consumer Electronics: A word on copycatting and infringement of designs
Now here is an interesting one, not because I am interested in copyright law but because marketing sells, not the schematics and/or internals of any equipment. There is a common belief that no matter how much we think we evolve, we stay the same. In the audio space, I find this to be largely true – technology has improved to such an extent in the digital field that things have became smaller, not necessarily better. The same applies to analogue audio gear, the boards get smaller, the power outputs go higher, loudspeakers have improved by a great margin but when it comes to extreme power, thermionic devices still rule.
We read about class A preamplifiers being better than class AB. My word, just go back thirty or forty years, preamplifiers were all mostly class A, (as in tubes) so what gives? Analogue chips we are told are noisy but yet the best microphone amplifiers use them. Think of the Texas Instruments INA217 – an instrumentation amplifier. Ever read about the cheap 5$ amplifier out performing a 1 500 dollar professional unit. If we only knew. OK, so what is the secret?
There is no secret, the preamplifier used is that very same INA217. I don’t know whether the test is entirely fair but do read it. So was the point here to humiliate the snob or put a simple theory into practice? The question I ask then, if I take ten of these preamplifiers and put them in a case, powered by an external source to reduce hum and noise would this be infringing copyright?
Texas Instruments give their customers mostly full access to their list of products which includes specifications, designs and bulk discount. Therefore the circuit used around the chip is not copyright – the manufacturing of the chip is. Good differential op-amps used for instrumentation are usually expensive. Building a circuit with ten of these preamplifiers plus power supplies plus phantom power will cost you then in the vicinity of 100$, much more if you want to make it look really classy. I own and use a Focusrite Scarlett 18i20 and an Art Pro Digital MPA ii. The Pro Art looks really great but yet the Focusrite, in all it’s simplicity is the better performer. Or so the reviews state. The Art Pro could have the same quality preamplifiers then (x 8 of them) but yet stuck to two. Because this gear is aimed at a specific niche buyer.
Behringer gets hammered for quality but yet dollar for dollar gives better value than most high end brands. Behringer have had their fair share of legal woes, both in and out of court and the sad thing is I don’t really see how they were copying anything. Electronics is very open source. Because they copy the looks and style of a Mackie everyone cries foul and buys another brand. How many cars have you seen on the road that look the same as rival companies. This is an argument one reads and hears about ad nauseam but the result, in audio circles at least, is “how does it sound?”. In all honesty, competition is rife and rightly so – it has driven the retail price down so it becomes affordable to the musician. Copyright should belong to the chip manufacturers, not on the look and feel of a product.
And now for something completely similar…
The advantages of buying a cheap mixing desk based on what it can do once stripped down to the bare essentials or how to not to break the bank when buying a mixing desk.
A very easy project here is to purchase an entry level powered mixer, remove the power amplifier and modify just the channel strips to your liking. In my own project I swapped out the JRC mixer chips for a better quality LM preamp chip. One could add in extra buses for routing etc. The power amplifier could be reused in another project – here the chief aim is to play around with and improve the original product. Please see the article on the Dixon PM121 USB mixer – by the way this mixer is not USB controlled, there is a USB port which is for flash drive use. The Dixon PM121 is actually the perfect testing ground for the experimenter, they are relatively cheap, easy to modify and has plenty of space inside for mods. They were available through Cash Crusaders in South Africa many years back for about R3000.00 and I think, way under rated.
Modifications
Most cheap mixing consoles have only one TRS insert. What they do have is a channel strip, completely dedicated to amplifying a microphone or instrument – the amount of mixing controls dependent on the amount of channels. You can remove one, you can add one, you can modify it, you can break it. What you want to do is break the signal between the channel strip output and the signal bus (the cheaper mixing consoles have only one main bus). By connecting a 6.3mm stereo socket to this break in connection so that the normally closed contacts completes the circuit will then act as a channel insert, or channel output. You can do this to all the channels. A 12 channel mixer as I have, will cost you about 20$ in 6.3mm stereo sockets and a further 10$ in wiring. At this point you can even become insanely clever by also adding a buffered and balanced XLR line output from each channel to feed your ADAT converter line and mic preamplifier so you can record multiple channels simultaneously (this does defeat the object slightly because most audio interfaces have mic/instrument/line capability in any event and you are only adding to the signal path i.e. more noise). What they don’t do well though, like the 18i20, is add FX, compression and limiting. Cheap mixing desks just don’t have sufficient routing or sub mixing facilities. Also cheap mixing desks have very dodgy FX, so this cheap modification can save you a lot of money in the long run.
Cheap mixing desks lend themselves well to op amp replacement. They actually lend themselves to a lot of things, most importantly you will never be able to build one for the same price. Locally the toroidal (50-0-50 at 5A) costs easily 150$. Hence the reason we use it elsewhere. Cheap mixing consoles also lend themselves to many modifications, they have lots of free space inside the chassis, even with power amplifiers inside. You can change the effects processor, add a matrixing adapter to make multiple routings possible, add a sub mix control and even add buses plus have extra stereo outputs without using a breakout externally. Again it comes down to the most important and vital part – the channel strip. I’ll add more details to modifications made in a later series of articles.
The old Dixon PM121USB powered mixer
The mixing desk I have is a cheap unit costing about 250$ in South Africa. The quality is surprisingly good compared to offerings in the budget Pro Audio range but lacks inserts and multiple outputs. Get the right tools for cutting holes and you’ll be a magician as well as an enterprising musician. Mass production of PC boards and various grade components soldered in place does not cost the same as good quality jack plugs so always use the best you can afford.
Pro Audio – the ins and outs
Most pro audio equipment is built to last. It doesn’t in the hands of the wrong people. Always treat as fragile and then you won’t be quick to say that such and such equipment is garbage. Pro audio equipment is designed around line and microphone levels, high and low input impedances and is based on mV potential difference across a known load impedance. You can get this knowledge elsewhere. Audio amplifiers must be capable of sustained output powers without the supply, output or power stages failing. They are also designed for a specific load impedance – don’t go lower in semiconductor designed for loads or higher in tube output stages. (power tubes don’t take kindly to running without a load).
Impedance mismatches
On the many forums it becomes pretty apparent that many newbies are connecting their equipment up incorrectly – in the case of power amplifiers and output loads this can be disastrous, in every other case damage should not occur. Pro audio class D amplifiers are not driven for lengthy periods of time to measure the power output. Many audiophiles feel this is defeating the object and customers are been ripped off. Something more to debate about at a later stage.
Watt about lighting?
Leave lighting to professional and licenced electricians. Lighting more often than not draws more power than all the on stage audio amplification so proper cable current handling and three phase power is often crucial. As an aside, DMX is another very interesting topic and very often misunderstood. The power switching and fading through DMX controllers are straightforward, setting the mood through lighting and sound is not. Most of the audio engineers found on the forums are very interesting people to talk to and learn from. Many of them have more than twenty years experience. They all have their favourite equipment and they all have one thing in common – the love of sound and the sonic difference between different brands. In the wrong hands good equipment can sound bad and in good hands bad equipment can sound good.
The weakest link
In many cases your weakest link is the loudspeaker and the freakin’ room acoustics. Good speaker boxes are heavy. Punchy bass will never be heard through a lightweight speaker system just as a bookshelf speaker system will not rock your Pink Floyd boat. Many years back Deep Purple played the loudest (SPL measured) with a 10kW sound system. The Who were next with 76kW (SPL measured), then came the mind numbing audio equipment of the 80s, 90s and 2000s. Over 100kW to crush your skull is not uncommon. These concerts have audio equipment costing upwards of tens of millions of dollars. And they fail. Spectacularly.
Loudspeakers are pretty dumb devices, not having changed much over the last century. Bi-amping and Tri-amping, sound reinforcement and sound enhancement, synthesisers and effects, condenser and dynamic mics, compressors and limiters, gates and VCA are all relevant – the loudspeaker, however, remains king. While good quality amplifiers have dropped in price, good quality loudspeakers have always remained horrendously expensive. Read up about SPL and crossovers.
Digital Pro Audio
One needs to be realistic when paying for equipment and sometimes the name-brand alone does not justify the high cost. What has become very apparent is the high cost of AD converters, more often than not a “build your own DIY project” is one you would not embark on at home. A good quality 48kHz / 24Bit converter used for 8 channel ADAT is not cheap. Do your homework and you won’t be disappointed. Be cautious of how all products are advertised – the equipment rarely has the inputs / outputs advertised if you do a straight count – one needs to know how they got the final result. This applies to mixers and microphone preamplifiers, analogue and digital. The top three websites for research as always is Musiciansfriend, SoundonSound and Sweetwater.
Read the reviews and keep an open mind, pro audio equipment can depreciate faster than your notebook.
Part Two