Audio Interfaces – Expansion of home theater systems

Focusrite Audio Interface


Stand alone audio interfaces: Flexibility is King

Ever found yourself in dire need of a schematic for an ADAC, an analogue to digital to analogue converter. Preferably USB, HDMI and multichannel analogue in/outs. The great news is that you can purchase them on eBay but the bad news is if you are looking for professional series devices you will be paying upwards of a thousand dollars. The interesting aspect to this is that expert opinion is not to make your own but to buy. Circuits are very scarce and the level of expertise to make your own board with the above functions varies from being very advanced to extremely advanced. My resources always lead to the same conclusion – buy. I have read some pretty good write-ups from critics and the general populace/end user about entry level equipment manufactured in China as well. Why not, the Chinese lead the rest of the world when it comes to digital consumer of course, just as the Brits, Americans and Japanese did with analogue audio. To jump to the chase, a good converter is very expensive. I like the Focusrite 18i20 because as a standalone unit it does have USB, multiple outputs and ADAT – all this lends itself pretty well to getting good quality 7.1 sound. The problem I have is that Focusrite and their reseller chain advertise this unit as having award winning mic preamplifiers – not the fact that it is USB and the home user would have unlimited fun to set this unit up for a multitude of functions and not just the recording artist.


I believe the same to be true of the Behringer FCA1616 as well. Having not been able to purchase the cheaper Behringer unit because of stock shortages I settled for the 18i20 and ART PRO Digital MPA ii.  I love the Focusrite (actually they are both great but the Art Pro has no USB) but the advantage of the 18i20 is the 8 channels and headphone outputs. The crux of the matter though is that many home users don’t look into pro audio gear when looking for a converter – if building your own unit is out of the question then I would definitely advise those at home to look at pro gear to split the signal from your PC or MAC. I am also assuming here that many home users do use their PC or a dedicated PC/MAC as their media center. I am also not advertising any specific name brand here as well – both Focusrite and Behringer equipment have been around for eons. Forget the made in China stamp – most, if not all audio equipment is made in Asia and if the QC is in place you should not have a problem. Yes, I did purchase the Focusrite Scarlett 18i20 and it is a phenomenal piece of gear, not just as an audio interface. Just be careful of counterfeits when it comes to a lot of audio equipment.

Focusrite - Audio Interfaces
Focusrite Scarlett 18i20 – a phenomenal USB audio interface

So why this article on audio interfaces?

I required a USB audio interface and some of the product brands listed on eBay at good price points just didn’t ring any bells. In fact many home audiophiles may not have heard of many of the big name brands because their market space is not necessarily home theater. A pity.  The thing is when purchasing an AV amplifier you will find that most are fully integrated i.e. decoder, preamp, power amp, receiver all in one. I wanted separate power amplifiers for each speaker because try as I might I just could not find any audio amplifier which reproduced music with the quality I liked. Harsh, tinny, feeble effects all spring to mind. I have an old Sansui DVD player with separate audio outs but the unit does not play specific codecs and some of the newer program material just did not play well, some not even being registered in the table of content. Your tried and trusted notebook makes a really great media center. But how many notebooks have multiple outs (as an aside it’s something many people don’t even lok for when they buy a notebook unless it’s specifically for multi-channel audio mixing) – so the first port of call is going to be eBay or Amazon to look for something which will give multiple channel outputs. After finding that Creative (and Logitech) made just such a device it wasn’t long before I started doing a check on the specifications and well, like all things PC, I was not sure whether this was also not just Creative writing. No, Creative make great stuff but it’s not in the same league as the pro audio equipment.  Of course you can take a few steps further up the ladder and buy ADA equipment but this is for people with very thick wallets. I think just having their gear on the shelf switched on but not doing anything is orgasmic but selling off all my assets to impress was not the route I planned. So after a week of wrestling with my conscience and extensive research I decided on the 18i20. The major stumbling block for the lazy home user will be the jacks which is XLR or TRS. You will need to build a breakout which has the necessary jack converters – RCA to TRS and XLR. (the unit is USB so if you have other pro gear this should not be a problem because of the interfacing). You won’t be running long cable lengths so line balance should not be a problem.  The end result is one iNuke 6400 (4 channel), one powered stereo mixer and one standalone stereo power amplifier with a total power out of about 3kW for home theater. Heck, you can even run your own trance party. I do believe the quality to be on a par with some very well known brands out there and more importantly, cheaper as well. With software driven routing on the 18i20 you can even make your own 7.1 channel recordings.

Audio Interfaces – breakout boxes for consumer electronics

I wish some of the known brands start manufacturing breakouts for their gear which would allow jack conversion and padding of line signals for the home user more intent on making their consumer electronics compatible with pro-audio. Many home users also see pricing of pro-audio gear as being out of their price range. Behringer have changed the mindset of most musicians in this regard. Likewise Focusrite but they do not occupy necessarily the same market space as Behringer and down pricing their products to make no margin is often financial suicide. Behringer moves volumes. It also adds that little bit more in snob value. But in essence for 3 000$ you will end up with a good sounding system which is way more flexible than anything at comparative price points of dedicated consumer systems. The price I have given includes loudspeakers. Of course if you are like myself you may also be a hoarder of audio amplification equipment and mixing and matching is pretty exciting. Years back we always knew that the weak link in the audio setup was the loudspeaker but if you do have a multitude of audio amplifiers bi- and tri-amping becomes a breeze and what may be a poor quality speaker system may just come down to it’s pathetic passive crossover. Experimentation is key.


Both the Behringer FCA1616 and Focusrite 18i20 have software driven mixers, the FCA1616 a DAW, the 18i20 has MixControl where you can edit tracks, insert FX etc. If you do not get 5.1 through your USB as many have claimed (your HT system has Dolby Decoding) then the analogue outputs, which is often 6 channel can be used to drive the interface but you will need to line match first – either with your own resistive attenuation pad or with a commercial DI.

Audio Interfaces – the Brands

MOTU, Focusrite, Presonus and Behringer all make comparatively cheap interfaces. It’s a great way to experiment but not necessarily to make money. We do not endorse any of these products neither do they endorse us. I have played with them and they are all good. I wanted the Behringer but the distributor was out of stock so I purchased the Focusrite. I was not disappointed and neither will you be. And yes, I will be buying the Octopre to extend my current setup.


In summary, the main obstacles I have come up against has been the mish-mash of connector differences between consumer electronics and pro-audio and signal degradation if there is any loading on the output signals. Stick to the tried and trusted principle of feeding low impedance signals into high impedance loads and you should not hit any snags. The forums are full of really great advice and of course the engineers and sales staff from most of the manufacturers advertising their interfaces often respond to queries no matter how silly they may seem. Again, my personal experience reflects what I have seen from Focusrite, Behringer and MOTU. There are many other brands of audio interfaces but the ones listed above seem to be the most popular.


Pro Audio – paying the price for what you don’t get

Pro Audio Yamaha M7CL Mixing Xonsole


Part One

Pro Audio – buying something to last….

When one buys any 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.


Pro Audio Yamaha M7CL Mixing Xonsole
Pro Audio Yamaha M7CL Mixing Console

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 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 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 we do have the entry level products always been lambasted by the press, musicians and the well-heeled. 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 is no different.  Professional musicians stick to one brand and whether it be quality, uniqueness or just plain sentimentality, professional sound 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 more because marketing sells, not the insides of any equipment.  There is a common belief that no matter how much we think we evolve we stay the same. Electronics is the same – technology has improved to such an extent in the digital field that things became smaller. Analog cannot except for the invention of analog SMD chips and low power audio. When it comes to extreme power, thermionic devices still rule.  We read about class A preamplifiers being better than class B. My word, just go back thirty or forty years preamplifiers were all mostly class A, so what gives?  Analog chips we are told are noisy but yet the best microphone amplifiers use them. Think of the Texas Instruments INA217. 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 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$, more if you want to make it look really classy. I have 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 the 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 or 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.





Purchase a powered mixing desk. (I hate that term, all mixing desks are powered unless it only has a passive arrangement of potentiometers which is a definite no-no for professional use, or is it? Read up on matrixing). Get the voltages of the supply and derate the transformer, remove the power amplifier board, usually stereo, put in smaller current carrying capacitors of equal value. Use the higher powered mains transformer/rectifier/filters in a separate box – you now have a power amplifier which can be used elsewhere.

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 opamp 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 torroidal (50-0-50 at 5A) costs easily 150$. Hence the reason why we use it elsewhere. Cheap mixing consoles also lend themselves to many modifications, they have lots of free space inside the chassis even with power amplifiers inside. You can change the effects processor, add a matrixing adapter to make multiple routings possible, add a sub mix control and even add buses plus have extra stereo outputs without using a breakout externally. Again it comes down to the most important and vital part – the channel strip. I’ll add more details to modifications made in a later series of articles. The mixing desk I have is a cheap unit costing about 250$ 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 or higher in tube output stages.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. In many cases your weakest link is the loudspeaker. 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 a million dollars. And they fail. Spectacularly.

Loudspeakers are pretty dumb devices, not having changed much over the last century. Bi-amping and Tri-amping, 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 one would usually 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. 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