Sound quality, tips and tricks

Home user audio setup without the hassle.

Sound in this case refers to the non-noise variety.

In many instances headphones are man’s ultimate friend. Unfortunately in the real world we also like to feel the sound, have the luxury of depth, colour, bass and all the magic that goes with it. Whilst a good set of headphones does the trick often just two tools in your briefcase make a huge difference:

i) A scientifically calibrated microphone and (ii) REW, the free but powerful software program, Room Equalisation Wizard. REW helps you analyse your living or sound room acoustic performance for optimal placement of speakers.

Tips and Tricks for Sound
Using REW – Room Equaliser Wizard

The part we won’t like is always in the final analysis – too many times your room is just crappy. I am in such a position, the listening or home theatre room is in the shape of a polygon. (concave, where one wall angle is more than 180 deg).  For home theatre use it is extremely difficult to set up and really needs acoustic treatment. Ditto for home studio use as well, just too many reflections and of course, there’s a road at the back.

There are many articles written about the treatment of a room to get the best in acoustics and reproduction which mostly applies to studio use – here we will apply some common sense to prevent things from going wrong from the outset.

Notes for those techno gurus:

The USB microphone UMIK-1 from miniDSP is not available in South Africa as far as I know. You will pick them up on Gumtree from time to time otherwise look at the resellers overseas. 2nd hand they go for about R1 000.00. This piece of kit plus REW on your notebook make for easy setup. I used a Behringer ECM8000, Focusrite Scarlett 18i20 (overkill but I had one on hand) and REW on a notebook. Note that condenser microphones need phantom power.

Noise, buzz and hum

Buzzing is a serious irritation. Often swapping the live and neutral leads on the amplifier can make a difference. Is it advisable though from a safety perspective? No.  Your live is always switched. Check your screened cables. Don’t you just hate those cables which have about a millimeter of insulation thickness with a micron of copper inside. Sold to look expensive. Make up your own cables using proper microphone cable – best to get the balanced type which can be used for RCA, XLR and 6.3mm stereo jack plugs or sockets. (RTS), this is twin core with a good quality screen.

Balanced over non-balanced

Big advantage of professional audio is balancing the signal but for shorter 2m lengths this should not pose aproblem. Most users complain of turntable hum or buzzing. Hum is often caused by noise from the mains transformer – this can be 50Hz or 100Hz, the 100Hz coming from the output of the rectifier (South African mains frequancy x 2).  More often than not the hum/noise comes from either too many ground points (use a central grounding point), broken ground point (screen) and never forget the obvious, the HOT part of the signal is missing due to a broken wire. This one is so obvious that we overlook it – cheap and nasty cables are always the problem here.

Hum and noise is a big problem and even seasoned audio engineers battle to get the ultimate signal hence the ground lift on injection boxes. For your home system try switching off the amplifier and listen for immediate changes.  It could even be a leaky reservoir capacitor but this will be heard with no signal input.

Turntables

My own nightmare – hum from one cartridge (Audio Technik) and nothing from a Stanton.  Grounding wire inside the turntable tone arm making no contact.  Using a jumper with croc clips from tone arm to signal shield clears the noise. Both cartridges brand new. Same problem with both turntables, SL-1200 Technics. Ah-ha, different amplifier and the hum disappears.

Here’s the problem.  The Stanton did indeed ground to shield. Reversing the L-N mains connectors of the first amplifier made a difference.  The on off switch also switches both N and L.  Make sure the metal casing (if it has one) is earthed.

Turntables generate only a few mV p-p and noise is often a problem caused by poor grounding, broken cables etc.  For a moderately expensive turntable the LT-1200s failed to impress in the cable area. Whether you are a DJ or not always pay attention to the condition and quality of this cable.

Likewise microphones also run at only a few mV and setting up a mixer to have little or no noise at it’s output can be a tedious exercise. For live shows and studio recording this is a strictly no-go area.

Most complaints come from users noting that touching the casing of the turntable or amplifier reduces the noise.  To troubleshoot you will need to think methodically – was this problem there before,  are you using the same mains outlet, are you using a multi-plug, etc? Even pulling an input signal RCA plug out half way to break the earthing can make a difference. Sometimes in very bad cases the amplifier has poor grounding inside the chassis.  This can heard in the form of clicks and pops, speaker protection kicking in and worse case scenario, burning of the speaker voice coil.  (Akai amplifier, multiple grounding points, chassis corrosion causing output voltages to swing to +40 or -40V without input signal. Believe it or not).

KISS

Keep It Straight and Simple.  In every case where I have had a myriad input connections it becomes difficult for family to switch the inputs and/or we have a noise problem with low level signals. Home theatre amplifiers don’t have a MC or MM input. When playing around with signal matching always have a low impedance plugged into a higher impedance and not the other way round.

A turntable cannot be played through a microphone input because the signal needs to be RIAA (Recording Industry Association of America) equalised known as de-emphasising.  During the recording process it is emphasised, emphasising the higher frequency notes over the lower.  The reverse is applied on playback.  Your vinyl will sound absolutely horrible playing back without the de-emphasis and if I recall, very tinny.

Speaker setup

Ummm. Not very evident but placement can be a nightmare.  As a rule of thumb, main speakers 6 foot from amplifier or 12 foot apart, sub to the side. Latency to rear speakers setup according to amplifier manual. Volume control on each channel set up according to manual. If all else fails use stereo.  No jest here.  Many purists don’t watch their movies in 5.1 or 7.2 or whatever.  Magical speaker wire?  A test in the 70s states that telephone cable (you know the solid wire type) had the best results). Move speakers away from the wall.  There’s a lot of trickery in placement and a lot comes down to the speaker design. Fiddle. Don’t forget spikes, metal or rubber.

Noisy speakers?  Damaged voice coil or loose wire. The worst one is shorting cables because the amplifier is not going to like this one bit.

Amplifier showing protection mode

Use a hair dryer before switching on.  Sony amplifiers just love to be over sensitive. They are not the only ones.

As an aside…

Whilst some of the tips mentioned above won’t necessarily eradicate the hum, buzzes, clicks and grunts on your system it may prove to be helpful – a noisy background no matter how small is irritating. Shorted speaker cables are a very common occurrence which usually happens when the phantom does house cleaning.  Although amplifiers have current protection don’t hedge your bets that it’s totally fail-safe or foolproof.

As a DJ in the 80s it was seriously stressful to start any show which was perfect the previous evening with a background hum of sorts, even clicks from a fridge thermostat. In most cases it was caused by broken cables – retailers should be banned from selling poor quality cables with so called gold plating and crystal coated silver wire. Time and time again making up ones own cable sets were the best solution. In those days professional audio was only for the deep pocketed.  It’s really time that a standard be reached where your audio pre and power amplifiers start using XLR above a certain price bracket.

Next edition:  Setting up REW

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