Sunday, March 18, 2012

Channel Path Vs. Monitor Path


The Terms “Channel Path” and “Monitor Path” are used in audio engineering to describe the two paths any audio signal runs through in order to be recorded and heard. Usually channel path describes the source signal most likely starting with a microphone plugged in to a microphone preamplifier and ends at some kind of a recorder – most likely a multitrack recorder. The monitor path is the path through which we monitor what we are recording. In other words it starts with the return or the output signal of the recorder and it ends at your speakers or headphones – (not the artist’s headphones). The way audio consoles deal with both of those paths - we have two main types of mixers – “In-line” and “split”. Split consoles are easy to understand – lets say you have a vocal microphone plugged in to channel 16 and routed to your multitrack recorder input 16 – That’s your channel path. The output of your recorder on the other hand is connected to channel 1 of the same console. Channel 1 is now routed towards the speakers, which serves the function of a monitor path. So the console gets split by the engineer. He/she decides what modules of the console to be used as monitor paths and which other modules as channel paths. Inline consoles, also referred to as dual path consoles have both the channel path and the monitor path built in to the same module. Meaning you may have a vocal microphone plugged in to “channel” 16 going towards your multitrack recorder and probably being recorded on track number 16 while the output of track 16 is also connected to “channel” 16 of the same mixer (this time the monitor path of it) and controlled by a separate fader going towards the speakers for monitoring. If that sounds confusing – it is because of play of words, which is always the case in the audio industry. A lot of times the terms “module”, “channel”, “monitor”, “track”, “buss”, “sub”, “group”, “send”, “return”, and many more are misused, misinterpreted or simply interchanged. And not from the lack of knowledge – Audio gear manufacturers seem to be trying to confuse everybody on purpose. Even professional console companies like SSL and Neve seem to have an internal disagreement. SSL for example calls their multitrack busses – “groups”. On the same console you may also find a “VCA group” and a “software group” which are completely different things. Also most large format consoles, like the SSL 9000J in MIX Mode use their dedicated channel paths and NOT the monitor paths for monitoring. So if someone in the middle of a session asks: “Is the vocal on group 5?”, or “Is that bass on channel 13?” - the question itself would mean absolutely nothing, because of the existence of multiple “group 5s” each one with a completely different function, as well as the term channel a lot of times implies both channel path and monitor path at the same time and it is also somewhat interchangeable with the term “module”. After a few years of dealing with multiple recording consoles people get a sense of all that misused terminology and no longer find it strange that the inputs to Pro Tools for example on the patch-bay are labeled as “Multitrack Sends”. On the other hand a lot of manufacturers simply mislabel or are absolutely wrong with their concept. For example Tannoy, which is a well respected speaker manufacturer, labeled their input gain knob on their Reveal 6 active monitors as going from the range of “-10dBU/+4dBU”. Every audio engineer knows that professional Line level standard is +4dBu and NOT +4dBU, and if Tannoy meant consumer standard, then it is -10dBV. Let alone the fact that -10dBV input is a lot more sensitive than a +4dBu input, which means the label should have been +4/-10 and not -10/+4 because that means the knob would be attenuating your signal as you turn it clockwise, which is not the case on the “Reveal 6”. Not to mention the whole issue of the entire recording industry of Phase vs. Polarity. When it comes to channel path and monitor path it is up to the user to deal with every manufacturer’s crazy idea of the use of those two paths and terms. As long as we understand what their function is, and how to use the channel and the monitor path, audio gear manufacturers will continue to intentionally confuse their main consumers, as different companies will never agree on a standard terminology.

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Thursday, March 1, 2012

Avstomusic Gear Tech. Specs Vs Good Sound


The eternal debate of technical specification of audio gear and the resulting quality of sound has been argued since the beginning of professional recordings. Unfortunately the nature of the topic always leaves the parties of the discussion in suspense, without getting to any conclusive, objective benchmarks. Here are some highlights to consider, which if not solving the dilemma, at least may give you an idea why the problem has no resolution.

I’m talking about how certain pieces of gear have great technical specifications in comparison to others and yet they may not sound as pleasing. On the other hand it is not uncommon to use some old “crappy” gear in the recording studio, which in comparison to modern technologies doesn’t measure up, and yet sometimes there’s something “sweet” about it’s sound or tone.

First lets look at transformers versus transformer-less gear. Due to the high DC (direct current) voltage requirements in vacuum tubes, which before 1955 were the heart of all electronic devices, transformers were widely used well in to the 60s and 70s. With the invention of the transistor, the use of transformers in audio gear became optional and today many manufacturers are going back to the roots, because transformers have some “magic” properties. Transformers work on a phenomenon called inductance. It is a process of transferring electromagnetic energy through the air or magnetic materials. The discrepancy with technical specification and the quality of sound of transformers comes from the fact that most measurements of audio equipment like Frequency response, Gain, THD (Total Harmonic Distortion) etc., are done using sine-wave signals:


Due to the induction process transformers when tested with sine-waves tend to show pretty linear characteristics for a limited bandwidth. When transformers deal with square-waves:





They tend to “distort” them and change the way they sound, due to damping or ringing and the above-mentioned limited bandwidth. 







Technically that means transformers don’t have as good of a slew rate as transformer-less gear, which also automatically means a higher THD (Total Harmonic Distortion). In other words on paper some transformer gear may look horrible, but what it comes down to is how it sounds. When listening to music we don’t look at music charts or chords progression to get an idea of the music piece. Music is a real time art and certain types of harmonic distortion actually sound musical or ear pleasing. Just like with another endless debate of digital versus analog audio, some of the sweetness of certain pieces of audio equipment comes from it’s basic design’s shortcomings, and it’s inability to represent the source signal “accurately”.
If we evaluate modern transformer-less designs of audio gear using discrete transistors, or ICs, then the comparison would be more fair, in which case a poor S/N (signal to noise) ratio for example, simply means - poor signal to noise ratio.
In other words we cannot compare apples and oranges and pick one over the other simply based on their color for example. If taste is what we are concerned with, we have to try both the apple and the orange before we show a preference. Which brings me to the question: Which piece of audio gear is best for you? Which one tastes better - an orange or an apple? A good orange or an OK apple, an average orange or an excellent apple, a bad orange or a spoiled apple? And who says you’re deciding between those two for eating? What if you are making some hard-sider? I bet a spoiled apple would be your best choice.
Audio gear is so distinctive and subjective, that good sound engineers always use their own ears when deciding what to use or purchase.

References:

Transformers – A few Basics, Retrieved March 1 2012 from:
Vacuum Tube, Retrieved March 1 2012 from: 
Transistor, Retrieved March 1 2012 from: 
Inductance, Retrieved March 1 2012 from: 
Total Harmonic Distortion, Retrieved March 1 2012 from: 
Damping ringing in LC circuits, Retrieved March 1 2012 from: 
Slew Rate, Retrieved March 1 2012 from: