By Darth Fader
A few weeks ago I had an experience that’s worth sharing so that (a) you won’t have the same problem and (b) because it reeled in my audio ego and stuffed it back into the confines of my helmet. I’d like to think I know a lot about audio but this goes to show that there’s always something new to learn.
I was mixing a show for Figrin D’an and The Modal Nodes at Chalmun’s Cantina. The PA system was (let’s be polite here) antiquated: a Yamaha PM3000 analog mixing console, some really ratty home-made speaker cabinets that looked like they were left behind on a supply ship heading for Dantari, and a rack of mid-level, analog processing (definitely pre-subspace transceiver). For you young ‘uns, back in the day the Yamaha PM3000 was a great desk but now those consoles are pushing 30 years of age. If a PM3000 has not been meticulously maintained, there’s a good chance that it will have issues. Solving such issues becomes more and more difficult as the parts disappear from the face of Tatooine. Looking at this particular desk, I was not hopeful. It looked like it had been subject to Dilnlexan cigars for most of its life: the plastic controls had that discoloration that stinks of nicotine. Nonetheless I was assured that everything worked with one or two small exceptions, and that the desk would perform fine.
As I started to get ready for sound check, I realized what a sound diva I have become. An analog desk? I have to patch the gates and compressors into each channel using wires? I have to start from scratch to build a show instead of recalling a show file and instantly having everything the way I want it? Well, OK it’s all good and it keeps my lightsaber bright. Plus Conan Antonio Motti was on site so I made him do all the grunt work.
The systems engineer (a Trandoshan whose family had defected years ago) showed me the processing rack. He and Conan had already patched the gates and compressors for me. The stage was wired and my crew was ready to test each line before D’an and the band arrived. We started in the typical manner, checking the drum channels first. The PA system sounded OK but as I dialed in the drum channels, I noticed a strange distortion on some (but not all) of them. The kick and snare channels sounded fine but the high hat and tom channels just weren’t right. To make sure I was not having auditory hallucinations I bypassed the gates that were inserted on the tom channels but still I heard this distortion. Worse yet, it was intermittent.
When I got to the vocal channels the problem again reared its ugly head. Most of the vocal microphones sounded distorted and were cutting in and out. The problems seemed more pronounced on the left side of the PA than the right, and this was compounded by the fact that the right side of the PA was louder than the left. I asked the Trandoshan to check the processor and the power amps to make sure that everything was set correctly, and it was. We changed the cables coming from the console’s main outputs. I tried swapping microphones to different channels. We checked the master meters to make sure the left and right levels matched — all to no avail.
When the Modal Nodes arrived and started to play the problems persisted. We were just about ready to find another mixing desk (not an easy feat on short notice). I continued to add more channels to the mix and noticed that the PA system sounded very compressed. I asked the Trandoshan if there was a limiter on the system and he said that although there was a limiter, it should not be kicking in until we played the PA at levels way louder than we actually were (he checked that, too).
As I gazed off at Tatoo II the processing rack caught my eye. Something wasn’t right. There were several two-channel compressors, some of which I was using for vocals but one just didn’t look right. Then it hit me: one compressor was patched on the L/R outs of the PM3000 and the settings were all messed up— which explained what I heard. I looked closer and found the root of the evil problems. The left and right channels were set differently, and they were not linked. One side was compressing more than the other, and the output gain on the right side had been turned up. That explained the audible compression, and the difference in level between the left and right sides of the PA. Then I found the source of the distortion and the intermittent audio: this particular stereo compressor also has an expander/gate on each channel, and the gates were on. It so happened that the threshold settings of the gates were set just high enough to cut off some of my channels when the whole band was not playing. Gate off, problem solved.
It turns out that Jar Jar Binks was using the PA system the night before to mix a show with a Bith Polka band. Now we love Jar Jar but he is kind of limited (poor soul) especially when it comes to his audio smarts. For some reason, the night before he had unpatched that particular compressor from the L/R bus and used it to process a couple of input channels for the show. Apparently each channel required different settings and he was also using the expander/gate function. At the end of the night he re-patched the compressor into the L/R bus but did not reset the controls to where they should have been set: the stereo link was off, the output gain of the right channel was higher, the ratio and threshold setting were different for each channel, and most importantly he forgot to disengage the expander/gate function.
Poor Gungan. I’m going to kick his ass.
Originally posted 2014-07-17 04:27:14.