On occasion, the company I currently work for does installation work. Thus, I am always keeping my eyes open for new equipment and tools to make that job easier. The cable comb seems like it is just such a thing:
Instructional video from youtube:
Then there is this:
Which is simply amazing. It is described as “1320 Category 6 cables, dressed and terminated.”
Incidentally, there is an entire sub-reddit: reddit.com/r/cableporn for all those cable geeks that like to look at neat cabling work.
As it turns out, 300 kbp/s or greater. At least in critical listening environments according to the paper titled Perceived Audio Quality of Realistic FM and DAB+ Radio Broadcasting Systems (.pdf) published by the Journal of the Audio Engineering Society. This work was done by group in Sweden and made various observations with different program material and listening subjects. Each person was given a sample of analog FM audio to listen to, then they listened to various audio selections which were using bit reduction algorithms (AKA CODEC or Compression) and graded each one. The methodology is very thorough and there is little left for subjective interpretation.
In less critical listening environments, bit rates of 160-192 kbp/s will work.
I made a chart and added HD Radio’s proprietary CODEC HDC, which is similar to, but not compatible with AAC:
Bit Rate (kbp/s)
HD Radio FM; HD1 channel*
HDC (similar to AAC)
96 – 144
HD Radio FM; HD2 channel*
HD Radio FM; HD3 channel*
HD Radio AM*
32 – 128
MPEG II, Dolby digital
192 – 256
PCM, DTS, Dolby digital
MPEG I,II,III, WMA, AAC, etc
32-320, 128 typical
128 – 256
96 – 320
64 – 256
**PCM: uncompressed data
This is the composite Mean Basic Audio Quality and 95% confidence intervals for system across all excerpts:
Over the years, we have simply become accustomed to and now accept low quality audio from mp3 files being played over cheap computer speakers or through cheap ear buds. Does this make it right? In our drive to take something good and make it better, perhaps it should be, you know: Better.
A little blast from the past. This was found in a transmitter manual at one of the sites we take care of:
I thought I would scan it and make it available here. As luck would have it, there is also a corresponding piece of equipment to go along with it. I had never seen a “CCA Optomod” (.pdf) before I was working at one of the radio stations in Trenton, Florida. This unit was rescued from under a pile of garbage out in the lawn shed. It was full of mud was nests and mouse droppings. Needless to say, it required a bit of TLC to return it to operation. I replaced the electrolytics, cleaned it up and ran some audio through it. It is probably as good as the day it left the factory. Bob Orban made some really good stuff in his day.
The original Optomod 8000 was an evolutionary design that made FM radio processing what it is today. The idea of combining broadband limiter, AGC and stereo generator in one box was a radical departure from the norm. The audio limiter functioned as a 15 KHz low pass filter and broadband AGC.
The stereo generator used very modest amounts of composite clipping to reduce overshoot and transients. Many people disparage composite clippers. If done correctly, it is transparent to the listener and increases perceived loudness by stripping off modulation product that is non-productive.
Some thirty five or so years later, there are still many of these units in service in various stations around the world.
As this is an older design than either the Gates Sta level or the Collins 26U, it may not be as useful to tube audio enthusiasts.
The main issue with the Gates and Collins unit is the GE 6386 remote cutoff triode used, which were great tubes, but very difficult to come by these days. This design calls for a 1612 or 6L7, which is a pentagrid amplifier. Feedback is provided by the screen of the following stage, a 6SJ7GT. Anyway, perhaps it will give somebody some idea on how to make a good tube compressor limiter.