How many here have used some sort of audio processing chain between your studio and the transmitter? If you do then what have you tried/used?
My AM rig sounds great on the medium wave band but it doesn't have the punch that the licensed stations do which is a bit discouraging. I run a bare bones audio compressor and 12 band EQ. It sounds great when playing around with it forever until I get the sound I like, but then different styles of music seem to prefer different settings so I find that I am forced to stick with a one size fits all EQ setting making the audio sound very basic. To make troubles worst all AM radios seem to sound different, so getting a consistent sound out of everyones radio is a challenge.
My transmitter is the one I posted about that I built. It's a 10 watt rig using series modulation so the audio is as pure as modern transmitters without the modulation transformer troubles some older rigs have. I just know with only 10 watts you would want every last ounce of audio you can push to make it sound like the big boys on AM.
Well I know licensed MW stations use professional equipment like multiband compressors, processing equip. to fix the wave form and make everything asymmetrical and so on to get that loud punchy sound.
I'm just wondering what pirates use to get the best sound they can on a lower than professional budget. Any tips and advice is greatly welcomed here for all.
Ah cool information there. I wonder if anyone has attempted to build a three band broadcast processor yet for a project? I assume the 5K LPF is for SW broadcasting since US MediumWave has 10k audio bandwidth. Not that it would matter, my transmitter seems to cut anything above 10k anyways because the way I built it. I wonder what a used three band compressor would cost?
Well AM sure is an interesting beast. Unlike FM it seems many AM stations sound vastly different from one another since the engineers have their own idea of what is best for AM processing. From what I gather most FM broadcasters just run the audio right in w/o processing, besides basic compression.
I have heard many pirates on SW and it amazes me how different each of their setups sound. Some are really good like the pros and others I swear hold their mic up to an old phonograph player Same with PART15ers. Some of them invest in a good audio chain and others just run bare bones it seems. That's what I find interesting, the differences and what everyone uses.
edit: forgot to mention there are "breakaway" computer processors now but I have never found a free one. It shouldn't be hard at all to design software to do what the classic expensive hardware does. Problem is I don't have a spare computer just to use for that purpose heh. Oh well.
AM channels are 10K, so 5K should be the LPF for low crosschannel
But that would explain why Seattle stations splatter the bejeezuz out of our Vancouver ones
FM radio can get very complex.... I know a local station that used 10-band digital processing (Z-95). They POUNDED out the music, but had less dynamic range than a normalized .mp3
CBC uses just a tad of compression and limiting, one reason why their Classical and Jazz sounds so good, but Pop /Rock sounds thin compared to dedicated Pop/Rock stations.
CBC and NPR share a similar technique... good for our US mates to do comparisons
Some SW pirates sound like crud, yeah. One sounds insanely professional on 6925 though in comparison. Either it's the equipment, operator or both, I dunno. I wish I could have ID'd him before the sun set and conditions with it
i use a chain of mixmatched gear and my audio sounds pretty good.
audio is from a laptop. currently using foobar2000 player running replaygain to get my mp3's sounding somewhat uniform, on the laptop i cut extreme highs and deep bass since my audience is listening on a 5" speaker anyways, from there it goes to a homebrew stereo to mono converter which is basically (3) 10k resistors in a "y" so everybody is happy, from there it hits a vintage tube mono preamp i rebuilt, that gives my mp3's some warmth, from there it hits a behringer compressor limiter running 2:1 or less and giving sufficient drive to keep the TX happy. tying the audio chain to the TX is a vintage RCA audio isolation transformer. TX is plate modulated 6aq5.
Just an update.. The breakaway software is good but has the advert that plays every 30 mins which is annoying. Of course it doesn't cost much to buy the software though.
MBL4 isn't quite as good as Breakaway but it still does a comparable job. Has 3 band compressor, settings for AM and FM. Allows for AM wide or narrow mode so you can set it up for the 5KHz shortwave bandwidth or the wide 10KHz American broadcast band (530-1700khz) bandwidth.
It does apply NRSC standard for the AM band. Has lots of other options. I tested the software for a short while and it definitely gets the job done. Almost comparable to a real optimod. It delays the audio a bit on slower computers so make sure to run it on a fast setup with a quality soundcard.
Just figured I would give you all a heads up since it's free and kind of a hidden secret in the broadcast world. There are a few actual stations using this software as their main processing. I'm sure glad I found it thanks to talking to a few licensed broadcasters on another message forum.
So if you have a spare computer to dedicate to running just this software it's well worth it. Not like a free optimod is gonna fall out of the sky into our hands as pirates so may as well use this instead
on my fm i was using soundsolutions and it kicked ass on the orban presets. i dont see why you cant go in there and kill the extreme ends of the audio bands and switch to mono and let it ride. an actual broadcast engineer complimented on my audio running soundsolutions.
I have a cheap Behringer Ultramizer Pro. It is a 2 band stereo processor, but it has a LOT of great settings, not the least of which is a brick wall limiter. I got mine new for less than $100.00 I set the band split at 160hz so it separates the bass from everything else and processes them separately.
If you can find one, the Behringer 9024 is a 4 or 5 band processor and is in use in many commercial setups. Sometimes you can find them on the bay for under $150. For AM, tho, I think the Ultramizer Pro should be fine.
I'm thinking of taking the plunge and designing an audio compressor from scratch. If I have the perfboard space and time I plan on going with a 2 or 3 band compressor. This will be a major undertaking but productive project. Sadly all I have right now is a 5x6" perfboard to build onto so I may just go for a basic audio processor.
Also I have no light dependent resistors (LDRs) to make the classic LED/LDR audio compressor so I will have to design it around a voltage controlled amplifier that somehow lowers its output with the amplitude of it's input from the final stage. For those who have no clue what I'm talking about put it this way I am going to have to start from freaken scratch and design an audio gain circuit or compressor using very basic components then add equalization to each stage and combine them on the output. It will be a complicated project for sure. I plan on not using OP amplifiers but rather all discrete components that is easily available or substituted. Then make the design as small and easy as possible while still retaining good sound quality.
So basically my next project here is to build a 2 or 3 band audio compressor for AM modulation using nothing more than the most basic components. First step is designing a compression circuit that doesn't require the photo resistor (LDR). Make it distortion free. From there it's a matter of adding a wide EQ stage. Then build a few more of the same but for different EQ ranges. Match the inputs with the output and hopefully I will have a basic design.
If all else fails I at least plan on building a really good microphone/line-level audio compressor.
Any ideas appreciated. This is going to be hell-o-techy and complicated to design. My oscilloscope sure will come in handy! The only online schematic I came across for a homebuilt 3 band compressor was from this link... www.mf2fm.com/zfm/transmitter_circuits.php
As you can see I am probably in way over my head but who knows. With time and skills anything is possible
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