Broadcast Audio limiter/compressor in audio chain for newbie

Discussion in 'Amplitude Modulation' started by KD6CXW, Jul 28, 2019.

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  1. KA4KOE

    KA4KOE Ham Member QRZ Page

    Bill, how can we boost the audio of our rack to drive the 707? I noticed this problem as well.
  2. KA4KOE

    KA4KOE Ham Member QRZ Page

    I got my 222 from Lightner Electronics for 450, if memory serves, and the 528E for $400.
  3. N6YW

    N6YW Ham Member Volunteer Moderator QRZ Page

    By using a peak limiter at the end of your chain, and using the make up gain afforded by the output level control.
    That's how I made the Bauer finally make consistent 100%+ modulation.
    My plan now is to finally install a Pacific Recorders RM-12 console, utilize
    the microphone channel insert to route audio into the 528E (for starters)
    in order to process to taste and proper level, then run the console output
    into the Dorrough DAP-610 processor leading into the 20V-2. This will be
    a good place to begin the journey of perfecting my station.
    What I would really like, is to replace the 528E with a Neve 1073 style EQ.
    The Pultec style EQP-1A is a great sounding box too, but not quite as flexible.
    When I say "style" I am referring to the fact that originals are stupid expensive.
    There are some great copies out there that are quite affordable and some
    are kit form you build yourself.
    Another very awesome EQ is made by API, the famous 550A and it comes as
    a mic/line pre all in a single rack package.
    These units I just described were used on 1000's of recording that we all have
    enjoyed over the decades.
    Oh hell, why not go retro cool! The hard to beat combination of the Universal
    Audio 610/1176 in one box. The 6176!
    There are so many ways to go.
  4. W2WDX

    W2WDX Premium Subscriber QRZ Page

    I'll avoid the drama in the thread and just add this ...

    I found a hardware solution (that I mentioned earlier in the thread) that I haven't tried, but could be an option for those of you who want AM specific processing in a hardware solution. I found this on eBay:

    Now ... I have no idea on the audio quality of this device, I haven't bought one; however, it seems to have all the right parameters for limiting, AGC and such for AM. It's a line level device, so you would need a basic microphone preamplifier to get the mic up to line level. A 528e would be overkill if using this AM processor. Any basic microphone preamp would be fine.

    As I said earlier, the 528e is nothing more than a microphone preamplifier with some RFI protection. It does nothing to prepare audio specifically for transmission or at least none of things one would prefer to really get audio loud but natural sounding on the air and prevent peaks. It only prepares a microphones audio for subsequent transmission specific processing. Sure ... you can use it short of anything else, but it does nothing for true effective peak limiting, AGC or multi-band compression, asymmetric adjustments, or LF tilt.

    Quite frankly, I always prefer not having to worry so much about turning my head or moving a few inches to and from the microphone. I just want to talk and sound consistent on the air. I'm not Johnny Mathis and creative microphone techniques do not make for comfortable conversation. So good AGC action, multi-band compression, along with good peak limiting make for not only much better on-air sound, but allows more comfort in simply talking.
    Last edited: Sep 1, 2019
  5. K9GAS

    K9GAS Ham Member QRZ Page

    Bill, I purchased a Klark, its a clone of the LA-2A. While it's not the Tektronics, it works pretty sweet for a box right at $400 new.
    It's my final limiter into the 21V2 that I have.
    Just thought I'd pass this on if you or Philip haven't used on. Gobs of gain on the amp stage, it's the output.

    If I only had deeeeep pockets like AD and ZUL, I'd have an LA-2A in my rack! :)
    N6YW likes this.
  6. W2WDX

    W2WDX Premium Subscriber QRZ Page

    Well ... using stuff like that on amateur AM is overkill. If you already have it fine. I have (2) LA-2's, along with White EQ's and tons of other hi-end pro audio gear, including original U-47's. Do I use them on air? Never. Just simply no advantage. I do use a Neuman TLM-103 mic, but mainly because of its small profile and I had it already. Essentially, using expensive studio audio gear for AM is dubious at best, unless it's being used to prepare the audio for more useful specific processing for the transmitter. Studio audio devices are fine when dealing with audio recording and putting things to "tape". However, what we need for transmission are a set of parameters this gear simply does not provide or does so in a way that is just inappropriate, such as problems with the aforementioned overshoot issues in studio limiters/compressors.

    I have Neve & SSL consoles, one analog and the other digital. Should I use them as microphone pre's or as mixers for my station? I think not. Should a ham spend this kind of money? Only if he chooses to, and certainly not to get any noticeably better audio quality on-air. There are better, more specific and less expensive options for transmitting than something like an LA-2 limiter.
  7. K9GAS

    K9GAS Ham Member QRZ Page

    I agree, but as you said, I had it, why not. Works just wonderful with the Wheatstone Vorsis. The KT-2A final limiter is very clean
  8. W2WDX

    W2WDX Premium Subscriber QRZ Page

    Ha ... well there ya go!
    N6YW likes this.
  9. KD6CXW

    KD6CXW Ham Member QRZ Page

    Picked up a Dorrough DAP 310 in need of some TLC, found bad transistor in power supply, have not fixed yet and need to find and order bad part.
    To many projects. Do I need some kind of isolator between the 310 and the transmitter?
  10. KD6CXW

    KD6CXW Ham Member QRZ Page

    the manual states terminate into 600 ohm 4 to 6 db pad fed into transmitter.
    should have read all of manual first !

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