Audio Equalizer placement question

[K1JJ]

I've often thought that placing a compressor AFTER an EQ allowed the deep voice lows to be enhanced / managed  better  than placing the EQ after the compressor.  I have been able to get a better sound this way.

However, since I added a Symetrix 528E, the compressor (called an audio processor) is now first -  ahead of the EQ.  The RE-20 mic goes into the 528E (low level preamp built in) and then into the outboard 31 band EQ - then to the transmitter.

Should I add a simple Aphex compressor to the output of the EQ to get back to this order, or am I mistaken about the need for the compressor to be after the EQ for best deep lows management?

I could always add a mic preamp for the mic, go into the EQ and then into the 528E, but that wud mean adding a mic preamp.  Is this the solution?

T

[WA3VJB]

I recommend having the compressor/limiter as the last unit driving the transmitter, placed as physically close as practical (short lead length).

If you put an EQ after it and exaggerate the amount of low end response, you've undercut the impact of the compressor on the dynamic range of that part of the audio spectrum. 

But hey, if it sounds better the other way, you've answered your own question !

[K1JJ]

I recommend having the compressor/limiter as the last unit driving the transmitter, placed as physically close as practical (short lead length).

If you put an EQ after it and exaggerate the amount of low end response, you've undercut the impact of the compressor to control the dynamic range of that part of the audio spectrum.

Yes, that's exactly what I've experienced.

So when using the built-in mic preamp of the 528E, unfortunately, we are stuck with putting the 528E first  - ahead of anything else.

I'll add a stand-alone mic preamp then.   For those of us with voices made for CW, there is an advantage to being able to boost the deep lows and have the compressor then keep them from becoming a 'big bottom."  


BTW, why the short cable lead?  Has this anything to do with audio propagation or for standard RF in the audio precautions?


T

[WA3VJB]

I re-worded my post a little for clarity, but you got the jist of it. I was trying to get across the point that EQ works on frequency, while the compressor works on dynamic range. Seems you could emphasize the lows going INTO the compressor, squash the variance in level on that part of the spectrum, and increase the duration the lows are part of the waveform.

The short lead length helps the peak limiter work its magic, according to a BC engineer who 'splained it to me years ago.  As I understood it, the longer the lead length, the greater the chance for overshoot regardless of having otherwise correctly set the limiter.

Our AM station at 900Kc was running a wee bit more than 125% positive at the time, and if we'd hit baseline & splatter there were stations nearby (bigger) markets that could file a complaint against us.

Also, this is back when people actually cared.

[K1JJ]

The short lead length helps the peak limiter work its magic, according to a BC engineer who 'splained it to me years ago.  As I understood it, the longer the lead length, the greater the chance for overshoot regardless of having otherwise correctly set the limiter.

Hmmm... interesting idea.

I wonder what would cause this?  Since there is no feedback loop (like with high level ALC) I don't see where the overshoot would occur in an open loop system in the path from compressor to transmitter.

Unless it was related to audio phase change over the longer cable.  Maybe someone can explain this to me.

* Maybe with a long cable the highs will shift phase faster than the lows. The result is sometimes the new shifted phases will vectorially add to the exisiting phases and cause larger spikes...?

My HPSDR and FT-1000D use short 3' cables, but the class E rig is farther away at about 8'.  Hope that isn't far enuff to matter.

T

[Jim KF2SY]

Many of the newer channel strips had the built-in compressor and EQ signal order-  fully selectable.
Such as this little beauty:

http://www.presonus.com/products/Studio-Channel

That said, I always had the eq before the compressor when running my junk.  I think eq'ing a signal after its been squashed doesn't make sense and defeats the purpose of the compression.  With the eq before the compressor you get IMHO a much more thicker sound.     MY 3 cents.

[KD6VXI]

Would the C introduced by the longer lead lengths be enough to store enough energy to "emphasize" the peaks, causing overshoot with longer cables?

--Shane
KD6VXI

[Chuck...K1KW]

The sequence of each audio processing module can be changed in the 528E.  You can put the compressor after the equalizer easily by using the patch panel on the rear of the 528E per the manual.

The compressor in the 528E was really intended to keep input from the mic up at a decent level for subsequent processing by each of the processing modules in the 528E.  It's compressor isn't really good as the last limiting stage into a transmitter.  You should have a broadcast processor for that like an Optimod, DAP, Texar audio prizm, Inonvonics, CBS Volumax or something similar.

Chuck

 

[K1JJ]

The sequence of each audio processing module can be changed in the 528E.  You can put the compressor after the equalizer easily by using the patch panel on the rear of the 528E per the manual.

The compressor in the 528E was really intended to keep input from the mic up at a decent level for subsequent processing by each of the processing modules in the 528E.  It's compressor isn't really good as the last limiting stage into a transmitter.  You should have a broadcast processor for that like an Optimod, DAP, Texar audio prizm, Inonvonics, CBS Volumax or something similar.

Chuck

Chuck,

Yep, after tearing down the chain I discovered the patch connectors on the back of the 528E.  Well, that will make it easier to arrange what I need.

OK on needing a BC processor at the end.  Guess I will put the Berhinger 9024  6-band unit back in for now.  I hate the complex menu, but it will do for now.

Tnx.

T

[ke7trp]

I think the 528 has a side chain..  Read the manual. If it does, You simply go OUT to the EQ, Then back IN to the 528.. Done.  Now you can use the preamp of the 528, EQ the signal and then send it to the 528 compressor.

Another option is if the 528 has an EQ in and out. You can put the EQ there.  The compressor, limiter, should be last...

C

[W1ATR]

I recommend having the compressor/limiter as the last unit driving the transmitter, placed as physically close as practical (short lead length).

If you put an EQ after it and exaggerate the amount of low end response, you've undercut the impact of the compressor on the dynamic range of that part of the audio spectrum.  

But hey, if it sounds better the other way, you've answered your own question !

Bingo! This is the proper way to wire the audio chain. In my opinion, limiting is the single most important part of any installation, and installing the EQ after everything is one of the biggest mistakes some of the ESSB crowd makes. (Most of us know how lousy they can sound. Muddy, tinny, hissy, are a few words that come to mind.) They don't take bone conduction into mind when talking to themselves into a minitor, so they never hear the artifacts that are being put out by the eq due to it's being overdriven by the compressor.

The eq should only be there to final shape the audio before entering the compression/limiting stage. It's that comp/limiting thats going to give you your loudness, clarity, steady levels to audio driver, while holding off muddyness, sibilance, and other distortions. A compressor should never be used to 'shape' the audio. That's not it's designed job. It's job is one thing, and that's loudness. The limiter keeps that loudness under control.

I would work on the setup a little bit more. I usually recommend 1/2hr intervals as your hearing will become accustomed to the tones your hearing and this can result in chasing your tail, so to speak. I used to have so much trouble setting up a rack by 'grinding' to get it perfect and it never works out. Now, I'll work on it for a short while, then just stop. Drop the headphones, walk away, and come back to it later. Now, my results are always spot on after a few tries.    

[K1JJ]

Hooked up the new arrangement and very pleased with the performance on AM.

The chain:

ElectroVoice RE-20  mic >  528E Symetrix leveler  (and noise gate for ssb) >  31 band EQ Ultra Pro Berhinger >  Berhinger Virtualizer Effects  unit >   Berhinger  9024  six-band processor/ limiter


The 9024 has really come to life now that I set its internal limiting up correctly. Also, I set the lower bands at a moderate compression ratio and put the extreme highs into hard compression. This eliminated the peak highs spitting problem, so the Desser was not needed.

Using this audio setup into the modified hi-fi FT-1000D > 4CX-350FJ linear gives a nice clean bandwidth of about + - 5 Khz and drops off quickly.  I am using EQ sliders to drop the highs at 5khz and above. There is also a high-cut filter on the EQ that I have set at about 5Khz roll-off.   Later I'll add a sharper roll-off 5 Khz filter. I want this thang to drop like a rock after 5 Khz, caw mawn.

So, in summary, it took some time to get everything set up, but I feel the average audio level, tailored sound  and bandwidth for my voice is about the best I've heard in the AM detector monitor.  Will need to get some on-air reports soon.

Thanks for the suggestions.



** QUESTION:  When I add the 5 Khz LP filter board, WHERE is the best place in the audio chain to place it?


ElectroVoice RE-20  mic >  528E Symetrix leveler  (and noise gate for ssb) >  31 band EQ Ultra Pro Berhinger >  Berhinger Virtualizer Effects  unit >   Berhinger  9024  six-band processor/ limiter  >  to balanced modulator of transmitter

T

[W2VW]

Tom,

     As much as I like the 9024, I do not like the limiter. It works fine for a balanced modulator which is more forgiving of slow attack. It is not up to par for high level modulated rigs.

Recently stuck the old Symmetrics 525 back in line just before the tx.

W2ONV once told me a person needs to give up their sex life to learn the 9024 programming.

[W1ATR]

ElectroVoice RE-20  mic >  528E Symetrix leveler  (and noise gate for ssb) >  31 band EQ Ultra Pro Berhinger >  Berhinger Virtualizer Effects  unit >   Berhinger  9024  six-band processor/ limiter  >  to balanced modulator of transmitter

Im sure this will sound excellent. IMO, you really don't *need* the 5kc LP with an eq anyway, but a little bit of brickwall surely wont hurt. I'd try it in front of the 9024 first. I think the 9024 might drive the cutoff on it a little too hard and maybe put something on the air you dont want.

VW is absolutely right about the slow attack on the 9024 and high level am boxes. I don't notice it personally, but I know it happens and I thing keeping the limiter and compression settings mild keeps it under wraps.