CBS Labs Volumax 4300 & Audio Chain

[kd4e]

I was considering the purchase of a CBS Labs Volumax 4300 and searched for a while before I finally found a discussion specific to the Volumax 4300 here:
http://www.radios.2y.net/590ckey.html
 
     At the bottom they list the devices in their audio chain and it occurs to me that some manufacturer may have imitated all of this in a couple of devices rather than require so many discrete ones.
 
     It seems from this discussion that the Volumax alone is not going to provide the desired result.
 
WDYT?  doc, KD4E
 
> -----------------------------------------------
> Equipment used in audio chain, in order:
>
> RCA BC-5B tube mixing console
>
> Frequency response 30-15000 Hz ± 1 dB ref. 1 kHz.  This is the
> broadcasting standard.
>
> Kahn symmetra-peak, a device that reduces the positive/negative
> asymmetry especially on voice signals, to manageable values so that at
> -100% modulation the positive peaks are under +130% modulation level:
> average power gain +2 dB
>
> (Without this device, the highly unsymmetrical nature of voice signals
> would require the negative direction to be peak limited to less than
> 100% because the positive peaks would exceed the transmitter components
> insulation breakdown, which is around +130% and no more.  The
> alternative is to clip the positive peaks more aggressively = too much
> distortion.)
>
> Linear pre-emphasis of frequencies above 5 kHz, reaching +15dB at 15
> kHz:  average perceived on-air power gain +3dB
>
> Gates Sta-Level tube compressor, attack time of 28 msec and dual
> constant release times of 2.35 sec and 10 sec:  average power gain +3dB
>
> Volumax 4300 volume controller/peak limiter
>        compressor section, 8.5 msec attack time, 260 msec release time:
>   average power gain +6 dB
>        limiter section, < 1 usec peak limiting of negative peaks for
> radio transmitter

[Ian VK3KRI]

I guess it depends if you'd rather have a rack full of classic audio gear, or a boring 1RU
high box with an LCD display doing the processing.

Comibined slow agc, pre-emph, multi band compressor/limiter/expander , peak
limiter , clipper boxes are pretty common. The most notable being the Optimod
line, but there are similar devices made by Omnia and even Broadcast Electronics.

I don't have any personal eperience with these , but I did a bit of research
while starting my own PC based AM audio processor project.

There may be software 'plugins' available for web audio streaming or audio
recording programs that will replace that audio processing gear. A PC and a bunch of
software plugins are a real popular way of building a home studio and effects
rack.

The only 'radio' processing software I am aware of is "Sound Solution"
http://www.tmsweb.dnsalias.com/ which seems to be designed as a winamp plugin to
process audio for FM. I think there are  ways to get 'live' audio into it though.

I don't know any more about it than what I read on the web page as I don't run
Windows
                                                       Ian VK3KRI

[kd4e]

I guess it depends if you'd rather have a rack full of classic audio gear, or a boring 1RU
high box with an LCD display doing the processing.

I'd love the full rack but at the moment both physical space and the cost of multiple discrete devices are significant challenges!

Comibined slow agc, pre-emph, multi band compressor/limiter/expander , peak
limiter , clipper boxes are pretty common. The most notable being the Optimod
line, but there are similar devices made by Omnia and even Broadcast Electronics.

Are any of them available used, reasonable in price, and still decent in performance?

I don't have any personal eperience with these , but I did a bit of research
while starting my own PC based AM audio processor project.

There may be software 'plugins' available for web audio streaming or audio
recording programs that will replace that audio processing gear. A PC and a bunch of
software plugins are a real popular way of building a home studio and effects
rack.

The only 'radio' processing software I am aware of is "Sound Solution"
http://www.tmsweb.dnsalias.com/ which seems to be designed as a winamp plugin to
process audio for FM. I think there are  ways to get 'live' audio into it though.

I don't know any more about it than what I read on the web page as I don't run
Windows
                                                       Ian VK3KRI

Sure appreciate the reply!  Rather than spend lots of time looking at the wrong stuff I thought it wise to consult the experienced AM/hifi folks here.

Thanks! & 73, doc KD4E

[K9ACT]

I have the 3 CBS pieces and started a thread a few weeks ago because I can't make any sense out of what the Volumax is doing.

Someone suggested chucking it and getting a $100 Bheringer that will do the same thing out of the box.

So I bought a 1600 Dynamic Processor a few days ago and have spent hours trying to prove that it does anything at all and aside from a few features that seem to work, it hardly seems to be of any value at all.

The expander is slick for cutting out background noise/sound but it the compressor is compressing or the limiter is limiting, it's not obvious at all.

How does one go about setting these things up?

I have earphones on the output and either a CD, my live voice or a recording of same going in and nothing much seems to happen when I diddle with all the other controls.

Any help?

js

[kd4e]

I have the 3 CBS pieces and started a thread a few weeks ago because I can't make any sense out of what the Volumax is doing.

He does a pretty good job of explaining the role of the Volumax 4300 in a complete audio chain here:

http://www.radios.2y.net/590ckey.html

73, doc KD4E

[KL7OF]

I use the Behringer VX-2000 and B-1 microphone with several different transmitters.  They work very well.  Testing with a tone generator and scope and much on-air testing  have shown that all the sections work as they are supposed to..The unit provides phantom voltage, mic amp, noise gate,expander, tube emulation, equalization, and compression. The VX 2000 is now sold under a different model number (296?) I have a volumax, audimax setup that I have used separately and in conjunction with the Behringer.  My BC rigs with 600 ohm audio inputs work best with the Behringer as a stand alone unit.  At amateur power levels and modulation levels of 100% pos and neg, everything has been working very well for several years. Very noticeable results when I diddle the knobs.
   I re-capped the volumax unit when I first got it but I was never able to get it to work to my satisfaction.  It  needs adjustment with even small changes in transmitter output or audio output.

[Steve - WB3HUZ]

Are any of them available used, reasonable in price, and still decent in performance?

Not Omnias or Optimods. But units like DAP-310s or 610s, and some of the CRL stuff from the 80's can be had for not a lot of money.

BUT, have you optimized you existing audio - that is the audio in your transmitter, or any external stuff you are using that is not processing gear? If this stuff isn't getting you stellar audio reports now, or isn't capable of full, clean modulation, adding processing boxes isn't going to help.

AND, if you aren't already getting good signal reports, adding processing boxes isn't going to suddenly make you loud.

Maybe you already know this. But I've seen guys spend lots of money on processing boxes when a few dollars for a better antenna would have done much more for their signal.

One other thing to remember: Boxes like the VX-2000 will only do some much processing. These type of boxes were sold as microphone processors, so by design, they only lightly process the audio, or make relatively smaller changes to the sound. In a broadcast station, an audio or transmission processor would be used after something like a mic processor. So, don't expect too much out of something like a VX-2000. Yes, they will make you voice/audio sound better when adjusted properly. They will never give the increased loudness like a DAP, CRL, Optimod or the likes would give. In most cases, you don't need such heavy processing anyway, so it's OK.

[kd4e]

I am in the middle of a variety of changes to the station here.

Because we may be moving the antenna side of things is undetermined so I am addressing the rest.  I agree that the antenna is a major place to start when attempting to improve signal strength and that the microphone is as critical in the audio chain.

I am presuming that the following 5 steps of processing are a logical reference point for a broadcasting context and if followed in a Ham station should result in maximized audio clarity and loudness.  Yes, No, Maybe?

If these steps are optimal then what equipment is recommended which is a) as compact as is practical and b) affordable within an "average" Ham's stingy budget?

1.  RCA BC-5B Tube-type Mixing console Frequency response 30-15000 Hz ± 1 dB ref. 1 kHz.

2.  Kahn symmetra-peak, a device that reduces the positive/negative asymmetry especially
     on voice signals, to manageable values so that at -100% modulation the positive peaks
     are under +130% modulation level: average power gain +2 dB
     NOTE: Without this device, the highly unsymmetrical nature of voice signals would
                require the negative direction to be peak limited to less than 100% because the
                positive peaks would exceed the transmitter components insulation breakdown,
                which is around +130% and no more.  The alternative is to clip the positive peaks
                more aggressively = too much distortion.

3.   Linear pre-emphasis of frequencies above 5 kHz, reaching +15dB at 15kHz:  average
      perceived on-air power gain +3dB

4.   Gates Sta-Level tube compressor, attack time of 28 msec and dual constant release
      times of 2.35 sec and 10 sec:  average power gain +3dB

5.   Volumax 4300 volume controller/peak limiter compressor section, 8.5 msec attack time,
      260 msec release time: average power gain +6 dB limiter section, 1 usec peak limiting of
      negative peaks for radio transmitter

[K9ACT]

HUZ says:

> So, don't expect too much out of something like a VX-2000. Yes, they will make you voice/audio sound better when adjusted properly. They will never give the increased loudness like a DAP, CRL, Optimod or the likes would give.

Assuming this also applies to the 1600 that I just bought, I think you have just put things into perspective but I am not clear on the difference between mic processing and what those other things process.

For a bit of background, my transmitter is a homebrew Class C running legal limit and with an EQ to compensate for a defecit of highs, people say it sounds decent.

When I add the CBS stuff, they like it a lot more but it seems like only the Audimax does anything useful.  When I A/B the Volumax in/out, no one notices any change nor do I see anything on the scope that looks like it would be doing anything.

After working through the trouble shooting in the manual, it seems to be nominally OK.
That is not to say there might not still be a problem with it but I can't find it.

At this point, my only interest is in increasing the "loudness" and I gather from what you say that the Bheringer sort of thing will not do anything of the sort.

I am still struggling with what these things mean and do but, am I correct in thinking that the "Peak Limiting" on the Bheringer is about the same function as the gain control on the Audimax?  Likewise, is the compressor doing what the Audimax is already doing?

All the reading I have done on the "loudness wars" and loud CD's never make any distinction between consumer stuff and the stuff you refer to.  Compression is compression and peak limiting is peak limiting.  Obviously, something is missing from the discussions and I seem to be spinning my wheels.

js
 

[Steve - WB3HUZ]

At this point, my only interest is in increasing the "loudness" and I gather from what you say that the Bheringer sort of thing will not do anything of the sort.

No, it will make things louder, just not much or nearly as much a real audio processor.

I am still struggling with what these things mean and do but, am I correct in thinking that the "Peak Limiting" on the Bheringer is about the same function as the gain control on the Audimax?

The peak limiter roughly equates to the Volumax.

  Likewise, is the compressor doing what the Audimax is already doing?

The peak limiter roughly equates to the Audimax.

All the reading I have done on the "loudness wars" and loud CD's never make any distinction between consumer stuff and the stuff you refer to.  Compression is compression and peak limiting is peak limiting.  Obviously, something is missing from the discussions and I seem to be spinning my wheels.

Start here

http://amfone.net/ECSound/processing101-1.htm

[Ian VK3KRI]

......
If these steps are optimal then what equipment is recommended which is a) as compact as is practical and b) affordable within an "average" Ham's stingy budget?

1.  RCA BC-5B Tube-type Mixing console

2.  Kahn symmetra-peak,

3.   Linear pre-emphasis of frequencies above 5 kHz, reaching +15dB at 15kHz:  average
      perceived on-air power gain +3dB

4.   Gates Sta-Level tube compressor, attack time of 28 msec and dual constant release
      times of 2.35 sec and 10 sec:  average power gain +3dB

5.   Volumax 4300 volume controller/peak limiter compressor section, 8.5 msec attack time,
      260 msec release time: average power gain +6 dB limiter section, 1 usec peak limiting of
      negative peaks for radio transmitter

My audio processing budget is pretty well non-existant, and if I had one I'd be using it to buy some new microphones, but here's my take on that line-up  - that will no doubt be
completely different from any one elses


1.   I Wish .   
      
2.   If you want symmetry try this .. http://www.w3am.com/8poleapf.html. I'm not sure if this gets you any advantage though, unless you can't modulate more than 100% positive , or cant work out which direction your voice assymetry is.
      
3.   I run about +6db/ocatave boost with a 3dB point of about 2Khz. Too much boost and you get complaints from people with wideband recivers. (All two of them!)

4 & 5  My observation would be that the best best improvements I've got was from a sloooow AGC and a fast limiter. The AGC has a gated release - that is if the release only
occurs if the input is below the AGC threshold, but above another threshold. This stops the gain rise during long pauses. The limiter has a negative
attack constant, that is the gain starts dropping before the peak arrives. Obviously this requires a delay in the signal line, which can be
disconcerting when speaking and monitoring yourself off-air.  I push the limiter pretty hard so its probably doing close to 10dB of limiting on regular voice peaks.


I found the best way to monitor 'loudness' increase was to repetitively play a recording though the whole signal chain and monitor the result in a receiver
that had quite a noisy signal. That puts the 'loudness' increase in more perspective than just listening to processesed vs unprocessed.

In the end I put a simulated noisy radio path, complete with typical rx audio roll off  into my processor so I could tweak it without requiring the transmitter to be on.

                           Ian VK3KRI 

[kd4e]

>>  1.  RCA BC-5B Tube-type Mixing console
>   I Wish .   

What affordable & available clean mixer is recommended?

Say for 2, 3 or 4 inputs?

>>2.  Kahn symmetra-peak,
>http://www.w3am.com/8poleapf.html

Is there a kit or assembled version of this available?

>>3.   Linear pre-emphasis of frequencies above 5 kHz, reaching +15dB at 15kHz:  average
      perceived on-air power gain +3dB
>  I run about +6db/ocatave boost with a 3dB point of about 2Khz. Too much boost and you get complaints from people with wideband recivers. (All two of them!)

What device do you use for this, please?

What devices are recommended?

>>4.   Gates Sta-Level tube compressor, attack time of 28 msec and dual constant
>> release times of 2.35 sec and 10 sec:  average power gain +3dB
>>5.   Volumax 4300 volume controller/peak limiter compressor section, 8.5 msec
>> attack time, 260 msec release time: average power gain +6 dB limiter section,
>> 1 usec peak limiting of negative peaks for radio transmitter
> 4 & 5  My observation would be that the best best improvements I've got was from
> a sloooow AGC and a fast limiter.

What devices are recommended for this?

I saw an updated retro-look Gates Sta-Level equivalent but it was $2,350.!
http://mixonline.com/products/review/audio_retro_instruments_stalevel/

The Volumax 4300 I saw was $75.

Is that typical?

What decent compact compressor and/or combo device is roughly equal
to the Gates Sta-Level and Volumax 4300 but affordable?

Thanks! & 73, doc KD4E