I'm looking for a CBS Audimax processor, preferably the Audimax III that pairs with the volume 400...
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Looking For CBS Audimax
- Thread starter AMRadioGuy
- Start date
Have you checked EBay? Is this for a part 15 or licensed AM?
I have checked eBay and there's not much there as far as the early style Audimaxes are concerned. This is mostly for a hobby setup to listen to 45s through with 60s processing. I do have an on-air position at a local AM station and would love to put a pair of 'em on air at some point there though that's not likely to happen... We're oldies so it would fit the format...
You might want to post on the engineering part of this site. Somebody might have one they have taken out of service. Since the PC based agc's came out for the low budget users I doubt there are a lot of 1960's equipment still around.
Unfortunately, the Volumax would need another processor after it due to the NRSC bandwidth rules. I have a spare Audimax and Volumax somewhere. I'll try to look over the weekend.
They do make old Top 40 tunes come alive, especially when sped up!
They do make old Top 40 tunes come alive, especially when sped up!
Since we are talking about “classic” AM processing, Inovonics (222), CRL, and Radio Design Labs all made NRSC filter networks back when the rules changed to require NRSC limited bandwidth. You might search for one of those to use with your Volumax.
IMHO One of the issues that is killing AM radio was / is low bandwidth. Since the AM band is clearing up thru stations dying I wonder if the commission would allow AM stations to bypass the NRSC filter daylight hours only. I seriously doubt there would be more interference daytime hours as a lot of stations have let their ground systems rot, and the over all "background" noise. I believe the few hybrids Digital or all Digital AMs would not be hurt.
All the Volumax would need is a filter network that cut off sharply between 9500 and 10000 Hz.
They really did did not color the audio, as both were single-band processors. What they did was level, compress and limit which made them louder than anything else at the time... particularly if you used the fabled "zero ohm resistor" in the Audimax to limit even more severely the dynamic range.
Awesome; thank you. Let me know if you are able to find one
I remember when I discovered the zero ohm resistor. What a difference it made in the compression . I found a station in upper Michigan that sounded great because they used a Gates compressor in the expansion range most times This kept modulation up but not the artifacts of compression
Has anyone ever taken a FM station that is playing oldies and used an AM Audiomax - Volumemax pair on each channel then into the audio chain? Would it would sound like an 1960's or 70's AM only in stereo without the static? Of course you would have to get some "high energy" announcers and jingles too.
It would have to be in a "retirement" market with most non agency sales or find someone that would sponcer it a weekend night.
It would have to be in a "retirement" market with most non agency sales or find someone that would sponcer it a weekend night.
IIRC, the literature for the Audimax and Volumax back in the day (early-to-mid-60s) made it clear that for FM stereo, the gain controls for the left and right channels had to be ganged to preserve the "stereo balance". Hence the reason CBS Labs made a STEREO Audimax and a STEREO Volumax. In fact, one of those processors (I forget which) had built-in circuitry to anticipate the effect of transmitter pre-emphasis in controlling/limiting the volume.
A separate Audimax and Volumax, both designed for single-channel AM and treating the left and the right channels INDEPENDENTLY would very likely not achieve the desired effect of "that 60's sound".
So the Audimax was the same for AM & FM stations. A lot of them had the ability to be ganged for stereo, too (depending if it was anticipated to be used for AM/FM mono or FM stereo). Where the difference comes in is the Volummax units - the 400 was for AM, 410 for FM, and the (I think) 411 for FM stereo (which was really just two 410 units ganged together). The 410 (& 411) have the preemphasis someone else here mentioned.
The AM Volumax does not alone sound like that 60s sound because it's not over a tube transmitter rig - that definitely would have added a lot to the sound. However... aside from that it sounds very 60s! The FM Volumax is a pretty similar sound, though I prefer the AM volumax (I have a 400 & 410).
Of course, a huge part of the 60s sound was the mono 45 mixes used... so honestly if I were running an FM oldies station and wanted that sound, it would be mono (which means in theory you could probably use the 400 or 410). Even just running stuff through my AM volumax, stereo folded into mono for it sounds significantly less "60s" than using the proper mono single mixes.
You would not want to use two AM units, one on each channel. The stereo image would get awful wonky because there is no communication between the processors and therefore channels. The ganged stereo units appear to run for around $1,000 each (so you'd need around $2000 for the Audimax & Volumax).
Sorry, that's a lot there but hopefully it helps to answer the question!
Also - I have now located an Audimax III, so the hunt is over (for now at least - the unit is not working quite correctly so I may still be on the hunt if I can't get this one back to life...).
The FM Volumaxes always sounded awful. That's why the Optimod was such a revelation when it came out. It was finally something that could handle the pre-emphasis curve without causing gross distortion and modulation overshoots.
Wasn't the FM audiomaxs "gated"? Which if you "popped a P" there would be about a half second of 50% output before it recovered? I recall everybody having his own windscreen.
The other system in the late 70’s to early 1980 that was competitive with the loudness of an Optimod 8000 was the Harris MS-15 exciter & stereo generator. Instead of using a low overshoot low pass filter and variable pre-emphasis like the Optimod 8000, it clipped the filter overshoot, “calculated“ a correction factor and subtracted it from the signal. It had a rather bright sound when used with the Harris MSP-90 processor although, since it was a stand-alone stereo generator, you could sue it with any processor. The Optimod 8100 arrived in 1980 and the competition began all over again but this time with Orban & CRL. Fun times.
I always liked the simplicty of the Optimod AM. It was difficult to make it sound bad but you could if you tried. There were easy instructions on how to set it up and you could vary it from there. It was okay as long as you didn't vary it too much.
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