Coliseum Audio Controller

[whitepaw]

I recently got this beast for free on craigslist (i basically died and went to heaven. free Sunn stuff!!!)  what info do you guys have on it? first two channels do not light up, but all the other voltage meters light up. no sound when plugged into speakers though...

[EdBass]

That is way cool! Can you post a pic of the back?

[boulderbass]

From a distance it reminds me of some Heil mixers I've seen.

[Isaac]

What a monster! And what, six channels?

[whitepaw]

I don't have a picture of the back, and the console is at my drummer's house at the moment, but i will ASAP.

there's a picture on the Who gear website of them using two of these (the 8 channel version) as part of the Bob Heil designed PA system. mine has connections for another two channels, and probably the two graphic EQ strips that would've gone above the voltage meters.

and yea, six channels, 2 inputs per channel. it is heavy as HELL.


I would love to get this working and use it as our PA and/or to record with. right now we're using a very small harbinger 4 channel PA, which is trying to compete with a concert lead and a beta bass being used on bass and guitar respectively (yes, we're using a guitar amp for bass and vice versa haha)

[Isaac]

I wonder if it will be quiet enough to be a good choice for recording. Old units can be noisy. Even good quality units can get to be hissy.

[EdBass]

I'm not exactly sure what it would be "good" for, but it's incredibly cool! l would love to play with one.

[Jeff Troy]

Hi, Whitepaw,

The CAC is not a powered mixer, which is probably why you have no sound. There might be something else wrong, but no power amps are one problem for sure.

Never saw a six-channel CAC. Never even knew they offered one. Back "when," I used my 8-channel Coliseum Audio Controller with a Coliseum Slave to power four 115SR PA bins, one Concert Slave to power two Large Radial Horns, and another Concert Slave to power two 11SR cabinets for side monitors and two smaller Sunn floor monitors. Speakers plug into the slaves, and the slaves connect to the outputs on the back of the CAC.

I have another CAC now, and it works nicely. I think there's an image of it somewhere in one of my collection threads. I purchased several replacement channel panels from another member more than a year ago. I keep them for spares, and could probably part with one if you need one for Channels 1 and 2.

Warmest regards,

[loudthud]

In the catalogs there are order numbers for 4, 6, and 8 channel versions of the Coliseum Audio Controller each available with 1, 2 or no Graphic Equalizers.

Going back to the 1971 "Sound Systems" catalog (Feel the sound of the 70's) all of the systems that used the Coliseum Audio Controller mention the two 120W power amps, even the ones that also came with Colisuem Slave amps.

In the "1972 Sound Systems" or the 1974 "Sunn 74" catalogs there is no mention of the power amps.

The schematics and service documents I have show two power amps. They are dated 1971 and 72. The microphone inputs use an IC with a no industry standard number, only "616a7739393".  Probably a ua739 dual opamp in a 14 pin DIP. That chip was also used in some TAPCO mixers.

Edit: Forgot to mention that the low impedance microphone inputs do not have an input transformer.

[Isaac]

How do the low impedance inputs work? Differential inputs on the op-amp?

[loudthud]

When a plug is inserted into the high impedance input, the low impedance input is disconnected and the signal is padded down to a low level comparable to the low impedance input level. Each channel has a three step attenuator to reduce signals that would otherwise clip the input stage.

[whitepaw]

thanks for all the info so far guys! the reason i thought that it was powered is because there are outputs on the back labeled "speaker" or something of the like, and when i was poking around inside, i saw large transistors that i figured were power amp transistors. i am hoping that channels one and two just have a loose connection somewhere, but i will definitely keep your offer in mind Jeff. thanks!

next time i'm at my drummer's house i will make sure to take this with me and see what i can do with it! i figure i'll test it with the power amps in my beta bass and concert lead.

[Isaac]

When a plug is inserted into the high impedance input, the low impedance input is disconnected and the signal is padded down to a low level comparable to the low impedance input level. Each channel has a three step attenuator to reduce signals that would otherwise clip the input stage.

Low impedance inputs are typically balanced. Are the low impedance inputs on the Coliseum Controllers balanced? If so, how is this handled in the absence of an input transformer? If not, how are the two inputs handled electrically?

[loudthud]

It's an unbalanced input. Pins 1 and 2 of the XLR are connected together. A 680 ohm resistor acts as a termination.