Outdoor sound system (not for movies)

[Tony Bandiera Jr]

Ok, here are the pics of my portable rack setup. It is in a 3RU Gorilla Case from Amazon. First up, the front. The empty top space is for my low power FM transmitter:

Rack front.jpg

Next, the rear view showing the input XLRs and Speakon Outputs, the 1/4" jacks assigned to other inputs and the AUX out. On the left is the 1/8 mini plug for stereo music input, I use an Ipod:

Rack rear.jpg

Closer look at mixer connections:
Mixer rear.jpg

Next is the Furman Power strip and part of my left foot for you foot fetish freaks:

Power.jpg

Amp inputs, I used the euro connectors here, but you can use the Dataport or the XLR:

Amp input.jpg

Finally, the outputs. No CHIMPS here, just CHVOLTS as this is the 70.7v Direct Drive model. The schematic is very interesting, it is totally identical to the CX 300, except for the final output stages, as it is set up to drive voltage rather than current. :

Amp output.jpg

As you can see from the pics, this gets VERY dusty at the mx tracks. And this whole kit got slammed hard into the front of the bed of my truck when it slid forward during a sudden stop (deer in the road.) I love the QSC amps, it survived that very hard impact which would have killed most other amps.

[Mike Blakesley]

The mixer and the first amp showed up today, woohoo! Now all I need is the other amp (and the rack it's all going to go into) and a few of the plug-ends, and I'll be ready to start wiring. The amp is the only thing that's a ways away, it's coming from Tennessee. Everything else should deliver in the next day or two.

I also have to install the XLR output kit into our audio player. (From the factory it comes with dual RCA and 1/4" outputs, the XLR is an add-on kit.) So I'll need to go audiobox-to-mixer, and then mixer-to-2 amps.

What kind of wire is used to make the connections to and from the mixer? Looks like a 2-conductor shielded?

And, since the mixer has only one set of L-R outputs, do I just connect two sets of wires to those output Euro connectors to the amps?

For the speaker wires from the amps, I ordered a set of Speakon connectors to do away with the damn bare wires, and will add Speakon terminals to the speakers. It'll be very nice to wave goodbye to those twist connectors. I thought about using banana plugs but for this application the Speakon seems better.

I'm sure I will wind up confused and have more questions, but thanks Tony and everyone else for all the help/advice/knowledge. It's been good hearing from John E. again too, it's been too long John!

[Tony Bandiera Jr]

The mixer and the first amp showed up today, woohoo! Now all I need is the other amp (and the rack it's all going to go into) and a few of the plug-ends, and I'll be ready to start wiring. The amp is the only thing that's a ways away, it's coming from Tennessee. Everything else should deliver in the next day or two.

I also have to install the XLR output kit into our audio player. (From the factory it comes with dual RCA and 1/4" outputs, the XLR is an add-on kit.) So I'll need to go audiobox-to-mixer, and then mixer-to-2 amps.

What kind of wire is used to make the connections to and from the mixer? Looks like a 2-conductor shielded?

And, since the mixer has only one set of L-R outputs, do I just connect two sets of wires to those output Euro connectors to the amps?

For the speaker wires from the amps, I ordered a set of Speakon connectors to do away with the damn bare wires, and will add Speakon terminals to the speakers. It'll be very nice to wave goodbye to those twist connectors. I thought about using banana plugs but for this application the Speakon seems better.

I'm sure I will wind up confused and have more questions, but thanks Tony and everyone else for all the help/advice/knowledge. It's been good hearing from John E. again too, it's been too long John!

No need for the XLR kit for your player, the stereo music inputs for the mixer (7 and 8) are unbalanced RCA. Don't waste the money on that kit.

Yes the cable to and from the mixer is 2 conductor shielded, Belden 8451 or equiv.

Yes, use the Left and right outputs to the inputs on the amps, use the screw terminals on the amps to save time and effort making up XLRs.

Speakons are the way to go with the speakers for sure. I even use them from the rack to the field wiring in permanent installs, to allow easy disconnect to protect the equipment from lightning. You can get premade 12ga Speakon cables online for reasonable cost, in lengths up to 200 feet. Amazon sells the connectors for your speakers and the rack cheap as well.

The connector panel I used was modified, I removed two of the XLRs to add the speakons. You will have to search for it to find a new vendor, MCM/Newark no longer shows it. It was made by Stellar Labs.

Check you messages on here, I will give you my contact info.

[John Eickhof]

thanks Mike! say hi to the Mrs too! you know where to find me if you have any issues, im glad to help if i can!

[Mike Blakesley]

Here it is, the finished sound rack that started this whole thread. We've run one test on it so far that sounded terrific, and I'm hoping to get one more test in later this week, after which it'll go into storage until we think of something to use it for. (Maybe around the holidays.)

Total cost around $800, which is less than the "list price" for one of the amps!

image1.jpg

[Tony Bandiera Jr]

Nice rack!! (That was kind of a boobie joke too.)

Very clean looking, like the casters too. It will serve you well. I'd possibly add some heavy duty handles to each side to help move it about.

[Mike Blakesley]

I'm definitely on the lookout for handles, the whole thing weighs about 90 pounds or so.

[Harold Hallikainen]

I assume it has a door on the back. Some sort of cover for the front would be nice so stuff does not get bashed in. I've seen these ATA racks like https://www.seismicaudiospeakers.com...e-with-casters used in a lot of portable sound applications. Then you jjust need to hire roadies!

But, yes, nice rack!

[Mike Blakesley]

I had kind of forgotten about this thread but then decided it deserved an update.

Our results for the July 4 show (which actually took place on July 6) were mixed, unfortunately. We had tested everything out last November and it all sounded/seemed great. Then when we went to set up for the show, one of the tweeters in one speaker didn't work, and one of the amps had decided to develop very scratchy / staticy volume control pots, despite having sat indoors in a nice heated building all winter. So after tinkering with it for about two hours in the hot sun, we got it to where it sounded OK and left it. It still sounded miles better than what we'd had before but I still wasn't as happy as I wanted to be.

On top of that, the radio broadcasting device that we use to (illegally) broadcast the audio wouldn't work, either. Hook it up, the whole system emitted a very loud HUMMM. So we just disconnected that. I expect it was too close to the amps or some other issue like that. So further fiddling is due there.

So I've ordered a couple of tweeters to fix the speaker issue, and will tend to the amp next. I might send it to our theater technician, he rebuilds amps in his spare time. I have a spare QSC over at the theater that he rebuilt a few years ago that I can swap in, too, although it's a different model than the ones in my rack.

I'm planning to set the whole rig up in the back of my day job and that way I can fiddle with it in my spare time.

Stay tuned for my 2025 report coming up in a little over 11 months!

[Marcel Birgelen]

Thanks for the update, always interesting to read this kind of stuff.

Doing stuff live is hard: a simple technical failure can give you a lot of headaches, on the other hand, coming up with a last-minute solution to save the day can give you a bit of that "superhero" feeling.

On top of that, the radio broadcasting device that we use to (illegally) broadcast the audio wouldn't work, either. Hook it up, the whole system emitted a very loud HUMMM. So we just disconnected that. I expect it was too close to the amps or some other issue like that. So further fiddling is due there.

If it sounded like 60 Hz, it probably was a ground loop. If so, check your wiring and if you can't fix it, a ground loop isolator/isolation transformer should fix it.

I might send it to our theater technician, he rebuilds amps in his spare time. I have a spare QSC over at the theater that he rebuilt a few years ago that I can swap in, too, although it's a different model than the ones in my rack.

Assuming that your issue came from an oxidized pot, have you tried the simple, but often very effective fix of spraying some contact cleaner into the pot and turning it around a few dozen times?

[Mark Gulbrandsen]

Thanks for the update, always interesting to read this kind of stuff.

Doing stuff live is hard: a simple technical failure can give you a lot of headaches, on the other hand, coming up with a last-minute solution to save the day can give you a bit of that "superhero" feeling.



If it sounded like 60 Hz, it probably was a ground loop. If so, check your wiring and if you can't fix it, a ground loop isolator/isolation transformer should fix it.



Assuming that your issue came from an oxidized pot, have you tried the simple, but often very effective fix of spraying some contact cleaner into the pot and turning it around a few dozen times?

Mike, your original QSC's had the bad pots in them that many older QSC's had. I remember about ten or 12 years ago making a trip back over from Bozeman a day or two after I made a service call, because your dialog was cutting out. I cleaned the pots then, but also ordered spares and changed some of them out on a later trip. There may be a couple extra pots in the drawer thingy on the bench in front of the window if you need them. The amps I installed when we upgraded your sound system don't have the problem with the level pots getting intermittent like the older QSC amps had.

[Mark Gulbrandsen]

Mike, those QSC's are the Chinese built amplifiers. They are actually about as reliable as the USA built amplifiers are...

[Tony Bandiera Jr]

Funny this came up... I am repairing 2 QSC CX amps right now, one a 302v and the other a 1202v. Both are 120v models. The 302v had blown main filter caps and a blown main fuse, (I suspect it was connected to 240v.) I replaced the bad caps, checked the outputs and some other stuff, I just need to do the power up tests. The 1202v is locked up in protect mode, that one's gonna be a bit trickier. The common failure mentioned in the service manual for the DCA series (99.8% identical to the CX) doesn't seem to be the cause here, so it'll take some very careful power-on probing to find the cause. The 1202v also has the older pots, I've ordered new ones from QSC. Here's the 302v board, out of chassis:
qsc cx302v.jpg
Note the pots on the upper right. They are the new style. (They cost about $10 for 2 sets from QSC.) The big black caps on the lower left were the ones that blew out.

Here's the 1202v still in chassis, it is similar to the DCA 2422 and 3022, which have the Class H dual rail outputs. Note that a lot more of the board is stuffed and it has the old style pots: (ALSO NOTE THE WARNING LABEL ON THE AIR DUCT COVER!)

CX 1202v.jpg
The cool part of this is QSC was smart enough to use the same boards (except for input, output and level /gain boards) for a full line of models. the output power and number of channels depends on how many components are stuffed. The power supply takes up the entire left side of the boards, and is where all the spicy voltages are found.

I showed this so anyone can see how well built these amps are. BUT: DO NOT attempt to service any part of the main board unless you are an experienced tech with the proper tools (Variac, current meter, and deadman switch to kill power) as there are a lot of very high voltages and currents present on the main board. (The 302v is awaiting my getting the deadman switch before I start testing it.) Thankfully the power supply is pretty robust, as there are some currently obsolete parts in them that I am trying to find substitutes for. (Specifically the IGBTs on the heatsink on the lower left and one of the PWM control IC's.) The 302 is a chinese made unit and I can't decipher the year, the 1202v is from 2009.

As for the pots, or input and output terminals, you can remove those boards from the chassis without taking out the main board and anyone who can solder could repair those. Parts are available from QSC, you do have to sign up (it's easy and free) to be able to buy them.

As for the transmitter problem: Mike, did you feed it from the AUX out on the mixer or did you try to parallel it with the amps? You can't (usually) parallel balanced line level outputs to dissimilar equipment without creating issues. And you can never parallel an unbalanced and balanced output directly together, that forces both to be unbalanced.

Mike, email me with a pic of how you connected the transmitter if you can. (And the info on the transmitter.)

[Mark Gulbrandsen]

Actually, the 1202V has a better heatsink system than the 302 has. In many dusty locations the air input ends of the 302 will clog up causing the amp to go into thermal shutdown. I have pictures of what happens in my files. Later QSC's heatsinks are machined slightly different on that end in attemp to stop the dust from clinging to the sink. Doesn't work though. Once a year that was somethung I always checked on that type of QSC. Mike's theater did not have this issue in spite of being right across the street from the RR tracks. Worst places I found for this were... Jackson Hole, WY, and Elko, NV. Jackson also had to change projector filters twice as often.

[Mike Blakesley]

Mike, email me with a pic of how you connected the transmitter if you can. (And the info on the transmitter.)

Tony, the transmitter is not ours, it belongs to the fairgrounds. It's a cheapo Chinese thing. (It's worked fine in the past though.) It's not connected to the rack, it's just plugged into one of the line outputs on our music player, which is a Cobra Firing Systems AudioBox. I'll see if I can get a picture of it.

In the past I used a couple of "Y" connectors to connect both the sound system and the radio unit to the the RCA line outs, but had decided to try the 1/4" cable this year...maybe that was the problem. I didn't have my Y-adaptors with me that day so I couldn't fall back to the old way. The Cobra documentation says you can use both outputs at the same time.

audiobox.jpg