qsc 1310

[frost_51]

Just bought one of these used. I have used an rca to 1/4 adapter to hook it up to the sub pre out on my Yamaha htr. The fan comes on. The channel 2 light is bright. The channel 1 light is dim. I have an absolutly dead output. No sound no signal on the dmm. Am I doing something wrong or did I get rooked?

Thanks
Frost

[wg_ski]

RCA to 1/4" should work fine. Whether you got rooked or not depends on how much you paid - because the amp isn't working.

If the LEDs are red, the output relays won't kick in and you get nothing. What causes that is some sort of fault. The LEDs turn green if there is no fault present (It's a 2-color LED).

The good (?) news is these amps are relatively easy to fix if you have a friend who can work on amps.

[frost_51]

The leds are green. I paid 250 canandian. Thi guy claims it works and was willing to demo if for Me but I didn't have time. That's why I'm afraid I'm overlooking something.

[wg_ski]

If the LEDs turn green a couple seconds after power up, with the sound of a relay clicking, it *could* be operator error, but I assumed you'd already checked the DIP-switch and gain pot settings on the back panel.....

[frost_51]

Yes I tried multiple setting on the dip switches and of course messed with the gain. Any other suggestions?

[exojam]

Silly question but since you mention connecting the sub out from your receiver so I assume you are trying to run this in a bridged mode. If so, is the switch set to bridged-mono?

[bobleeqsc]

I'm guessing it's a USA1310? We had a Series One with models 1080, 1100, 1200, 1400, and 1700 (no 1310). It was the only QSC amp series with just numbers and no prefix. We had a USA series with the USA400, USA900, and USA1310.

If it's a USA1310 and the green power LED is dim on one channel, then there's probably a fault in that channel's power supply (causing one or both rail voltages to be abnormally low), or perhaps there is a fault in the transistor (or the surrounding ciruitry) that operates the channel's output relay.

[frost_51]

thanks Bob. It sounds like that may be my problem.

I also read about possibly needing an ART cleanbox to convert the signal from -10dba to +4dba?

Could that be my problem?

[wg_ski]

I also read about possibly needing an ART cleanbox to convert the signal from -10dba to +4dba?

That results in "It's not loud enough". If I were dedicating one or more of these to an HT setup, I'd just swap a few resistors in the diff-to-SE converter in the front end, giving it 14 more dB of gain.

The problem does sound like relays failing to click in - perhaps with no actual fault in the power amp section. An actual fault condition, like a shorted output transistor bank or a bad op amp, usually results in the power LED going red. Along with the clip LED lighting. The power supplies for each channel are independent - a fault in one side isn't supposed to shut down the other. If the whole thing is out, look for something simple.

[frost_51]

The relays do click.

[Paul O]

If you haven't done so already go to the QSC website and download the manual so you can be sure you have all the switches setup correctly for your applciation. http://www.qscaudio.com/products/amps/usa/usa.htm

FWIW when setup correctly it's entirely possible your AVR simply doesn't generate enough output on the LFE channel to drive this amp correctly, it needs 1.13v input to reach full output and you'll be lucky to get 0.5v from the AVR. The solution is to use something like the Art cleanbox or another component like an EQ or crosover to pass the signal through and convert it to a balanced feed.

[frost_51]

Well the problem was a faulty 1/4 inch to rca. Adaptor. Went to long and mquade and bought an xlr to rca cable. And now I just have a not loud enough problem. Where is the best place to order a cleanbox?

If I plan on using a feed back destroyer with eq will I need the clean box?

Thank you all for your help.

[wg_ski]

If your processing equipment has gain, then you won't necessarily need a cleanbox. A lot of the Behringer gear has switchable -10/+4 on both input and output.

If you have ground loop issues, the cleanbox may help that.

[frost_51]

My processor is my Yamaha HTR and the sub pre out gain is at maximum. The gain on the 1310 is also maxed before I get any substantial output. I could swap some resistors on the op amps of the input section but its been a while since i was in school and i don't really trust myself.

[Paul O]

If I plan on using a feed back destroyer with eq will I need the clean box?

No, signal gain will be accomplished with that equipment when the signal is passed through. I'd suggest you look at the DEQ2496 instead of the FBQ and seperate EQ, there's nothing like having a visual display when trying to set a parametric filter, and there are other features like auto EQ and such may that come in handy

[wg_ski]

I could swap some resistors on the op amps of the input section but its been a while since i was in school and i don't really trust myself.

I would only do this if I trusted myself, and if not using other processing equipment (which has gain). If you haven't got the EQ yet but it's in the plan, that could be a dilemma. Because you want the gain now but want to put it back the way it was later (better S/N).

[frost_51]

I found a FBQ 6200 for $60. It has a high and low pass cut as well as input sensitivity gain. I think this should work? Any opinions on this device?

[exojam]

Have you tried placing the amp in stereo mode and only running the sub from the channel question?