Axe Ultra + QSC PLX1602

S

squalaxe

Member
Hi everyone,
I'm a very new user of the axe ultra and it works fine true my sound card (Presonus). But i've bought a QSC PLX1602 to play "live" with my Rectifier 4*12. The power amp is a 1600 watts via the stereo channel but while ply on it it's like if i had a 10w amp ...
Is there anything on the Axe that i have to do ? The Cab sim is disabled and that everything i did ...
Thanks for your help.
Ciao,
 
Describe exactly how you have it connected. Lowest output would be if your cab is 16 ohm and you run it from one side of the amp. That amp is 300w per channel @8ohm, so would be about 150w @16ohm. Check that the bridge switch is not engaged. Check what impedance the drivers in your cab are, and how they are wired. It looks like that cab stock had 8 ohm drivers wired in series/parallel for 8 ohm total cab load. If this is the case, I would suggest wiring it for stereo, each pair of 8 ohm speakers in parallel for a 4 ohm load connected to each channel of the power amp. This is my preference for a 4x12, you won't get a big stereo spread but you will get some ambience from the stereo FX.
 
Hi and thanks for your reply,

Well, it's plug from the unbalanced output1 in the ch1 input of the power amp and to the 8 ohms input of the rectifier cab.
I've tried with the bridge, with out, in // or in stereo mod but it didn't change anything ... I think i should have made a mistake on the axe configuration, something i can check ?
 
Turn the Cab Sims ON. See if the volume comes back.

Also, just do a MONO setup first. Go Left out of the AXE, Left in on Power Amp, then to Mono cab.
 
You should try using a 1/4" to XLR patch cable. The 1/4" inputs on the QSC are TRS, and may not match up impedance wise with a mono 1/4" cable. Use the XLR inputs on the amp.
 
Can you take a picture or tell us how all the switches on the qsc amp are set? This sounds like nothing to do with the axe.
 
squalaxe said:
The power amp is a 1600 watts via the stereo channel
Click to expand...
That is NOT correct.. The amp will produce 1600 watts in bridged (mono) mode into a 4-Ohm speaker load. You are NOT using it in that manner - based on your posts.
If you have the standard Rectifier 4x12.. it's a 240w cab at 8-ohm mono, 4-ohm stereo (or bi-amped).
IMHO - YOU HAVE TOO MUCH AMP for that CAB !!
If you power it with the 1602 in bridged mode, you will instantly blow up your V30 speakers. A 1202 would have been plenty. if you follow the steps below, you will get max volume out of your setup, but BE CAREFUL as each side of the 1602 can produce 550 watts into 4-Ohms stereo... that's 1100w going into a 240w cab - if running it in stereo mode - which is also WAY TOO MUCH POWER - unless you know what you are doing.

You should connect the XLR (OUT1) on back of Axe, to input CH1 on 1602.
If you want to run in stereo, connect the 2nd XLR OUT to XLR in CH2 on 1602.

I HIGHLY RECOMMEND that you DO NOT RUN STEREO, as you run a serious risk of DESTROYING YOUR SPEAKERS with the PLX1602. I SUGGEST a single connection from Axe to CH1 of 1602 and single speaker cable into the MONO (8-Ohm) jack!
That will give you 325w into the cab. Loud, but pretty safe!~

NOTE: for anyone else reading this, the following steps DO NOT APPLY TO ANY TUBE AMP, SOLID STATE ONLY !!!
Click to expand...
BEFORE you connect the cab, you will need and gain-stage (optimize) your system - as follows:
  1. Turn down [off] OUT1 level on front of Axe. Power it up.
  2. Turn the amps level controls all the way down (to the left), then power up the 1602
  3. If you have an Axe-II turn OUT1 all the way up - to unity gain output level.
  4. While playing your loudest preset - you may need someone to help with this - slowly turn up each of the level controls on the 1602, until the RED clip light starts flashing (or comes on), then back down each level until the clip light is no longer on.
  5. Turn off the 1602, then the Axe.
  6. Connect your cab to the amp.. USE SPEAKER CABLES (TS/Mono), not TRS.
  7. Turn down Axe OUT1 level, Power up the Axe
  8. Power up the amp.
  9. CAREFULLY - turn up the OUT1 level...
At this point, your ears should be starting to bleed.
PLEASE - PAY ATTENTION to my suggestions above. I accept no responsibility for any damage you may cause your cab from following these steps. If you read/understand what I said, you should be OK.

Better still, trade the amp in for a PLX1202 or something with similar specs.
 
Great post. Let me 2nd the notion that you must follow the instructions exactly as stated but then it will work and be optimized.
 
Ok thanks so ; it's plug from the unbalanced output1 in the ch1 input of the power amp (after i plug the spekon cable to the real cab).
on the power amp it's set like that for my last test :
QSC_set.jpg
Thanks for your help.

Just seen your reply s0c9.
I knew that i had a too much amp for my cab, and that why i was very suprised not to be bleed :eek: while i've tested it.
I gonna try your procedure carefully and really thanks for your long post.
Ciao,
 
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squalaxe said:
Ok thanks so ; it's plug from the unbalanced output1 in the ch1 input of the power amp (after i plug the spekon cable to the real cab).
on the power amp it's set like that for my last test :
View attachment 8501
Thanks for your help.

Just seen your reply s0c9.
I knew that i had a too much amp for my cab, and that why i was very suprised not to be bleed :eek: while i've tested it.
I gonna try your procedure carefully and really thanks for your long post.
Ciao,
Click to expand...
Squalaxe - if you are connecting your cab via a speakon jack using the settings above, i now understand why you are hearing what you say you are. It will not work with the settings posted above.. You have BRIDGED MODE set to ON !! Only the top Speakon will work in that mode and you have Parallel inputs ON, so you CAN'T run stereo either.
Turn amp off.
Flip that bridge mode switch OFF, then follow my recommendations above and protect your ears.
 
Hi,
could you put red dots on my pict abrove to show me how all should be set 50hz or 30 hz ?Filter ?
thanks a lot.
Ciao,
 
squalaxe said:
Hi,
could you put red dots on my pict abrove to show me how all should be set 50hz or 30 hz ?Filter ?
thanks a lot.
Ciao,
Click to expand...
Filters are fine @50hz, will make little difference for electric guitar. Turn off bridge mode, to use it you must connect to pins 1+/2+ of Ch1 NL4 or to the two positive banana jacks. Turn off parallel inputs. You should have plenty of power from just one side of amp. But I disagree about "instantly blowing speakers" in stereo mode, it is possible to overpower but I've run guitar cabs using similar or larger amps with no ill results. I think having the extra clean headroom is beneficial with a solid state amp. Tube amps are capable of more output, most can approach doubling their rated power. They will be distorting at that point, but it's musical for electric guitar. Solid State amps for the most part do not sound good when pushed into distortion. It's typically recommended to use a solid state amp rated 2x the RMS power of cab/drivers. Pro sound guys are more concerned about underpowering, as clipping an amp can damage drivers more than clean power.
 
i didn't try it yet, but gonna follow all your advices. Thanks again and hope i won't blow everything up (ears included :eek:ops)

I have to used the 12k Balanced input ?

I'll give you a feed back on satuday ... Thx again.
 
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So here it is, i've tested it as you adviced me but nothing more than before, even whit the 8 or 4 ohms input of the cab. Is the power amp dead ???
 
Nobody ???

Just to know, what is your "based" setting for the main output on a preset ? Do start from 0 and put more while you want to push a preset or do you start with an hightest value than 0 ?
Thanks
 
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