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Guitar amps have preamp sections (think unpowered audio mixer) and power amp sections (Crown rack-mount amp). An excellent way to isolate audio problems if amp is still producing audio is to check the preamp out (line out). Preamp output distorted = preamp failure. Connect MP3 player to "Power Amp In"...sound distorted = power amp failure. In your case the latter is the case as your "line out" is clean. Also test each speaker for clear sound as speaker cone damage from being overpowered is fairly common. At 300w. I'll assume the failure was not from cranking the volume to loud but a shorted speaker or speaker wiring could zap the power amp in an instant.
Try connecting them to another amplifier...you can use the speaker output of a guitar amp as a quick test. If the amp (and mixer) check OK, it sounds like you are about to become good friends with your local speaker reconing shop.
Remember...Distorted Audio Can Kill Speakers even at low volumes. It happens because sine waves become square waves. Google it for additional information.
this is a electronic problem. there must be a capacitor/s in the output section that's swollen and will keep giving the same problem unless its replaced.
It seems it is a power supply problem; distorted sound, no meters, solo buttons not working, headphones low level and distorted. One of the power supply voltages might be too low or even missing. The Helix series mixers use mainly 4 supply voltages: + 15 V and - 15 V for the analog part (audio), + 5 V for the DSP and logic and +48 V only for the phantom power. If for example the + or - 15 V is too low, clipping of the positive or negative parts of the waveform (dependng on which voltage is too low) will occur. If possible, first measure the voltages coming out of the power supply. You could use a metal part of a jack as ground reference. For the FireWire board an extra voltage supplied by the switched PSU is used. It is specified as +12,2 V, but I measured 14 V. This voltage is lowered to + 5 V by a resistor on the FW board and a 7805 regulator. (Not very efficient!) But as far as I can see, the FW voltage is not the problem here. I have some service documentation of the Helix series mixers (12, 17 and 24, so if you need more you can conatct me: frankdevries [at] versatel.nl.
Realize that the number on the volume control is only relative... it means nothing regarding what the amp can produce. With a high level output guitar you can easily drive the amp into distortion at very low volume control level settings... what counts is the actual output sound volume and specifically the voltage output going to the speaker. Once the amp reaches saturation, any further input just pushes it into distortion or "flat topping".
An oscilloscope on the output will quickly show when amp starts to flat top.
1. The master volume control on the SR16 is at least half way up. Turn down the amp as needed. Running very low output of the SR16 and high amp gain is sure to get distortion.
2. Check power adapter is the original and is producing correct voltage.
3. Check that audio cable is high quality instrument cable and not consumer or speaker cable.
The distorted and low volume output plus noise is usually caused by using the wrong power supply adapter. The Alesis SR-16 takes a 9V "A/C" supply not "DC". The A/C supply provides a negative voltage swing which wouldn't exist with a DC supply. So check and make sure you have 9V A/C output supply not DC.
I have just taken it to a repair shop. Thank you. P Middleton.
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