Hi this is a real mystery to me, and wonder if there are any solutions. when I turn on my Q2 connected to my fender amp, all is quiet for about 5 minutes, but then I experience an awful hissing coming from the amp,which can last up to an hour, now here is the twist, if I disconnect the Q2 from the amp, and plug it into my PA system, it is completely silent ? plug it back into the amp and the noise is there...arrgg. I can plug my guitar directly into the amp bypassing the Q2, and it is silent, no background hiss just clean sounds. So my dilemma is, is it the amp, or is it the Q2, is there something not compatible ?? any ideas. Colin
Check your amp mains cable connection for a possible bad earth. Also try a different signal cable from the Q2 to the amp. The Q2 does not have an earth connection as it relies on the signal cable to the amp for an earth. Also try a different mains socket to see if it changes anything. Regards, Charlie
Hi Charlie I have tried everything you have suggested, but without any success, even swapped the original alesis power adaptor for another, still have the frying - crackling sizzle, the longer the Q2 and Amp are on the more increased it gets, the puzzle for me is why does it disappear when plugged into my PA, I have read that the Blues junior has had some issues with the pre-amp valves creating background noise, but trying that could be costly and a gamble, I have read on this website sometime ago that the output control knob can be noisy due to the lack of movement, in my case it does increase the noise slightly when turned up. Regards colin
Sometimes you'll get dc leakage from the first 12AX7 which will lead to a small degree of dc back to the input jack. (The blues junior has no input cap to prevent this!). As the Q2 also has a dc coupled output, this could produce annoing noisys effects!.
You may try swapping the first tube with one of the other 12AX7 (as you have three of them in the blues junior) and see if that makes anny difference...
Hi I may try what you suggested this weekend, do I assume that the first valve is the one on the right as you look at them, I used to have some 12AX7 valves , can't find them at present .. but can try without, will let you know. regards colin
Hi Well unfortunately, removing the tube and repositioning it hasn't cured the noise issue, although at first I got really hopeful, due to the fact that when I removed the back of the amp, the middle valve was hanging halfway out at an angle, but having swapped the valves and made sure they were all in straight it still has the frying sound, and also when I select bypass on the Q2, there are all sorts of weird hunting and tracking noises, plug my guitar directly into the amp, and its as quite as a mouse hardly any noise at, even sat right on top of it. Many thanks for your suggestions, and Roger, I understand, and thank you for your interest, its back to the drawing board, or a new delay regards colin
I have a service manual for the Q2 which I can send you if it might help (message me via this board with your email rather than posting it on a public forum).
It was common practice to remove the 2 input capacitors so the Q2 matched the guitar output better. I doubt this would be the cause of your problem though, but it might be worth checking if it's been done on yours and whether it's done properly.
Some Quadraverbs (though not specifically the Q2) suffered noise from the power supply rails and a fix is to replace and/or increase the value of the electrolytic smoothing capacitors.
I've come across a couple of Quadraverbs (Q2 and Q20) where the system clock signal could be heard at the output. There is a compander (NE571 from memory) that had failed. I can't recall if this is an easy fix as I don't remember if it's soldered to the board or socketed.
A noise gate will stop the noise when nothing is being played, but the noise will still be there when you play something and open the gate. As long as the noise isn't louder than the note(s) being played you shouldn't notice it. That is the idea of a noise gate.
This is assuming the noise is coming from the Q2 and not being generated from some outside source.
Well after much consideration, I decided on buying a noise gate/reducer, and I am happy to say it has done the trick the awe-full noises that kept accuring from my Q2 have been put to rest, after 2wks of use it is still hush quiet . I eventually bought the Behringer NR300 it got great revues against all the more expensive models, and as it was a bit of an experiment, it was the right choice , plus it has threshold/decay adjustments … and the price @£22 is amazing, if you are experiencing similar noise levels from a Q2 or other models ...it does the trick