This problem does not exist when when the reverb is turned to 0.
But if I turn up the reverb, it will be fine, for a few minutes, then all of the sudden this hum starts appearing, at first, very subtle, but progressively getting worse. IF I turn the reverb to 0...it immediately goes away.
Any suggestions will be appreciated. Thank you in advance.
jay
But if I turn up the reverb, it will be fine, for a few minutes, then all of the sudden this hum starts appearing, at first, very subtle, but progressively getting worse. IF I turn the reverb to 0...it immediately goes away.
Any suggestions will be appreciated. Thank you in advance.
jay
my guess
Mechanical feedback from the pan to the speaker ?
Try moving pan out of the box, and retesting....just a thought.
Mechanical feedback from the pan to the speaker ?
Try moving pan out of the box, and retesting....just a thought.
ok...how do you stop mechanical feedback...it seems very inconsistent...I did take out the pan and that appears to be the reason...but what can be done about this?
Try soft foam mounting pads or suspending on rubber bungees.
It could also be electromagnetic hum pickup if it is at 50/60Hz.
Andy
It could also be electromagnetic hum pickup if it is at 50/60Hz.
Andy
Solutions
If the reverb pan is not inside a reverb pan bag, it should be.
http://www.mojomusicalsupply.com/item.asp?pid=17453&pg=45002&id=4042100
Or:
http://www.mojomusicalsupply.com/item.asp?pid=58213&pg=45002&id=4042110
You could put some acoustic foam over the tank (between tank and speaker too).
The pan can also be treated with silicone, applied to certain spots to control resonance. Don't do this without some guidance though, or you can damage the pan.
Hope this helps.
If the reverb pan is not inside a reverb pan bag, it should be.
http://www.mojomusicalsupply.com/item.asp?pid=17453&pg=45002&id=4042100
Or:
http://www.mojomusicalsupply.com/item.asp?pid=58213&pg=45002&id=4042110
You could put some acoustic foam over the tank (between tank and speaker too).
The pan can also be treated with silicone, applied to certain spots to control resonance. Don't do this without some guidance though, or you can damage the pan.
Hope this helps.
Thanks for the suggestion. It is in a reverb pan bag, with a piece of cardboard underneath it in the bag.
I will try to isolate it with some acoustic foam and see if that helps. Trust me...this is driving me wacko...
I am honestly clueless on determining if it is "it is at 50/60Hz"...but if the isolation attempt doesnt prove fruitful, I will attempt to learn how to find out.
I appreciate the responses.
I will try to isolate it with some acoustic foam and see if that helps. Trust me...this is driving me wacko...
I am honestly clueless on determining if it is "it is at 50/60Hz"...but if the isolation attempt doesnt prove fruitful, I will attempt to learn how to find out.
I appreciate the responses.
well...
sometimes, reverb pans become mechanically sensitive and start to do what you describe. A replacement pan might fix that, assuming it's not a design issue. You could try silicone on the pan as well:
Often, the transducers get loose on the core at each end. These are like small transformer coils, which induce or detect magnetic waves through a laminated metal core. This causes the springs to vibrate and produce reverb.
Adding some RTV Silicone to the transducer and cores (to minimize vibration and stop the coils from moving around), can sometimes fix this. Make sure you DO NOT get silicone on the springs !! You only want to deal with the transducer coils themselves. I also like to add a dab of silicone to the wires at the shell too, which minimizes failures during transport.
Have fun.
sometimes, reverb pans become mechanically sensitive and start to do what you describe. A replacement pan might fix that, assuming it's not a design issue. You could try silicone on the pan as well:
Often, the transducers get loose on the core at each end. These are like small transformer coils, which induce or detect magnetic waves through a laminated metal core. This causes the springs to vibrate and produce reverb.
Adding some RTV Silicone to the transducer and cores (to minimize vibration and stop the coils from moving around), can sometimes fix this. Make sure you DO NOT get silicone on the springs !! You only want to deal with the transducer coils themselves. I also like to add a dab of silicone to the wires at the shell too, which minimizes failures during transport.
Have fun.
Attachments
Alright...thanks for the pics, those helped alot to understand your post...and that does appear like something I can try w/o getting in too much trouble...
Is this possible...
could it possibly be the big 15" magnet on the speaker is the culprit. When I took the tank out, the magnet grabbed the tank on the way out (and way back into the case) and I just wondered if the magnetic field was affecting the springs or something. I put a folded up towel on top of the tank (which is in a tank case) and didn't get the hum, but of course it could be the watched pot doesn't boil syndrome...
Any thoughts ....
Is this possible...
could it possibly be the big 15" magnet on the speaker is the culprit. When I took the tank out, the magnet grabbed the tank on the way out (and way back into the case) and I just wondered if the magnetic field was affecting the springs or something. I put a folded up towel on top of the tank (which is in a tank case) and didn't get the hum, but of course it could be the watched pot doesn't boil syndrome...
Any thoughts ....
Magnet
No, the magnet is not at fault. That's normal for the pan to be attracted to it...it's metal.
No, the magnet is not at fault. That's normal for the pan to be attracted to it...it's metal.
I am going to take a guess here since you didn't say what king of hum it is, but sounds like your going into self oscillation. This amp uses a Opamp for the tank driver and for some reason you may be getting way too much gain. You can get a schema from here if you dont have one. http://www.freeinfosociety.com/electronics/schempage.php?cat=1Just just my .02! Cheers
Yes...
It indeed sounds like self-oscillation, but the poster has not mentioned whether this has always happened, or recently started happening. If it's started recently the pan more than likely has become microphonic. If it always happened, then it's a design issue. You could easily roll off the low end on the pan return amp, and tweak it, but let's first make sure it's not a matter of the pan acting up first...
😀
It indeed sounds like self-oscillation, but the poster has not mentioned whether this has always happened, or recently started happening. If it's started recently the pan more than likely has become microphonic. If it always happened, then it's a design issue. You could easily roll off the low end on the pan return amp, and tweak it, but let's first make sure it's not a matter of the pan acting up first...
😀
Gosh, you guys are great. Thanks for all the attention.
No, it just started happening the other night. I was playing an acoustic electric viper nylon and it started in the background and then continued to GROW. Happened with and without a guitar hooked up.
No, it just started happening the other night. I was playing an acoustic electric viper nylon and it started in the background and then continued to GROW. Happened with and without a guitar hooked up.
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