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    GM36: Feedback on Boosted Gain

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    Eam

    Posts : 2
    Join date : 2018-02-21

    GM36: Feedback on Boosted Gain

    Post by Eam on Wed Feb 21, 2018 11:27 pm

    Been playing a GM36 at home (do not gig) for the last 2-1/2 years at bedroom volume. Noticed in the last month or so that when boosted gain is engaged, especially in the lead and ultra channels, I start to get feed back. While the feedback is eradicated by engaging the noise gate, this was never an issue before. An example of a typical setting that will feedback would be Preset channel 3 - banks 10 and 12. Note that this happens when I stop playing, and occasionally when I am playing. Long and Mcquade, here in Canada say this is normal - their tech checked the amp. I beg to differ since this did not happen before (I think). I have changed the tubes thinking this would help, since tubes can become microphonic. No luck; however the new tubes TungSols have improved the tone imo (much warmer now) and reduced the hum. Btw I have tested multiple guitars on it with the same results - issue is not the pups. Anyone else experience this? Can someone try preset channel 3, banks 10 and 12, and let me know if there is feedback without engaging the noise-gate. Much appreciated.
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    bordonbert

    Posts : 1045
    Join date : 2015-01-28
    Age : 98
    Location : Southern England

    Re: GM36: Feedback on Boosted Gain

    Post by bordonbert on Sun Feb 25, 2018 7:47 pm

    Odd that it should come in after so much time and that does suggest something ageing with the most likely culprit being valves. Feedback with boosted gain on the Lead and Ultra channels would not be unusual, there is a shed load of gain in there on tap, but if it didn't do it before with the same settings it does seem odd.

    You haven't done anything like rearranged your bedroom layout have you? Just changing the location of the amp in relation to where you are playing or the soft absorbent and hard reflective surfaces within the room which would reduce or enhance reflections will affect this too. Stage players often look for "magic" spots on the stage where the reflections focus to create feedback, and they mark them with tape so they can use that spot to get feedback when they want it.
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    Eam

    Posts : 2
    Join date : 2018-02-21

    Re: GM36: Feedback on Boosted Gain

    Post by Eam on Sun Feb 25, 2018 8:15 pm

    Haven't changed the location of the amp so that variable can be eliminated. Can't be tubes since i changed those recently. Could be other components - capacitor, transformer, etc. - not sure since I am not an expert. Anyway it is not too bad since i can always roll back the gain to eliminate the feedback. Just find it a little irritating. Thanks for your feedback though (pun not intended).
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    bordonbert

    Posts : 1045
    Join date : 2015-01-28
    Age : 98
    Location : Southern England

    Re: GM36: Feedback on Boosted Gain

    Post by bordonbert on Sun Feb 25, 2018 8:24 pm

    It's not likely to be other components becoming microphonic enough to cause that level of feedback, possibly if their values are drifting seriously.  I would just keep an eye on things and see if they continue to drift and get worse.  If you are just using the standard presets and have no custom voices to lose then I would do a factory reset to make sure everything is really as it was.  It is always possible you have corruption in, say, the gain values for some of the current presets.  Let us know if it keeps on getting worse.
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    Egads

    Posts : 84
    Join date : 2014-05-26

    Re: GM36: Feedback on Boosted Gain

    Post by Egads on Thu Mar 15, 2018 4:38 pm

    Just out of curiosity, what settings are you running on the lead and ultra channels? Ultra isn't really my thing, but I can get instant feedback on that channel with the gain at 9 o'clock and almost any volume in the room. I'm not asking in doubt of your experience, but wondering if you previous experience was more of an anomaly.

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