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    Sound coming out of the Head & High Gain Squeal

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    Flo97

    Posts : 5
    Join date : 2018-01-22

    Sound coming out of the Head & High Gain Squeal

    Post by Flo97 on Mon Jan 22, 2018 10:21 am

    Hey Guys,

    I recently purchased the GM40D and instantly ran into two issues.

    My Setup:
    - Fender AM Std Strat with Custom Shop fat 50s pickups directly plugged into the Amp
    - Using only RedBox AE, with no speaker cabinet connected, directly into an Audio Interface

    1. At high gain settings (Lead channel, gain ~ 50%, with boost engaged) I expierience a terribly loud high gain squeal, which changes with certain amounts of gain, channel & master volume. It also varies depending on my distance & angle facing the amp: At a ceratin distance to the amp it's completely gone, just hearing the  classic 60-cycle hum from my single coils, which can be easily handled with the inbuilt noise gate. Also, at a 90° angle (tip of the head stock facing the amp) it's completely gone and increasing in volume if I face the amp more and more. I also got a Schecter with Seymour Duncan Invaders in it. The Squeal just starts at even higher gain than with the strat. I also heard of the phenomena of EMI, so I turned everything else off in my room (computer, lamps, etc.) but that didn't make a difference at all.

    I do know that it's pretty normal, but is there a way to get rid of it? I read smth about shielding the guitar & waxing the pickups, but does this really make that much of a difference? Would really like to hear how it turned out for smb that had the same issue in the past or your overall opinion.

    2. With nothing but the guitar connected to the head, there is even sound coming directly out of the head. No buzz or hum or smth like that, it's literally my guitar signal how it wound sound with a speaker connected, just overall high, sharp & harsh. It occurs mainly in crunch, lead & ultra channel, and can get pretty loud the higher I put the gain, volume & master controls. You obviously can't hear it with a speaker connected but it's there and it bothers me, since it really sounds unhealthy. I searched for this issue but didn't find anybody else expieriencing it. I also turned in the amp to my dealer which instantly sent me a new one, just to find out that there's the same problem. I really want to know if it's meant to be like that, or if I just had bad luck, with both amps!


    I really dig this amp, and I'd hate to turn it back in. Would really like to know if it's the same case with your amps.

    Looking forward to your answers!
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    bordonbert

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

    Re: Sound coming out of the Head & High Gain Squeal

    Post by bordonbert on Thu Jan 25, 2018 6:44 am

    Sounds like it's just high gain feedback as it changes as you move and turn the guitar in relation to the amp.  A single coil pickup guitar like yours will be sensitive to EMI and that isn't just the 60Hz mains hum region or the higher buzz from fluorescents etc.  It's also the signal from inside the amp where there are large voltages and currents at your playing frequencies running around.  At some angles it will link very well with the fields around the amp and reach a point where the amp generates the field and the guitar picks it up generating a signal which it pushes into the amp which in turn strengthens the field around it and so on.  You have a loop which increases the signal level until it just squeals as you are hearing.  The only answer is to break that loop at some stage.  Just plain move away from the amp or introduce some shielding to the guitar to prevent the pickup.  Even your body between the amp and guitar is going to help a little.

    The usual advice is to fit bits of copper foil around the cavities and ground them.  That will have some effect but nowhere near as much as the average young guitarist led by his "guitar guru" insists it does, the Physics can't lie!  ("Blah blah blah he said Faraday cage.")  Copper is non-magnetic and therefore can have absolutely NO effect on magnetic fields.  It can help a little with some electric fields depending on how well you fit it (and I don't mean how neatly) and ground every single little piece you use, and also how thick it is in relation to the wavelengths of the signals involved which is where the usual limits come in.  It may help, how much depends on the frequencies we are talking about and the sensitivity of the guitar in the first place.  Fitted poorly it may even make the problem worse (no one ever tells you that).  You would have to just try it to see but don't expect anything like perfection.  Don't believe the "Awesome dood i fitd sm n mi axe z now uz gud z nethng joe satriani playz itz stohn cold cole blak silenz" posts, they are plain hyped up bollocks!  It won't make it immune, it can't, huge amounts of money are spent trying to deal with this problem in industry and even with setups of multiple layer stacked boxes of varying wall thickness setups it still gets through.  A bit of copper foil is going to solve the problem in guitars?  I think not but it could give you a little breathing space which might just be enough.

    Waxing the pots?  That's not to solve this problem and there are arguments as to how well that works too if it isn't done absolutely right.  Some say it can even make pickups sound worse!  (What am I saying, it's RADICALLY AWESOME of course, as all home mods are nowadays Very Happy ).

    And also remember, there is a lot of gain in the H&K amps.  Make sure you are only using as much as you really need.

    I'm not really surprised there is some sound from the amp when you are playing in silent mode, there are still large signals moving around in there and that creates physical tensions between parts which pull them together and push them apart.  I'm not a user of silent mode myself so I couldn't say if my own amps do it but there will be others here who can tell you if that happens in their amps.  If it has happened in two new models as you say then it could really just be a normal phenomenon.  I would think valves could be a culprit here knowing what goes on inside them but transformers sing too.  Do you have any valves handy to swap out temporarily to check whether you have one that sings?  I wouldn't have thought it would be a problem in itself, assuming that nothing is actually rattling and rocking about of course.
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    Flo97

    Posts : 5
    Join date : 2018-01-22

    Re: Sound coming out of the Head & High Gain Squeal

    Post by Flo97 on Thu Jan 25, 2018 2:26 pm

    Thank you for your time and advice bordonbert!

    Well I think I will try to properly shield my guitar in the near future, even if it wont help that much. I found a pretty sweet spot in my room now, where the squeal is completely gone. I hope I'll find that spot when rehearsing with the band haha Smile

    To the topic rattle and sound coming out of the amp:

    I recently contacted the H&K Support, which doubled your suspicion; It's due to the high load on the head itself when run in silent recording mode, leading to a few parts in the head oscillating. Obviously you wont hear it when run through a speaker, since it's never that loud. But it should diminish the more wattage you're running the head on. So it's "normal" in their opinion, but I've got the feeling it will lead to sooner malfunctions. But I guess that's the price I gotta take, since I really dig the amp Laughing

    I should have mentioned that I switched the tubes on the first amp that I purchased, but it did nothing to the problem, just reducing hum a tad & improving the sound a lot.



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    bordonbert

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

    Re: Sound coming out of the Head & High Gain Squeal

    Post by bordonbert on Fri Jan 26, 2018 11:02 am

    Flo97 wrote:...but I've got the feeling it will lead to sooner malfunctions.
    No, I wouldn't assume that unless it is extreme.  This is not an unknown phenomenon in electronics and, in moderation, it shouldn't overstress components or  their mountings.  My guess is that you would be hearing the power soak resistors vibrating with the signal, maybe also the output Tx, and they are all pretty strong devices.  The power resistors in particular are mounted across cutouts in the PCB, a very clever way of minimising the effects of heat (which isn't excessive at all despite what people have said here in the past) and this sort of vibration issue. It takes only the tiniest of vibrations, probably not enough for you to really feel with your finger, to make an audible sound.

    Gotcha with the tube swap, that should more or less rule out a valve as the source of the problem.  It's a good move as long as you don't start getting precious about the swap and believe that finding the "right" alternative is the key to sounding exactly like a vintage Fender/Marshall.  The age old forum quote is "the difference is subtle at best".  (I miss those posts from Voodoo Jeff.)

    Seriously, you are obviously one of us who loves what the H&K amps can do, don't sit and worry about it at all, just enjoy the amp and play it.  We have very few reports of anything in the design which is suspect and leads to early failure and I can personally report, as someone who has a lot of experience of this through work, that the design, implementation and build quality are excellent.  You can love or hate the sound of these amps but they do what they were designed to do and are very good workhorses.
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    Flo97

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    Join date : 2018-01-22

    Re: Sound coming out of the Head & High Gain Squeal

    Post by Flo97 on Sun Jan 28, 2018 6:41 am

    After using the amp more and more, I found that a tiny change in master volume dramatically decreases the noise. Had my master usually at around 13/14 o'clock to get some Power Tube saturation. Got it at around 11/12 o'clock now and now it's practically gone.

    Yeah changing the tubes only resulted in a subtle improvement in tone but it DID improve it to my liking and now I love the amp even more. Having read the GM36 Tube Swap Thread, I ordered some JJ 5751 for positions V1 and V2, since I found the gain quite a lot on these amps. Not that it's bad, I just think you can get some more headroom in adjusting the gain knob; some sort of finetuning Smile . Also heard that these sound a bit warmer which I'd love to hear.

    I just love the amp more and more, so versatile, so easy to use and sometimes I just like to sit in front of it and watch the tubes glow haha Laughing

    Ty again for the kind and useful answers, bordonbert!
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    bordonbert

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

    Re: Sound coming out of the Head & High Gain Squeal

    Post by bordonbert on Sun Jan 28, 2018 12:13 pm

    With you on the 5751 front.  Thank God you went for them and not 12AT7s or some other totally non-matching valve (as you probably read Wink ).  The other 12A*7 valves are good valves with real benefits in some uses, but not in a stage properly designed to suit an ECC83/12AX7.  For me there is no major tonal difference with the 5751s just, as you said, more usable area on the Gain control with my less than extreme gain taste.

    I also run a Marshall JVM205H for the band I'm currently in and that has responded to the same sort of swap.  It has an ultra switchable all valve preamp configuration, you can select to add gain stages from 2 to emulate the early non-MV types to 4 for the later high gain types.  There are 6 voices on tap in the 205H, the 410H has 12.  I never used the High gain selections at all until I put in a 5751 into the V2 slot and that made those higher gain types much more accessible for me.  It really did give me usable tones at more sensible gain levels.  Like I said, it's not for everyone but it is an easily validated change, I mean it actually does what is claimed and can be demonstrated doing it on a scope.

    No problem with the answers Flo97, I do look on posts like this as something of a chat break for me during working time, (not "at work" I hasten to add).  If people just want advice or a solution and go that's great but when we chat and swap thoughts it gives me something to think about in return.  I may not agree with a lot of what is posted by younger guys nowadays, it contains a lot of total crap fed to them by older people who are not really knowledgeable but had assumed guru status over the years, but I always think about it carefully and examine any evidence as to true or false before ruling it out.  (Or accepting it of course!)

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