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    Annoying Buzzing from Amp

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    Pelmog

    Posts : 1
    Join date : 2014-09-18

    Annoying Buzzing from Amp

    Post by Pelmog on Thu Aug 06, 2015 1:19 pm

    I've had a Grandmeister 36 for about a year and play my PRS Studio into an average 2x12 cab.

    The amp has always been sweet and perfect, but over the last week it has developed the habit of buzzing on certain notes on the high E string. It's not a harmonic or anything, it's an unsubtle buzzing noise - like an amp fault.

    I contacted the seller, but as the amp is more than a year old, they only suggested that I swap out the tubes.

    Is this a reasonable course of action?

    The amp is played each day for an hour or two, and is safe and secure on top of the cab. It's only been moved once, about a year ago for a gig.

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    gravydb

    Posts : 193
    Join date : 2014-06-22
    Location : PA

    Re: Annoying Buzzing from Amp

    Post by gravydb on Thu Aug 06, 2015 2:08 pm

    Swapping out the tubes wouldn't be the first thing I'd try.

    I need to ask some questions that might seem silly.... Is the amp physically buzzing (IE the chassis)? Or is it electronic in nature (IE the buzzing comes thru the speakers)? I've owned amps that had a physical buzz when certain notes were played (sympathetic vibration or whatever it's called) and I'm surprised I didn't end up in the loony bin trying to figure it out.
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    VoodooJeff

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    Age : 43
    Location : dfw, tx

    Re: Annoying Buzzing from Amp

    Post by VoodooJeff on Thu Aug 06, 2015 2:12 pm

    A year with daily use and still stock tubes? I wouldn`t rule out the need for new ones (and if you`ve been using the 5 watt or lower settings, you`ve imposed enormous heat to the inside if the amp). It`s not a big deal, especially with this amp. And don`t let anyone kid you...on newer (read: modern) amps in particular, tube choice makes very little difference in sound. You may notice subtle differences here and there, but tubes are just not going to give your amp a different personality. I use JJs mainly because reliability and consistency are top of the game.

    And generally speaking, preamp tubes will last a looooonnnnngg time. They don`t deal with the same kind of heat that power tubes do so don`t feel guilty about just swapping power tubes.

    (edit: that`s not to say preamp tubes don`t wear out. They most certainly do. But the question at hand is whether or not it could be tube related, not how and why tubes fail Laughing )


    Last edited by VoodooJeff on Thu Aug 06, 2015 2:16 pm; edited 1 time in total (Reason for editing : adding final thought)
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    namklak

    Posts : 185
    Join date : 2015-01-30
    Location : Denver, CO

    Re: Annoying Buzzing from Amp

    Post by namklak on Thu Aug 06, 2015 6:33 pm

    Sorry for the stupid obvious question, but have you tried that PRS into a different amp/cab?

    The output tubes can be "hurt/aged" if you come out of standby too soon after power on. I've do that by accident about twice a year.
    A funny little thing, EL84s were designed for a plate voltage of 300V. A little ohms law, that's about 8W per tube. Many EL84 amps run the plate voltage at 400V, resulting in about 12W per tube. For example, I know of a Carvin amp that uses four EL84s and puts out 50W. Our friend the GM36 puts out 36W from four EL84s. Point being, the EL84s last longer in the GM than other amps. In fact, a well made EL84 can go 5000 hours with a plate V of 300V.
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    bordonbert

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    Age : 97
    Location : Southern England

    Re: Annoying Buzzing from Amp

    Post by bordonbert on Fri Aug 07, 2015 6:46 am

    Got to say Voodoo I strongly disagree with your comment on swapping out valves, though it's great to come across another sceptic.  Coming from a long electronic engineering background, I'm the arch sceptic of mojo!  I promise you, you could not be more against the idea of differences in sound caused by capacitor types, transistor types, diode types, than I am!  It's all hogwash and generates money for people who don't generally deserve it.  Double blind testing proves that no one, not even the golden auricularly gifted brigade, can hear differences when tests are done rigourously.  And I used to feel the same way about valves.  That was until I got my hands on a TM36.

    Generally I loved it but found it could be strident, fatiguing and lacking bottom end.  So I sorted out speakers and bottom end appeared, but it was still a tad fizzy and harsh at the top.  So I bit the bullet and tried a couple of Electro Harmonix ECC83s I had lying around, never expecting things to alter.  And what do you know, things genuinely improved.  Now with the easy valve changing capabilities of the H&Ks it is simple to swap and retry without too much delay between.  I swapped and tried a good number of times before I was convinced that I was not tricking myself.  I was forced to admit that it was a real phenomenon.  So I invested in a set of JJ EL84s and it really made more of a difference.

    Now I have a GM36 as well, I have gone a stage further and introduced a JJ 12AX7 in V1 and a Mullard NOS 12AT7WA CV4024 into my V3 position as the phase inverter.  The gain has gone down a tad, the last vestige of roughness has been removed and I can leave it alone and just play.  Sadly I had to admit that valves are not only electronic components, they are reliant on mechanical construction and materials for their electrical action.  If there is one component which will show differences, as you said not night and day but discernible, it is them.

    And I still preach (endlessly, apologies to all  Embarassed  ) against the crap talked about capacitor choice in guitar tone controls, mojo diodes in distortion pedals, and magic transistors in amps and pedals in general.  None of it makes a Scooby Doo of difference in a guitar application.  The only difference is in your wallet afterwards.

    And as to the heat issue....  Have you seen my thread on a forced cooling plinth with computer fans in the TM36 forum?  Wink  That diy unit also fits the GM36 of course.  I have it better finished now and it really does the job splendidly, although I do believe it's actually not quite the problem people may think.  The extreme heat comes from the valves, everything else, even the power soak, is in the range that electronics copes with every day.  The valve generated heat travels upwards in the upper chamber and is soaked away very effectively by the top and back metal.  UYou don't get that with an old school wooden case head.  The lower compartment is actually fairly well insulated from it.
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    VoodooJeff

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    Age : 43
    Location : dfw, tx

    Re: Annoying Buzzing from Amp

    Post by VoodooJeff on Fri Aug 07, 2015 9:12 am

    bordonbert wrote:Got to say Voodoo......

    Meh, tubes can be swapped on this amp in ten minutes and it`s (more or less) self biasing. I may do a little experimenting. I turned a cold and harsh Legacy 3 into the warmest, almost EVH sounding device by playing with tubes and a little liberty with the bias (the only problem with that amp is that it`s impossibly loud. You`d think that wouldn`t be a "problem" for guitar players but to record with....it was a PITA). I was actually an electronic engineering major before I got fed up and got a music degree hahaha.

    Regarding heat, we all know it`s the enemy, and anything we can do to keep our stuff cooler is good. I noticed it gets incredibly hot on 1w or silent mode, so I devised a very simple fan set up and it stays cool to the touch. Just because a funny car engine "can" turn 10Krpm doesn`t mean it`ll last long kept there. Cooler = better (I will concede that power tubes do sound best when heat soaked).

    As for the other internals (caps and so forth), I totally agree with you. I don`t mind spending a bit more for "good" parts, and by good, I mean more durable. A 50 year old NOS capacitor may indeed sound different, but it`s because it`s f***ing OLD and it`s capacitance is struggling to hold on to life LOL.

    Back to tubes for my wrap up, I`ve had a tube amp or two (or twelve) in my day, and at anything less than ear splitting volumes, the differences are subtle at best in my experience. I`m actually glad to hear the GM36 may respond to some tube experimenting. I do find it to be a little brittle at times.

    afro
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    bordonbert

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    Age : 97
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    Re: Annoying Buzzing from Amp

    Post by bordonbert on Fri Aug 07, 2015 12:59 pm

    Good man. Interesting observations. Make sure to keep us up to date with anything you find in your messing around, it's all good info at the end of the day.

    So you won't be paying £40 for a couple of those "amazing" paper in oil NOS types that are going around on ebay then? Razz Absolutely agree with you in the "struggling to hold on to life" thing, great description of the whole rip off! (Time to get on the bandwagon and fund my next amp.) I've actually got a box load of unused original 60s OC71s if you don't mind paying me £25.00 each? I promise they sound awesome in a 2 transistor fuzz unit that's as rough as a dead bear's bum (read s**t) just like the originals I played in the late 60s. Laughing

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