Valve noise

RichardjRichardj Frets: 1538
So I'm playing around with my amp following the tone stack discussion and, because I'm listening carefully to it, I notice that there is a bit of springy reverberation sound coming from the EL34's.  These are fairly new matched TAD's that have come direct from Koch ready tested to fit without any biasing (no-one anywhere near here I would remotely trust to fiddle with the bias so have to use them). The amp sounds exactly as it should so I don't immediately think they are failing. Is it usual to hear them reverberating a bit or is something loose or on it's way out?
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Comments

  • ecc83ecc83 Frets: 1589
    Microphonic EL34s are (now) quite common.
    I have in the past had to change them because they really coloured the sound of an amp and in at least one case, caused it to "take off"!.

    I have written "now" because although I had been "out of" valved gear for the last  20years or so I do not remember output valves ever suffering this problem in days of yore? I would urge anyone who fits new op valves to give them a "flick" and if they make more than a very slight noise, complain!

    Dave.
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  • ICBMICBM Frets: 71952
    I have an entire matched set of near mint vintage Mullard XF2 EL34s which *all* rattle audibly in a guitar amp :(.

    Sadly I may have to sell them to a hi-fi bod...

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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  • ecc83ecc83 Frets: 1589
    ICBM said:
    I have an entire matched set of near mint vintage Mullard XF2 EL34s which *all* rattle audibly in a guitar amp :(.

    Sadly I may have to sell them to a hi-fi bod...
    I understand that there is at least one guitar amp that has feedback around the OP valves."ultra linear" taps? That gain reduction should all but eliminate the rattle? 

    Dave


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  • ICBMICBM Frets: 71952
    ecc83 said:
    I understand that there is at least one guitar amp that has feedback around the OP valves."ultra linear" taps? That gain reduction should all but eliminate the rattle?
    Not completely. The amp in question does have negative feedback (usually!). The rattle is mostly just mechanical and is annoying when the amp is at low volume, but it does appear to be in the amplified signal a tiny bit as well.

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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  • ecc83ecc83 Frets: 1589
    ICBM said:
    ecc83 said:
    I understand that there is at least one guitar amp that has feedback around the OP valves."ultra linear" taps? That gain reduction should all but eliminate the rattle?
    Not completely. The amp in question does have negative feedback (usually!). The rattle is mostly just mechanical and is annoying when the amp is at low volume, but it does appear to be in the amplified signal a tiny bit as well.

    Ah! My turn to apologies! I took all the noise to be coming out of the speaker. We therefore have two issues, microphony AND mechanical/audible rattle.

    Dave.

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  • ICBMICBM Frets: 71952
    ecc83 said:
    Ah! My turn to apologies! I took all the noise to be coming out of the speaker. We therefore have two issues, microphony AND mechanical/audible rattle.

    Definitely, but I would guess that the two are (probably strongly) related, in that both are caused by loose internal components. It's perhaps possible that some things that rattle (eg mica spacers) wouldn't cause microphonics, or that some things that cause microphonics (eg vibrating grid wires) might not be audible mechanically, but I'd guess that by and large the two go together to one degree or another.

    Now if you want real bother, why are some ICs microphonic?!

    :)

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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  • RichardjRichardj Frets: 1538
    Just about following this, the noise actually just seems to be mechanical, it doesn't seem to be colouring the speaker output in any way, I'm just noticing it more as the amp is set low so I can listen to it more carefully.
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