S
stonabus
Guest
sorry, im amp-dumb.
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Gearjoneser
Gear Ho
Re: why do 12AX7s have covers?
Probably because tube socket vendors sold them that way. The other reasons would be to dampen microphonics, and to protect them from being broken or falling out.
Probably because tube socket vendors sold them that way. The other reasons would be to dampen microphonics, and to protect them from being broken or falling out.
sosomething
Seymour Duncan Customer Support
Re: why do 12AX7s have covers?
Yup.
They come with the amp, not the tubes. Not all amps have tube shields, either.
Yup.
They come with the amp, not the tubes. Not all amps have tube shields, either.
PUCKBOY99
Irish Flagologist
Re: why do 12AX7s have covers?
I always thought it had something to do with microphonics or the tubes picking up some type of interference :dunno:
The Hiwatt I used to have actually had a "sheild" separating the power tubes(in the rear) & the preamp tubes (in the front). It was annoying because you had to pull the chassis every time you wanted to change a tube.
I always thought it had something to do with microphonics or the tubes picking up some type of interference :dunno:
The Hiwatt I used to have actually had a "sheild" separating the power tubes(in the rear) & the preamp tubes (in the front). It was annoying because you had to pull the chassis every time you wanted to change a tube.
Rich_S
HomeGrownToneBrewologist
Re: why do 12AX7s have covers?
Those are tube shields - similar to the shielding on your guitar cables. They keep electro-magenetic interference from getting into the tube. Pre-amp tubes need these shields because they amplify small signals, the noise from EMI would be significant compared to the guitar signal, and then the combination would be amplified hundreds of times.
As you move through the amp, the signal gets stronger so that the noise would not be significant as compared to the guitar, and the shields are no longer needed. So, phase inverter tubes probably don't need shields. Tremolo oscillators definitely don't need them, since they're not in the audio path at all.
However, many manufacturers put shields on ALL their 9-pin 12A_7 tubes, because the spring loaded twist-lock shield also prevents the tube from vibrating out of it socket. Cheap insurance.
Those are tube shields - similar to the shielding on your guitar cables. They keep electro-magenetic interference from getting into the tube. Pre-amp tubes need these shields because they amplify small signals, the noise from EMI would be significant compared to the guitar signal, and then the combination would be amplified hundreds of times.
As you move through the amp, the signal gets stronger so that the noise would not be significant as compared to the guitar, and the shields are no longer needed. So, phase inverter tubes probably don't need shields. Tremolo oscillators definitely don't need them, since they're not in the audio path at all.
However, many manufacturers put shields on ALL their 9-pin 12A_7 tubes, because the spring loaded twist-lock shield also prevents the tube from vibrating out of it socket. Cheap insurance.
