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#1
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Triode tube construction
Anybody--help
In a dual triode tube such as the 12ax7, used to amplify both left and right channels, how is channel separation maintained? Is there some sort of partition inside the tube or is it dependent on the distance separating the two sections.? Thanx for any info. ESTG/ |
#2
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Triode tube construction
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#3
Posted to rec.audio.tubes
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Triode tube construction
In a dual triode tube such as the 12ax7, used to amplify
both left and right channels, how is channel separation maintained? Is there some sort of partition inside the tube or is it dependent on the distance separating the two sections.? The gubbins of each valve is mostly cocooned in its anode. Capacitance arising from proximity between the anodes, and between other pins, is given in datasheets. Ian |
#4
Posted to rec.audio.tubes
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Triode tube construction
On Jun 11, 11:01*pm, "Ian Iveson"
wrote: In a dual triode tube such as the 12ax7, used to amplify both left and right channels, how is channel separation maintained? Is there some sort of partition inside the tube or is it dependent on the distance separating the two sections.? The gubbins of each valve is mostly cocooned in its anode. Capacitance arising from proximity between the anodes, and between other pins, is given in datasheets. Ian Visually, this capacity seems quite small (I've not checked it!) Assuming the plate load are, say, 100K each, my guess it that any cross-talk is at a very high frequency, way out of the audio spectrum... sketch the equivalent circuit and calculate it as homework! Cheers, Roger |
#5
Posted to rec.audio.tubes
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Triode tube construction
Engineer wrote:
On Jun 11, 11:01 pm, "Ian Iveson" wrote: In a dual triode tube such as the 12ax7, used to amplify both left and right channels, how is channel separation maintained? Is there some sort of partition inside the tube or is it dependent on the distance separating the two sections.? The gubbins of each valve is mostly cocooned in its anode. Capacitance arising from proximity between the anodes, and between other pins, is given in datasheets. Ian Visually, this capacity seems quite small (I've not checked it!) Assuming the plate load are, say, 100K each, my guess it that any cross-talk is at a very high frequency, way out of the audio spectrum... sketch the equivalent circuit and calculate it as homework! Cheers, Roger ISTR the capacitance between the two triodes is about 0.4pF which with 100K has a turnover frequency of close to 4MHz. Old Mr. Miller comes into play well before that. Cheers Ian |
#6
Posted to rec.audio.tubes
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Triode tube construction
Anybody--help In a dual triode tube such as the 12ax7, used to amplify both left and right channels, how is channel separation maintained? Is there some sort of partition inside the tube or is it dependent on the distance separating the two sections.? Thanx for any info. ** Aside from the replies here relating to plate to plate capacitance - there is another and rather nasty mechanism for crosstalk in tubes like the 12AX7. It is possible for electrons emitted by the cathode in one half to be attracted to and reach the plate of the other. Crosstalk coupled this way is usually highly distorted, even with small input signals to the side doing the emitting. In the mid 1980s, Philips sold tens of thousands of 12AX7s that had severe distorted crosstalk due to the cathodes of each half protruding beyond the plate structures. The crosstalk was at a level of about -30dB. IIRC - the usual crosstalk figure quoted by makers of 12AX7s is -60dB - which is obviously not all due to inter plate capacitance. These Philips tubes caused havoc when fitted in many guitar amps, as it rendered the volume pot between the two halves ineffective even at zero setting when a very distorted signal was still heard. ...... Phil |
#7
Posted to rec.audio.tubes
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Triode tube construction
On Jun 13, 3:27*am, "Phil Allison" wrote:
Anybody--help In a dual triode tube such as the 12ax7, used to amplify both left and right channels, how is channel separation maintained? Is there some sort of partition inside the tube or is it dependent on the distance separating the two sections.? Thanx for any info. *** Aside from the replies here relating to plate to plate capacitance * - there is another and rather nasty mechanism for crosstalk in tubes like the 12AX7. It is possible for electrons emitted by the cathode in one half to be attracted to and reach the plate of the other. *Crosstalk coupled this way is usually highly distorted, even with small input signals *to the side doing the emitting. In the mid 1980s, Philips sold tens of thousands of 12AX7s that had severe distorted crosstalk due to the cathodes of each half protruding beyond the plate structures. *The crosstalk was at a level of about -30dB. IIRC - *the usual crosstalk figure quoted by makers of 12AX7s is -60dB *- which is obviously not all due to inter plate capacitance. These Philips tubes caused havoc when fitted in *many guitar amps, as it rendered the volume pot between the two halves ineffective even at zero setting when a very distorted signal was still heard. ..... * *Phil Thanx for all the responses. I have owned a cj pv5 since '85 and have done my own upgrades (changed all the caps) and some light trouble shooting (tracked down the source of a loud boom after warmup relay connected the output stages). I was always curious about the principles that made the dual tube useable with acceptable x-talk. I did note that in the phono of the preamp, 2 12ax7 tubes were used for the first stage voltage gain- one for each channel, but followup stages used both halves of the triodes. Clearly there are cost, space as well as other design considerfations to be made. ESTG/ |
#8
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Triode tube construction
Thanx for all the responses. I have owned a cj pv5 since '85 ( snip spew inducing crapology ) ** Never post your demented, audiophool **** under any words of mine again - ****head. Autistic morons like YOU need to be taken out and SHOT. In the public interest, of course. ...... Phil |
#9
Posted to rec.audio.tubes
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Triode tube construction
On Sat, 13 Jun 2009 12:47:38 -0400, Phil Allison wrote:
..... Phil ***( snip spew inducing crapology )*** -- Jesla http://www.pipesmokersforum.com Using Opera's revolutionary e-mail client: http://www.opera.com/mail/ |
#10
Posted to rec.audio.tubes
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Triode tube construction
On Jun 13, 11:47 am, "Phil Allison" wrote:
Thanx for all the responses. I have owned a cj pv5 since '85 ( snip spew inducing crapology ) ** Never post your demented, audiophool **** under any words of mine again - ****head. Autistic morons like YOU need to be taken out and SHOT. In the public interest, of course. ..... Phil Has anyone told you lately that you are a big ****ing stinky ****, Phil? |
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