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Triode Naming Convention



 
 
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Old October 5th 20, 04:30 AM posted to rec.audio.tubes
Phil Allison[_4_]
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Default Triode Naming Convention

Big Bad Bob wrote:

==================
Phil Allison wrote:
> > Xtrchessreal wrote:
> >
> >>
> >>> ** The 2 triodes of a 12AX7 / ECC83 are identical,
> >>> one doe not "hum" more than the other.

> > ================================================== ===
> >>>
> >>> Internal connection arrangements for grids and heaters vary
> >>> between versions and brands, maybe having a small effect
> >>> on capacitive coupling if high impedances feed he grids.
> >>>
> >>> It is very common to use DC voltage for the heaters to
> >>> eliminate any issues whether grid or cathode related.
> >>>
> >>
> >> Just read the REMARK on the bottom of page one. https://drtube.com/datasheets/ecc83-philips1970.pdf

> >
> >
> > ** My post is *about that exact remark* - explaining it.
> >
> > An *earthed* internal link from pin 9 travels past grid pin 7 in the scenario described. A link carrying 3.13VAC travels past grid pin 2.
> >
> > This might inject up to 1mV into pin 2 if the grid source impedance were *10Mohms*. However, for a MM phono cartridge, the impedance is 1kohm at 50/60Hz and for a guitar PU about 10kokms.

>
> Actually it's more like 100k for a typical guitar amp pre-amp input,
>


** The source impedance is what matters, and is as I stated.

Guitar PUs and phono PUs are both low value resistors at 50/60 Hz.


> The thing about the phono cartridge amp
> is the RIAA curve which I believe is around 40db higher gain at the low
> end of the frequency spectrum as compare to the high end.


** The RIAA curve boost gain by 16 dB or 6.3 times 50/60Hz compared to mid frequencies. It also boost tube noise by the same amount.

There is NO audible supply frequency hum caused by stray C *inside* a 12AX7.

The OP has misconstrued the comment on the data sheet.


..... Phil
 




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