vmanj

12AX7 question
« on: February 04, 2019, 04:21:47 AM »
Greetings to all.

I have a 12AX7 question.

I want to connect only one half of the triode.

What needs to be done with contacts that will not be used - connect them together or just leave them unconnected?


RuudNL

Re: 12AX7 question
« Reply #1 on: February 04, 2019, 04:25:29 AM »
Leave the unused pins open and don't use the filament for the half you don't use.
There is a solution for every problem!

http://www.vansteenisaudio.nl

Mylithra

Re: 12AX7 question
« Reply #2 on: February 04, 2019, 05:59:52 AM »
Leave the unused pins open and don't use the filament for the half you don't use.
This is fine if your heaters are 6.3v. If your heaters are 12v, you'll have to leave that triode heater connected but you dont need to hook up the other 3 elements.

vmanj

Re: 12AX7 question
« Reply #3 on: February 04, 2019, 01:55:57 PM »
I see, thanks.

clintrubber

Re: 12AX7 question
« Reply #4 on: February 08, 2019, 07:33:26 AM »
Leave the unused pins open and don't use the filament for the half you don't use.

That's interesting. I'm well aware of the three heater pins, but hadn't realized that beyond the 12,6 & 6,3 V possibility
it enables heating up each section separately.

So I figure the 1st section (pins 1,2,3) is heated by the heater connected between pins 4 & 9.

Nice, despite using tubes we can save a bit of energy here ;-)

Re: 12AX7 question
« Reply #5 on: February 08, 2019, 10:24:16 PM »
In the AKG C 12 Mike they tied cathode, grid & plate (anode) toground, in the unused half of the 12AY7 (6072) tube.

clintrubber

Re: 12AX7 question
« Reply #6 on: February 09, 2019, 07:12:25 AM »
In the AKG C 12 Mike they tied cathode, grid & plate (anode) toground, in the unused half of the 12AY7 (6072) tube.

Curious to the benefits, if at all. Or possibly just keeping everything tidy & defined, without much second thought (the latter not that likely though for such a company).

But in the unlikely case that any small tiny parasitics between the tube sections are playing a role, then they're increased by the ground-connections of the unused triode section.

scott2000

Re: 12AX7 question
« Reply #7 on: February 09, 2019, 11:23:23 AM »
this circuit leaves center tap unconnected and grounds one heater? This has to do with using dc??

Shows "one channel only"

Is the other channel using the same tube with this configuration left on heaters???

I'll say yes..... ok,,,,maybe?
« Last Edit: February 10, 2019, 10:36:27 AM by scott2000 »

abbey road d enfer

Re: 12AX7 question
« Reply #8 on: February 09, 2019, 12:48:10 PM »
But in the unlikely case that any small tiny parasitics between the tube sections are playing a role, then they're increased by the ground-connections of the unused triode section.
In some cases, having increased but controlled parasitics is preferrable to random.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

clintrubber

Re: 12AX7 question
« Reply #9 on: February 19, 2019, 12:02:57 PM »
In some cases, having increased but controlled parasitics is preferrable to random.

Check!  :)


Mylithra

Re: 12AX7 question
« Reply #10 on: February 19, 2019, 02:01:29 PM »
this circuit leaves center tap unconnected and grounds one heater? This has to do with using dc??

Shows "one channel only"

Is the other channel using the same tube with this configuration left on heaters???

I'll say yes..... ok,,,,maybe?

You need 6.3v per heater triode. If you're running DC heaters at 12v, you have to have the heaters in series. If you're DC heater supply is 6v, your heaters should be parallel.


 

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