Tube Question: Triodes - do they or can they be configured to invert?

[frequencycentral]

People around here may have noticed my current obsession with triodes.

However - I'm still learning and would like some help.

1. Do they or can they be configured as inverters?

2. Can anyone supply a schematic example of triodes configured in inverting and non inverting modes?

Thanks tube gurus!

[puretube]

I even can do the amplifying inverter! 

http://www.diystompboxes.com/smfforum/index.php?topic=34107.0

http://www.radau5.ch/basics_1.html

[JDoyle]

People around here may have noticed my current obsession with triodes.

However - I'm still learning and would like some help.

1. Do they or can they be configured as inverters?

2. Can anyone supply a schematic example of triodes configured in inverting and non inverting modes?

Thanks tube gurus!

I seriously hope you weren't scared to ask this!

They can be (or, were first) configured as both. And it is the same overall theory as transistors - you can get both and get similar results from both.

So take a look at any basic transistor stage, common source/emitter or common collector/drain, and substitute a tube for the transistor and the functionality is the same. With the addition of lethal voltages! :-)

Of course all supporting part values will have to be scaled to match the voltages used, including power dissipation.

So, for unity gain inverter, use the same value for the cathode and anode resistors. Non-inverting you only need one resistor. You can get voltage gain from the inverter, but only CURRENT GAIN from the non-inverter.

Anyway, I'm not so hot with tubes - I'm guessing Wikipedia may be a good starting point for you.

Regards,

Jay Doyle

[Fox]

Take a look at a standard guitar amp, say a marshall.....the first 1/2 triode is an inverting amplifier and the triode just before the tone controls is an cathode follower which is non inverting with a gain of almost 1, used to increase the current flow thru the tone circuit (kinda), impedance etc.... as per this circuit :-

http://www.freeinfosociety.com/electronics/schemview.php?id=95

Hope this answers your question

cheers
Fox

[puretube]

http://www.tubecad.com/

tells truth
tells all

[frequencycentral]

I even can do the amplifying inverter! 

http://www.diystompboxes.com/smfforum/index.php?topic=34107.0

http://www.radau5.ch/basics_1.html

http://www.tubecad.com/

tells truth
tells all

Thank puretube - thats a LOT of reading I have to do

I seriously hope you weren't scared to ask this!

They can be (or, were first) configured as both. And it is the same overall theory as transistors - you can get both and get similar results from both.

So take a look at any basic transistor stage, common source/emitter or common collector/drain, and substitute a tube for the transistor and the functionality is the same. With the addition of lethal voltages! :-)

Of course all supporting part values will have to be scaled to match the voltages used, including power dissipation.

So, for unity gain inverter, use the same value for the cathode and anode resistors. Non-inverting you only need one resistor. You can get voltage gain from the inverter, but only CURRENT GAIN from the non-inverter.

Anyway, I'm not so hot with tubes - I'm guessing Wikipedia may be a good starting point for you.

Regards,

Jay Doyle

Never afraid to ask Jay, I'm fully aware of how much I DON't know! The comparison with transistors is really helpful.

Take a look at a standard guitar amp, say a marshall.....the first 1/2 triode is an inverting amplifier and the triode just before the tone controls is an cathode follower which is non inverting with a gain of almost 1, used to increase the current flow thru the tone circuit (kinda), impedance etc.... as per this circuit :-

http://www.freeinfosociety.com/electronics/schemview.php?id=95

Hope this answers your question

cheers
Fox

Thats great Fox, thanks. I need to see working examples to get all this stuff figured.

So let me get this straight:



The triode on the left in inverting, with unity gain?

The triode on the right is non-inverting with a gain of 1? How would I make it unity gain?

Thanks gurus!!

#

EDIT: The triode on the right is non-inverting with a gain of 1? How would I make it unity gain? I would add a 100K resistor between the plate and +ve???

I'm planning to make a tube phaser and a tube multimode VC filter if you're wondering why the question. Anyone want to drop schematics on my lap? Spoonfeed me - save me from my breadboard!

[R.G.]

So let me get this straight:



The triode on the left in inverting, with unity gain?

To a first order, tolerances and so on considered, yet.

The triode on the right is non-inverting with a gain of 1? How would I make it unity gain?
EDIT: The triode on the right is non-inverting with a gain of 1? How would I make it unity gain? I would add a 100K resistor between the plate and +ve???

Um, gain of one is unity gain. I don't understand the question.

The right side is a cathode follower. Because of the limited amount of gain in a triode, it's gain is noticeably less than 1 (=unity), perhaps 0.94 or 0.95. If that's not good enough, you have to go to considerably more complex circuits to get the gain to really be 0.9999999999 instead of 0.94.

[frequencycentral]

Um, gain of one is unity gain. I don't understand the question.

The right side is a cathode follower. Because of the limited amount of gain in a triode, it's gain is noticeably less than 1 (=unity), perhaps 0.94 or 0.95. If that's not good enough, you have to go to considerably more complex circuits to get the gain to really be 0.9999999999 instead of 0.94.

Showing my ignorance again - but learning: unity gain means a gain of 1 (almost)!

Thank you R.G.

[R.G.]

No biggie. Techspeak is a language, just like Etruscan was.

[Derringer]

I've always liked the detail of explanation on this site

http://www.valvewizard.co.uk/


if you look in the left column there, you'll see several phase inverting styles
Cathodyne
Paraphase
DC Long Tailed Pair
AC Long Tailed Pair
Floating Paraphase

download and print this, from the same site,  http://www.freewebs.com/valvewizard1/Common_Gain_Stage.pdf to get a better understanding of setting up triode stages ... I suggest storing it on the back of your toilet as I do

I think it's written very well for the novice/me to understand

[comfortably_numb]

I'll second Valve Wizard as an excellent source of information in an easy to understand, accessible, yet suitably sophisticated style.  I have been exploring low voltage tubes as well, spurred by the Valvecaster thread, and this website has been invaluable in my designing.

Someone else has mentioned looking at tube amp schematics, and I have to second that as well.  I have learned quite a lot by going over the 18 watt Marshall schematics in particular, and referencing the ideas there with what is written on Valve Wizard. 

Anyway, good luck in your experimenting.  I look forward to seeing the fruit of your labor if you choose to share.

Joey

[John Lyons]

Valve wizard
I missed this somehow, thanks for the link.
Between this and the Aiken amps site there is a lot to absorb.
Start printing!

john

[frequencycentral]

I've always liked the detail of explanation on this site
http://www.valvewizard.co.uk/

Amazing! Thank you Derringer.

I now have a pretty good idea of how to create:

1. a stereo tube Leslie simulator
2. a tube phaser

Breadboard set to 'stun'!

I suggest storing it on the back of your toilet as I do

Hahaha - sitting there right now!

I also found this last night: 12 volt submini pentode VCF.       

[Derringer]

haha .. no problem ... glad you guys can use it!

Aiken is awesome, I've read through those sections plenty of times!

comfortably_numb has a good tip there too of looking at valve amp schems

I still consider myself a novice at this stuff but I've definitely come a long way since building a P1 after I first visited www.AX84.com


I need to get a hold of some of those sub-mini tubes ... look like fun !

[Fox]

Yup the Valve Wizard site is good for explanations, highly recommended. 

cheers
Fox

[frequencycentral]

Ok, next question:

EDIT: hmm, maybe I'll start a new thread!