PP Amplifier output impedance matching

[Diabolical Artificer]

"the valve wizard articles posted by Diabolical Artificer are the easiest texts I found to understand" Yep, I found his articles the easiest to understand too. Morgan Jones book Valve amplifiers isn't too bad either, available online as a PDF. there is also a PDF called - Designing Vacuum Tube Amplifiers and Related Topics that is very extensive and detailed that might be worth a look.

A.

[Terry]

... there is also a PDF called - Designing Vacuum Tube Amplifiers and Related Topics that is very extensive and detailed that might be worth a look.

But don't forget that American is a different language to English! *

I don't know if there is such a thing as a US/UK electronics conversion table but one would be useful if such a thing exists!

* For example, plate (US) = anode (UK).

[Mike Watterson]

Voltages:
A = LT (not just 1.5V batteries)
B = HT (Not just HT batteries)
C = Grid Bias (always negative)
Also older USA schematics show the HT (B+) below the 0V rail on the page rather than at the top. Also often uses /\/\/\ rather than - - - - for grid and draws valves (tubes) on their side with cathode/filament to left and plate to the right.

UK Ever Ready used A and B prefixes for LT and HT packs, though AD probably was from "All Dry" as the first AD packs were combo LT and HT in 1939. The USA had All Dry radios (i.e. 1.4V rather than 2V filaments) from 1938.

The Anode was called a Plate in the UK too, once. Perhaps when the car carburettor air flow control was called a "Strangulator" rather than "Choke".

[Diabolical Artificer]

"I don't know if there is such a thing as a US/UK electronics conversion table"
Tube = valve
Plate = anode
B+ = HT
That's about it Terry, no table needed really.

Andy.

[Refugee]

There is also a long list of amplifier style names on American websites too.

[Terry]

That's about it Terry, no table needed really.

I'm not so sure, Andy.

For example, this being a vintage radio forum, how about a picture of a vintage US radio with two tuning scales marked SW and BC?

I'm sure there are many other differences, some quite subtle, to confuse the uninitiated.

[pwdrive]

That's about it Terry, no table needed really.

For example, this being a vintage radio forum, how about a picture of a vintage US radio with two tuning scales marked SW and BC?

How many do you want?.....Here's one for starters:

https://www.flickr.com/photos/51764518@N02/32127931573

Lawrence.

[boater sam]

We seem to have them all Lawrence! Nice collection.

[Kalee20]

In a pushpull output, does the transformer need to present an Impedance on its entire primary to match the individual R.a. of the valves used, or does it need to match the R.a. in each half of the winding?

Easy part first - in Class A push-pull, you need the transformer to match double what each individual valve would require.

So if a valve single-ended requires 6kΩ, then two valves in push-pull would require 12kΩ anode-anode. This is because you have the same current as a single valve, but double the voltage swing between the two anodes. (If you had connected them in parallel, you'd need half the individual or 3kΩ, makes sense because you'd have the same voltage swing as a single, but double the current).

I was stuck indoors yesterday, and did some experiments, based on what I've read in several books on the subject, or, what I understand of what I read, I should say.

The quote from "Kalee20" is the concise answer to my original question, its a more difficult subject to completely understand than I can manage at the moment......the valve wizard articles posted by Diabolical Artificer are the easiest texts I found to understand.

Thanks! When I first read your post, I was not sure of your knowledge - I have now got a better idea from the recent posts so hope that my subsequent bit did not overcomplicate things!

From a learning point of view, Class A push-pull is the one to understand before moving to Class AB, Class B. These are capable of really good results, understandable in general principle but it is hard to see what is the ideal load, because none of them are 'right', just different compromises.

Class A pentodes or tetrodes are the easiest because generally you do not need to worry about grid current. The valvewizard articles you mention, the treatment of the single-ended case is pretty good, I agree with you. The article could have described a theoretically ideal pentode, and how to load that (you can choose your own operating point as long as you under-run the valve, and then calculate the optimum load for your choice of quiescent Ia very simply), and then gone on to a few fiddle-factors for 'real', non-ideal valves. It didn't, but it is still good.

Luckily, valves are pretty tough electrically and if you get things a bit wrong they will not instantly die. Further, you can get encouraging results even if the load is 'wrong' by a factor of 2, and have a lot of fun in the process.

[Ed_Dinning]

Hi Amie, I think you are finding that there are no correct answers in all branches of engineering .

The making of a good engineer, as was your father, is down to making the best compromises for a given situation, as well as a good degree of pragmatism.
Long may this continue as it keeps engineers brains working well.

Ed