On Line Tube Learning for newbies....

[taj]

Originally Posted by sdinfo

To me, this makes the book very much incomplete and borderline ludicrous.

Wow, you have much to learn, grasshopper. Keep reading.

..Todd

[sneakers563]

I know this is supposed to be about online resources. However, some people have brought up books, and I wanted to point out that several of them are actually the same book. Namely, Van Valkenburgh's Basic Electricity and Basic Electronics are functionally the same as both the Navy's and the Army's Basic Electricity and Basic Electronics courses.

My understanding is that Valkenburgh et al. developed those course materials for the Navy in the early '50's. That course was later made available to the public in both the original Navy form, and by Valkenburgh directly. The presentation differs somewhat (Valkenburgh has more illustrations and makes more use of repetition / review), but the topics are covered in the same order and using the same language.

This is nice because the list price for Valkenburgh is $70, while the Navy's books are only $15.

Interestingly, the Naval course was later used as the basis for the Army's course. I have a copy of the Army's Basic Electricity from 1977 and the text is exactly the same as the Navy's Basic Electricity from 1970. There's even drawings of ships on the cover and references to the naval promotion schedule.

[SY]

Originally Posted by sdinfo

I...I am very surprised at the fact that Chapter 5, on Power Supplies, uses transistor circuits almost exclusively in the schematics for the chapter... Does anyone have any idea why he wrote the chapter that way?

Actually, he discusses tube regulators in that chapter, but explains carefully why performance considerations would discourage their use. If one wants to optimize the performance of the amplification, one wants the tightest, purest DC possible, which is not the strong point of tube regulators.

You'll see a similar conclusion reached in Allen Wright's preamp book, the difference being that Morgan uses series regulators, Allen uses shunt regulators.

[coffeedj]

I have also found that regulators are less than stellar in many applications. The one exception is low current, early preamp stages. There, a shunt regulator, isolated from the stage by a further RC filter (bybassed) gives excellent performance by isolating the most sensitive stage(s) from the power line variations--which are random in frequency and size, but non-periodic and slow enough to be filtered by the regulation.

I have come to use--on an almost regular basis--tube regulators for the first stage of phono or mic preamps. It adds a presense to music--don't know any better way to explain it.

[escopunk]

Here is a great resource for new people, I have the real copy.

Enjoy

http://jricher.com/NEETS/14178.pdf

[CSlee]

In Allen Wrights Preamp Cookbook, he says that valves are more linear than transistors.

Is anyone aware of some support for this? I have soft copies of Radio Designers Handbook etc, could someone point me in the right direction of a few lines on the subject?

I need to reference it for some uni work.

Thanks

Charlie

[CSlee]

that wasnt meant to sound as lazy as it did, I am looking myself... honest guv

[coffeedj]

Originally Posted by Charlie Slee

In Allen Wrights Preamp Cookbook, he says that valves are more linear than transistors.

Is anyone aware of some support for this? I have soft copies of Radio Designers Handbook etc, could someone point me in the right direction of a few lines on the subject?

I need to reference it for some uni work.

Thanks

Charlie

Morgan's book on valve amplifiers (3rd edition) talks about his attempt to determine average linearity of transistors through profiling their curves. He makes the comment that the final result was like throwing random spagetti at a page--thus supporting the 'non-linearity' problem of transistors, and resulting in the reason that large amounts of NFB are required for transistor amplifiers. (If I remember all his points correctly.)

From the quantum mechanical point that makes sense. Transistors require energy to get over the junction hump--and this is not a linear process, based on the quantum function difference of the junction potential. Valves, on the other hand, are current limited by the space charge effects existing in the vacuum and require no energy to emiss--rather they need potential to retard emission. Thus for tubes, geometry, which can be varied by the manufacturer, plays a huge factor in the linearity--and tubes were designed to be primarily linear.

[CSlee]

Thanks, very helpful

[DF96]

Both valves and transistors need energy to get charge carriers past potential barriers. Transistors use voltage to do this, and so have an exponential response. Valves use heat to get electrons from the Fermi level past the surface barrier, so also have a partly exponential response to cathode temperature. Once out, the electrons form a space charge which then gives a 3/2 power response to voltage (modified by details of device geometry, ageing etc.).

It may be true to say that valves are more linear, but BJT are more predictable as there is a precise relationship between current and gm. Triodes gain extra linearity from feedback, as the anode voltage and grid voltage have similar effects apart from scaling. The predictability of BJT means that you can build (and simulate) complex circuits. Simple circuits may work better with valves. Horses for courses.