[sdiy] tube ladder

[metasonix at earthlink.net]

>>yes, in fact any device having control grids can be used.
>Any reason why it hasn't been done??

I personally haven't had the time. Perhaps disinterest on the
part of certain experimenters who think they have tried everything 
and know everything?.....

>Are there any particular remote-cutoff pentodes that you would recommend
>for audio applications such as a VCF??

Anything will do, there are not huge differences between
various small-signal pentodes of the same type, except
you have sharp cutoff, semi-remote cutoff, and remote
cutoff--the latter will work best as a voltage controlled gain.

Surplus 6136s are available--the "five-star" premium
version of 6SK7. 
Lower cost desired, use 6BA6s.

If you want to build a big, physically impressive filter, 
type 39/44s are VERY cheap and plentiful.

On the other hand, if you want low microphony and small
physical size, look into subminiatures. Types 5633 or 5907.
Bonus, no sockets needed, just solder them to circuit points.

>devices I've seen use brass or steel, couldn't the sockets be mounted on a
>sheet of plywood in a metal rack box, or is that a fire hazard??

;) remember, all radios were made of tubes at one time, and
were usually enclosed in wooden boxes....fires due to hot radios
didn't become common until the arrival of the plastic cabinet.

In fact, that's one reason why Catalin radios are 
now scarce and selling for insane prices. 
Catalin is a primitive cast phenol thermosetting resin that 
ages poorly and catches fire somewhat easily.....
but it's pretty, so radios were made from it....
http://www.maarc.org/catalin%20corner/catalin_corner.htm





E. Barbour
metasonix