[sdiy] tube ladder

media.nai at rcn.com media.nai at rcn.com
Sat Jun 22 22:57:26 CEST 2002

At 1:08 AM -0700 06/22/02, metasonix at earthlink.net wrote:
>>Can a VCF be made with variable mu pentodes??
>yes, in fact any device having control grids can be used.

Any reason why it hasn't been done??

>A vari-mu device simply has a more gradual negative
>Ia/Vg slope, making it easier to control.

Yes, I've seen the charts in reference to RF amplifiers.

>A bonus with vari-mu pentodes is that you can buy
>tens of thousands of them for absurdly low prices...

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

Perhaps a VCA/VCF using the same tubes could be built to run off of the
same PS.  That could make a nice diy project, especially considering that
etching PCB's might not be necessary.  While all the point-to-point tube
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??

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