[ETF] [JN] blog the talk...

Guido Tent Guido at Tentlabs.com
Tue Dec 1 01:51:26 CST 2015


hi Thorsten,

You surely do know how to motivate people !

Guido

On Dec, 1, 2015, at 3:17 AM, Thorsten Loesch via Sound wrote:

> Peter,
> 
> I think this strategy of optimising the cathode cap value is way outdated. 
> 
> Why not cover measures to work around the cathode cap (WE/Ultrapath/Monkey)?
> 
> Or if there is a coupling cap ahead of the tube, fixed bias alows a Rk and Ck of 0R and 0uF?
> 
> Or if you can bias on 1.5V, 3V or multiples, you can always wire a primary battery in series with the Grid (add a few MOhm resistor in parallel to drain any rid emission and I like to add a 10nF Silver Mica Cap) to bias a Tube from a 0V DC source that is not cap coupled. Coin cells are available in 1.5V & 3V, small size batteries are available in 1.5V, 3V, 9V & 12V, multiple combinations can get you almost any bias you need, usually in a package much smaller than a high end coupling cap. 
> 
> I know some people like to place rechargable batteries or Solid State Voltage sources (Zenners, LED's etc) in cathodes, I find that inserting a non-linear element in the cathode loop is not a good idea.
> 
> Ciao T
> 
> On 30 November 2015 at 23:12, peter sikking via Sound <sound at soundlist.org> wrote:
> hey everyone,
> 
> thanks again for the thumbs-up. here is part 3 (of 4):
> 
> <http://ultra-fi.blogspot.de/2015/11/cap-decoupling-of-triodes-3.html>
> 
> this time the focus is kathode caps and it gets really interesting here.
> 
> I got fed up with that in every article or book I read on tubes,
> they are either very vague on kathode caps, or give what is
> plainly the wrong formula (just sim or measure it).
> 
> so I investigated myself and got lucky. there is a straightforward
> formula to calculate a kathode cap for your ƒ-3dB. read all about
> it here. there is also a cookbook for those who just want to cook.
> 
> enjoy,
> 
> 
>     --ps
> 
>         street photographer : ultra-fi builder : on drums...
> 
>         (new adventures in) http://ultra-fi.blogspot.com
> 
> 
> 
> 
> 
> 
> 
> 
> 
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Guido Tent
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