VT-25 linestage + step-down trafo

[Klimon]

Hi,

I'm contemplating a vt-25 linestage terminated by 4:1 step-down trafo. How many DBm should the transformer be able to handle in this circuit, no parafeed?

Thanks a lot!!!

Simon

 

[Gluca]

Working on that right now but using a ccs loaded VT62 (801A). Well, the answer depends on the gain you need.

If your source is 2Vrms (CD player) your VT25 will step that signal up by a factor of 8 (actually less) so your transformer will see 16Vrms ... or 25dBu if you like.

4:1? So this seems to be a 10K:600R tranny, make sure it has enough inductance to load the tube. I would consider to parafeed it btw.

For your info, the tranny I am going to use is a 7.5K:600R with +160H @ 30Hz (no gap).

Ciao
Gianluca

 

[Klimon]

Thanks for clearing that up Gianluca.

Looks like I'll better do things right the first place and save for some $$$ Lundahls

Simon

 

[Zoran]

If You use VT25 as preamplifier,
You can lower the Load resistance,
even the inductance of primary windings
(based on that and capacitance...)
because:
You use the small voltage swing...
*
I wrote some article for Costruire
"designing high-end tube preamplifier"
i used 10Y like example...
with excelent results...
But the PDF is too large to post here
*
tip
try to lower load line (and inductance)
bearing in mind the distorsion,
the dynamic load line You can see
with spice simulation...