6S4 as an output tube US made not Russian

[battradio]

I have several 6S4 triode laying around , what would be the impeadance of the output transformer .
The plate resistance is low , something like 3.6 k ohm most tube usaly have the plate load something like 1/5 th the plate resistance




http://www.nj7p.org/Common/Tube/SQL/Tub ... ?Type=6S4A

[Geek]

Ed and Terry Smith both did some work with these. I can't remember if they found 5K or 3.5K load the best sounding?

Cheers!

*edit*

There's info if you put 6S4 into search.

Here's an amp that uses 5K:
http://www.the-planet.org/6S4.html

[battradio]

It looks like it would a good subsitute for a 45 using only using 6.3 volt filament .

[Geek]

I've heard both... uh-uh. 6S4 ain't no 45.

6AH4GT is closer to a 45 in sound

Cheers!

[battradio]

I was thinking more like vintige radios from the late 1920 , with the 80 year old speaker you wouldn't hear the differance .

[Geek]

LOL, OK

[EWBrown]

With 325VDC B+, and 390-400 ohm, 2W cathode resistor, the 6S4As will idle at around 25 mA, and this is the tube's "sweet spot".
Cathode value should be 9.8VDC, +/- 0.2V, with NOS tubes, old beat up used ones will be "all over the place"

Figure on about 3X the tubes' internal P to K resistance, (3.6K) for the OPT primary impedance value, that is, 11-12K for a single 6S4A.
Always - use a grid stopper resistor, 1K, is good, foor each of the 6S4As.

I like to parallel two of the 6S4As, and use 5 to 6.6K for SE operation.

I've not tried more than two in parallel, no valid technical reasons not to try 3 or 4 of them in PSE

I prefer to use an SRPP driver stage, I use 6CG7s or 5963s with 1K RA/RK , and use at least 0.22 uF coupling cap for parallel operation, the 6S4As' internal capacitance starts getting "up there" when the numbers go above 2 in parallel. The grid resistor value may have to be reduced with 3 or 4 in parallel, try 150K or even 100K, that eliminates any vexingand annoying instability issues.

I look atthe 6S4A as being the apocraphyl "6BQ5, without the screen and suppressor grids" HaslowerPD thana triode strapped 6BQ5, 8.5 W vs 12, but I'd pushed them harder, just for the halibut , but there is no valid reason to do so...

HTH

/ed B

[battradio]

Will look fo some output tansformer for them .The only SE ones i have right now are for a pair of WE 300 's and would ned 4 of the 6S4 to make them sing .

http://fth-scans.com/