30P1S - How to use them?

[oDoh5]

I have 4 tubes of 30P1S, metal base, manufacture by MELZ and i search everywhere but i am not find any schematic to make an PP amplifier! Help me to use them! Thanks all !

[Vikt0r]

Oh, I know a person who knows a lot about this wonderful tube. The resource is in russian however, but the schematic talks for itself.
ONG 2 (Маразмы ua1ong. Звук без формул.)
Allthough it's not PP but 2xSE topology, this design is still worth of attention.
The only significant thing you should remember before using these tubes is that they have a 30V filament.

[azazello]

I have SE with this amazing tube! PP probably decrease quality of sounding!!

[oDoh5]

Thanks Vikt and azaz!
This is my schemtic of 30P1S which i've finished last night. Is there anything wrong? Is that right when i make Paralel SE, only need to replace OPT with 2,35K? Thanks all!

[oDoh5]

My schema:

[azazello]

Your output transf must be apr. 5 kohm. in case parallel tube - 2,5-3 kohm.
U on primary tap and preampl. tube- 150-160 v. Ia out.tube = apr.60-70 ma, You must adjust with Rcathode.
Ia pre tube = 5-8 ma, Ra pre tube=apr.6-8 kohm, R cathode pre tube=apr.500-
800 ohm, but all You will try and measure!
R grid pre tube = apr. 300-500 kohm.
Input potentiometer will be 2,2 - 10 kohm.
Good luck!

[Vikt0r]

oDoh5,
for 6SN7 input tube I would recommend anode voltage around 300V, and fixed (not cathode) bias for 30P1S. You'd loose some punch of bass (generally this happens all the time if you use cathode bias instead of fixed) - and for such a low power SE design - this is significant. As azazello mentioned already, 150-160V for 6P30S would be just the case. Also you may consider a triode/pentode switch, some may conclude this tube sounds better in pentode mode.
Regarding the schematic you drawn - it will work as is, but I strongly recommend bypassing at least the output tube's cathode resistor with a LOW-ESR electrolythic cap. Better, of course, bypassing both. Don't forget the 30V filament - combining with 6SN7 you'd need 2 filament supplies.

[oDoh5]

Thanks azaz and vikt.
And this is my new schema which built follow your showing. Is there anything wrong?

[azazello]

Hi!
It seems OK! In my case Rcathode30P1S is 270 ohm per tube. PSE tubes must be matched!!
You can add and 1000 uF/25v parallel to every cathode pre and output tubes.
And connect serial 1 kohm between potentiometer middle point and grid
pre tube.
Good luck!

[Vikt0r]

well, I would also recommend higher plate load for 6SN7 combined with higher plate voltage (300V, 20Kohm), and a smaller cathode one - 330 ohm would be pretty enough.