Hello mates,
I have several questions, cause I want to build SE amp with RL12P35 tube.
I have OPTs Ra 4k9/20VA suitable for UL also, output is 4/8R. I think I can use this one for RL.
Big question is driver. I want to use some old school tubes, I have in stock some EF6, EF11, EF14, or also nice looking 6F10 Tesla or 12SJ7 Toshiba. Which of these can be a suitable for this work please?
Recitifier will be probably PV200/600.
My first idea was to use some EL34 SE schematic and replace output tube.... but I cant find anything nice with tubes stated above.
Thank you.
I have several questions, cause I want to build SE amp with RL12P35 tube.
I have OPTs Ra 4k9/20VA suitable for UL also, output is 4/8R. I think I can use this one for RL.
Big question is driver. I want to use some old school tubes, I have in stock some EF6, EF11, EF14, or also nice looking 6F10 Tesla or 12SJ7 Toshiba. Which of these can be a suitable for this work please?
Recitifier will be probably PV200/600.
My first idea was to use some EL34 SE schematic and replace output tube.... but I cant find anything nice with tubes stated above.
Thank you.
So then you have a choice of triode strapped, with much reduced anode voltage, or regulated G2 and pentode mode? What did you have in mind?
That 200 V limit for Ug2 concerns pentode mode. You can use higher Ug2 voltage at UL and triode mode.
The perfect option is to have a ultralinear output transformer with a seperate tertiary winding for the screen, so that the g2 limit is not an issue.
Triode mode you can get away with higher screen volts since the screen current is defined, and can be kept within the limits of screen dissipation, but I don't think UL is a contender since the screen dissipation is likely to be exceeded.
For example, an 807 has an anode limit of 600V, and a screen limit of 300V, but 400V is possible in triode mode.
Aren't your tubes museum pieces?
NB: My UL comments relate to push-pull, so not sure how the screen limit works with an SE OPT.
Triode mode you can get away with higher screen volts since the screen current is defined, and can be kept within the limits of screen dissipation, but I don't think UL is a contender since the screen dissipation is likely to be exceeded.
For example, an 807 has an anode limit of 600V, and a screen limit of 300V, but 400V is possible in triode mode.
Aren't your tubes museum pieces?
NB: My UL comments relate to push-pull, so not sure how the screen limit works with an SE OPT.
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I will try also 807 in UL on 1650HA OPTs (maybe in next days 🙂 ).
Back to topic. I want to use only pentode connection. Maybe later I can test other posibilies, but basicaly I need nice and good SE amp first.
Maybe my tubes are museum pieces, but I have them quite a lot, so why not use them.
I made a little research again, and probably with 12SJ7 it can be a great pair. What do you think?
Back to topic. I want to use only pentode connection. Maybe later I can test other posibilies, but basicaly I need nice and good SE amp first.
Maybe my tubes are museum pieces, but I have them quite a lot, so why not use them.
I made a little research again, and probably with 12SJ7 it can be a great pair. What do you think?
807 with the B+ at 400V and UL mode.
Scenario:
Plate swings from 400V to 50V (350V swing)
Screen swings 350V x 0.4 = 140V swing
Screen 400V - 140V = 260V
Check the 807 Beam Power curves for Screen at 250V.
How much is the screen current when the plate swings to 50V?
That is just a transient/momentary condition, probably OK.
At least you know what the transient screen current is.
Hi Fi is one thing.
For a push pull or single ended Guitar Amp very heavily into clipping, the screen dissipation occurs 1/2 of the time.
260V x the peak screen current x 1/2 of the time (50% duty cycle).
May, or may not be OK.
Your mileage may vary.
Scenario:
Plate swings from 400V to 50V (350V swing)
Screen swings 350V x 0.4 = 140V swing
Screen 400V - 140V = 260V
Check the 807 Beam Power curves for Screen at 250V.
How much is the screen current when the plate swings to 50V?
That is just a transient/momentary condition, probably OK.
At least you know what the transient screen current is.
Hi Fi is one thing.
For a push pull or single ended Guitar Amp very heavily into clipping, the screen dissipation occurs 1/2 of the time.
260V x the peak screen current x 1/2 of the time (50% duty cycle).
May, or may not be OK.
Your mileage may vary.
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Keep in mind that with not insane high plate supply voltages the RL12P35 cries for class A2 operation. You'll want a cathode/source follower to provide this.
Edit: You 4k9 OPT doesn't appear to be very suitable with this tube, unless you'd feed insane high plate voltages indeed.
Best regards!
Edit: You 4k9 OPT doesn't appear to be very suitable with this tube, unless you'd feed insane high plate voltages indeed.
Best regards!
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My info was, that this tube is quite simillar to EL34 tube. So my proposal is use it with Ua around 400V, Ug2 200V. I think that with this Ua it is not A2 class yet...
Sorry, no. The RL12P35 was developed by Telefunken in the 1930's, while the EL34 is a modern tube from the 1950's. Compare both transconductances and you'll see the huge difference.
Best regards!
Best regards!