Bottom line is you need 100Vp-p swing... how do you do it?. - 1:4 will be 16x input capacities reflected back, try it. Maybe it works.
46 drive 2A3 (should drive 2a3 even without input transformer) :
As for the control of 2A3 (voltage oscillation), with a polarization of -45 V, complete control in class A1 (negative voltage on the grid) is required, Vpp = 2x45 V, or 90 Vpp, or 90 x 0, 3535 = 31.8 V RMS. That's all 46 needs to give.
Tube 46 is polarized -33 V on the grid, i.e. maximum voltage swing = 2x33 V = 66 Vpp, or 66 Vpp x 0.3535 = 23.3 V RMS. This must be multiplied by the gain of the tube, i.e. approximately 5.6x, so we have 368 Vpp = 130.4 V RMS. So we have a great offer and tube 46 is suitable for this role. (N.B.: 130.4 V RMS: 0.3535 = 368 Vpp)
Maybe I miscalculated ... (?)
As for the control of 2A3 (voltage oscillation), with a polarization of -45 V, complete control in class A1 (negative voltage on the grid) is required, Vpp = 2x45 V, or 90 Vpp, or 90 x 0, 3535 = 31.8 V RMS. That's all 46 needs to give.
Tube 46 is polarized -33 V on the grid, i.e. maximum voltage swing = 2x33 V = 66 Vpp, or 66 Vpp x 0.3535 = 23.3 V RMS. This must be multiplied by the gain of the tube, i.e. approximately 5.6x, so we have 368 Vpp = 130.4 V RMS. So we have a great offer and tube 46 is suitable for this role. (N.B.: 130.4 V RMS: 0.3535 = 368 Vpp)
Maybe I miscalculated ... (?)
RMS is calculated Vx0.707 (approx.) or Vpp / 2sqrt. (divided) this gives you here ~ 69Vrms
Without an input transformer you drive the 46 very hard and you'll get plenty of distortion already in the driver stage. Measure it on the workbench! In my opinion an IDHT driver with more gain - like the ECC99 - and low plate resistance is better suited for this.
+1 i have tried DHT like 26 , 01a as driver for my 2A3 amplifier and finally ended with my preferate little pendode the E55L in triode mode and choke loaded , more silent , more beefy ( i run it at 35ma) more gain X30 , very low plate resistance . i could simply use it as a SPud Amp but i prefer the E55L/2A3 combo ..
E55L are very rare but 6e5p can do the job too 🙂
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x Joao@AltheaMusica
I can't understand the mathematical formulas well. Can you explain in a simpler way (or step by step) how you calculated ~ 69Vrms.
I'd like to learn this kind of calculations better.
Thanks for the replies
I can't understand the mathematical formulas well. Can you explain in a simpler way (or step by step) how you calculated ~ 69Vrms.
I'd like to learn this kind of calculations better.
Thanks for the replies
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no need to run it hard , it 's a very linear tube , running it at 30ma is perfect too ,
80uf for 100R is not enough it must be 800uf to get the full band untouched .
don't forget the 1K grid stopper or it can oscillate..🙂
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Superb amps !!!
Can I know what you use as a preamplifier? Or they have enough gain to use them as integrated?
Can I know what you use as a preamplifier? Or they have enough gain to use them as integrated?
thanks;, no preamp direct from Dac with 2,5V output .
but if i had to build a pleasure preamp machine sure it will be with a 26 tube 🙂
but if i had to build a pleasure preamp machine sure it will be with a 26 tube 🙂
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I take advantage of your patience to ask you one more thing. Are those Hashimoto transformers the interstage A-305?
At the input, in front of the E55L, do you have the usual 220K resistance or have you used any other transformer?
If you have the scheme and want to share it here I think it is interesting for everyone.
At the input, in front of the E55L, do you have the usual 220K resistance or have you used any other transformer?
If you have the scheme and want to share it here I think it is interesting for everyone.
don't ask me to draw something or you will be very disappointed 😀
i try to keep it simple the E55L driver is choke loaded with 40h lundhal choke , 100K on the grid , 100R on the cathode bypassed with 1000uf NPolar cap ( dont like sic diodes on the E55L) capacitor coupled with the 2A3 with grid choke ( old RCA 2A3 have grid current ) , Rod coleman regulator for the filament , 890R on the cathode and 3.3K Monolith magnetics amorphous Ooutput Transformer . the hashimoto is the power supply choke for the CLC .
i try to keep it simple the E55L driver is choke loaded with 40h lundhal choke , 100K on the grid , 100R on the cathode bypassed with 1000uf NPolar cap ( dont like sic diodes on the E55L) capacitor coupled with the 2A3 with grid choke ( old RCA 2A3 have grid current ) , Rod coleman regulator for the filament , 890R on the cathode and 3.3K Monolith magnetics amorphous Ooutput Transformer . the hashimoto is the power supply choke for the CLC .
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It is all clear and simple that it seems to see the schematic.
I have marked everything on my database.
I have several vintage 2A3s (no single plate) but I think I'm going with a pair of AVVT2A3 Mesh Plate purchased a long time ago and still waiting to be turned on.
Thanks again for the valuable information.
I have marked everything on my database.
I have several vintage 2A3s (no single plate) but I think I'm going with a pair of AVVT2A3 Mesh Plate purchased a long time ago and still waiting to be turned on.
Thanks again for the valuable information.
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Yes they are, I'm thinking of trying a SPUD with them for experimenting as tweeter amps...
Sorry, typing error it's around 63.63V...
I took his 90Vpp and multiplied it with 0.707
I think I understand.
The 2A3 needs a driver that produces (minimum) 90Vpp x 0.707 = 63.63 V RMS. This datum can also be calculated with 90Vpp: 1.414 (square root of 2) = 63.64 approximately.
I hope it is right.
The 2A3 needs a driver that produces (minimum) 90Vpp x 0.707 = 63.63 V RMS. This datum can also be calculated with 90Vpp: 1.414 (square root of 2) = 63.64 approximately.
I hope it is right.