Yes
I think that -3V point is good because it giving 3 optiopns for biasing, leds, 2 series Batteries and classic Rk II Ck.
Will be slight less hum with higher -Ug...
And higher Va is preferable then lower Va/higher Ia. Again tube is not the current device but voltage one...
Gain is 33X (with bypassed Rk), and with 2.8Vpp input about 92Vpp output delivering.
Req is again low 2.17K
The load RL on the diagram is 12K
With L load distortion will be less than 0.5% with same input
(I put the 120K load line to emulate almost parallel load to X axes...)
.
Sorry I consult other diagram from datas one with 0.7W G2
(That is why the Ia was too low...)
right one is this for 3.5W max A+G2
I think that -3V point is good because it giving 3 optiopns for biasing, leds, 2 series Batteries and classic Rk II Ck.
Will be slight less hum with higher -Ug...
And higher Va is preferable then lower Va/higher Ia. Again tube is not the current device but voltage one...
Gain is 33X (with bypassed Rk), and with 2.8Vpp input about 92Vpp output delivering.
Req is again low 2.17K
The load RL on the diagram is 12K
With L load distortion will be less than 0.5% with same input
(I put the 120K load line to emulate almost parallel load to X axes...)
.
Sorry I consult other diagram from datas one with 0.7W G2
(That is why the Ia was too low...)
right one is this for 3.5W max A+G2
One 'common thread' of this "The 2A3 Tube Amplifier" thread is the combination of output power and distortion.
Example:
If we get too picky about loosing 0.1 Watt and increasing distortion by 0.1%, we have to remember something that is not in any 2A3 data sheet:
The insertion loss of the output transformer.
An output transformer insertion loss of 0.5 dB, and the 2A3 data sheet classic output power of 3.5 watts, results in:
-0.5 dB (-.89 x the 3.5 Watts from the 2A2); 0.89 x 3.5 = 3.12 Watts.
Need more power?
Either:
1. Parallel 2A3 tubes and use a new power supply and output transformer.
2. Use a more powerful output tube and use a new power supply and output transformer.
3. Push Pull 2A3, and use a new power supply and output transformer.
Or:
4. Live with the output power and distortion of the single ended 2A3 amplifier that you have.
I have designed and built, and enjoyed 2A3 amplifiers: single ended, and #1 and #3 with a 2A3 tubes.
And, I have designed and built 300B amplifiers, single ended, and # 1 and # 3.
The 2A3 might just be the world's best turnip, but do not try and squeeze blood out of it.
Just my experiences
Example:
If we get too picky about loosing 0.1 Watt and increasing distortion by 0.1%, we have to remember something that is not in any 2A3 data sheet:
The insertion loss of the output transformer.
An output transformer insertion loss of 0.5 dB, and the 2A3 data sheet classic output power of 3.5 watts, results in:
-0.5 dB (-.89 x the 3.5 Watts from the 2A2); 0.89 x 3.5 = 3.12 Watts.
Need more power?
Either:
1. Parallel 2A3 tubes and use a new power supply and output transformer.
2. Use a more powerful output tube and use a new power supply and output transformer.
3. Push Pull 2A3, and use a new power supply and output transformer.
Or:
4. Live with the output power and distortion of the single ended 2A3 amplifier that you have.
I have designed and built, and enjoyed 2A3 amplifiers: single ended, and #1 and #3 with a 2A3 tubes.
And, I have designed and built 300B amplifiers, single ended, and # 1 and # 3.
The 2A3 might just be the world's best turnip, but do not try and squeeze blood out of it.
Just my experiences
sorry yes this is OK
from link
http://www.sengpielaudio.com/calculator-amplification.htm
.
But this tinny 3W from 2A3 always "looks" to me when listen as much "bigger"
I cant explain this. And 2A4 has "something" that other power tubes dont?
I listened only double plate RCA mostly 2A3
Never listened or build with single plate 2A3, old or new models...
Friend said that FIVRE single plate 2A3 was the best.
That was long time ago when they still was obtainable and costs was about 120eu or less per piece... 🙁
from link
http://www.sengpielaudio.com/calculator-amplification.htm
.
But this tinny 3W from 2A3 always "looks" to me when listen as much "bigger"
I cant explain this. And 2A4 has "something" that other power tubes dont?
I listened only double plate RCA mostly 2A3
Never listened or build with single plate 2A3, old or new models...
Friend said that FIVRE single plate 2A3 was the best.
That was long time ago when they still was obtainable and costs was about 120eu or less per piece... 🙁
I can suggest 5687 tube as input stage.
for 2.3V rms (6.4V p-p) input signal to 90V p-p output signal.
and very very low output resistance about 1860 ohms per section (930 ohms in parallel).
This is much much better solution to use with high input signals and tuve preamps in the system.
-6V of Ug can be optionally achieved by battery, led-s or classic RK II Ck network...
Ua of about +158Vdc to +160Vdc is friendly to use within the Loftin White configuration.
And Vb of about 350V is fit into the total Vb, with not huge difference.
This low internal resistance is more friendly to classic L load and deserves not large amount of Hy in L.
THD is wery low too.
All of the working poits are on the graph as well as the spice parameters.
Capacitances are low too and with moderate amplification Dynamic capacitance wil be low too even in parallel.
one section of about 25pF with 0,7pF of socket capacitances included, parallel sections about 50pF of Cdyn.
with these 50pF of Cdyn, Rinput (internal resistance of the pre-input stage) is max 24K for -3db@132KHz (-0.25db@20Hz).
So the input stage will more than tolerant to higher input impedances of tube preamps up to 24Kohms.
.
for 2.3V rms (6.4V p-p) input signal to 90V p-p output signal.
and very very low output resistance about 1860 ohms per section (930 ohms in parallel).
This is much much better solution to use with high input signals and tuve preamps in the system.
-6V of Ug can be optionally achieved by battery, led-s or classic RK II Ck network...
Ua of about +158Vdc to +160Vdc is friendly to use within the Loftin White configuration.
And Vb of about 350V is fit into the total Vb, with not huge difference.
This low internal resistance is more friendly to classic L load and deserves not large amount of Hy in L.
THD is wery low too.
All of the working poits are on the graph as well as the spice parameters.
Capacitances are low too and with moderate amplification Dynamic capacitance wil be low too even in parallel.
one section of about 25pF with 0,7pF of socket capacitances included, parallel sections about 50pF of Cdyn.
with these 50pF of Cdyn, Rinput (internal resistance of the pre-input stage) is max 24K for -3db@132KHz (-0.25db@20Hz).
So the input stage will more than tolerant to higher input impedances of tube preamps up to 24Kohms.
.
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Old stock bi-plate…I like Sylvania coil springs and RCAs
New build single plate…I like JJ 2A3-40
I listen to all DHT…pre-amp to power amp.