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never mind that, look at the 2nd photo in post 31, here we have a naked amp, rated for over 1kV and yet an open bottle of beer - could be dangerous !
SE pentode EL3010 2.3V 16W comes close but then you would at least want a speaker happy with current drive
Several years ago in this thread I already offered a bunch of 4P1L tubes.
I myself was seriously thinking about 10 of 6P1P in parallel for SE amp. 🙂
I myself was seriously thinking about 10 of 6P1P in parallel for SE amp. 🙂
Yup, excellent triode curves for 4P1L. Just need a bunch in parallel. pics 1 & 2
Could also go for a new series Schade N Fdbk on a big beam pentode, like a 36LW6. Pics 3 is using 21HB5A as a similar sample. Looks like a DHT 211 I think.
Could also go for a new series Schade N Fdbk on a big beam pentode, like a 36LW6. Pics 3 is using 21HB5A as a similar sample. Looks like a DHT 211 I think.
Attachments
I am going to need a couple beers tonight before I bring myself to calculate the input capacitance of this thing. Having a driver would be better.
The cheap, good looking but a bit "kinky" GU72 tetrode could be a good candidate for a 20W SE without having to use overly high voltage.
As triode
g1/g2 mu 7-12
gm 15-23mA/V
pa 85W, pg2 15W
As triode
g1/g2 mu 7-12
gm 15-23mA/V
pa 85W, pg2 15W
Im sure there is some bazillion watt triode with a bazillion gain out there that you could run at 20 watts, but you would become your power companies new best friend.
If you take a closer look at it, there are not too many toobs to choose from. As to power, it depends where you liv. For instance, i need at least 15ooo kWh just to keep my house at 18°C during the winter, and amp dissipation would not change one yota on my bill. During summer i want sand, preferable between my toes, on a beach
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My just for fun contribution.
https://frank.pocnet.net/sheets/111/8/845.pdf
.SUBCKT 845 A G K
+PARAMS: MU=5.355 ERP=1.5
E8 8 0 VALUE={(V(A,K)-va0)/KP*LN(1+EXP(V_6()))}
Eam am 0 VALUE= {2*Pow(V(8),ERP)/KK1}
GA A K VALUE={V(am)}
D3 5 k DX ; FOR GRID CURRENT
R1 g 5 {RGI} ; FOR GRID CURRENT
Rak A K 1G
Rgk G K 1G
C1 G K {CGK}
C2 G A {CGA}
C3 A K {CAK}
.MODEL DX D(IS=1N RS=1)
.ENDS
https://frank.pocnet.net/sheets/111/8/845.pdf
.SUBCKT 845 A G K
+PARAMS: MU=5.355 ERP=1.5
- KK1=6323 KP=85.64 KVB=65.8 vg0=3 va0=0
- CGA=13.5E-12 CGK=6E-12 CAK=6.5E-12 RGI=4000;
E8 8 0 VALUE={(V(A,K)-va0)/KP*LN(1+EXP(V_6()))}
Eam am 0 VALUE= {2*Pow(V(8),ERP)/KK1}
GA A K VALUE={V(am)}
D3 5 k DX ; FOR GRID CURRENT
R1 g 5 {RGI} ; FOR GRID CURRENT
Rak A K 1G
Rgk G K 1G
C1 G K {CGK}
C2 G A {CGA}
C3 A K {CAK}
.MODEL DX D(IS=1N RS=1)
.ENDS
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Finding a 150:100k audio step up transformer capably swinging 134 volts p-p: consider switching to bourbon.
That is not actually the harder part if there is no DC current in it. It's a reverse 26:1 transformer where you can use mumetal, for example, that has got permeability 10+ times better than GO laminations. Enough turns to deal with the voltage and a good winding geometry. The harder part is driving the 845 through such SUT trnaformer...35-40 nF at least up to 20KHz..
I guess the guy who built that power amp with the 211 was driving it with a preamp using the same transformer in reverse mode: 100K:150R.
Only practical side of this is that you can put them in separate cases....
Otherwise it looks more like a tube amp that needs a strong SS preamp. Maybe even using some specilized OP-amp...
Only practical side of this is that you can put them in separate cases....
Otherwise it looks more like a tube amp that needs a strong SS preamp. Maybe even using some specilized OP-amp...