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A 6C45-PE Single Tube Amplifier

    This Amplifier  produces  astounding results in terms of transparency and musicality. The only drawback is  a very low output power (less than 2Wrms in SE mode). Other tubes useful fot this work are :



E55L in Pseudotriode


 417A (very very low output power) and so on.

    This tubes, excluding 417A, are rare and expensive. During the search (back in the late '90)  I found a wonderful alternative given by the  6C45-PE (ab initio code named  as  VTW to avoid 3A167M-like speculations), a small tube with the following caracteristics:

m=50, gm=50mA/V, rp=1k; Plate Dissipation 8W.

I have designed a compact, easy-to-building, power amplifiers with 2 6C45-PE.

Fig. 1 Full Schematic


The 6C45 is also excellent  as driver  for big transmitter triode as VT4C/211, 845. We can easily design a Two Stage Class A2 211 single_ended amplifier for example. Further, a parallel cathode follower of '45s has only 10ohm of output impedance. In the full schematic of Fig. 1 you can observe  a quiet high load; this is detrimental for the output power, nevertheless distortion figures are better and the sonic response more satisfactory.

Plate Curves










Click on it to enlarge


Pspice Model

.subckt vtomega 1 2 3 ; plate grid cathode

+ params: mu=47.4501 ex=2.374193 kg1=268.615545 kp=485.735371 kvb=501.503636 rgi=300

+ ccg=2.4p cgp=4p ccp=.7p

e1 7 0 value= {v(1,3)/kp*log(1+exp(kp*(1/mu+v(2,3)/sqrt(kvb+v(1,3)*v(1,3)))))}

re1 7 0 1g

g1 1 3 value= {(pwr(v(7),ex)+pwrs(v(7),ex))/kg1}

rcp 1 3 1g

c1 2 3 {ccg}

c2 1 2 {cgp}

c3 1 3 {ccp}

r1 2 5 {rgi}

d3 5 3 dx

.model dx d(is=1n rs=1 cjo=10pf tt=1n)


VG=[0, -0.5, -1, -1.5, -2, -2.5, -3, -3.5, -4, -4.5]



Recently I have designed a small stereo PCB for this monotube amplifier. Look at the following for its "artistic" representation:



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