Rerurn to Romy the Cat's Site

hagtech wrote:

Note the '63 has much higher gain.  The horizontal spacing is basically "mu".  Interestingly, the 6e6p has lower gain than both of these.  To me, the curves are beautiful.  Spacing is relatively constant, indicating superb linearity.  The tube can also push huge amounts of current.  That is not shown here, as I zoomed in to a 5mA/div scaling.  Previous posts were at 12.5mA/div.  The high slope of the curves means very low output impedance.

Fascinating! The used up tube has lower gain but we do not relay have clew as we do not have the trace of the same tube when it was new. Since it is Russian tube then even the new tubes might up to 30% difference in gain. Anyhow, I agree that the curves look examplenary, although I have no idea how this “perfect” picture would affect sound. Another interesting observation, and I do not know if I am correct in it, is that the new tube and the used tube have practically no difference in a tracer (the same is for 6C33C) beside their gain. So, are we looking back to measure just cathode emissions?

hagtech wrote:

Each tube here appears to be very good.  I see no anomalies.  There will be sonic differences, as a circuit biased for one of these will be sub-optimal for the other two.  This is a pretty large sample-sample difference.

Yes, what would be necessary is to measure a couple dozens of them and to learn where is common denominator among the 5E5P…

hagtech wrote:

Ok, next is my attempt at a 6c33.  Clearly there is not enough grid voltage to sweep this tube.  Again, 50V/div horizontal, but 25mA/div vertical.  The sweep cuts off at 200V plate because there is not enough grid volts.  Lines are at 10V/div.  Starting at 0V.

Actually 200V is enough…

hagtech wrote:

So I zoom in.  This is at 20V/div plate.  So it still gets up to 200V.  Note the distortion characteristics.  One, the curves gradually get closer together with more negative grid voltage.  Two, the slope changes.  The spacing indicates a nonlinear gain when used in circuit.  The slope means output impedance is changing.  Both will affect performance in an amplifier.  Oh yeah, I wired the tube up to do only one half at a time.  This is the 1,2 heater.

Yes, it is know that 6C33C is not as linear at trace as some other tubes. Once again I do not know how it manifest itself sonically.

hagtech wrote:

The older tube has less gain.  But something really funny showed up.  And I am not used to seeing this.  On the 76 side, notice the loop in the curve!  This must be some hysteresis.  The curves are generated by ramping plate voltage up, and then back down.  Generally, the two curves fall on top of each other.  In this case, something split them.  I can sweep slower and faster.  And the loop (I forget already) I think is larger at slow tracing (which is supposed to be more accurate as it gives the grid step more time to settle).  My guess is that the loop might be caused by grid current.  I dunno.  However, we may have stumbled upon some practical indicator.

Jim, it might absolutely everything with 6C33C. It is very low standard tube with huge run off of it’s parameters. I would need a couple days to absurd what I see and to interpret how the seen might affect the way in wish the tubes are being used in my amp.

Rerurn to Romy the Cat's Site