In Reply to: Holy S*** . I screwed this up big time. posted by Kurt Strain on February 28, 2002 at 18:49:18:
I had to make some further changes after being pointed out my mistake about missing the cathode resistors in the model. The links shown in the original posting are now correct.I changed the grid resistor on V2 to 22M and its now completely grid leak biased. Damn, what a difference. I thought it was just awesome and now I have awesome some more. The bass delves deep down to the bottom. It also appears from new simulations that Dave's autoformer step attenuator has about 125H of inductance if it were to work as well as it did with 60K of output impedance driving it! Now I have it back to 6K output impedance and shakes the foundations. In fact it still goes down more than I like, with me now hearing LF noise from the turntable again. The grid leak is a peculiar beast. It's the same plate voltage whether I use 16M or 22M as the grid resistor, about 70-90V depending on tube. I tried upping the CCS to 5mA and it made the sound go dead! Go figure. There's some shunting diode-like element in the grid model or something like that.
Should I go to 417A or 6S45P for the output stage? It doesn't sound like I need more drive, but who knows.
Okay, Thorsten, now what do you think? I'm going to have to sit before thinking about a new step-up transformer or tubes. I'm out of spending money for now.
Kurt
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