18v LPB question....

[Caferacernoc]

If I want to run a LPB style booster at more than 9 volts, do I need to change the collector resistor's value to bias it properly? And, in general, is that where you would put a bias pot say if you made a LPB with a germanium NPN Tranny? Thanks.

[MikeH]

I'm not sure what the voltages are supposed to be, but if you measure a properly biased LPB at 9v, the voltages should be biased for double at 18v, I'd assume.  Not sure about the Ge tranny, seems like it wouldn't do anything special for the LPB.

[Caferacernoc]

Well, so then my question is do you fine tune the bias on a LPB with the collector resistor? I realize it should be approximately 1/2 the battery voltage. Thanks.

[amz-fx]

Well, so then my question is do you fine tune the bias on a LPB with the collector resistor? I realize it should be approximately 1/2 the battery voltage. Thanks.

You can tweak it to run on 18v by adjusting the collector resistor...   6.2k should get you in the ballpark.

regards, Jack

[John Lyons]

So at 18v the circuit would have more headroom/be a cleaner and less noisey? Just wondering what your thoughts are.
John

[Gus]

You need to think about what you want that sets the rules.

Do you want more headroom etc........

You need to think about collector current and the gain you want and the input Z you want the current drain from the battery etc............

[Caferacernoc]

Yes, I just want the extra headroom. I am messing around with a diode to ground stairstep array like the limiter in the Dogzilla amp. I want to really hear the changes without the tranny clipping and I need it to be able to swing enough current for up to 3 leds per side. My ultimate goal is to have a symmetrical soft clipping limiter circuit to add after an assymetrical harder clipper(jfet/ROG type design) for the ultimate  tube amp simulation. This is based on the idea that tube preamps are best simutated by jfet designs or a circuit that clips fairly hard, but only assymetrically on one side since that is what 12ax7's do. But the ever elusive power amp distortion is really more of a soft clipping compressor. Symmetrical in the case of a push pull amp. There is also a dynamic loss of frequency response at the extremes of the bandwidth as the output transformer saturates, but I have no idea how to do that. I do really think it's backwards to put a compressor in front of a distortion pedal if you want a true "cranked" amp tone.