What's wrong with a higher hfe tranny in the RM?

[JimRayden]

The GEO article says it should be 75-100 or I'll have to adjust the Rb1 value. Okay, let's say I've adjusted it for a larger hfe tranny. Will I then have more output or is the hfe merely affecting the bias?


---------
Jimbo

[formerMember1]

from my experience, higher gain transistors are harder to bias, i like an OC44 around 75-80 for my Rangemaster.  I think the OC44 sounds the best, followed by the OC71,...

this doesn't mean you can't use a higher or lower hfe transistor,

in my opinion smallbear has the best RM transistors, and they are already tested for you,....

hope this helps,....

[JimRayden]

From Banzai, I have any choice of hfe range for the AC128. Which would be the most optimal to choose. With optimal, I mean the relation between the ease of biasing and amount of boost. I want the most boost I can get. But I don't want to take any risks or start using a bunch of resistors in series/parallel to get the exact values.


-----------
Jimbo

[petemoore]

  Not exactly sure what the intent is, either going for as much clipping [which would mean harsher sound I'd guess] as you can [higher Hfe gain would mean more clipping]
  or gettin gthe CCt to just go over threshold a certain amount.
  I like thour idea of just get a buncha Rm transistors and find the bias on the one that makes your amp sing.
  The formula, or equations thereof, are well laid out at GEO, but if you're like me with 'E' equations, just go by the recommended Hfe #'s and your ears for finding your ultimate Rm.
  Ive been through a slough of them, and use two of them, One is a DarlingRangePig [my own concoction], the other is a 79hfe Ge Rm.