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Re: Benefits of better balance.


 
2/12/2005 6:24 PM
loudthud
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Re: Benefits of better balance.
Chris,  
 
I had forgotten about those amps. I was thinking more of the ones where they use like a 47 ohm resistor below a bypassed cathode resistor. I wonder what the gain implications are using an un-bypassed cathode resistor. Would it be the same as any other common cathode amp with an un-bypassed cathode resistor ?  
 
It's amazing what you can do with some iron and a fat wallet.
 
2/13/2005 9:57 AM
Chris @ CMW amps
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Hi loudthud  
 
Oops... I didn't have done all A-B-tests with all the configuartions.  
Anyway: because of the neg.feedback loop in those amps the effect of the presence-cap is somewhat stronger then in a regular triode-stage.  
In general: I do experience somewhat more punch when using cb-caps in lower gain pre-amps, as soon as you start using 3 or more gainstages most of the time some needs to be unbypassed imho.  
 
Send me a fat wallet and I'll try some more iron and circuits :D  
 
Kindest regards,  
 
Chris
 
2/14/2005 8:25 PM
BaliJukka Cascoded PI ???
Ray  
Is the Admiral PI you mentioned the cascoded type that was in a thread sometimes age. The one with gain of 300. AND has ANYONE any experience of it???  
Thanks  
Jukka
 
2/15/2005 6:27 AM
Ray Ivers
Jukka,  
 
Yes, it is - I thought no one read that thread. :)  
 
The Admiral circuit is very similar to the 'Self-Biased Totem Pole' (SRPP) circuit in TubeCAD's SRPP section, except the top tube has a plate resistor, and the Ra/Rk/Rg node between the top and bottom tubes is bootstrapped to the bottom tube's cathode, where NFB injection would occur if used. The outputs are taken from the top tube's plate and cathode. As I look at it now, the "other" circuit is identical, just redrawn.  
 
I haven't used it myself, but it looks pretty easy to implement; just add a cap and resistor to the 5F6A PI circuit and rewire it.  
 
 
 
Ray
 
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