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Dual triode with more gain than a 12ax7


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6/25/2004 4:49 PM
Joey Dual triode with more gain than a 12ax7
Does anyone know of any dual triode with more gain and around the same size. The pinout doesn't matter.
 
6/28/2004 10:24 AM
Ben N

Not me. But there may be other ways to get where you want to go--so where do you want to go?  
 
Ben
 
6/28/2004 1:02 PM
Joey
I need about 3-6db more of gain than I'm getting. It's just in simulation though and I realized it's not simulating correctly at all so I guess I'll just have to bread board it.
 
7/4/2004 8:35 AM
jeremy

a post was made about a year ago about a dual triode that does what you want. gain of about 150 or so. i think telefunken made it, and stock is super scarce. not to mention pricey (150). i just cant recall the tube number at the moment.  
 
jeremy
 
7/4/2004 8:38 AM
Chris - CMW amps

Hi Joey  
 
What circuit are you using ? Tell about the used values and I'll try to help out .  
 
Chris
 
7/7/2004 10:05 PM
Matthew Springer

Joey,  
Do you mean a higher mu (transconductance) or more linear voltage gain? The Voltage gian of the standard cathode biased triode stage (most) everybody uses in guitar amps is based on the plate resistor size, You should be able to double the plate resistor and the cathode resistor to realize 3dB more gain from a single stage.  
 
You'll have worse output impedance and it'll be a noisier circuit. If you need to squeeze every last once of mu out of the tube, you'll need some sort of active load like a cacode circuit. The voltage gainis maxed as the load goes to infinity (which is obviously not possible given a simple resistor), so you need something with infinite AC resistance and a non-infinite DC resistance, which is an active load. The essence is you put another active device where the plate/load resistor would go and bias it so it "fights" the bottom tube.  
 
Of course, there's always the EF86.
 
7/8/2004 8:07 AM
kg

quote:
"If you need to squeeze every last once of mu out of the tube, you'll need some sort of active load like a cacode circuit."
 
 
http://ken-gilbert.com/techstuff/ccs_input_stage.htm  
 
i'm still using that circuit.  
 
ken
 

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