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previous: Soren Ray,The push pull triod sta... -- 9/20/2003 2:28 AM View Thread

Re: Transformer Phase Inverter

9/20/2003 2:48 AM
SorenRe: Transformer Phase Inverter
Sowter has many transformers to choose from, many are shielded.  
 
One unit 9041 and 9042 are "ideal for 6SN7 or ECC83 tubes". These handle 30mA and give a low output impedance. So if I insisted on sticking with high plate resistance tubes, I guess a 9041 tranny can be used before the IT PI to lower the output impedance.  
 
Would you use a tranny like this in place of a cathode follower ? Instead of trying to find one that can handle the output of one ?  
 
Maybe this could work as a cathode follower:  
 
12AX7 (High plate resistance)  
9041 (Low 100 ohm output impedance)  
Tone Stack  
 
Maybe this could work for phase inverting:  
 
12AX7 (High plate resistance)  
9041 (Low 100 ohm output impedance)  
TI PI  
Power Tubes  
 
It seems logical that an IT PI with a higher impedance on the primary (20k instead of 10k or 5k) is helpfull for high plate resistance tubes.  
 
I made a little chart from data sheets, with relevant data for driving ITs:  
 
Plate Resistances:  
 
12ax7 - 63k  
12ay7 - 25k  
12at7 - 11k  
12au7 - 8k  
6sn7 - 6.7k  
5842 - 1.8k  
6b4-g - 800 (The winner !)  
 
Mu:  
 
12ax7 - 100  
5751 - 70  
12at7 - 60  
12ay7 - 45  
5842 - 45  
6sn7 - 20  
12au7 - 19  
6b4-g - 4 (Not much voltage amplification here!)  
 
Plate Current:  
 
12ax7 - 1.2mA  
12ay7 - 3mA  
12at7 - 10mA  
12au7 - 10mA  
6sn7 - 10mA  
5842 - 23mA  
6b4-g - 60mA (for the power hungry like us!)  
 
So it seems a 30mA tranny can handle the 5842. And a higher handling is needed for a 6b4-g.  
 
Prices I have found:  
 
Sovtek has the 6b4-g for $50.00.  
Some brand 5842 for $20.00.  
EH 6sn7 for $11.00.  
 
Soren

 
Replies:
Ray Ivers Soren,Wow, you've been busy... -- 9/20/2003 5:31 PM