how to calculate unbalanced summing bus

[ruffrecords]

i am not sure if i am following you correctly!
change R1 on NYD pre to 10k log audio for master fader ?

i am totally lost on omitting the mic pre transformer... can i just omit the micpre trx with my current 15k bus resistors, and also omit the 220 ohm slug resistor...

what i am really asking is, how should i decide for the resistor value, according to tube stages...
is it depends on output Impedances of my line inputs?
ie: lets say my output Impedance  is 4K  on my line inputs, unbalanced bus is 10k/4 = 2k5  ! ?

OK, for the moment forget the NYD mic pre.  I was talking about using an additional input module for the gain make up instead of the NYD mic pre. So, for the gain make up amp you use your current input module design but remove the input transformer. Replace the preset pot R1with a 10K log pot. The top of this pot is the input to your gain make up amp. Just connect all your 15k bus resistors to the top of this pot .

The resistor value is chosen so that it is a nromal load for the tube stage. The tube stages yiu have should be OK driving a 15K load.

Cheers

ian

 

[kambo]

ohhh, i c what u mean now
thank you so much Ian,

 

[kambo]

ok, i tried using one of my input module as summing amp, with 10K pot, it works nice,
except i get higher THD, (changing prest_gain didnt help)
i changed plate and cathode resistors to different values from data sheet of 6SN7
0.1Meg/2200 - is sounding best.
all is now back to normal THD figures of my choice - 1.4% nice second harmonics.