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removing balance pot from Naim preamp

K

klingklang

pfm Member
I know I need to replace with good quality resistors. Does anyone know the values and which pins should be connected? It's a NAC 32.5 so there are 6 connections in total.

Thanks
 
Simple really. A 1k2 resistor matches the mid point of the 10k pot that Naim used and to identify the correct links to make, trace the two connections to the Ov...then link the other two in each channel.
 
I'm sorry but I'm lost here. Can't you simply remove the balance pot and link each channel of the volume control straight to each input stage?
 
In theory, yes. Think about how the balance control works at each end of its travel.
 
MJS said:
In theory, yes. Think about how the balance control works at each end of its travel.
Click to expand...

Nope, I still don't get it. I've modded my 42 and made it dual mono with separate regulated supplies etc so obviously the balance control has gone too. I've linked the volume control straight to the input coupling cap on each channel and it all works fine. I must be missing something?
 
Chops54 said:
Nope, I still don't get it. I've modded my 42 and made it dual mono with separate regulated supplies etc so obviously the balance control has gone too. I've linked the volume control straight to the input coupling cap on each channel and it all works fine. I must be missing something?
Click to expand...

Yes, I know what you mean. I too have never managed to understand this. I wonder if there is something in the circuit design that demands that there be some resistance somewhere along the line? But presumably if you turn the balance all the way to, say, the right, there will be no resistance for the right and infinite resistance for the left. But in the middle there is "some" resistance for each channel?
 
OK, so here's my logic:
  • The two tracks in the balance pot are reversed, so as one goes up the other goes down.
  • At one each of the pot, one track has minimal resistance the other maximum resistance.
  • The mid point represents even balance - where both tracks should measure equal resistance.
  • The mid point of a 10K Naim pot (as measured) is close to 1K2.
So to remove the balance pot and keep everything the same as Naim originally intended, a 1K2 resistor makes absolute sense. That is not to say other solutions will not work - of course they will. But the 1K2 resistors are a higher quality substitute for having the pot in place in the center position. But is it critical to have the resistance in line? No.
 
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