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Passive Balance Control?

post #1 of 4
Thread Starter 

I need a universal pseudo-balance control to move between stacks.  I say pseudo, because I don't need a full/classical sort of balance control.  Just an adjustment on one side.

 

Reason: I have hearing loss on the left side that varies from 3 to 10 db, depending on volume levels.  I'd like to simply turn down the right side as needed.  Using software plugins works in some situations, but not on everything I like to do.

 

Ideally it would be a passive box with RCA connectors that can be used in different stacks.  Here's what I'm thinking:

 

 

 

 

So I have 3 questions:

 

1. Is this a viable idea in terms of not screwing up the fidelity?

 

2. What value should the POT be?  I want about 0 to ~12db of attenuation.

 

3. Should I add R1 as if it were a normal balance control?  In other words, if the POT is 50k, should I have a 50k resistor for the left channel to keep things even?

post #2 of 4

Hope this link helps:

 

http://www.angelfire.com/electronic/funwithtubes/Amp-Bal.html

 

Try circuit "C" with modifications necessary to get low output impedance, and desired range. 

*values as a starting point*

Omit the 120Kohm resistor between input and pot

Use a 5Kohm linear pot

10Kohm resistor from pot to ground. 

*values as a starting point*

 

Please let me know if my guessed values work. They could be totally off, I did not even use a cocktail napkin to estimate...

post #3 of 4
Thread Starter 
Quote:
Originally Posted by nikongod View Post
 

Hope this link helps:

 

http://www.angelfire.com/electronic/funwithtubes/Amp-Bal.html

 

Try circuit "C" with modifications necessary to get low output impedance, and desired range. 

*values as a starting point*

Omit the 120Kohm resistor between input and pot

Use a 5Kohm linear pot

10Kohm resistor from pot to ground. 

*values as a starting point*

 

Please let me know if my guessed values work. They could be totally off, I did not even use a cocktail napkin to estimate...

 

Thanks for the starting values nikongod!  I'll pick up the parts and give it a go.

post #4 of 4
Thread Starter 

 

I found the calculations for DB drop (easier than I thought). Given R1 = 5k and R2 = 10K, there is only a 3db drop without load. However, with load it all changes and I really don't know what that might be.

 

Before I hook up the Minimax with fixed resistors as a test, I'd like to double check.  Is R1=25k and R2=10K a safe combo?  Or would 100/47 be better?


Edited by SteveSound - 6/4/14 at 4:14pm
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