How to convert Gain Pot into Gain Switch?

[cactus]

I have a 312 design and I want to convert the 10k Reverse Log pot to a switch.
How do I calculate my needed resistor values and determine if I should use shorting or non-shorting?

Thanks a bunch!

 

[3nity]

http://www.quadesl.com/attenuator.html

 

[Michael Tibes]

I'm not good at math at all, I'd just temporarily install a pot (doesn't need to be reverse for that), set the desired gain, measure the pot's value and find the closest possible resistor (or combination). I haven't looked at the circuit, but I'd go for a shorting switch and see if it works fine.

Michael

 

[ruairioflaherty]

I've done an excel spreadsheet to work out the resistor values for my 312s. The results depend on several variables -

-What size gain steps do you want?
-What input and output transformer are you using - you need to know the ratios to calculate gain)
-Is your op-amp a 2520?

With the above info you can calculate the exact values needed to get particular gain settings.

I'll try to stop back tonight if work allows and post some numbers.

Cheers,
Ruairi

 

[cactus]

http://www.quadesl.com/attenuator.html
this looks like a really neat site, but on my browser, most of the numbers are covered up. damn.

ruairioflaherty - i'll be using a 12-position switch, and I'd guess ~5dB/step, 1:10 (Cinemag 75101apc) -> @pi 2520 -> crimson audio 1:1

thanks, guys!!!

 

[Harpo]

have a look at this excel sheet .
-Harpo

 

[cactus]

OMG! Thanks for that spreadsheet!