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Old 28th December 2003, 07:14 PM   #1
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Default Logarithmic attenuation

Hi All,

I'm currently in the process of designing a preamp using the Burr Brown PGA2310 as a volume control (with a pic and a rotary encoder).

It's amplification range goes from +31.5dB to -95.5dB (in 0.5dB steps), but I'll only be using 0db to -95.5dB part of it. This leaves me with 192 steps in total which seems to be too much.

Does anyone have an idea of how to calculate a decent logarithmic curve using say 50 or 60 steps ?

Something like this http://img.cmpnet.com/planetanalog/f...inPot/Fig3.jpg

Thanks, Stu.
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Old 30th December 2003, 10:38 PM   #2
IVX is offline IVX  Russian Federation
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Hi,
I did similar(127 steps(MIDI controllers rate) for 8bit DAC (Ref. as audio input)) 7 years ago.. by MS Exel.
Best regards
Ivan.
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Old 31st December 2003, 01:38 AM   #3
x-pro is offline x-pro  United Kingdom
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Default Re: Logarithmic attenuation

Quote:
Originally posted by FunkyStu
Hi All,

I'm currently in the process of designing a preamp using the Burr Brown PGA2310 as a volume control (with a pic and a rotary encoder).

It's amplification range goes from +31.5dB to -95.5dB (in 0.5dB steps), but I'll only be using 0db to -95.5dB part of it. This leaves me with 192 steps in total which seems to be too much.

Does anyone have an idea of how to calculate a decent logarithmic curve using say 50 or 60 steps ?

PGA2310 is already logarithmic - just use larger steps (1.5 or 2 dB) when controlling it from the microprocessor. You don't need to calculate anything

x-pro.
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Old 31st December 2003, 10:15 AM   #4
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funny
ps: Алекс, с новым годом Вас! .
Best regards
Ivan.
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Old 31st December 2003, 02:54 PM   #5
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happy new year to you to !
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