PIMETA v2 component values
Jun 12, 2013 at 9:08 PM Thread Starter Post #1 of 4

NotJimCarrey

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I have all the stuff to build my PIMETA v2, and wanted to get some input on values used for the capacitors & resistors.
Do these values seem optimal?
Here's the schematic: http://tangentsoft.net/audio/pimeta2/misc/sch-2.01.pdf
Sorry, couldn't edit the post from work.
 
R1 = 1.5kΩ
R2 = 100kΩ
R3 = 220Ω
R4 = 2.2kΩ
R4G = 1.5kΩ
R5 = 1.2kΩ
R6 = 100Ω
R7 = 100Ω
R11 = 8.2kΩ
 
RCCS = 82Ω
RLED = 10kΩ
RBIAS = 5kΩ
RBLIM = 1kΩ
VOL = 10kΩ
 
C1 = .043µF
C2 = 470µF
C3 = 0.1µF
C4 = 10µF
C5 = 0.1µF
C6 = 10pF
 
Jun 13, 2013 at 9:08 AM Post #2 of 4

tangent

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C1 is way too low. It will give a corner frequency of 37 Hz. You can make C1 bigger or R2 bigger to fix this. I assume you have dropped R2 because you are using a 10k pot, so to make all else equal, you should have increased C1 by 5x from the schematic value, not cut it in half. You don't have to go that far, but at least going back to 0.1uF would be adequate.
 
Your R3/R4 ratio gives a gain of 11, probably too high. For most systems, a gain of 1-5 is enough.
 
I assume with an 8.2k R11, you are planning for a fairly low supply voltage. Some "9V" NiMH variant?
 
Jun 13, 2013 at 4:11 PM Post #3 of 4

NotJimCarrey

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Sorry about that, C1 was a typo, meant to put 0.43µF. And yeah, I'll be using a 9v NiMH. Also, I used your Gain Calculator for a gain of 5 and got 77 results. Does it matter which set I use? Lastly, thanks a ton for helping, I'm really looking forward to building this.
 
Jun 13, 2013 at 8:05 PM Post #4 of 4

tangent

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Does it matter which set I use?

 
Exact gain value isn't important here.  They're sorted in order of how close they are to the goal you gave the calculator, but if one further down the list has a "nicer" pair of resistor values, by all means, go with it.
 
You do want to keep the resistor values low-ish, of course.  If you have a choice between 10k and 39k, or 1k and 3.9k, go with the latter. (But don't go stupid-low. Scaling it to 10 and 39 ohms would be silly.)
 

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