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PIMETA v2 component values

post #1 of 4
Thread Starter 

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


Edited by NotJimCarrey - 6/12/13 at 11:26pm
post #2 of 4

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?

post #3 of 4
Thread Starter 
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.
Edited by NotJimCarrey - 6/13/13 at 1:16pm
post #4 of 4
Quote:
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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