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Which Resistors Would Benefit From Being Very Precise?
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Which Resistors Would Benefit From Being Very Precise?

by jdmcs on Fri Oct 13, 2017 11:41 pm

I recently purchased a set of x0xb0x PCBs from Adafruit, and am trying to piece together components to build a (more or less) stock x0xb0x. However, I'm willing to make mods where they make sense to me, or where component obsolescence forces the mod. This question deals with the former.

I've been doing some reading, and it seems as if Roland used some 0.1% resistors in the TB-303 where it mattered to ensure accurate note generation. However, I have not found which resistors there are, or which these would equate to on the x0xb0x.

Since I am a stickler for accuracy, and because I've already figured out that a few components are going to be really expensive compared to the rest, spending a little extra on a few high-precision (0.1%) resistors will be cheap in comparison. Which resistors would these be?

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Re: Which Resistors Would Benefit From Being Very Precise?

by Nordcore on Sat Oct 14, 2017 12:58 pm

The 200k Ohms should have 0.1%. Gives better VCO tracking.
R74, R75, R76, R77, R78, R79, R80, R81, R82, R83, R84, R85, R86, R87, R88, R89, R90

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Re: Which Resistors Would Benefit From Being Very Precise?

by jps2000 on Thu Jul 05, 2018 1:32 am

As a rule of thumb you can look at the values first
Component values follow E series https://en.wikipedia.org/wiki/E-series_ ... ed_numbers
so if 200k appears somewhere they are <1%.
Some circuits require good matching of components. So equality is more important than absolute value.
You may measure them before assembly or choose (expensive) highly accurate components.
However usually newer components from same batch are much better than guaranteed tolerance.
Another point is thermal and aging drift. Metal film resistors are superior in that

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