rebote substitutions

[Barcode80]

I'm building the rebote from the tonepad layout. there are a few of the parts i don't have, and i was wondering if you guys could shed some light on subs for me. left is stock, right is what i want to sub:

( 12k resistors -> 10k
(3) 24k resistors -> 22k
(1) 240k resistor -> 220k
(2) 510k resistors -> 470k

(1) 51pF Cap -> 56pF
(1) 5pF cap -> 7 pF

anyone know if these subs will have any adverse effects?

layout file and schem at tonepad here:
http://www.tonepad.com/getFile.asp?id=98

[oldrocker]

I triangled resistors in series to get the resistor values and paralleled some caps to get close to those values.  I perf boarded mine so this might be difficult to parallel caps using PCB.  I used tant's for the 1uF caps and it sounds great.

[Barcode80]

i can't remember the formulas. resistors in series for example. i know that 2 of the same value halves the resistance, but i don't know the actual math behind it so i can adjust for the values i need.

i'd be okay with going ahead on the cap selections since there are only 1 or 2 so i can replace if it doesn't work. but with so many resistors needing subbed, i probably need to stack some resistors and try to match closer to true value.

[Meanderthal]

 Resistors in series add up. 220k + 20k = 240k(in series) Caps paralell add up. Your cap values should be fine, they're like 20 % tolerance anyway. Your resistor values should be ok too, but it's easy to add em in series.

[gaussmarkov]

i can't remember the formulas. resistors in series for example. i know that 2 of the same value halves the resistance, but i don't know the actual math behind it so i can adjust for the values i need.

for resistors in series you add up the reisistances.  for resistors in parallel valued R1 and R2, the effective resistance is R1 x R2 / (R1 + R2) so that if the resistors are equal value, say R1, you get R1 x R1 / (2 R1) = R1/2, or half the resistance.

if we measuread caps in 1/farads, all the formulas would be the same for caps.    but unfortunately we don't so everything is reversed.  the capacitance of two caps in parallel is the sum of their capacitances.  for capacitors in series valued C1 and C2, the effective capacitance is C1 x C2 / (C1 + C2) so that if the capacitors are equal value, say C1, you get C1 x C1 / (2 C1) = C1/2, or half the capacitance.

all the best, gm

[Barcode80]

okay, i may do some series resistor building then, but in case i get lazy, you guys think the subs i listed up top sound reasonable?

[oldrocker]

Yes.

[Barcode80]

one more question and i'll leave you guys alone for a bit i don't have any 25k's on hand. i only have 1 50k, but a few 100k. so, i'm going to use a 100k, another 100k with a 100k resistor to make 50k, and a 50k with a 50k resistor (47k actually) to approximate the 25k. do i put the resistor across the outer lugs (lug 3 to lug 1) or from 3 to 2 or from 2 to 1?

[BN]

If you go for the lazy version I would be glad to hear how it comes out. I've been thinking about doing the same thing... 

/BN

[Andre]

do i put the resistor across the outer lugs (lug 3 to lug 1) or from 3 to 2 or from 2 to 1?

Across the outer lugs (3 to 1).

André

[Fp-www.Tonepad.com]

To the original post: Using those substitutions should work ok.

Fp

[Barcode80]

okay, thanks for all the replies, when i get home i'll finish wiring up the pots, jacks, switch and let you guys know the outcome. i'm also going to have to use all audio taper pots. we shall see how it turns out...

[Barcode80]

Oh... My... GOD! This thing is awesome!!! I can confirm to everyone that the subs above work VERY well. i've never built with the exact values, but i can't imagine it sounding much better! This one will definitely get boxed up! The only problem i have is a faint motorboating sound at max delay time. not sure what causes that, so any help is appreciated, but i will not likely use delays that long, so i still ROCKS! pics to come once i get it boxed...