April 29, 2020 at 4:44 pm #12664
I’m building a ToneTwEQ board, in series after the Squishy Octopus, and found two resistor values that I don’t have, but I do have others that are close to values on the parts list. The first is for R7 and R9. Both need a 3k6. I have 3k3 and 3k9 value resistors. The second is for R3, a 300k. I have 270k and 330k. Does it matter all that much that I use the exact value on the list or will one that’s close bee good enough? Should I go higher or lower and if I go higher how will affect the circuit and it I go lower how will it affect the circuit.
Thanks very much,
JimApril 29, 2020 at 5:14 pm #12665
They’ll be ok the circuit will still work
With metal film tolerance is + or – 1%
Carbon film + or – 5%
I’d probably use the 330K rather than 270K
The 3K6 I’d use the 3K9 it won’t make any noticeable difference I’d err higher because 1 is in the op amp negative feedback loop the other part of the mid filter network even though it’s K ohm it’s not significantly different
You could use sockets and try both values and if you wanted change them later
Or you can tepee, solder a 100K and a 200K in series for 300K
Any 2 values added together and soldered in series that add up to what you want will do, albeit it don’t look greatApril 29, 2020 at 5:21 pm #12666
Excellent. Thanks very much Billy!April 29, 2020 at 5:44 pm #12668
As I say doesn’t look great but does the job
I think I did 3 on this build only to discover I actually had all the values
This pair were the best of the bunch I’ve edited out the other 2 pairings that didn’t make the’ kinda looks ok’ grade!April 29, 2020 at 7:36 pm #12669
Thanks. I’ll have to keep that in mind if I don’t have what I need.
Now I actually have the same question about capacitors. The parts list calls for a 56nf in C4 and C9 and a 33nf in C5. I don’t have either of those but I do have 22nf, 47nf and 68nf. Would you use any of those to replace what’s on the parts list or would you buy the correct values from the parts list?April 29, 2020 at 8:40 pm #12670
Again you can join values this time for capacitors to add up it would be in paralell but not something I do often
C9 is in the power section so 47 or 68 is fine there
C4 and 5 are again part of the Low and Mid filter network putting a 68 or 47 in C4 and a 22 in C5 wouldn’t stop the circuit working it would just alter the frequencies slightly in this case I’d go 47 for C4 and 22 for C5
Not to get too technical but you can alter resistance to compensate for cap changes but imho 22n for mids is still ok as is 47 for lows I again would just socket them and change when you get the correct values if you want to, your ears may well be happy with it
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