# Resistor Value Up or Down



## joelorigo (Apr 14, 2022)

I am needing a 5M resistor. Currently Mouser has 4.99 OHM or 5.1 OHM with 1% tolerance. Would either be fine? Would either be better?


----------



## spi (Apr 14, 2022)

joelorigo said:


> 4.99 OHM or 5.1 OHM



Make sure you mean MEGAOHM.  And yes, a 4.99M or 5.1M would work fine here, and I doubt you'd notice a difference.


----------



## joelorigo (Apr 14, 2022)

D'oh. Thank you I was looking at the wrong one. And there're out.


----------



## JamieJ (Apr 14, 2022)

You could use a few resistors together in series to make the right value. Or use two 10M in parallel.


----------



## joelorigo (Apr 14, 2022)

Oh yeah! I've never done that.


EDIT: Oh, Tayda had 5.1








						5.1M OHM 1/4W 1% Metal Film Resistor Royal OHM Top Quality
					

Royal OHM - Get It Fast - Same Day Shipping




					www.taydaelectronics.com


----------



## JamieJ (Apr 14, 2022)

That will work well.


----------



## joelorigo (Apr 14, 2022)

Thanks. Oh while I have you, is this going to be a big pain for the 2 speed pots in the Electrovibe? Having trouble finding any with PCB pins









						Alpha Dual-Gang 24mm REVERSE Audio Taper 100K
					

Small Bear Electronics DIY Parts




					smallbear-electronics.mybigcommerce.com


----------



## JamieJ (Apr 14, 2022)

Yeah id say that probably not worth the hassle personally.


----------



## joelorigo (Apr 14, 2022)

Yeah. Thanks!


----------



## ICTRock (Apr 14, 2022)

joelorigo said:


> Thanks. Oh while I have you, is this going to be a big pain for the 2 speed pots in the Electrovibe? Having trouble finding any with PCB pins
> 
> 
> 
> ...











						16mm Dual Gang Potentiometer - Short PCB Leg
					

Top Quality Parts for Guitar Effects Pedals and DIY Music Devices. Knobs, Pots, Switches, Kits, LEDs, Enclosures, Jacks, Wire, Resistors, Capacitors, Semiconductors




					stompboxparts.com


----------



## joelorigo (Apr 14, 2022)

ICTRock said:


> 16mm Dual Gang Potentiometer - Short PCB Leg
> 
> 
> Top Quality Parts for Guitar Effects Pedals and DIY Music Devices. Knobs, Pots, Switches, Kits, LEDs, Enclosures, Jacks, Wire, Resistors, Capacitors, Semiconductors
> ...


Thanks!


----------



## Chuck D. Bones (Apr 16, 2022)

4.7M is also plenty close.  

Ah pity the foo who sticks two resistors in series!


----------



## fig (Apr 16, 2022)

Chuck D. Bones said:


> 4.7M is also plenty close.
> 
> Ah pity the foo who sticks two resistors in series!
> 
> View attachment 25393


Mr T.,

Is that because each resistor does not take total voltage but divide it, or what? Go easy on me B.A.


----------



## Chuck D. Bones (Apr 16, 2022)

I know you're asking "for a friend."
Hooking resistors in series to hit a specific value is silly because 99% of the time, you can get plenty close with what you already have.  Failing that, go buy what you need, you can get 100 for $1US.


----------



## fig (Apr 16, 2022)

Yeah, I saw a 33.6kΩ in a BOM this morning. Imagine my utter shock when I checked the bin.


----------



## fig (Apr 16, 2022)

Would it be a good idea to make substitutions consistently across a circuit, in the event of say, a voltage divider?


----------



## Chuck D. Bones (Apr 16, 2022)

Only if you're changing the resistance by a substantial amount, say more than 10%.  On the other hand, if you maintain the resistance ratio, then you don't have to bother with analyzing the effect of unbalancing the voltage divider.


----------



## fig (Apr 16, 2022)

Chuck D. Bones said:


> Only if you're changing the resistance by a substantial amount, say more than 10%.  On the other hand, if you maintain the resistance ratio, then you don't have to bother with analyzing the effect of unbalancing the voltage divider.


One last question sir, and you've been amazingly patient. 

Do the same tolerances that apply to guitar pedal circuits also apply to......say........a big telescope in space? 

I'm guessing 'no'


----------



## Chuck D. Bones (Apr 16, 2022)

Some places yes, some places no.  We used every trick in the book to be able to measure & control the temperature of the 6K coldhead to within ±10mK.  The power converters and class-D power amplifiers could get away with 10% tolerance resistors.


----------



## DAJE (Apr 16, 2022)

I just tented two resistors to make an unusual value. I know it won't make a difference but I felt "why not?" since it was easily done. Wouldn't do it in something I was making for someone else, probably, but since it's for me, I don't mind.

EDIT: 348K resistor for a Pharmacist, if you're wondering. 330+18. I didn't bother with the 57.6K because the first 56K I measured read 57.2K anyway.

EDIT 2: I'm sure makers source (or order specially made) resistors in wacky values specifically to annoy cloners.


----------



## Chuck D. Bones (Apr 16, 2022)

Neither of those resistors are critical.  I tend to avoid jumping in on a troubleshooting thread if parts are standing up, but there are plenty of other folks who aren't so finicky.


----------



## MichaelW (Apr 18, 2022)

Uhm……I’ve done this a couple times. I don’t know what it or isn’t critical. 

I’ve also gone through and tested a pack of “the next closest value” to find one out of spec to match. 

I just pulled all the components for 2 Pete Cornish builds I’m planning on working in this week. Lots of really obnoxious resistor values in his builds.


----------



## giovanni (Apr 18, 2022)

Chuck can correct me here, but given that transistors are inherently non linear devices and so are capacitors (and resistors too?), a slight difference in resistor value won’t make a huge difference compared to all the other non linearities in a circuit. There are techniques to increase linearity (used for analog mixers etc) but they don’t usually rely on very exact resistor values.


----------

