Resistor Color Counting
Today I will be discussing the necessary art of resistor color code counting. There’s nothing more useful when prototyping pedals on a breadboard, putting parts back in storage bins after use, identifying resistors on a circuit board should you need to troubleshoot without being able to see the silkscreen value on a PCB, as well as preventing the use of a multimeter to detect values. When I first started building pedals, I had to use a resistor color code calculator which took up more time than one would think. Knowing how to count resistor codes has literally changed my life as a pedal builder and tinkerer, and I’m hoping if I share with someone else what someone shared with me a few years ago, I can also make a huge difference in someone’s pedal building experience.
I will cover the two most popular resistors in pedals today: The carbon film resistor, and the metal film resistor (obviously excluding SMD resistors). I won’t be covering the difference between the two, but here is a good article on the actual composition of the resistors, and Beavis Audio has this article which covers the basic differences of the two regarding price and tolerance, which I believe is the main delineator when pedal companies choose which components will go into their pedals.
A very small side note about Beavis Audio is that they are an incredible resource for new builders, and even experienced builders. I spent many hours on his website looking over schematics, articles, and breadboard projects, but funny enough, he admits to using a color code calculator.
ROYGBIV.. sort of
The main part of being able to count codes is understanding that a color is always associated with a number, and luckily it mainly follows the ROYGBIV spectrum that was learned at a very early age. The only outlier is that Indigo isn’t part of the color chart but Black (0), Brown (1), Gray (8), and White (9) are. If you can memorize the main colors of Red (2), Orange (3), Yellow (4), Green (5), Blue (6), and Violet (7), the rest will fall into place. There are no weird rules, exceptions combining colors, or math involved really, it’s simply counting zeroes and making sure you read from the correct direction.
A great and simple example of the main two resistors most people use in building modern pedals.
The image above does a great job of visually explaining how to count a 3-band carbon film resistor (tan) and the 5-band metal film resistor (blue). It’s important to note that you must read a resistor in the correct direction! I always read mine from left to right like the image shows, call it OCD or whatever you’d like, but it’s a thing I must do. You’ll know which direction is correct based on the brown or gold strip on the right side, which is the tolerance band of the resistor, and luckily that’s not important whatsoever to determine what the value is. Different types of resistors might have a different color tolerance strip as noted below of the image, but the most common with resistors used in guitar pedals will be these two.
The quick and simple description of what the tolerance means is that it lets you know how close the true value of a resistor is, as many resistors can sway in either direction (+/-) of its true value. That is the main difference between the metal and carbon film aside from price (why the blue ones are more expensive), and why most pedals you see have the blue ones. If a resistor is rated at 100k, the blue metal film resistor will be or should be closer to 100k if you measure it with a multimeter (+/- 1%) than the tan carbon film (+/- 5%). It’s worth mentioning that there are other differences between them that a designer can take into consideration like temperature and voltage coefficients mentioned in Jak’s article and overall long-term stability, but I think most hacks like me would only truly consider or understand the two mentioned above.
I personally haven’t heard a difference in my breadboarding experience over the years, but I’m sure that a real engineer can design a circuit where these small differences in tolerance would certainly matter. If I am using a resistor to bias a transistor, or to create a reference voltage, I might consider using a metal film resistor here where I’d want those values to be really close to the actual value. Something like a pull-down resistor or a standard high pass/low pass filter which you see at the input of most pedals would likely be fine using a carbon film. It’s also worth noting that a lot of early EHX pedals for example and some of the most expensive vintage pedals on the used market today likely use old carbon film resistors.
Counting 3-Band Carbon Film Resistors
Most color charts on the internet have confusing images or directions when it comes to the multiplier part of the resistor. If you know which number corresponds to that specific band’s color however, you simply add that many zeroes to the end of the first two bands. Before I discovered this chart and it was explained to me that simply, counting resistors became SO easy.
Let’s look at the carbon film example of the 6.8k resistor in the above image. You’ll see band one is Blue (6), band two is Gray (8), and the multiplier is Red (2). That leaves you with the combination of 6-8-2. Once you add 2 zeroes behind 68 because the multiplier band was Red (2) you get 6800 = 6,800 = 6.8k. The decimal in the final value is where the comma would be if you were to write out the number. With carbon film resistors, the most common multiplier bands will be Red (2), Orange (3), and Yellow (4). Carbon film is great for prototyping because they’re easier to read and see the colors on the tan backdrop, less bands make my brain hurt less, and over time you start to easily identify them visually.
Let’s discuss a few more examples of simple carbon film codes before moving on to the metal film. My favorite carbon resistors are 2.2k and 33k because they’re common values and extremely easy to identify, and they’re also the first two I memorized. Why is that you might ask? Well because a 2.2k resistor is three bands of Red only, and a 33k resistor is three bands of Orange only. Red, Red, Red would be 2-2-2 which is 2-2-00 = 2,200 = 2.2k. Orange, Orange, Orange would be 3-3-3 which is 3-3-000 = 33,000 = 33k. There isn’t really a Yellow, Yellow, Yellow because that would be 440k, I’m sure it exists but it’s not a common value. The cost common near that range would be 470k. Finally, another popular resistor is 100k, and one that will incorporate the Yellow band as the multiplier. A 100k resistor will have Brown (1), Black (0), and Yellow (4) bands which is 1-0-4 which is 1-0-0000 = 100,000 = 100k.
The more time spent breadboarding circuits with carbon film and counting codes, you’ll start to understand and see patterns. With carbon film resistors and pedal building, at least for me, it’s extremely rare to use anything outside of the Green band as a multiplier. If you see a Green band, it’s in the MegaOhm or “millions” (M) range and 1M is a commonly used value that has the Green band as the multiplier, but if you break it down just like we did with the 100k it makes sense. 1M would be Brown (1), Black (0), and Green (5) 1-0-00000 or 1,000,000 = 1M. 2.2M is also a common value which would be Red (2), Red (2), Green (5) 2-2-5 or 2-2-00000 or 2,200,000 = 2.2M.
Counting resistors became quite easy when the multiplier bands are Red, Orange, and Yellow because most resistors in a circuit are within that KiloOhms or “thounsands” (k) range, but things start to shake up a bit when the multiplier is Brown or Black because it gets a little more confusing. A common value that uses a Brown multiplier in the Ohms (R) range is 100 Ohms or written as 100R. That would be Brown (1), Black (0), and Brown (1) 1-0-1 or 1-0-0 = 100R. For me, I kept wanting to count Brown as 1 at the end, but it’s still a multiplier band so you still must treat it as 1 zero and not 1 itself. Another common component in the Ohms range is 470R which would be Yellow (4) Violet (7) and Brown (1) 4-7-1 or 4-7-0 = 470R.
A black multiplier is rare to find in pedal building because it’s such a low value, at least for me, but you simply treat that as no multiplier essentially, or that’s how I taught myself to understand it. Let’s use the example of a 10R resistor, that would be Brown (1), Black (0), Black (0). 1-0-0 or 1-0-(no multiplier) leaving you with 10R. Do not confuse this with the 100R example above, as I’ve done countless time.
I’m not sure if this puts the lower rated values into perspective or not but it’s a fun fact, nonetheless. I conducted an experiment once to see how low I can go on a resistor value in series with and LED before it blows up. If you were to hook up a LED to a standard 9v battery it would explode after a few seconds. You need a resistor in line to not fry it, so naturally the more resistance the dimmer the LED, the less resistance the brighter the LED. I got down to 390Ohms before it exploded. So if you’re ever wondering what’s the lowest value you can go that will give you a really bright LED but never explode on you.. 390Ohms is the answer.
Counting 5-Band Metal Film Resistors and Realizing This Has to End
I feel like I would be beating a dead horse if I continue, and there’s nothing I could explain further that you can’t ascertain from studying the example image. Just know that the process of counting a 5-band resistor is the same as the 3-band resistor, but there’s more bands to count. The third band in the metal film resistors are usually Black (0) and unfortunately that means rethinking the patterns that you’ve mastered in the carbon film pattern because the multiplier doesn’t mean the same thing.
Let’s look at the example above of the metal film resistor of 470k. The multiplier here is Orange, but in a carbon film resistor the multiplier for a 470k resistor would be Yellow. That would look like Yellow (4), Violet (7), Yellow (4) 4-7-4 or 4-7-0000 = 470,000 = 470k. By adding the third band (black – 0) in the metal film resistors however, you would count that as a normal number in the flow like 4-7-0-000 because Orange (3) is now the multiplier. Now you can write it out the same way 470,000 = 470k. This generally sucks for 1k, 10k, and 100k. These value colors are burned into my memory on carbon film but change when you count them on metal film. I couldn’t tell you how many times I thought I was grabbing a 10k metal film resistor which is Orange on carbon and used a 100k because the metal film multiplier is different.
A great example (and my worst enemy) of why an Orange multiplier doesn’t mean the same thing across the two types of resistors. Carbon film 10k resistor on the left, and a 100k Metal film resistor on the right. Also notice the carbon film resistor reads from left to right, but the metal film in this example reads from right to left (that’s going to be a no for me dawg). It can be tricky with the 5-band resistors since the dark red tolerance strip and the brown band are very similar in color. It takes experience and some general understanding of common values to know this is a 100k resistor and not a 130Ohm resistor if you read it the wrong way around.
This gets even more increasingly confusing when you are counting metal films in the Ohms range. Our example from above counting the 470R carbon film resistor was 4-7-0 or Yellow, Violet, Brown where Brown (1) means 1 zero as the multiplier. With the 5 band it would be 4-7-0-0 or Yellow, Violet, Black, Black, as we stated above the Black at the end means no multiplier, so 4-7-0-(no multiplier) leaves you with 470R.
Conclusion
Basically, it all comes down to practice, and forcing yourself to do it. Try to count in your head and then use a multimeter or color code calculator to verify if you’re correct. This is a must have skill for anyone building pedals and I couldn’t image what putting parts back on the shelf would be like after breadboarding if I didn’t know how, not to mention the one time both of my parts bins fell off the wall and scattered a few hundred resistors all over the place and I had to pick them up one by one, and put them back in the correct bin. The main part of this article was to simply say whatever the multiplier band is, add that many zeroes behind it and then write the number out like you would normally and there it is.
I hope this somehow helps someone, because when it was explained to me this way everything finally clicked. Brown and Black as the multiplier band are the most confusing when you first start counting, just remember Brown is still a multiplier of 1 zero and not just the number 1, and black means “no multiplier” and not the number 0, that obviously changes if Brown or Black is in the first, second, or third band because then you would use the actual number, but you get the idea. It does require a bit of memory at first to memorize which colors go to which number, but once you look at the colors enough, you start seeing numbers and your life will literally never be the same. At least the relevant parts about it that revolve around pedal building.