This can be quite intense and varied based on what regional ramen style you are after but to simplify broth there are two main types (and many sub-types):
Shintan, which is a clear soup broth. It has a density of 4-6%.
Peitan, which is a white soup that can be further divided into,
Kyushu which is a lighter, Southern regional flavor with a density of 5-7%
Kanto, which is primarily the Tokyo region has the strongest flavor and a density from 8-10%. In Tokyo metropolitan area this boldness increases and is often in the 10-12% density range. Kanto is not really white, it is brown and sometimes referred to as the ‘wild’ broth because just about anything goes. I like this one.
Sensei says, "You use my picture, you pay double." He wasn't kidding.
Just so it’s clear we use a refractometer to measure the density of the broth. Place a few drops of the cooled liquid onto the prism, press the cover plate to eliminate possible bubbles as well as air and observe the light/blue boundary in the scope to see the result value.
Dashi is a flavoring that adds glutamine and guanylic acids which are 2 of the 3 acid profiles that make up umami. Dashi is quite simply water + kombu + dry shiitake brought to a boil. It is important that this flavor is very light. You don’t want to infuse the dashi with too much flavor, but you do want to extract the acid profiles that will mix in with the inosinic acid in the tare. It is ok to add the inosinic acid by way of dry fish directly into the kombu but this is a personal preference. Inosinic acid also comes from the chicken and pork so just keep in mind where the various sources of acids are coming from and make sure they are balanced.
A ramen recipe I used before, which is the well known Momofuku Ko variation by Chef David Chang, uses smoked bacon in the dashi. I quite liked that and it was a strong dashi flavour!
For the purpose of the broth we will make, which has 35L water, use 5L of dashi.
10g dry shitake
Combine all and bring to a boil. Immediately switch of heat and let shiitake and kombu infuse and cool. Remove shiitake and kombu before combining into broth.
These are large 50cm diameter stock pots. The larger one is 60cm. All of these (plus two more you don't see) will be filled with various ramen stocks very soon. Each stock pot feeds 100 people. There are 3 of us.