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Guitarist's Tech Workshop

Lesson 9 of 18

Reading a Schematic

Kurt Bloch, Ben Verellen

Guitarist's Tech Workshop

Kurt Bloch, Ben Verellen

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Lesson Info

9. Reading a Schematic

Lesson Info

Reading a Schematic

Moving along to talk about the different circuit diagrams that air handy when you're talking about guitar amplifiers um schematic is the most important one that you need in a schematic is really an ideal map of how the circuit functions so it's going to tell you exactly what the circuit is supposed to dio if everything's connected right if everything is working as it should, this is how the circuit works and it's the best place to start if you're if you need some guidance for what it is you're doing or what it is you're looking at if you're looking at your aunt there, what not ah wiring diagram is different a wired wire diagram is a picture of real world circuit layout, so it would be an actual either a drawing or a photograph of the actual innards of the amp and what wires connect aware and maybe even colors or it's just the how to so if you don't know anything about how the thing is supposed to work, this at least tells you what to connect, aware and so if you're not trying to break ...

down all the inner workings of an amplifier but you just want to know where does this thing go? I might somebody modeled my amp and it's all screwy, but I want to bring it back to stock you can kind of just connect a to b and just be very step by step about it, and this will tell you most of what you need to know and then third diagram this useful is the block diagram, and this is just a real basic overview of how the thing works. You can glanced at it and get an idea. So have examples of each of these to stand up for second. So the block diagram. This is a common kind of signal flow for guitar amplifier, so you can see the guitar comes in and enters this checkered box. That kind of gives you the basic gist of what's inside the amplifier. But this picture gives you the entire picture all the way from your guitar to the speaker. So your guitar comes in, enters the pre amplifier, and we'll talk more about what each of these does, but just to kind of get a basic idea goes into the pre amplifier. And then that pre amplifier drives the power section of the amplifier. And then that power section hits the alba transformer, which translates that signal to the speaker and the power supply, which you can see hovering over the top. Here is kind of an all reaching component of the whole picture that supplies each of these sections, both preempt power and etcetera, so that gives you at least a basic overview. And then the wiring diagram is if you had some amplifier you were looking at and like I said before this would tell you exactly what goes where if you're looking at the thing you can kind of figure out what to connect to what sometimes it'll have actual values if you need to know what resistor is what some of these air helpful some of these are really messy and kind of hard to navigate my opinion but it can tell you things like grounding scheme if it's important where you connect the ground of an amplifier we'll talk about more about what that means and what that is but anyway this would be a tool that's useful for that schematic again the most important thing to think about as far as diagrams that I'll tell you something about how amplifier works use lots of different uh images and these are just a handful of the common ones so to familiarize resistor is this jagged squiggly thing capacitor you'll see a couple different images this one here just two plates crossing each other that's that's a common one and it usually indicates that it's not a polarized capacitor it khun if the type of capacity that could go either way but over here you can see that this one has two different shapes and even a little positive sign on the top so that tells you what type of cap and how it should be oriented transformer it's kind of like the two coils across the magnetic core this is a sign for ground um potential murder over there in the upper corner that's a resistor with an arrow pointing at it which indicates that you have a third piece of metal on there that connects to a wiper that chooses however much resistance and we'll talk about how that actually works in the fire later um silicon die owed its silicon diet is the sort of offspring of the tube dial that we talked about before but instead of using a seal vacuum in a cloud of electrons tio flow between two metal electrodes they eventually figured out that what you were doing in this big glass envelope you can actually do with a little piece of sand if you just make part of the sand more positively charged you know the part of sand not so that can serve the same function which there's benefits to two bands that are great but there's some certain places an amplifier that silicon die owed it just makes sense to use so you'll see that in a lot of guitars, amplifiers even vintage guitar amplifiers often use silicon diets for certain things so that's the symbol of a silicon die owed you can see that there's two different sides to it they're different it's a polar device there's the an outside the cathode side and it's important which one is going where um fuses another common symbol switch and a battery and that's a d c battery not very often do you see that in an amplifier, but it is helpful just to know what it is in case you do come across that schematic so looking at an actual schematic uh working away from left to right is the way that signal works through it and this is this isn't a rule schematics come in all different sort of formats, but I think it's a pretty good rule of thumb to first assume that you're looking at a schematic that they haven't mapped out this way where on the left hand side is where your guitar comes in and it works its way through the signal path on its way to the speaker and I love it when people adhere to this kind of idea and most dramatic steel but sometimes it's stickier than that so just be forewarned, andi other thing to consider when you're looking at a schematic is that they're usually set up such that the d c voltages that supply your circuit are at the top of the deal and they're finding their way down towards ground zero potential and so that's kind of a convention that is useful just to kind of get a glance of the schematic and know what's going on and most of them like I say it here to that kind of idea but not always but yeah current falling from top to bottom signal. Moving from left or right, it's the kind of place to start anyway.

Class Description

Performing a proper setup for your guitar can seem like a dark art requiring a copper chalice filled with incense. Reading a schematic of a tube amplifier can seem like you’re staring at ancient Sanskrit. Guitar and tube amp masters Kurt Bloch and Ben Verellen are here to help.

In this two-part workshop, Kurt and Ben will show you exactly how to get the best sound out of your gear.

In part-one Kurt will teach the basics of setting up your guitar – you’ll learn about:

  • Truss rod adjustment
  • Bridge and nut adjustment
  • String gauge and playing style
  • Guitar maintenance and upkeep
  • Guitar electronics and pickups

Part-two is your primer on tube amplifiers. Kurt and Ben will explain how they work and show you how to keep them sounding great. You’ll learn:

  • Tube biasing
  • Block diagrams and understanding schematics
  • Basic amplifier maintenance
  • Capacitor, resistor, and transformer replacement
  • Speaker repair and power-matching

Kurt Bloch is not only Gibson Guitar’s in-house guitar guru, he’s a legend in the Seattle music scene. He plays in The Fastbacks and Young Fresh Fellows and has a producer credits for his work with The Presidents of the United States of America and Tokyo Dragons. Ben Verellen started Verellen Amplifiers in 2000 and now has a full-time staff churning out hand made custom tube amplifiers for some of the most respected artists in rock and metal. He also fronts Helms Alee, a rock band based in Seattle.

Don’t get caught with crappy tone and blown out speaker – let these two masters show how to take care of your gear and get the best possible sound.


Patrick Marc

This is a fantastic course. I was forever looking up Youtube videos on how to set up all of my guitars for different things, and opinion varies wildly on-line, so it's really great to have these videos detailing the entire process in clear and easy terms. The information on the amplifiers is intensely interesting too. Fantastic!

Alan Williams

Excellent course. Slow start with the guitar set up but Kurt knows his stuff so worth watching it to the end before deciding you don't like it. I came across valves (tubes) at the age of 12 (I'm 66 now) and it was a great refrresher for me. Ben really knows his stuff but he can put it into layman terms that are easy to understand. I definitely recommend this course.

Andrew Synowiec

I bought this course for the amplifier section and skipped straight there. It's fantastic. Right at the perfect level for me, a newbie DIY-er with a few pedals, a kit amp and an Electronics 101 course under my belt. Well done! I'll update my review if I have time to watch the guitar section.