Fratus Amplification repairs tube amps and other audio gear.

Learning

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My New Book, Just Released!

The perfect gift for that tech-head musician or technician that loves to work on guitar amps.
My New Book! inside peek:
New book: "Guitar Amps and Their Problems" by Mike Fratus
Over 2200 entries of service records for the most popular makes and models of (mostly) tube guitar amps and other audio gear!

Some interesting videos about tubes and tube amps

Mullard - The Blackburn Vacuum Tubes Factory


Tesla Tube Factory Visit in Czech Republic 1998


How It's Made - McIntosh Tube Amp. Published on Jun 9, 2014


Winding the output transformer for vaccum tube audio. Published on Mar 17, 2012


Unique Marshall Factory Tour as you have NEVER seen it before



Amp Tone and Mods

Article: Tube Biasing - How it contributes to Amp Tone, and other considerations.

Copyright Mike Fratus, Fratus-Amplification.com 9/2014

Output tube biasing effects two major things: Clean Headroom and Breakover.
These can be balanced out so that half of the usable volume level is clean and the upper half is compressed and breaks over easily.
What contributes to this is the type of circuit (Class A or AB), the B+ voltage, output transformer resistance.


A Little Theory...

Class A operation makes both halves of the push-pull output section draw current constantly. This reduces crossover distortion, increases linearity, and makes the tubes stay close to the point where hard playing runs them into the rounded-top distortion that makes that "tube-y" sound tubes are famous for.

Class AB, on the other hand, is a good compromise when done right. One tube is always drawing current, and sometimes both, but always in a small amount. AB is more like an electronic see-saw, where when one tube is up, the other is down. Careful adjustment of distance from the ground (bias) and position of the balance of the see-saw board (bias balance) can make for a wonderful result.

In the world of amp tone seekers, though, there is a big difference in the Class A and Class AB structure when it comes to tone.
The Class A amp has a fuller sound (my opinion) and breaks over sooner.
The Class AB amp is cleaner for a wider range and breaks over with difficulty. You can bias a Class AB "Hot" and get more of a Class A sound, but usually the supporting circuit isn't able to carry the extra load.


The next consideration is the tone stack. That is where many amps get their distinctive sound. On amps that do analog modeling, the tone stack is one of the sections of the amp they switch out.

For a comparison of the response curves of different tone stacks, Duncan Amps has a Tone Stack simulator the is really nice. I've used it to experiment with responses BEFORE I even build the circuit. Its accurate, and FREE!
See Tone Stack Calculator for the Win version. You can run it in Linux if you are using Wine.

There are lots of sites that list great discussions and tutorials about tone. One that comes to mind is the Tone Lizard site Tales from the Tone Lounge. Be aware, it is not for the faint of heart. If you can't bear to hear a few well-placed cuss words about the stuff some people put out as truth about tone, do not click on their link... but I really enjoy the way the author presents his case for BS standing in for truth.
Warning, some of the links have expired. In fact, the home page itself announces that this site may soon expire, but that announcement was in 2009! All the same, get there quick and get the knowledge.

R. G. Keen has been on my list of references for a while. His site at www.geofex.com is full of electronic stuff, all good, but I want to point to one section in particular, the Tube Amp FAQ page. Lots of learning experiences there.

More to come later...

Search the web for examples of the tone you want, then you have something to show someone when words fail. Send me the links to your clips at Design Your Next Amp on my site.
If nothing else, just leave the link in the link place, so I can get an idea of what people like.


Be safe. Observe rules about measuring high voltages, which can absolutely kill you or at least ruin your day.

This Month's Tube Amp Video: Vacuum tube amp theory - This vintage film is from the US Army from when tubes were the thing.


Can't see it? Here's the Youtube link.
(Have suggestions of videos to put here? Send me a message!)
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Solid-State Tubes are here! See My Products Page for details. Get the tube sound without the tube problems!
See how much a new amp might cost with Amp Feature Selector. List the features you want, such as watts, channels, options, and get an estimated price immediately! I can then send you a detailed description and an invoice for a down payment to start work on your amp.
Need parts? I have a parts request page for you. Use my new Amp Parts link.
Hints and links concerning the sound of your amp at AmpTone.net
Build it yourself DIY information and links at Amp-Kit.com
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Electricity and Electronics

Electronics Hobbyist Web Site GREAT Links! Don't pass this one by! It has electronic references, circuits, data, and repair info.
www.electronics-tutorials.ws/ has some great general electronics tutorials.
Making Electric Circuits and Other Electronics Projects: Lesson Plans
The ARRL Handbook has set the standard for Ham Radio enthusiasts and communication engineers through the years. You learn enough about electronics and radio from one of these handbooks to build radio receivers, transmitters, amplifiers, and to get your FCC license! Great tube information! This is the 1959 edition. Caution: 59MB - Large PDF File!
How to repair circuit board problems, by billm. I use these same methods as well. Good guidance.
THE ELECTRON AGE - 100 years of progress in electronics - by Carlos Fazano In case you missed the last 100 years. In English and Portuguese. Excellent!
ElectronicsTeacher.com - This portal is dedicated to Students, Amateur and Professionals in the electronics field.
I have to point you to Michael Hoffman, BSEE, at Amptone.com. I saw his site years ago but couldn't find it again until recently. His site may have been my inspiration for starting this one. Be sure and give him a visit. His site is really complete and full of good info, suggestions and tips.

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Vacuum Tube Knowledge

Tube Terminology for Dummies is the name, but it really should be your first reading about tubes, especially if you are trying to fast-track the technical stuff to do something specific.
J.B. Calvert's wonderful and scholarly reference on Vacuum Tubes. Lots of theory and practice on amplifiers, both solid-state and tube-based.
Fun With Tubes! Great site! This non-commercial site is dedicated to passing on and preserving knowledge of vacuum tube circuits and electronic techniques.
Tube Amp Debug Page by R.G. Keen. This page is designed to lead you through debugging a problem with a tube-type guitar amp. Mr. Keen knows his stuff. You can learn a lot from him.
Bonavolta's Tubes for Newbies Tutorial should not be skipped. Lots of good drawings and simple illustrations.
Amplified Parts presents 12ax7's - a comparison of current-production tubes.
The Tone Lizard Lounge site unfortunately is no longer reachable. I even wrote and asked him if I could mirror his pages, and he said the site was not down... well, it is. If I ever get permission to post his pages, I will. Lots of great stuff there. Excellent for theory and practical information. Visit all his pages. Caution: Strong Opinions (usually right!)
TubeCAD Journal is an offshoot of Glass Audio, and is associated with the TubeCAD series of software packages. Loads of articles about tube amp design if you are interested.

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Vacuum Tube Amp Building and Repairing in Particular

Instructables.com - Building your own Tube Guitar Amp
eHow.com - Troubleshooting Tube Guitar Amps
DIYGuitarist.com Amp Stuff
Fratus-Amplification.com presents DIY Amp Kits
DIY Guitarist - Amp Stuff

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Stomp Box Electronics


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Tube Amp Output Biasing

Off-page video...
Mojotone's "How to bias a tube amp". Good, solid instructions!
Fratus-Amplification.com article: Tube Output Biasing

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Guitar Amp History and Evolution

This extremely informative article by Keenan is about how amps have developed over the years.
GUITAR AMP EVOLUTION by Keenan
Here is a pretty good article, Guitar Amp Primer about amps in general.
Here is an excellent article on how the design of guitar amps came to be where it is today: Guitar Amp Tone History
Ampwares.com- The Amp Guide - Historical Guitar Amplifier Information
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Speaker Technology

A guide to replacement guitar amp speakers from Loudspeakers Plus
is here. (Look for the small links just under the title that lead to separate Eminence and Jensen replacement charts, too.)
Choosing Speaker Wattage and Ohms to maximize Sound Output and minimize burnt speakers and amps! A techish article from Antique Electronics and tubesandmore.com! Speakers and Power Explained
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Science and Electronics

ePanamorama.net Vast array of references, resources, nearly everything!

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Software

Tucows shareware, freeware, free programs

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General Knowledge

ResearchBuzz - The Ins and Outs of Searching. Learn to search like a pro!
SoYouWanna - tells how things are done. Simple to complex explanations.
Reference Desk - whatever you want to know: Dictionaries, encyclopedias, etc.
BabelFish - translate to/from any language! (now part of Google Translate)
Internet Archive has lots of media files, movies, art, books, and the famous Wayback Machine!
Make your own paper! Instructions from the State of Wisconsin Department of Natural Resources, Make your own Paper! EEK!
How to Make Your Own Recycled Paper - Video on Youtube Make Paper!
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Musicians

Listen to my friend's Industrial Shred style. Visit his website at
Irron!
My friend Dennis Odocharty on lead guitar with videos of the Houston band Lady and the Tramps.
Videos of some Local Bands

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Other Artists and Craftspeople of Interest

My friend Cathy is a wonderful crafts-person with years in the theater biz... See
Cathy's Theatrical Costumes for any purpose. Maybe you could use a new look onstage for you next tour! She does props and sets, too. Check her out and see what she can do for you. Recently she sequined a jacket for Dewey Wayne, a really talented up-and-coming country star. He looked good in it!

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Web-Only Stuff

FreeWebSubmission.com

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Schematics

Amp Schematics

All Brands

Prowess Amplifiers has a large collection of guitar amp schematics.
DrTube.com - Tube Amp Schematics
Guitar-Parts.com Parts Lists and Schematics for Korg, Marshall and VOX
BlueGuitar.org - Schematics
TDSL DuncanAmps.com Schematic Links
The Free Information Society - Audio Electronic Circuit Schematics
Tube Data Schematics & Links Site. It's mostly about tube amplifiers & particularly guitar amps with a little hi-fi stuff thrown in.
Schematic Heaven Where All Good Amp & Effect Designs Await Resurrection...

Single Other Brands

The Carvin Museum - Technical Documents

Fender

Fender.com - Fender Schematics

Marshall

MarshallSchematics.com
DrTube.com - Amp Info and Schematics

Mesa-Boogie

Click on "Schematics" on left for Mesa Boogie Schematics

VOX

VoxAmps.co.uk - VOX VINTAGE CIRCUIT DIAGRAMS

Traynor

Traynor Amplifier Schematic Archive

Professional Audio

AnalogRules.com - Free Pro Audio Schematics and Manuals
WaltzingBear.com - Pro Audio Equipment Schematics
One-Electron.com - Pro Audio Equipment

Tube Amps (but not particularly guitar amps)

AmpsLab Vintage Tube Amplifier Schematics -

Electronic Product Schematics - all sorts of products

eServiceInfo.com - Manual free download

How to Repair Electronic Equipment and Products

RepairFAQS How to Troubleshoot from Sam Goldwasser

Guitars

FlatEarthGuitars.com - Guitar_Schematics

Pedals and Boxes and Other Music-related Electronics

www.SynthDIY.com
REDCircuits.com Designs - Audio
DIYStompBoxes.com - Selected Pedal Schematics
General Guitar Gadgets - Stompbox Kits
DiscoFreq's Effects Database Site
Electroconducive DIY Audio - Schematics
Vintage German modules (Neumann, Siemens, TAB, IRT, Lawo, ANT, Eckmiller, Adis, Monitora and Telefunken modules and Braunbuch scans)

Other Electronic Circuits

WhatCircuits.com - Electronic circuits
Discovercircuits.com - Electronic Circuits
ElectronicsTeacher.com - Various Schematics and Circuits
Technician's Filing Cabinet from One-Electron.com
Schematicx.com - Schematics, Circuit Diagrams Sharing & Download
Tonepad.com -- fx projects
Analogguru Schematics

Radio

CliftonLaboratories.com

Advertisements follow... then more good links!

Did you find something good? Like what you see here?
Or, just bookmark this page and come back to buy things through these links. I didn't put in anyone I would not buy from, so don't worry. Also, last I checked on them these were real links, not spam links. (You have to buy your own Spam at the store. Hey, do they even MAKE Spam links? Mmmmm... tasty-sounding. Kinda.)
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Call Mike at my name and number, but please don't call until after 9AM.

See this great tone capacitor video!
If you ever believed that the type of cap made no difference, watch this! Need parts? I'm trying to make an outlet for parts. Don't call for parts, please. Use my new Amp Parts link.

Books:

You can go crazy with books, just like anything else. The thing that I have learned is that first you need to understand electronics, that is, learn how electrons behave and how to tame them. Then you have to learn the skills and practices that make it safe and effective to work on stuff in general. Then you need to learn about the particular type of product that you are interested in.
Alibris is a great place to buy books at severely reduced prices.
ePanamorama.net Vast array of references, resources, nearly everything! Electronics Hobbyist Web Site GREAT Links! Don't pass this one by! Electronic references, circuits, data, repair info.

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Entire site Copyrighted by Mike Fratus, webmaster at Fratus-Amplification.com 3/5/2017 - don't snag! Leave email with suggestions or requests at: webmaster@tubemodules.com
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