Writing the book....

[talbany]

What is lacking is information on how to tweak circuits and how they will then sound.

This is a VERY subjective topic and very hard to analyze as well as document and display the data.. Most of this is done through empirical testing and trial and error and years of building all kinds of different type amps.. It's also a big part of the art and interpenetration of amp building and many other things..Much of it takes years to obtain and most are very protective of this info..It's like you can follow your grandmothers recipes but it's never quite the same when she makes it in her kitchen..
IMO..after you do it long enough and find your own unique style of building and tweaking amps you can make anything sound good using any number of different parts and combination of parts,and know exactly how it will sound while your building it..Some things you just cannot get out of the books,experience is the only teacher

As far as general amp theory goes my advice there is SO much great info in the RCA Radio Design Handbook (RDH4) written by the founders of tube amps.. It's The Bible!..read it.... Read it again!

Tony

I agree with all of what you've written but that doesn't mean you can't try to cover that. I did already state that it was empirical and I agree that every designer has his own style just as each guitarist does. Bruce was looking for input. I still feel the areas I mentioned have not been covered well previously, despite the fact they may be more amp or circuit specific. Hey, who wouldn't want to read a book by Dumble or Fischer if that were possible?

Dave

Dave
Maybe you could ask Bruce some straight forward questions perhaps he will be kind enough to answer a couple since he started this discussion give us a preview...I would be interested in hearing his opinion as well!!

Good Luck!

Tony

[jtn191]

I'm a big fan of Merlin's book as well. There are few books written by those with technical knowledge that are easily read by musicians/tinkers.

I'd like a book about switching/tweaking for Mesa-like amps. What components should I put on a switch to come up with an awesome array of tones and responses?

[teemuk]

What is lacking is information on how to tweak circuits and how they will then sound.

This is a VERY subjective topic and very hard to analyze as well as document and display the data..

I have to agree. ...at least partially. Effects of circuit tweaks actually are not subjective at all; they follow strict laws and they are perfectly predictable. The way we perceive those effects, however, that's entirely subjective.

When writing about such stuff there's always a trap that information that is entirely subjective is presented as objective.

Another trap are generalisations.

I don't think making a book could fall on such issues (certainly didn't in my case) but they are those things that requires a lot of thought so the information is presented without excessive bias, subjectivity or generalisations on the matter.

Who wouldn't want to read a book by Dumble or Fischer if that were possible? Wink

Maybe for laughs. But I'm not too keen on trying to "learn" stuff about wire insulation's colour effecting the tone, fragile harmonics getting squashed in a crystal lattice or other equally obscure ideas. However, I have played on an idea of writing an "Amp Bogus" book, where I just collect every stupid myth and piece of information revolving in this scene. Shouldn't be hard to compile. The book would be entirely parody, just for laughs with zero educational value.

[bruce egnater]

Please, ask away. If I don't know the answer, I will find out for you. It's probably in some book....somewhere.

[Structo]

I also like online references, but there is no substituting actual print on paper.
I find it kind of hard to read online manuals.
Because sometimes you need to flip a few pages back to refresh your brain as to what they are talking about.

Like Merlin's Preamp Book.
Sometimes you need to flip back a few pages to refresh what you are reading.

A long time ago I was told there are three different types of learning depending on what a person's attributes are.

Some people learn by listening, some people learn by seeing, and others learn by actual physically being shown how to do it.
Or visual, aural, and physical experience.

I am lucky enough to be able to learn by reading tech details, but others are not as fortunate.

I still like to own actual printed words in a book.

[talbany]

I have a few questions?..(This is not directed at any 1 person!)


1 What is the best bias point for a 6L6 output tube (or any other tube for that matter?) for best tone?...@450V
2 What's the optimal plate load and bias resistor and bypass cap for a 12AX7 for a good blues sound
3 For the best possible sound should I use an Aluminum or Steel Chassis?
4 Should I use stranded or solid core wire to get the best sound
5 I hear paper interleaved output transformers sounds best in guitar amps is this true?
6 what type wire should I use in my output transformers M6? or something else, what about the size?
7 Which should I use in the signal path Metal film resistors or Carbon film or Carbon comp?
8 Should I use pot's that are molded plastic or carbon trace
9 Will my amp sound better if I use a choke
10 What tube should I use in my amp? 6L6 KT/88 etc
11 What PF rating should my shielded wire be
12 What is the optimal plate voltage on a 6L6?
13 what's the best tube to use in a Phase inverter? a 12AT7 or a 12 AX7 12 Au7, 12BH7
14 For best tone what should my primary impedance be on an EL-34 amp running 470V?
15 Should I be using Monster cables
16 What should I use Ceramic or silver Mica caps?
17 What other coupling caps should I use
18 What Speakers should I use
19 Should I use octal pre amp tubes or miniature 9 pin?
20 Should I use a turret board or PCB or PTP
21 Should I drive my tone stack with a Cathode follower?
22 How many gain stages do I need in my Overdrive amp?
23 Should I use tube or SS rectifier
24 What brand of tubes should I buy that sound the best?
25 What works better tubes up or tubes down,or a combo
26 Do I add reverb in my amps?
27 What brand filter caps should I use?
28 What should I use Fixed bias or cathode bias output section?
29 should I use a PPIMV or any other kind of Master volume?
30 Is an effects loop a good thing?


30 very basic things amp designers deal with off the top of my head real quick.. If there were a book written that answered any of these questions and everyone agreed with the answer you bet I would be ALL OVER IT!!!.. If not I guess I'll just have to rely on my tube manuals and my ears,and experience and what my customers want!...
Check out Randall Aiken as he too has some pretty good tech info and the data to back it up!

Tony

[ampdoc1]

I think any prospective amp builder who believes he can get everything from a manual is wrong,..and lazy.

It's all about experimentation, and that's the fun of doing this!!! Start with a basic circuit you like and try some different values in it. The best sounding amp I've built was done over the course of a year by starting with a known circuit, listening to live performances and making (many) small changes until both the player and myself were satisfied.

a'doc

[Jana]

1 What is the best bias point for a 6L6 output tube (or any other tube for that matter?) for best tone?...@450V

Bias them to exactly 68.724% of the rated plate dissipation.

2 What's the optimal plate load and bias resistor and bypass cap for a 12AX7 for a good blues sound

Load your plate with roast beef, mashed potatoes and lots of gravy. Don’t bypass cap--it helps keep your hair out of your eyes.

3 For the best possible sound should I use an Aluminum or Steel Chassis?

Steel, of course. You will have a much better sound when filing out the IEC connector hole with a rat-tail file.

4 Should I use stranded or solid core wire to get the best sound

Doesn’t matter. It’s the insulation color that is important.

5 I hear paper interleaved output transformers sounds best in guitar amps is this true?

Absolutely! If it wasn’t true, companies wouldn’t be making the higher priced transformers with paper and charging more for it.

6 what type wire should I use in my output transformers M6? or something else, what about the size?

The wire is copper. M6 refers to the metal in the laminations. M27 is better--M27 just kind of roles off your tongue. M6 sounds like a British spy agency.

7 Which should I use in the signal path Metal film resistors or Carbon film or Carbon comp?

Metal film is for metal and grunge amps. Carbon film or comp is for a more earthy, blues sound.

8 Should I use pot's that are molded plastic or carbon trace

If in doubt, always go with the old, obsolete, hard-to-find technology.

9 Will my amp sound better if I use a choke

Of course. It has to sound better--I use chokes in my amps and they sound great.

10 What tube should I use in my amp? 6L6 KT/88 etc

Use the one that you currently don’t have.

11 What PF rating should my shielded wire be

You use shielded wire? Silly goose--you must use green wire.

12 What is the optimal plate voltage on a 6L6?

465.523 volts

13 what's the best tube to use in a Phase inverter? a 12AT7 or a 12 AX7 12 Au7, 12BH7

Um--let’s see, this is the end of March almost April, I think it’s going to be 12BH7 as the flavor of the month.

14 For best tone what should my primary impedance be on an EL-34 amp running 470V?

5000 ohms--if you don’t have that one on hand.


15 Should I be using Monster cables

Are they expensive? Then yes.

16 What should I use Ceramic or silver Mica caps?

The color of the caps is more important. The warm orange color of ceramic caps tend to coordinate much better with the yellow ochre color of mustard caps.

17 What other coupling caps should I use

British amps have to use yellow caps, American amps blue or red.

18 What Speakers should I use

The most expensive one that you currently don’t own.

19 Should I use octal pre amp tubes or miniature 9 pin?

Use octal. Like the kids with their pants falling off their asses, this is the new rave.

20 Should I use a turret board or PCB or PTP

Turret board. Only the military and nasa would think to use a circuit board in an amp.

21 Should I drive my tone stack with a Cathode follower?

Absolutely. Unless you don’t.

22 How many gain stages do I need in my Overdrive amp?

At least 7.

23 Should I use tube or SS rectifier

If you are going to sell the amp, use tube rectifier--it will be a great selling point.


24 What brand of tubes should I buy that sound the best?

Again, it’s most likely the ones you don’t currently have on hand.

25 What works better tubes up or tubes down,or a combo

Oh, this is easy--the tubes should be point up!

26 Do I add reverb in my amps?

I don’t know, do you?

27 What brand filter caps should I use?

Old ones that are no longer made. You have to carefully test them, reform them, and then hope to get one year of life out of them.

28 What should I use Fixed bias or cathode bias output section?

Use a combination of both--it worked great in the Fender Silverface amps.


29 should I use a PPIMV or any other kind of Master volume?

Master volumes are for wimps.


30 Is an effects loop a good thing?

No, loops of any kind are to be avoided.

[cbass]

Dont come at me with all this book readin and shit. Nerds!

[Jana]

cbass,
There might be some pictures in the book, will that help?

[M Fowler]

Around my area the Norwegians love to poke fun at themselves and one of my favorite jokes is:

Hey did you hear the Norwegian library burned down? Yup, both books were destroyed and one wasn't even colored in yet.

I do read all the latest tech books we all talk about but I learned more from you guys and doing actual amp building.

[Aurora]

Those are the kind of jokes norwegians tell about the swedes, - and vice versa....

Books are still good, - it is kind of difficult to make notes the swedish way ,- writing on your screen as you go alomg..
The old classic books about tube tech are also still available and new ones are still written.. Some that are not mentioned here are by Morgan Jones,- 'Valve amplifiers' and 'Building valve amplifiers'. Although mainly directed at HiFi amps, they are still very valid on a more general level of tube amps.
What I would like to see is something really analysing some of the more popular old designs as to why and how various choices were made, and what were the concequences in terms of sound...

[teemuk]

^ I was under the impression that Kevin O'Connor had some books in that vein.

[talbany]

Around my area the Norwegians love to poke fun at themselves and one of my favorite jokes is:

Hey did you hear the Norwegian library burned down? Yup, both books were destroyed and one wasn't even colored in yet.

I do read all the latest tech books we all talk about but I learned more from you guys and doing actual amp building.

Mark..

T

[xtian]

2 What's the optimal plate load and bias resistor and bypass cap for a 12AX7 for a good blues sound

Load your plate with roast beef, mashed potatoes and lots of gravy. Don’t bypass cap--it helps keep your hair out of your eyes.

Jana for the WIN!