I'm writing a new book - suggestions?

[Merlin]

I have an intuition that the gain structure of an amp has a lot to do with this. Where does distortion occur?

The other topic I'd like to see more about is choosing an appropriate primary impedance for the output transformer in a push-pull output stage. Because the speaker impedance varies so much with frequency, I would expect a certain amount of compromise to be necessary.

Your first question is kinda broad, but on the whole I think the new book mostly answers these.

[rumpus]

I have an intuition that the gain structure of an amp has a lot to do with this. Where does distortion occur?

The other topic I'd like to see more about is choosing an appropriate primary impedance for the output transformer in a push-pull output stage. Because the speaker impedance varies so much with frequency, I would expect a certain amount of compromise to be necessary.

Your first question is kinda broad, but on the whole I think the new book mostly answers these.

Yes... deliberately broad and open-ended, because I don't think there's a single universal answer, and I didn't want to get too long-winded with the question.

In more detail, my questions relate to: at the onset of saturation and distortion, where in the amp does it distort first? And as the signal level continues to increase, where does it distort next? Obviously, this will be affected if there are separate gain and master volume controls, it may also be affected by EQ settings, and some preamps include "cold clipper" stages. What are the characteristics of distortion at different points in the amp? How can the gain structure in a design be manipulated for different styles of playing?

Sorry to create extra work for you - but I think there's another whole chapter of the book implied in this question... or perhaps another whole book!

I have some solid theoretical understanding but I don't have the practical experience designing, modifying, and using as many different amps as the people on this forum collectively have. I want to learn more and so I'll have a lot of (sometimes vague and perhaps ignorant) questions.

[Lectroid]

[Edited]

[HotBluePlates]

After reading Merlin's new book, go grab a copy of "Guitar Amplifier Overdrive: A Visual Tour."

That book addresses your questions, but you will very likely still want to read Merlin's book first:  the book above assumes the reader has a pretty good knowledge of amplifier building blocks & design.  You will get more out of it after gaining a solid grasp of the foundational issues.

I'll go looking for that. (The URL isn't actually a URL, but I bet a web search will find it from the title.)

Fixed.

I have a fairly good grasp of the foundational issues. What I'm lacking (and hoping to learn from this forum) is the practical knowledge that's not immediately evident from just knowing theory.

I'll have to re-read, but it's a book by 2 PhDs...  They're covering an advanced topic, and assume the Reader has already connected many dots before they dive in to examine distortion.

There are some results they obtain that naturally follow from the test set-up used, and won't always apply in a guitar amp.

... my questions relate to: at the onset of saturation and distortion, where in the amp does it distort first? And as the signal level continues to increase, where does it distort next? Obviously, this will be affected if there are separate gain and master volume controls ...

The answer changes depending on whether we're talking an amp from the 1950s, an amp from the 1970s, an amp from the 1980s-1990s, or a recent amp.

There have been several-volume works that attempt to dive into the shifting design-trends over decades, from different designers, who leveraged different design approaches.  Those different-approaches give a different answer to your one question.

[AlNewman]

Where does distortion occur? The preamp (which stage?), phase inverter, power tubes, output transformer saturation?

Yes

[rumpus]

I'll go looking for that. (The URL isn't actually a URL, but I bet a web search will find it from the title.)

Fixed.

Thanks for the fixed URL (there's still a couple extraneous characters at the end, but that was easily resolved). I'll add the book to my next order at Antique Electronics Supply.

... my questions relate to: at the onset of saturation and distortion, where in the amp does it distort first? And as the signal level continues to increase, where does it distort next? Obviously, this will be affected if there are separate gain and master volume controls ...

The answer changes depending on whether we're talking an amp from the 1950s, an amp from the 1970s, an amp from the 1980s-1990s, or a recent amp.

There have been several-volume works that attempt to dive into the shifting design-trends over decades, from different designers, who leveraged different design approaches.  Those different-approaches give a different answer to your one question.

After I read the first book you referenced, I'll probably want to see the others. It's those shifting design trends I'm curious about.

Thank you!

[SoundmasterG]

Yes... deliberately broad and open-ended, because I don't think there's a single universal answer, and I didn't want to get too long-winded with the question.

In more detail, my questions relate to: at the onset of saturation and distortion, where in the amp does it distort first? And as the signal level continues to increase, where does it distort next? Obviously, this will be affected if there are separate gain and master volume controls, it may also be affected by EQ settings, and some preamps include "cold clipper" stages. What are the characteristics of distortion at different points in the amp? How can the gain structure in a design be manipulated for different styles of playing?

Sorry to create extra work for you - but I think there's another whole chapter of the book implied in this question... or perhaps another whole book!

I have some solid theoretical understanding but I don't have the practical experience designing, modifying, and using as many different amps as the people on this forum collectively have. I want to learn more and so I'll have a lot of (sometimes vague and perhaps ignorant) questions.

The sequence that the stages distort can be designed into the amp, and often some of the best ones distort in the power stage first, and then the phase inverter, and so forth towards the input of the amp. This approach allows for the most touch response.

Greg

[rumpus]

... often some of the best ones distort in the power stage first, and then the phase inverter, and so forth towards the input of the amp. This approach allows for the most touch response.

Thanks, that's very interesting information.

Do you have any examples of "some of the best ones"?

[passaloutre]

The Fender 5F6A Bassman does this, and the Marshall amps based on it. I think the Trainwreck amps were designed for same.

[pdf64]

In a competently designed amp, the output stage must clip first. An amp couldn't make full clean power output if a stage prior to the output clipped before it 
Of course any master volume must be turned up full, and other controls set appropriately, to achieve that.

[rumpus]

In a competently designed amp, the output stage must clip first. An amp couldn't make full clean power output if a stage prior to the output clipped before it 

Well, that's a good, pragmatic way to look at it!

I think there's still some interesting territory to explore in the region just before full clipping. The characteristic I like about tube circuits is that they can be designed to saturate (distort the signal a little bit) well before hard clipping (as opposed to typical BJT circuits that tend to be pretty clean and then just slam into the wall). That saturation adds even harmonics and provides a certain amount of compression. When this happens in an earlier stage of amplification, it seems like it should slow the transition into hard clipping in the later stages.

So I would expect the the nature of the transition from saturation into clipping both in the preamp and in the output stage could make a big difference in the overall feel of the amp?

I think I need to get that "Guitar Amplifier Overdrive" book HotBluePlates mentioned....

[UncleRuckus]

Merlin,
So glad you are undertaking this - I've two books of yours, very helpful blend of understandable and some math.
Couple of bits I have struggled with overall (not necessarily because not in your book - just suggestions for topics):
-Keeping track of gain over a circuit
-Estimating node voltages (I made an Excel sheet, still validating)
-Using non-traditional valves in amplifiers (6DX8 for single tube reverb, no transformer, for example?)
-Believe it or not, plans for a chassis holder?
-I can't seem to create good faceplates (at a reasonable price) - Closest I've come is 3d printing one in ABS with raised or sunken letters, painting it then sanding it. All the CAD software I've found has been too steep a learning curve to date. Got a laser engraver - works 'ok' on plexiglass. . .
-Trouble shooting the amp that pops it's circuit breaker after 10 minutes... but not sooner... : )  (causes of excessive current drain you may not have thought about?)
-Toroidal vs. Traditional transformers - design implications and ways to manage them (thermistors?)

Anyway, best wishes, I'll buy whatever you write.
J 
-

[stratomaster]

How about the super secret reverb mod you teased at the end of this post?

https://el34world.com/Forum/index.php?topic=31718.msg349548#msg349548

I'd definitely buy that.

[kagliostro]

http://www.tubebooks.org/technical_books_online.htm


Franco

[tubeswell]

http://www.tubebooks.org/technical_books_online.htm


Franco

That’s a real treasure trove. And the some of guys that contributed to it were well known on various guitar tube amp forums until recent years (and have since sadly passed).

[Willabe]

Links not working.

[kagliostro]

To me the link performs correctly 

However there you can find good documentation about the basic of tube function, Mr Merlin books are specific to our interests (and I'm waiting for the new book with a lot of interest)

Franco

[Merlin]

I am now close to completing the first draft. Here is the contents list, in case anyone is interested. https://valvewizard.co.uk/contents5.pdf

[rumpus]

Oh, man... count one copy sold just on the basis of that table of contents (and having found lots of useful information on your website in the past).

[theRagman]

This looks like it will be awesome! Looking forward to the output stage stuff in particular.

[jbrrrrr]

I'm definitely in for a copy - very excited for this new book!

[stratomaster]

Will this be hard copy or ebook?

I'm buying either way... Just want to know what I'm buying.

[pullshocks]

sign me up too

[Merlin]

Will this be hard copy or ebook?

Hard copy only, same as my other titles.

[Willabe]

I am now close to completing the first draft. Here is the contents list, in case anyone is interested. https://valvewizard.co.uk/contents5.pdf

Looks very good. 

[rumpus]

Hard copy only, same as my other titles.

Excellent! From lifelong habit, I am fond of having a real book that I can sit and read without needed to stare at a screen, put bookmarks in at particularly interesting or relevant places, and of course take care to preserve in good condition.

With that said... I used to buy a lot of O'Reilly computer books back when they were a proper publisher. They offered hard copy, electronic only at a slight discount, or if you bought the hard copy book the e-book was available at a nominal extra cost. I always bought the bundle because there are some advantages to modern technology (it's easy to search a PDF for all mentions of keywords).

If you offered such a bundle, I'd happily pay extra for it. Just saying....

[kagliostro]

I noticed that Mixed Bias is covered in the contents — thank you for including it. I find it to be a compelling feature that, when properly applied, can add a unique character to an amp. I'm keen to explore it further

Franco

[Carlsoti]

I will buy this book to go along with the other two I've purchased from you, Merlin.

[scstill]

With that said... I used to buy a lot of O'Reilly computer books back when they were a proper publisher. They offered hard copy, electronic only at a slight discount, or if you bought the hard copy book the e-book was available at a nominal extra cost. I always bought the bundle because there are some advantages to modern technology (it's easy to search a PDF for all mentions of keywords).

I got a  complete set of John Rider hard covers a few years back for radio repair and knowledge (also as CD). While they have all the info you need (somewhere), it is by far easier to use the internet for info. And now even smarter with AI. If only AI knew how to create a proper schematic.  :-)

I also have the Tube Amp Book with all its schematics but still find internet and EL34World my go to.
I love and depend on Valve Wizard and RobRob websites.

[acheld]

The internet is good, but nothing beats a proper Merlin book!   I read them like novels.

I do agree that it would be nice to have a searchable copy, but I bet that would be pirated in a split second . . .

[rumpus]

I do agree that it would be nice to have a searchable copy, but I bet that would be pirated in a split second . . .

Sigh... you're right, of course.

There are ways to personalize PDFs (I have a MISRA C standard document with my name on every page), as well as less obvious ways to watermark them so they can be tracked back to a unique original copy. This isn't an insurmountable obstacle for determined thieves, but it would certainly discourage casual sharing. But I'm sure Merlin has better ways to spend his time than pursuing thousands of small-change pirates all over the world.

AI scraper bots are another matter. But there are ways of "poisoning" various sorts of content so they are worse than useless for AI training.

[rake]

Will there be autographed copies available? 

[Wardy]

Look forward to reading this. I have got a lot from studying your work. Thankyou.

From my perspective as a newby. I have been studying this subject quite hard for last 8 months and have made some progress in my understanding. Often times I am looking for a simple answer to a question only to find very in depth discussions and explanations going into electronic theory. Whilst I know I need to improve my understanding of this I guess there must be others like me who are simply trying to build the best sounding guitar or bass amp we possibly can, and we are most interested in the outcome. Therefore what I think would be very useful to me and many others would be a "rules of thumb" guidance section. keys things to do or consider to:- reduce noise. increase gain, get the cleanest possible sound, get different flavours of distortion from tubes. what changing the values of components around tubes does to the tone, (most discuss the electrical signal) how does this work in cascading arrangements. There is so much to learn and it is difficult if your starting from scratch with little electrical engineering knowledge.
best
Steve

[SoundmasterG]

I am now close to completing the first draft. Here is the contents list, in case anyone is interested. https://valvewizard.co.uk/contents5.pdf

I'll be buying the book as usual - I've got all the rest of yours, even the ones you discontinued because you didn't like them. :)

One thing I noticed in the contents list - a typo!

1.2: The Vave Constants


Thought I'd point that out for you....I'm not sure what a Vave is but it sounds risque and not meant for a tube amp book haha.

Greg

[Merlin]

Up until now my books have always been hardback. But with the rise in prices, I'm wondering if I should make this one softback as it would make it at least $10 cheaper. What do people think? Do you want the premium feel of hardback or do you not care and would prefer a cheaper price?

[tubeswell]

Happy to pay more for hardback FWIW

[kagliostro]

I also prefer an hardback

if not, It would stick out like a sore thumb among the others, which are all hardbacks 

No, an hard back will preserve the book from aging for a very long time, this is the reason

Franco

[pullshocks]

Please do it in hardback and pages sewn together as on your previous.

[danhei]

Hardcover please.

[pdf64]

Most of my textbooks from uni are softback and they're fine. Not that they've been consulted much since 
Whatever, a big price saving is pretty persuasive 

[CascoSieg]

No big preference; equally happy to have the $10 in my pocket as to support those who want the premium kit... but I'm going to buy it no matter what. :)

[Carlsoti]

I'd like a hardcover to match the other two books of yours that I have. If you made both hard and paperback available, I'll buy both and use the paperback for reading and referencing. Having the set of three in hardcover would just feel right, like buying a matched quad of valves (for an amp that only uses a pair) just before hitting the road.

[Dom]

...For me: a good hardcover. I prefer this type.  Pay more for hardback ( $10 ) it's acceptable.

[Lectroid]

Hardback please.

[RoadShow]

I vote for hardback to go with your other 2 that I already have.

I'm willing to pay more.  That's $10 less inheritance for my kids, so what, 

[rumpus]

I'll buy it either way - but I'd prefer a well-bound hardback.

[jase128]

Put me down for one - prefer Hardback!

[Merlin]

Well that settles it, I will do hardback as usual. I may offer a softback version aswell, next year.

[scstill]

hopefully in large print :-)

[Sonny ReVerb]

hopefully in large print :-)

I'd bet more readers will have gray hair than not   
Looking forward to the book, Merlin!