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4 of 4 people found the following review helpful
on 2 November 2010
Expanding on his useful Valve Wizard website, the author spends about the right amount of time on the theory and calculations before moving onto how to practially implement the ideas shown. Taking the signal chain in the amplifier from input to phase inverter, the book also looks at the effects of negative feedback and differing earthing schemes.

One interesting aspect covered is distortion. The author investigates differing types of distortion and how to optimise distortion for musical instrument amplification. This is the only in-depth scientific treatment I have seen on this subject in print.

Overall, a great book for the professional or the keen DIY'er, just don't expect the book to be a "how to build a DIY guitar amp" book. It is in-fact more than that type of book could ever be.
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12 of 13 people found the following review helpful
on 26 April 2011
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As someone with a sideline interest in restoring, designing, building and using guitar amplifiers I looked forward to reading "Designing Tube Preamps for Guitar and Bass" by Merlin Blencowe. I have formal training in electronics at the highest level and have made a career in the area but I am well aware that there are always new things to learn and new insights to be had, especially in an area such as guitar amplifier design.

Overall, I was disappointed - primarily because the book is mistitled. It is mistitled in two ways. Its scope is in some ways wider than just preamps - the three chapters on phase inverters and on feedback are more relevant to power amplifiers than to preamps. On the other hand, it does not cover preamp design comprehensively enough to justify its title.

I think it has both good points and deficiencies. For some potential readers, the good points will greatly outweigh the deficiencies. For other potential readers, the opposite will apply.

GOOD POINTS

I think that many enthusiasts will appreciate being able to read in detail the descriptions of valve circuit operation and will get a very good physical understanding of what is actually happening and thus be able to make genuine design decisions, rather than blindly following cookbook recipes with no real understanding. Such enthusiasts will probably find the book very helpful.

The author, apparently self-taught, is enthusiastically willing to share the knowledge that clearly required hard work over a long period to gather. Generally he explains things very clearly. Just occasionally, the explanations get bogged down in a swamp of words. His enthusiasm shines through and I think that many readers will find this inspiring.

The book contains many oscilloscope images, showing actual waveforms and many readers will find this very helpful. A scope image will often show what is really happening far more clearly than any number of words, as well as being more convincing.

I was delighted by the author's comments on writings that talk about the relative tonal superiority of (for example) ECC83 valves from a particular manufacturer. Someone without formal training in circuit analysis is liable to absorb such nonsense as if it were fact. After all, it is widely put about on the Internet - especially by so-called audiophiles. Merlin Blencowe writes:
"These subjective differences are not a consideration for the circuit designer and will not be mentioned here again. (...) Real tonal control comes from the choice of topology, frequency shaping and manipulation of overdrive characteristics, and from a complete understanding of the circuit's functionality, not from the particular manufacturer or vintage of the actual components used."
How very well expressed.

DEFICIENCIES

>>Does not address the overall design problem

Although the book gives lots of information on (for example) deciding the component values for a circuit, it hardly touches on the major choices that a designer needs to make before ever getting to detailed circuit design. Such choices might include:

- the sensitivity required from each input
- frequency shaping characteristics to be provided built in to the preamp.
- what controls are to be provided in addition to the tone controls (gain? drive? sustain?)
- what effects (such as tremolo or reverb) are to be incorporated into the preamp
- how many stages are needed, the signal voltages to exist at each stage and which controls should be placed between which stage.

>> Slags off other books and makes unjustified claims

The preface states: "Of the handful of books which are available, they are at best only descriptions of pre-existing or 'classic' amps, and at worst badly written, badly presented, rife with errors and heavily overpriced". It is unbecoming for the author of a book to speak badly of the work of their fellow-authors like that.

The dust jacket states: "Designing Tube Preamps for Guitar and Bass is the world's first comprehensive guide to the design of tube-based preamplifiers, specifically for musical instrument use, in a single volume". This statement of uniqueness is unjustified and comes across as hollow boasting. Two predating books which cover the topic of preamp design for guitar are:

"The Ultimate Tone" by Kevin O'Connor (1995)
"Guitar Amplifier Preamps" by Richard Kuehnel (2007)

>> Editing deficiencies

The book seems not to have benefited from professional editing. One sign of this, which gives it a somewhat amateurish air, is the excessive use of quotation marks and exclamation marks. The book frequently puts words in quotation marks for no apparent purpose except that the word is a bit vague. Professional editors usually eliminate all such so-called scare quotes.

Exclamation marks are grossly overused in the book - there is probably not a single instance where their used is justified. Some readers find repeated use of exclamation marks irritating.

The level of typos is quite high - most seem to be where a typo has apparently resulted in a different word than what was intended, so that it would not be been found by a spelling checker.

Editing deficiencies such as these do not invalidate the information in the book but they will, for some people, greatly mar the enjoyment of reading it.

>> Structure

Another sign of the apparent non-involvement of a professional editor is the structure of the book. An editor would probably have insisted on an introductory chapter. As it is, chapter 1 dives straight in to dealing with analysis of the common-cathode triode, without covering things that you might have expected to find in an introductory chapter, such as:

- Motivation for why you might want to use vacuum tubes in a preamp
- Explaining the scope of the book - what it covers and what it does not cover.
- Outlining the steps involved in designing a preamp and the trade-offs that need to be made.

It would have been good to have had a brief biography of the author, such as many books include on the inside of the dust jacket. The title page carries the letters MSc after his name - but the subject of his master's degree is not revealed.

>> Misconceptions

If I come across a fundamental misconception in a technical book, this greatly reduces my confidence in the book's treatment of other topics.

Chapter 7 is titled "The Cathodyne Phase Inverter". This circuit is more widely known as a phase-splitter - a triode with equal valued load resistors in the cathode and the anode circuits. The author is confused about the output impedances of this circuit and yet he states that "many authors" have been puzzled by the matter.

He states (p. 161):

"The output impedance of the cathodyne is a troublesome subject, as it varies hugely depending on whether or not it is equally loaded. (...) The fact that not only is the output impedance equal at both outputs, but also very low in value (...) has puzzled many authors, yet it is true. The theory behind this is beyond the scope of this book; interested readers are referred to Jones and Preisman."

But if you look at the quoted papers by Jones and by Preisman, you will find they make no such statement. In fact, they explicitly state that the output impedance from the anode circuit is high and the output impedance from the cathode circuit is low.

That is how it is - from a stage that, from its cathode output, is essentially a cathode follower with a cathode follower's low output impedance and, from its anode output, is essentially a triode whose unbypassed cathode resistor ensures a high output impedance. Anyone doubting the facts can look them up in Langford-Smith (formulas 33 and 34, section 7.2) or they can make an actual measurement of the output impedances of a phase-splitter stage - you'll find one in a Selmer Zodiac 50 power amplifier.

The chapter on feedback gets the author skating on thin ice here and there, when he mentions poles and zeros and output transformer high frequency characteristics.

OVERALL

I think that an enthusiast who could already build a guitar amplifier and understands a bit about electronic circuits and who is willing to make the effort to read this book in detail could get a lot of benefit from it and I would recommend it to them - subject to the reservations I have made.

Someone who is not already familiar with circuit design would probably find it over their head and get no benefit from it - notwithstanding the rear dust cover statement "An essential reference text for any amp enthusiast!" .

Finally, an experienced electronics designer who wanted to get clued up on valve guitar preamplifier design would, in my opinion, find that it does not give them the information they need. I'd suggest potential readers in that category should give it a miss.
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2 of 2 people found the following review helpful
on 25 December 2010
The book says it is not intended for the beginner so for the record, I've been a professional audio electronics designer (solid state) in the past and have a degree in electronics. Valves were not covered.

The author says he has omitted derivation of formula etc. and this "will irritate electronics graduates" but so far I have not found anything to irritate me in this book. The style is easy to read and the information you get is great. You get what you need without too much theoretical complexity. Anyone with a basic electronics knowledge should be OK. I read it end to end hooked like a good novel.

The level of maths is as much as is needed to design the circuits and by no means heavy. By design I mean have some idea of how it will sound before it is plugged in rather than copy an existing design not really understanding how it works and then blindly fiddle with components which seems the method preferred by some other authors.

Getting your sums right is mostly missing in other guitar amplifier `design' books I have read. I'm not saying don't read these other books as there have been many happy accidents in designing guitar amplifiers but it is nice to understand why doing X will result in a Y. If you do find a particular change has a beneficial result you can reverse engineer it and find out why.

Unlike many audio books where all you have is the authors say-so that they are right and the rest of the world is wrong, there are, to pick a non-random example many references to Langford-Smith's book. There is much misinformation on audio and valve amps about. This book has solid foundations and references. Many thanks!

Books on hi-fi valve amplifiers will tell you how to, for example, bias a stage for minimum distortion. This is fine but a guitar amp is all about distortion. If it was not we (well I at least) would use transistors. This book fills that missing gap. For example it has oscilloscope screen shots to show you what the effect of e.g. overdriving a cathodyne phase inverter is. So instructive.

There is a super section (22 pages) on cascode. Much better than the others I have read which always concentrate on the ECC88 (which was designed for this) and a quick blast about the Miller effect. I have to now try an ECC82 stage.

I've got the power supply book by Mr. Blencowe on order and just hope it is as good.
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8 of 9 people found the following review helpful
on 18 January 2010
I have been trying to understand a number of concepts around valve electronics and have bought all manner of books.
I have had quite a level of difficulty in understanding various concepts until I bought this book.
It isnt for beginners but if you have some prior knowledge this book will be invaluable in learning about valve amplification and as a real bonus it specifically covers guitar amp design.

There is not too much maths just enough to understand the theory being covered and explains things in a very user friendly way.
In terms of value I have bought books costing considerably more that I have learnt very little from and I think it is excellent value and I will be looking to purchase any further publications from this author.
Webste is excellent too.
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7 of 8 people found the following review helpful
on 15 March 2010
As a Physicist, Engineer and teacher I found this book superb. I have used valve amps (Vox, Marshall, Hiwatt, Sound City, Fender, DIY) for over 35 years. I have worked on them but until now had not given the time and effort to fully master the underlying design principles. The text explains the concepts and design principles in just the right depth. It presents you with the knowledge and tools required to design and implement valve pre-amps. The mathematics is presented at the right level and if you are not mathematical the examples are sufficiently detailed to work and build on. Not a book for the complete beginner (as it states in the preface), nor a set of recipes. In a few cases presented a little more detail e.g. values & voltage would save effort for the would be designer. The definitive text and I hope Power Amps, Power Supplies and construction techniques appear as a subsequent set of texts.
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7 of 8 people found the following review helpful
on 31 March 2010
The book contains just right amount of theory with nice examples how it can be applied in practise. Things like how seemingly innocent choises of resistor values actually affect sound are discussed in depth.

The book also covers phase inverters, which was a pleasant surprise. Altough I've always concidered phase inverter to be part of power amp, the inclusion does make sense, since post phase inverter master volumes seem to be the thing nowadays.

So, content is very good. Typesetting quality could be better, however, and some images appear blocky. Those are very minor issues, of course. I do recommend this book to anyone who wishes to understand tube guitar amplifiers.
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6 of 7 people found the following review helpful
on 28 December 2009
This book is just what is says. Not for the beginner, it delves right into the essence. It contains piles of valuable knowledge which does not come easily from other literature. The material is treated very much in-depth, revealing many aspects of seemingly simple building blocks which would normally take a lot of experience to figure out oneself. It is very practically-oriented but contains all the math needed for the reader to completely design a circuit on his own.

On the down side, I would have liked to see more information on overall tube preamp 'architecture', i.e. different arrangements of the discussed building blocks and their interplay. This is briefly touched upon in the chapter on coupling and in some other places, but I would have loved to see this in its separate chapter with the same level of detail as displayed by the rest of the book.

The book could do with another round of proofreading since some typos and grammatical errors remain. Finally I initially found the book to be a little pricey, though I suspect this is not unusual in a low-volume niche such as this, and after reading I feel it's definitely worth the money.

I give the book the maximum star rating because I am impressed by the sheer quality and depth of the information it contains. As far as I know this level is unique in the field of guitar (pre)amp design.
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2 of 2 people found the following review helpful
on 5 March 2011
Not suitable for beginners, but is very useful for electronic technicians. I would like anyone who buys this book to ask the author: when your book about power stage comes...
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on 31 May 2012
I bought this book after building an 18watt amp kit that I bought from Ampmaker.co.uk. After spending quite a while on the 18watt.com forum, this book came up time and time again as the book everyone goes to trouble shoot amp builds and come up with innovative designs to mod their amps.
I agree with many of the reviews that say that this book is not for the absolute beginner but I'm on really a beginner amp builder and I now use this book to help me design my own circuits.
I own many many books on valve amps and this one is the most thorough, the best researched and best written of the lot of them.
If you are planning to build or mod an amp this book is a must!
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on 6 May 2013
This book is an excellent resource for anyone who wants to build their own guitar amp projects, or just for getting a better understanding of how things work.

Merlin doesn't get bogged down into maths, but gives excellent explanations of how things work, with plenty of worked examples. However, he includes full references if you need more details.

With the help of this book, and the companion on Power Supplies, I've started building my own amp projects that have worked out as expected.

I highly recommend these books to anyone interested in the subject. Thanks Merlin!
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