Writing the book....

[gingertube]

It is true that power amps are not covered well in the existing selection of DIY guitar amp texts.

Of-course you can just do what everone else has done for the last 25 years - copy a Bassman, although I'm pretty sure that stacked "schmitt" splitter has serious warts:
The 82K / 100K loads were calculated for BEST balance with a particular differential amp "tail" resistance and has been copied slavishly even when the "tail" resistance has been changed and that ratio is no longer valid. (also "schmitt" had nothing to do with this design).

The Output Tube Rg1 values are way too high for any sort or reliability

Output Tube Screen voltages are way too high for any sort of reliability.

ASIDE:
Was looking at a 1942 design yesterday. They used a voltage divider for screen voltage with the divider current flowing in the cathode bias resitor to give part fixed bias / part cathode (auto) bias. A lot of the "simple" but "elegant" things seem to have been lost.

Cheers,
Ian

[Structo]

In one way, most power amps are pretty simple affairs, but there some exotic designs out there to play with.

Probably why not many books have been written about them.

Preamps on the other hand, have so many variations, styles and attributes which may be the reason more books are about them.

Merlin has threatened to write a power amp book but may be down the road quite a bit.

How about a book on phase inverters?
Yeah I know Merlin's books covers at least one (long tail).

[renshen1957]

I guess this is something old guys do after gathering a lifetime of knowledge. You feel like it's time to share. I've always thought about writing an amp related book. What sort of information is difficult to find in other books? What subjects are most useful?

Hi Bruce,

Your reputation precedes you.

I am glad you want to share your knowledge. I would stand in line to purchase a copy.

Here is what I found useful in books, for what it is worth.

The how and the why.

How something was done and why it achieves an effect. Not only the theory, but actual applications in circuits; real life examples. The 6 Volumes of The Ultimate Tone by Kevin O'Connor series provided this, however both a schematic and a layout in Volumes 3 and 5 (projects) helped loads in my understanding (especially the layout). The chapters in Vol. 3 prior to the projects have been invaluable.

Volume 5 showed applications of Kevin's past amps. A Chapter Volume Six went into analysis of his and other people's ideas and application in High Gain amp. Kevin went in to also who stole from whom. (And yes, the Egnater TOL preamp was one of the circuits featured of original design). History and amp evolution is fascinating, at least to me. Peter Traynor made Master Volume production amps in Canada beginning in 1962 (and in Rental models for Long & McQuade. ) Garnet's Herzog was included as an early example of amp chaining. These gems I picked up in volume 3

I read Gar Gillies Garnet, and his book was informative in what he used, and also by comparison of other companies (Gibson, Horner, Guild, as well as Fender).

I found Dave Funk's tube amp book Vol 1 Fender (unfortunately the only volume of a planned series) interesting for it discussed why he did what he did in his amps (where he put the mains fuse, a safety issue). His book had the better explanation on how Vacuum tubes work (and how Solid State compares with tubes).

He had the philosophy, learn from everyone, but copy no one.

So the long explanation made longer, what I look for in an author is why you do what yo do. How do you bias your power tubes. What components did you choose and why if this was important?

Your work in high gain amps and modded is well known. What's your approach to gain scheduling? Filter caps in a High gain preamp and why?
Do your amps (I haven't been inside one) use PCBs. What do you look in a designing a board.

Who influenced your approach to building amps (this can include what you built in reaction to something negative).

What was the origins of the Modular series? How did the Randall amps based on the Modular series differ? Was this a dollar driven decision, or a change in design philosophy.

Finally, what do you look for preamp tubes? Low noise, high gain, tonal qualities, or ????

Just my two pence worth.

Great luck in your endeavor.

Best regards,

Steve

PS As soon as you write a book, you become an acknowledged AUTHORity. However, I believe your amps gutshuts word also be worth a 1000 words.

[renshen1957]

ASIDE:
Was looking at a 1942 design yesterday. They used a voltage divider for screen voltage with the divider current flowing in the cathode bias resitor to give part fixed bias / part cathode (auto) bias. A lot of the "simple" but "elegant" things seem to have been lost.

Cheers,
Ian

Hi Ian,

Another Down Under Amp design? Any chance of the schematic being drawn?

Best regards,

Steve

[renshen1957]

Switching, more importantly developing the switching logic for channels, output tubes (mixing types), rectifiers etc... Flexibility.

Going beyond the standard 2 and 3 button "Marshall" foot switches.

Triple X chapter, TUT Vol 5 is a good start for theory.

Best regards,

Steve

[renshen1957]

The main problem with most books about amp and building is the organization of the information and a lack of and index...

+1 on lack of index.

[gingertube]

Steve,
I got it wrong - it was 1947
http://frank.pocnet.net/other/AWV_Radio ... cs_124.pdf
Back to the regular thread.
Cheers,.
Ian

[Structo]

I was set to order TUT 5 when it showed $22 for shipping.

I'll pass.

[LeftyStrat]

What I have not found is a good discussion of the theory behind selecting the primary impedance in an output transformer, and what the effect on tone is by slightly mismatching up or down. I can go look up the data sheet for the tube and see typically values for a given voltage and operation, but I'd love to know more details.

[renshen1957]

I was set to order TUT 5 when it showed $22 for shipping.

I'll pass.

Hi,

AES (tubesandmore.com) carries the book, call and ask if they will ship flat rate USPS. The book weighs 2 pounds 1 Oz on my postal scale. Might save some money over international post charges.

Best regards

Steve

[renshen1957]

Tubes do have a frequency response!.. here is why..

So you meant to say that CIRCUITS have a frequency response? ...Because a tube surely will amplify from DC to megahertz's and it's the surrounding circuitry that defines the response.

So, why keep on repeating that tubes have a frequency response when in fact they don't? Yes, I know the underlying principles where the electrical characteristics of the transformer, tube and everything else in the circuit interact and create certain frequency response but this is not the same as tubes themselves having it. BIG DIFFERENCE.

Hi,

You raise a point. I don't know if I get it, though.

There is so much variance in tubes from batch to batch even with in one brand or specific tube type, etc , but following as to frequency response in a circuit all things being equal, according to your logic a 6L6 tube in a specific circuit should sound the same as a EL34 and a 6550 should sound the same, and should sound the same as KT88, and a 6CA7 should sound the same.

It is a given that everything reacts, from your post, one draws the conclusion that a preamp tube has a frequency range, limited in a 12AX7 but extended in a ECC88 (or 6922, it was used in TV tuners) in to UHF ranges. But even these have sample to sample variance, especially in gain.


Or how do you account that in the same circuit a Kinkless Tetrode (which does have a Kink in its curve) and a 6L6 tube (which does) do not sound the same?

Or maybe you mean the same tube designation. A 6L6 by GE sounds the same as a RCA 6L6 Blackplate, the same as a Tong Sol 6L6, the as a Sylvania or Phillips 6L6 JAN tube? Or by extension any modern production 6L6.

A switch from an East German dimple top RFT EL34 (sold under the name Siemens and other names in the US), in a Matchless amp with a JJ KT77 was noticeable enough for Country Band that even the drummer commented on the "improvement." (More headroom, less tube compression, and a better "Country Clean" sound. Different tubes (a pentode and a tetrode, even if listed in substitutions) reacting to the same circuit.

Or a GZ34 by Mullard sounds the same with Dow Chemicals in the Cathode as DuPont chemicals in the Cathode. (The late Ken Fischer would have debated you on this one).

Or in a preamp, a cheapie Shuguang 12ax7 in a specific circuit, sounds the same as a Raytheon Blackplate, the same as a Mullard Long Plate Smoothplate and a Mullard short plate sounds the same as the long plate, and the same as a TFK Smooth, Ridge plate, ECC803S (heard one in the flesh recently) grid frame plate in comparison with the Shuguang? And a NOS stock tube RCA black plate sounds the same as a RCA Gray plate, or a Sovtek 12ax7 LPS is the same as a JJ 12AX7 gold pins, the same as ad nauseum fill in the blank.

Gee, to think all that time wasted by musicians and the hi-fi golden ear boys tube rolling preamp tubes, and the case of the SET 300B crowd, the power amp tubes by brand.

Yes different construction and materials, a miller capacitance, different Grid to Anode capacitance and Grid to Cathode capacitance, but from your description any old tube of a type (i.e. 12AX7 or 6L6 for example) in a circuit will amplify from 0 Hz to 20,000 Hz (lower or higher) and be no different from the next in frequency response. And yet, I clearly hear a difference in highs, mids, and lows between tubes, especially after 100 hours burn in when the tube outgrows its infant tone.

Maybe I did not catch the drift of your post correctly. I (and others) have noted a tonal change (high end extension, different mid range characteristics) which we assumed was tube frequency response varying in the same circuit from tube to tube (of a specific tube), and frequency response varies from brand to brand, hot batches to cold batches in the same brand in a specific circuit. And also noticed (in audio playback of recorded samples) between types of recordings (vocals, instruments, rock, jazz, classical or pick a genre) as recorded on the same equipment played backed through the same sound system.

If you could illuminate me in context of your statement as to the perceived differences, with varying real world frequencies (not sine waves) which I heard with the same recorded of samples played through an amp (hifi) of the different tonal qualities among preamp and power tubes. As these playbacks were recorded and then auditioned (from tape playback) I and others found similar differences between a family of tubes in 6L6 cathode bias amp similar, without a cap bypassing the power tube power resistor in design to a 5E3 guitar amp. The amp has sufficient heater current that I also tested a variety by type (EL34, 6550, KT88, KT77, KT66) by type against each other (again recorded).

Best regards,

Steve

I can't think of anything as variable, except maybe Disc Caps above 450 PFs varying frequency response with voltage variances. (Sound grainy).

[LeftyStrat]

I think another angle to look at is writing about what is not in the the Radiotron Designers Handbook.

The authors of that incredible tome would probably be horrified by what tube amps have evolved to on the musical side. But how many great things have come from those studying that book?

Perhaps a great book is one way to achieve a little immortality.

I am a software developer, and I have written some deeply complex and innovation software over my career, but it will probably be obsolete before I even pass away.

Meanwhile Fender amps older than me (I'm the same age as a 5F6A) are still treasured, and still sound amazing.

Anecdotes are another interesting area from experienced amp builders. John Suhr shared a story on here about a combo head that sounded great outside the cabinet, and like shit when it was put back in. Turned out to be a phase issue. That kind of insight and experience is pure gold to me.

[talbany]

Generally when Guitar amps are over designed (which there seems like there are allot of them out there these days) There IMO is a lacking of both dynamics as well as an organic quality about them, sterile and flat feeling..Generally taking ideas and circuits more from a Hifi approach (like Fender did in their UL and other amps like, Mesa Boogies, and a zillion others that are IMO over designed)..I usually prefer a simple design built by someone who is mostly a player with a good ear and taste for tone than someone who has an extensive background in electronics and does not play the instrument (or play well enough) to recognize all the nuances in their builds?..So IMO opinion you have to have both!!..IMO you can't borrow someone else s ear for this!
Guitar amps are tone generators and sometimes it's the in-perfections that gives it it's personality (an un-blanced PI or using less filtering using GNFB than most for example) and harmonic character...
BTW..I never really got the Trainwreck thing nor do I think Ken Fisher did really anything unique as far as amp design goes so I would not be that inclined to read his books( Maybe if it has gut shots ).. However Ken did have a great ear and built a very simple but good sounding amp for many people who like the TW sound..SIMPLE!,Raw organic and very Dynamic!!..This is all my opinion of coarse!!

Don't bore me with all the caps and pots.... Get me to the TUBES!!!

Tony

[romberg]

Information that I would buy if put into book form can be summed up simply by:

"How to build a tube amp from scratch"

Things such as:

- Planning the layout of the circuit board

- Planning the layout of the chassis

- Mounting transformers

- Chassis fabrication

- Control panel labeling

- circuit board fabrication

- Obtaining parts (not from where but what and how to deal with ratings)

- Wiring

- Cabinet construction

I've seen bits of information about all of these all over the place. But if it would be gathered into one book, I would be a customer.

Mike

[Paultergeist]

Yeah, he doesn't like his own PS book any more, even though there is still a lot of good stuff in there.
etc...

Well......crap......I bought that one and read it cover-to-cover.....though not everything stuck to my brain by a longshot. Still, sorry to hear that the book has been dis-avowed......