Source of Dumble Tone.....

[Fischerman]

I think there is a common trend.

HAD developed his skills through hard work over a long time.

Brandon developed his skills through hard work for a long time.

Scott developed his skills though hard work over a long time.

So it appears there is no easy route...put in the hard work over a long time and you'll probably have good results.

Like the guy in Shawshank Redemption said...All it takes is time...and pressure.

[dogears]

Scott alienated everyone in his family by disappearing for hours on end, sometimes until sunrise, in his basement "bat cave" studio. For four years! Lots of solder fumes and many thousands of dollars of parts. The good news is that I am pretty content for the moment. LOL

Maybe part hard work, but also unhealthy obsession...

[John_P_WI]

Thanks to all for the input. I studied and prototyped last night comparing and contrasting to the plexi circuits that I am familiar with. I now have a much better understanding of the topology and values that Mr. Dumble selected.

Sorry if I offended anyone.....

John

[Bob-I]

The good news is that I am pretty content for the moment. LOL

I don't believe you for a second... you'll be soldering again before the sun comes up tomorrow

[TimS]

I believe the key words HAD mentioned were, "...time constants". HAD knows what type of coupling and frequency roll offs to use, when and where. He also knows what components to use in order to achieve them. Learning all that from an iterative process could take a lifetime, and don't believe that's only how HAD achieve his tone. I believe, and it was mentioned in past posts, that HAD not only understands how to calculate time constants but also used a spectrum analyzer in the past to help view the circuits from a frequency domain. Knowing how to achieve the most harmonics from the circuit, using an analyzer cuts down on a lot of guess or calculated work. This is true epecially in learing what type of caps, resistors, etc, achieve the most harmonics.

What would be great would be if someone would write the definitive book on guitar amplifier design from a methodical, engineering-based perspective as opposed to a tweaker's. Richard Kuehnel's preamp book is a step in the right direction but only skims the surface. Kevin O'Conner's books are more comprehensive but are light on the engineering aspects.

Of course, anyone with the expertise to write that sort of book is probably making his living designing amps and wouldn't want to give his hard earned knowledge away to people who might turn around and use it to compete with him. At the same time, however, a book like that might sell quite well given the rise of the boutique amp industry, and would probably cement its author's place as a legend in the field. Doyle Brunson may have regretted writing Super System at one point, but it's made him famous around the world.

In any event, it would be a shame to see that sort of knowledge die with the few people who have it.

[Funkalicousgroove]

Try "Valve Amps" and "Building Valve Amps" by Morgan Jones, they are based around Hi Fi amps, but it translates well to what we do.

There is also the "Audio Cyclopedia" by Howard Tremaine, but it's more of a text book, and not fantastic reading-Unless you enjoy reading encyclopedic information.

[Robert]

HAD developed his skills through hard work over a long time.

Brandon developed his skills through hard work for a long time.

Scott developed his skills though hard work over a long time.

So it appears there is no easy route...put in the hard work over a long time and you'll probably have good results.

Gil Ayan's name should be added to this list as well, as he was the earliest sleuth to discover the amps circuit. Gil, Brandon and Scott learned much of what they did before this forum existed (it began in January, 2006) in a climate of great secrecy regarding the Dumble amps. An article like that shared by Brandon was a real treasury at the time, and it's worth reading again. One had to beg and if you were lucky you might get a new piece of info here and there. Another very, very important point to keep in mind is all three of them have been extremely gracious to share all they have with our community. This forum wouldn't be what it is without their generosity. They could just as well have kept it to themselves and started an amp company to sell their products for outrageous money.

It's just that I've been building these for quite some time, and I get alot of rave reviews, my favorite of which was Mr. Robben Ford who played a gig in CT in August using one of my amps, and upon playing his first few notes made the comment "That's my sound, How'd he do that?"

Wonderful quote Brandon. I can't imagine how shocking that would have been to RF to have his signature, unique Dumble tone captured by a stranger and in effect able to share it with others who can't afford a Dumble.

Frankly John, if you had taken the time to read the forum's posts and info they have in effect already given you RF's freakin amp.

[TimS]

Try "Valve Amps" and "Building Valve Amps" by Morgan Jones, they are based around Hi Fi amps, but it translates well to what we do.

There is also the "Audio Cyclopedia" by Howard Tremaine, but it's more of a text book, and not fantastic reading-Unless you enjoy reading encyclopedic information.

Thanks, I'll check them out.

This is a subject that I am very interested in. There are a lot of concepts that experienced amp designers/tweakers seem to know intuitively after years of iterative experimenting, but which surprisingly haven't been addressed in a systematic manner - at least not publicly that I'm aware of.

For instance, someone like Scott might know without even having to think about it that to produce a desired change in the tone of his ODS clone, he needs to increase this resistor or decrease that capacitor. What he's doing, of course, is altering the gain, frequency response, etc. in a particular area of the circuit. People who design amps go through a similar process - most probably start with a known circuit and tweak from there, while a relative few might start completely from scratch and modify their designs until they've achieved their sonic goal.

There are plenty of resources available that explain what is going on in this process. Changing capacitor A moves the roll off frequency from B to C. But there's little to explain why C would work better than B as the roll off frequency at that particular point in the circuit, or why the change should be made at location D within the circuit rather than location E. Nor is there really a comprehensive understanding (apart from people like HAD) of how to use these concepts to create a design from the ground up and be able to produce predictable results.

A lot of this is probably due to the same nonlinearities that make tube amps so difficult to model digitally. It's difficult to "black box" a circuit when a centimeter of difference in placement can have a huge aural effect. Still, one would think that a systematic approach using the concepts of frequency shaping and harmonic buildup could be developed which, while not perfect, would still allow someone to get in the ballpark of their design goals. After all, while a digitally modeled tube amp may not sound as good as the real thing, it's usually close enough to be recognizable. Why shouldn't the process work in reverse - instead of taking an existing analog design and using math models to replicate it, start with the math models and use them to design an analog amplifier?

What do you guys think?

[TimS]

Another very, very important point to keep in mind is all three of them have been extremely gracious to share all they have with our community. This forum wouldn't be what it is without their generosity. They could just as well have kept it to themselves and started an amp company to sell their products for outrageous money.

Amen to that. The generosity of them and others on this forum is amazing and should not be taken for granted.

[blinddog]

[Amen to that. The generosity of them and others on this forum is amazing and should not be taken for granted.]

and a Second Amen! Brandon and Scott have always treated me with respect when answering any newbie question. Gil, Gary, the Bobs, Normster, and Heistel and the countless others are always sharing and helping and I for one really appreciate it. And thanks to Omar for being such a gracious host.

By the way Brandon, I saw that post prior to deletion and greatly appreciate the 2X4 between the eyes explaination. I kind of got most of those concepts by lurking here and reading that article but you just tied everything together. I really appreciated.

Now to finish building the Grail!
What Honey, I have to change his diaper now?!? Kids first huh? They are worth it!

Really thanks everyone
[/quote]

[ayan]

Gil Ayan's name should be added to this list as well, as he was the earliest sleuth to discover the amps circuit.

OK, money to be PayPal'd as promised. Really, thanks for the mention.

But, the story goes like this: back in the late 90s I was trying to see if Dumble would sell me an amp, after I had passed back in 1994 because I thought they were too expensive (around $5K) when he sent me some ordering (Yes, all those docs -- price list, secrecy agreement, etc. --floating around the net were mine at some point). Andy Fuchs was posting on alt.guitar.amps, asking if anyone had a Dumble schematic to share with him, and Two Rock was not even on the map yet. Visualize that scene, all of us pretty much the dark -- although I believe Andy had some X rays of amps, for real.

However, there were a couple of people without whom I wouldn't have acquired any knowledge whatsoever of these amps, which means that whoever got anything from me (which, with all modesty, directly or indirectly means 100% of this forum) wouldn't have gotten anything either had it not been for these two fellows. These guys are too modest and prefer to not be named, but you know who you are, and I still thank you for your generosity. They did spend money buying amps and shared info with me for no good reason, while I personally never bought any amp in the name of research (or otherwise).

At the end of the day, however, all the credit for the good sounding amps still goes to the Big Guy. It's very easy to tweak based on a platform that someone else came up with. I have said this over and over again... I have yet to see an "improvement" to the real thing that is worth keeping. And for all the claims that someone has come up with something greater than great, there will be later claims that the achievement has been superseded... That is until a new real amp is disected and we all start wondering why or how something was done.

Last but certainly not least, to those that have given something back out of gratitude, much appreciated, I am still so pleasantly surprised sometimes. Those who have soaked without giving anything back to anyone, love you too, just not as much.

Cheers,

Gil

PS: OK, Mr. Dumble, can I get an amp now?

[Funkalicousgroove]

You can all thank Gil for the chassis I sell, that's for sure!!!

[dr. who]

Has anyone read the book By Kuehnel- Vacuum Tube Circuit Design: Guitar Amplifier Pre Amps?
I've been into the Building Valve amps book and this one seems like it might be useful.

[ayan]

You can all thank Gil for the chassis I sell, that's for sure!!!

Hmmm... my chassis were not nearly as pretty as the ones you make avaialble to all of us now.

Gil

[TimS]

Has anyone read the book By Kuehnel- Vacuum Tube Circuit Design: Guitar Amplifier Pre Amps?
I've been into the Building Valve amps book and this one seems like it might be useful.

It is. The information on load lines and their effect on the rate of onset of distortion alone is worth the price of the book. I just wish it went into more depth on the topics it brushes on.