I've been building Plexi / Bassman style amps for the last 12 years or so and am very comfortable in setting up / voicing gain stages to obtain any Marshall tones one would want.
Now, I am looking for the Dumble tone that so many of you have posted sound clips of. In your opinion, what are the 3 major contributors to the mid-tones of the Dumble?
Is it the tone stack in front with the "parallel" mid and bass caps (not the cathode followers that I am used to)? Preamp cathode R and C values? Snubbers etc....
I am a mechancal engineer by schooling, therfore I over analyze everything and have a need to understand. Anything that you experts would like to share I would appreciate it. I just might give up the cathode followers.....
by Dan ForteJackson Brown is wandering the back stage caverns of San Francisco's Cow Palace looking a bit worried. "Where's Lindley?" he asks his road manager [...] "We're onstage in 15 minutes!" A door at the end of the hallway is seeming blasted open by a torrent of beefy sustained lap steel licks. Inside, Lindley is squatting precariously, his Hawaiian guitar balanced on his knees. Crunching chords and crystal-clear single notes are pour out of a crude-looking amplifier about a foot in front of his face. "I want this one, Howard," David says to a large man who is smiling like a proud father. "Not this model, not one like this, but this one, OK?" "It's just a prototype." Howard Dumble points out. "Fine," nods Lindley. "I'll take it." David Lindley, of course is notorious for using a vast array of exotic guitars from an instrument collection that number well over 100. But on the road, he uses only one brand of amplifier, a fact that makes Howard Dumble understandably proud. As Lindley told Guitar Player in a July '77 interview, "I've got a lot of little amps, but on the road, I always use Dumble amps because they never break down. We went about getting the sound in those amps by taking an old Fender Deluxe to Howard Dumble and saying, 'We want this, but bigger and louder.' And Howard got the closest of anybody I've heard." Howard Dumble, 40 [in September of 1985], grew up in Bakersfield, California, and began building transistor radios from scratch at age 12. He took up guitar at 16 (he later did his fair share of studio dates in Hollywood, which included working with songwriter Jim Webb), and in 1965 built a series of amplifiers for Mosrite that were used by the Ventures. An extensive tour backing Buffy Sainte-Marie financed Dumble's first "out of the backyard and into a building" amp shop in 1968, in Santa Cruz, California. The following year, Dumble came out with his Explosion model amplifier (his original prototype still works), which later evolved in the Overdrive Special. His line of amplifiers currently includes seven basic models: the Overdrive, the Steel-String Singer, the Winterland and the Dumbleland for bass and guitar, the rack-mount Phoenix, a no-frills 50-watt Dumbleman, and the Dumblelator--a tube vs. sold-state impedance translator--as well as the Big Tex reverb unit. From the beginning, he has remained a one-man operation, personally building every one of his amplifiers by hand. In spite of their steep price tags--a standard 100-watt overdrive head sells for $1,925.00; the Steel-String Singer and Dumbleland each go for $5000.00 before options--Dumbles are always in demand, and Howard has his hands full keeping up with orders. Besides Lindley and Browne, the impressive roster of Dumble users includes Larry Carlton, Bonnie Raitt, Graham Nash, Stevie Ray Vaughan, Jay Graydon, Ry Cooder, Tom Verlaine, Eric Johnson, Steve Lukather, Robben Ford, Dean parks, Carlos Rios, The Beach Boys, Christopher Cross, Tiran Porter, Jimmy Haslip, Jerry Miller, Thom Rhotella, Randy California, Terry Haggerty, Rick Vito, Kenny Loggins, and many others. In discussing what's so special about his amplifiers, Dumble uses aesthetic more than technical terms. "That's the bottom line," he stresses. "It's the emotional influence that's really important; technology is secondary--it's just a vehicle. The idea is to have lots of fun." Improvisational specialist Henry Kaiser elaborates on what sets the Dumble apart from the rest of the amp crowd: "Number one, you could drop the thing out of a four-story building, replace any tubes that break, and it'll work fine. It does appear to be the most durably built amp possible. Number two, it seems to me that Howard, through a long intuitive working process, tunes the amps and designs
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by ear so that they're very sophisticated machines for producing a wide variety of tones and distortion colorations. Because of my specific avant-garde bent, I'm really interested in tone and timbre, and I need to have a really wide palette of tonal color available to me, and I've got about four times as many colors available on the Dumble. Any other amp sounds awful to me. I feel terrible if I play anything else--except for a Fender Champ." In an august '77 Guitar Player feature, the late Lowell George of Little Feat was more succinct. "It's like a Fender made right," he said of his Dumble. "It's the best amp I've ever played through." Your amps have a reputation for almost never breaking down. How do you build in such durability?Those are absolute guarded secrets. In fact, if you take the amplifier apart, you can't detect how I do it. I definitely have secrets that make the amp perform and last the way it does. With most companies, it's just a misapplication of technology. you don't have to destroy the product--you don't have to get a Variac and turn it up to 170 volts--to get good results. An extreme amount of attention is paid to every connection. Plus, I found which parts last and which ones don't. What made you gravitate towards electronics in the first place?I loved music, for one thing. Music's always been a passion. I used to listen to Les Paul and Mary Ford as a kid. Also, I come from an engineering family; my father developed one of the first automatic transmissions. It wasn't hard to absorb the technology; it was just there to do. I also saw that I could make some bucks at it. I started making small pocket radios from scratch for the kids in school for $5.00 a pop. I was doing real well until one day everybody had one, and there were enough radios in the class that you could hear the local rock station at a small din through all the earpieces. So, the teacher finally busted me. What inspired you to first build an amp?I was a junior in high school, and this guy named Jack smith came over and wanted me to build a piece of equipment for the junior baseball association. He said that he had access to a "mountain of parts"--I said OK! We went down to this big warehouse, and there were heaps of parts, so we gleaned as many as we could--all free. We built this huge 200-watt power amplifier so they could announce to nine baseball diamonds. As I understand it, it still works today. Then, Jack and I made some Dual showman-type amps, although we couldn't get Fender transformers--they were very tight about what they'd send you--so we used David Hafler transformers, which made the amp sound quite extraordinary. Prior to building your own amps, had you taken apart others amps such as Fenders and Gibsons?I can draw some of the those schematics from memory [laughs]. Of course, I had to absorb other approaches. In fact, my old Fender mods I did in the late '60s were exactly the same as the schematics a lot of the later high-gain amplifiers used. How did you come to make amps for the Ventures?I was an 18-year-old kid in school in Bakersfield, and I went to see Semie Moseley, who was the only person I had access to there. I walked in and just bold-faced said, "I've got something that sounds like nothing else. You better hear it." And it flipped him out; he said, "This is the best thing I've ever heard." He offered to go in with me to build 10 amplifiers. He bought the parts and paid me $90.00 a week--for about four weeks, and then I had to work for free. But I still got to build 10 amplifiers on a production basis when I was only a kid. They were called Mosrite amps, but they were my design. Actually, I built 11, so I still have the original one I built. The Ventures played through them and were really interested, but it was a little too much rock for them. They wanted me to go into business with them, but I decided against it, and went back to playing in studios and in rock bands. Did your early amps have certain qualities lacking in commercially available amps of that period?Yes, I definitely made sure they had more frequency bandwidth. One thing I noticed about the early guitar amps was that they were real limited, especially in the lower end. But you have to be careful to make sure you still keep the proper midrange and treble response. I found that out early on. You can't build a hi-fi circuit and expect it to be a good guitar amp--it just doesn't work out. you need a whole different response curve. But I did notice that if I put a little more low-end into the preamp circuitry, it was much more tasteful and fun to play. Once you got started, did a Dumble philosophy evolve?
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I try to be flexible. I've always been aware that whatever I make has to be crafted with the best intentions. Never have anything shoddy. Always makes sure that it works and looks perfect. The actual techniques I use to get the sound that I go after have evolved extensively. It's a growing process. That's the toughest thing about staying with one thing. you're always thinking of new ways to do it. Basically, I've kept the Overdrive the same but the other models are open to flexibility. What changes did the Explosion undergo before it became the Overdrive Special?The active circuitry changed quite a bit, and the tone circuitry did also. But the concept of processing the signal post preamp stayed the same. Most other high-gain amplifiers use a pre-preamp gain boost, but I broke away from that quite early, in the late '60s. I found that trying to build the signal up before the preamp had a tendency to really overload the preamp, and you got nonharmonic tones and a very unmusical end result. Plus, you ran into a lot of vacuum-tube problems with harmonic's. So, what I wanted to do was get all that wonderful oomph and beautiful sustain and harmonic richness without the electronic troubles. Were you making what was to become the overdrive before you made the Steel-String Singer?The Steel-String Singer came later, but I actually started making a series of amplifiers called the Dumbleland in about '66, and I still make them. That was the forerunner of the Steel-String Singer. I didn't change a whole lot about that; it was a design way ahead of its time. It was too much power and too silky clean for people. It's perfect for Stevie Ray, though. He has a hard time playing an Overdrive. Why is the Overdrive so sensitive?It's a different kind of signal handling. In the Overdrive, I approach gain levels that are extremely intense; within the linear region, I have a signal gain capability of one million. So if you stuck 10 microvolts in, you'd get 10 volts back. And I do it with stability, and it's still very musical. The best way to approach an Overdrive is real slow. Walk up to it, look at the knobs, have it turned down real low, and then get a feeling for it. Learn what to do with your fingers to make it respond well. If you walk right up to it, it has a tendency to absolutely frighten some people. The secret control on the Overdrive's panel section is the ratio control, which controls how much overdrive is fed back into the circuit. If you turn that up, it's Rock City. How different is the Overdrive Special you customized for David Lindley from a standard model?I might have changed the value of a capacitor to some extent, so that it has a different treble response, but the circuitry is basically the same. Lindley says that for certain sounds he's looking for, you sometimes borrow his guitar and Dumble for the weekend to match the amp to the guitar?That's true. The amplifier responds so differently to each guitar that to get some effects, I need to use the player's guitars, instead of my own. That's one the great things about the amplifier; it doesn't modify any guitar into any one sound or homogenize it. It expands whatever you start with. The amplifier is a real important part of the sound regeneration system, but it needs to be very responsive to whatever the guitar is delivering. The philosophy I try to keep in the amplifier is that whatever you can hear in your head, this will help you get it. Stevie Ray Vaughan calls his Steel-String singer the "King Tone Consoul."There are some different things about Stevie's. His is set up more like a bass amp, modified to accommodate the guitar range. It's not the usual lead guitar "Singer" approach. One thing he liked was that he could turn the volume control all the way up and it didn't distort--it just got louder. He does make it distort sometimes because he has about 50 megatons of pressure when he attacks the strings [laughs]. He gets an incredible amount of signal out of his guitar, and most amplifiers can't take it. He did his first album with a bass amp I'd made for Jackson Browne. Some players describe Dumbles as different, more powerful, more durable more efficient versions of a Fender DeluxeThat's a good way to describe it--in a limited fashion. There are some great qualities to a small Deluxe. You get a great harmonic structure at a small acoustic volume. It's real pleasing, especially when you're playing by yourself. But that sound is not convertible into a group ambience--it's gone. So, in the respect that I try to get something comfortable and very musical, only in a bigger fashion, that's a good analogy. But the circuitry is not even close. I use vacuum tubes, and transformers and
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knobs, but the similarity stops there. To get the result I want, I have to use unique circuitry. It's my tone circuits and coupling circuits and the way I process phase-inversion. Can you "Dumble-ize" a Fender amp to the point that it shares the Dumble philosophy and sound, or would it be a compromise? It's a compromise. The actual physical construction of the Fender limits what can be done. In fact, after the last Steel-String Singer mod I did to David Lindley's amps, he no longer uses the Fender Bassman I Dumbleized for him. He wanted this luscious transparency and response--like floating in white clouds--and I came up with special circuitry. I can use a Fender chassis, but you have to rip everything off of it, fill in all the holes, and re-drill it. They're just a little bit too squashed. A distance of half a centimeter makes a big difference in the way something sounds. It's a science involved with what's called circuit constants. Instead of a single bright/deep switch, most of your amps have separate bright and deep switches. Can you use both at the same time?Oh, you bet. It gets luscious low notes that you could float on and beautiful, crystalline highs that are silky as glass. How many watts are the various models?The overdrives are 100 watts, but they're switchable down to 50, and I do make a special 150-watt Overdrive, which is a lot of fun. The range in power goes from a 25-watt recording amp called the Hotel Hog up to the 450-watt Winterland, named after the concert hall in San Francisco. Could there be an ultimate amp for you, or are the Overdrive and Steel-String Singer too distinctive to be combined?Well, the Phoenix series is where I've done that--so you can combine things--because it's a rack-mounted affair. You can by all the separate preamps, with or without overdrive, and a choice of 50-, 100-, or 150-watt power amplifiers, and hook them together. The overdrive section is expanded--instead of two overdrive controls, you have four. After experimenting with various speakers, what do you favor?I've gone with everything, there are a lot of things I still like. The most versatile is the EV. But all manufacturers, include Altec and JBL, make wonderful speakers that do specific jobs other speakers can't do. I divide speakers into two classifications: the efficient and the low-efficient. Both are very useable. Low efficiency speakers are things like Celestion and Jenson and PAS. Usually because of the physical construction, they don't get the same acoustic level per watt as the Altecs, JBLs, and EVs do. There's an advantage to that, because you can make the amplifier work harder to get the same acoustic level, and a whole different kind of harmonic structure results. I love the sound of JBLs, especially for chords, but I had a lot of trouble with 4" voice coil not traveling in a linear fashion. The actual coil would short out against the magnet structure. The Altecs didn't do that, so I was using them up until '79, when EV started coming out the the EVM series. How does your philosophy on speaker enclosures contrast with other companies?I think mine's different. I just don't believe in a baffle board with a couple of sides. Everything is designed to respond tonally. Even my open-back enclosures use air to the optimum. It's an ongoing process; I'm still finding out things that are useful. There's a definite technique to developing enclosures. Instead of increasing the output all from the front by feeding more watts in, I designed a
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special series of open-back enclosures so that there's actually an air pole inversion process--I make the air respond in an in-phase relationship, both in front and in the rear of the enclosure. So, from the same amount of speakers, it's almost a doubling of sound. Does that change the tonal quality?Yes. The low end is absolutely luscious. You feel like you're floating on a football field filled with marshmallows. And it gives a singe to the midrange that puts solos right out there. It works great for chords and solos, but especially well for slide. It's the kind of enclosure that Lindley and Lowell George used. Is there a single emotional aim you're shooting for, or many?It's a whole panorama. I don't believe in being confined. There are hundreds, perhaps thousands or millions, of valid guitar tones. When the air becomes electric, that's the right sound, no matter what the one is. It's that sound exciting the senses. Guitar Player Magazine - September 1985
Thanks Funk! I guess I could have pulled out my original Guitar Player mag and read it if I felt there was any importance to it.
Seriously, some of you guys are nailing the tone without all of the associated hoodoo BS. I'm not looking for schematics, but general info on how that tone is generated, remember I'm a Bassman / Plexi guy.
Look at the OD stages of the Hybrid A schematic [good as any reference point]. The plate and cathode resistors stray from the Fender 100K/1500 standard. The cathode cap is smaller than the 25uF Fender also. Each stage gently distorts one half of the waveform. Since these are inverting amplifers, both sides are distorted after the 2nd stage. There are a ton of details surrounding the whole enchilada, however, that's imo, the crux of what's happening. The tone stack yeilds a continuous range of possibilities when compared to a BF Fender, where imo, each tone knob has at most three useful zones.
Anyone who has toyed with these circuits knows that seemingly small value and part changes can have dramatic results. Flexibility is perhaps the value of the design.
For posting with useable info. Besides what I mentioned in the first post it is interesting to see the smaller value coupling caps and resistors in the preamp section (compared to the Plexi / Bassmans).
John_P_WI wrote:Thanks Funk! I guess I could have pulled out my original Guitar Player mag and read it if I felt there was any importance to it.
Seriously, some of you guys are nailing the tone without all of the associated hoodoo BS. I'm not looking for schematics, but general info on how that tone is generated, remember I'm a Bassman / Plexi guy.
Peace, John
Unfortunately the "hoodoo BS" seems to go with the territory. Personally despite having a background in electronics, music and science I've never felt the need to characterize folks with a rare talent in a negative way.
From your post it sounds like you want "the answer" - if that were possible then I don't think this forum would exist and making exceptional amps would be easy. Fact is - it isn't - surely you found this with your plexi/bassman clones?
Your response to Funk handing you the best info available to him (that has helped him produce great sounding amps) seemed pretty dismissive.
Nick, No offense intended towards Funk, sorry to seem dismissive. Your right in that I am looking for a technical answer(s) to the strong midrange that the Dumbles have, and as I said some of you guys are "nailing the tone" without the mystical voodoo. Part of being an engineer for 20+ years, is asking why and what makes things different. I am fortunate to work with extremely talented engineers in the medical field in which we have to have black and white technical answers.
John_P_WI wrote:Nick, No offense intended towards Funk, sorry to seem dismissive. Your right in that I am looking for a technical answer(s) to the strong midrange that the Dumbles have, and as I said some of you guys are "nailing the tone" without the mystical voodoo. Part of being an engineer for 20+ years, is asking why and what makes things different. I am fortunate to work with extremely talented engineers in the medical field in which we have to have black and white technical answers.
John
No worries - I guess it's just that Funk builds amps that have held their own against actual Dumbles so I'm inclined to listen to him.
Can understand your point of view with respect to B&W answers. Been looking for them myself for 40 years with respect to guitars, amps and music (to no avail ). Suspect the answer is "there is no answer".
Anyway welcome to the forum (if a noob like me can say that!) - hope you find *your* answers.
John_P_WI wrote: Part of being an engineer for 20+ years, is asking why and what makes things different.
John
I'm with you John, I'd love to understand what brings out the tone and feel of these amps, but I'd bet the secret will die with HAD.
I believe much has to do with the way the stages are coupled. There seems to be some bandwidth limiting, and focus on specific frequencies. There are some factors that are hard to exactly nail in my little pea sized brain. The series resistors with bypass caps, coupled with the Miller capacitance of the next stage, the multiple series resistors and divider network entering the OD stages, the position of the OD (it follows the typical Fender pre).
You'd really have to analyze every stage with a frequency analyzer and scope out the distortion charictoristics.
All that said, just built it and tweak it and the tone will come.
I've been building Plexi / Bassman style amps for the last 12 years or so and am very comfortable in setting up / voicing gain stages to obtain any Marshall tones one would want.
Now, I am looking for the Dumble tone that so many of you have posted sound clips of. In your opinion, what are the 3 major contributors to the mid-tones of the Dumble?
Is it the tone stack in front with the "parallel" mid and bass caps (not the cathode followers that I am used to)? Preamp cathode R and C values? Snubbers etc....
I am a mechancal engineer by schooling, therfore I over analyze everything and have a need to understand. Anything that you experts would like to share I would appreciate it. I just might give up the cathode followers.....
Thanks, John
I thought everyone knew :
It's the tube screamer hiding under the goo.
A retort to the dismissive engineer isn't worth the stomach lining.
John, Hope you find what you're after. Sorry my info wasn't "Useful."
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?"
I guess I thought I had some clue of what is going on, but now faced with the knowledge that my info isn't useful- I guess I'll just shut my mouth.
Funkalicousgroove wrote: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?"
That's a heck of a compliment, Funk. As someone who can convince Robben that you're able to see beyond the goo, so to speak, I know that there's a ton you can add to this discussion. I'd hate to see you duck out because of a careless comment. How is everyone who seems to have a good handle on this (Funk, heisthl, dogears, etc) nailing it? Is it all trial and error? Are there any resources out there I don't know about that shed any light on the generation of harmonics with non-linear amplification? I've also been curious about the function of the series resistors on the grids and in the OD entrance. The only time I've heard of these is in reference to killing oscs, and even then they way anything over 30k or so will start to suck tone. It's a mystery to me.
I can understand your frustration, John, about the bs involved in this. With the seeming lack of academic study on non-linear amplification, it appears the only information readily available is poetry (floating on a football field of marshmallows?!?).
"In this world you will find hardship and trials; but take heart, for I have conqured the world."
John 16:33
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.
The good old ears are also a great indicator, but that too makes it more of an iterative process. I don't know if HAD's ears are as good as Dogears' are, but would find it either hard to understand how HAD achieved his tone using his ears alone, or just find it simply amazing.
Scott (Dogears) has been able to achieve the tone using his ears alone, and although he had a good starting point to tweak from, I still find that amazing.
Congrats to everyone who is happy with their tone. Mine unfortunately, is great one day, and am readjusting the next. I am truly hooked.
Anything that you experts would like to share I would appreciate it. I just might give up the cathode followers..... 
). Suspect the answer is "there is no answer". 
