Want to build your own tube amplifier for guitar? There are many options: build a kit, build from an existing schematic, or branch off like I did, and try something different.
Maybe, like me, you'll design and build from scratch...
Check out the last steps-- information's been added since this guide was first published.
Among the goals for this build:
--Build an amp with that MMM-good tube sound...
--Design it myself.
--Reuse salvaged and vintage components whenever possible, and save good stuff from the landfill.
--Make something unusual (6DG6GT's in a parallel single-ended configuration qualifies as unusual...as does the tone control....)
A whole lot of tweaking later, I've got an amp that pleases me. A small, but surprisingly LOUD amp that outputs something in the neighborhood of 8 watts (see the Power Amp Stage step for more info.) And the combination of 12AX7 and 6DG6GT tubes, though unusual, works quite well...
Oh, and this is a fairly hi-gain amp--i.e., it has a good amount of natural tube clipping and distortion, and a decently "dirty" sound. However, hi-gain and high volume are not the same....this amp is loud for it's wattage, but it's not a Marshall stack. It remains a studio type amp, but it is louder than all those Valve Jrs., Champs, Blackhearts, etc. which are so popular today....
Clean signal, no F/X.
Settings: volume 50%, tone 60%, presence 30% :
Clean signal, no F/X
Settings near max :
(Some "ghosting" on the highs is a resonating glass-door china cabinet about 5 feet from the amp...)
In fact, there's a little too much gain...
One thing's for sure...tackling such a project means many happy hours pouring over data sheets, studying schematics, checking output transformer specs, and tracking down NOS tubes....
Noteworthy: there's a certain aspect to this build.... I wanted to retain the feel and budget of the radio-amateurs and home-builders of the past. You can easily spend in excess of $1000 USD for a small tube amp kit alone (nothing but the best audiophile components.) There's an elitism about modern tube amps I tried to avoid (or maybe I'm just cheap ;0)
Maybe, like me, you'll design and build from scratch...
Check out the last steps-- information's been added since this guide was first published.
Among the goals for this build:
--Build an amp with that MMM-good tube sound...
--Design it myself.
--Reuse salvaged and vintage components whenever possible, and save good stuff from the landfill.
--Make something unusual (6DG6GT's in a parallel single-ended configuration qualifies as unusual...as does the tone control....)
A whole lot of tweaking later, I've got an amp that pleases me. A small, but surprisingly LOUD amp that outputs something in the neighborhood of 8 watts (see the Power Amp Stage step for more info.) And the combination of 12AX7 and 6DG6GT tubes, though unusual, works quite well...
Oh, and this is a fairly hi-gain amp--i.e., it has a good amount of natural tube clipping and distortion, and a decently "dirty" sound. However, hi-gain and high volume are not the same....this amp is loud for it's wattage, but it's not a Marshall stack. It remains a studio type amp, but it is louder than all those Valve Jrs., Champs, Blackhearts, etc. which are so popular today....
Clean signal, no F/X.
Settings: volume 50%, tone 60%, presence 30% :
Clean signal, no F/X
Settings near max :
(Some "ghosting" on the highs is a resonating glass-door china cabinet about 5 feet from the amp...)
In fact, there's a little too much gain...
One thing's for sure...tackling such a project means many happy hours pouring over data sheets, studying schematics, checking output transformer specs, and tracking down NOS tubes....
Noteworthy: there's a certain aspect to this build.... I wanted to retain the feel and budget of the radio-amateurs and home-builders of the past. You can easily spend in excess of $1000 USD for a small tube amp kit alone (nothing but the best audiophile components.) There's an elitism about modern tube amps I tried to avoid (or maybe I'm just cheap ;0)
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Signing UpStep 1: Danger, Will Robinson, Danger!
Here's the standard disclaimer:
This is dangerous, high voltage stuff. OK, it's not "High Voltage," technically, but it's high enough to kill you. The power supply in this projects kicks out 200V, which is plenty, with startup spikes near 240V or more...
Don't believe it when they say "it's not the voltage, it's the amperage that kills you"--because it's both. Amps AND volts together dictate the danger level. If it were amps alone, then even a AA battery can supply many times what's needed to stop a human heart. The volts do the "pushing," and overcome the natural resistance of your skin. And there's plenty of current available to harm you in any tube audio amp...
Remember:
--Always drain the power supply filter caps before touching the circuitry.
--Always unplug the mains cord before working.
--Double-check (with a VOM) to be sure the filter caps are drained.
--DON'T mess with this stuff unless you have a decent understanding of the dangers.
--DON'T mess with this if you believe you know EVERYTHING about high voltage, and think that makes you immune to electrical shocks.
This is dangerous, high voltage stuff. OK, it's not "High Voltage," technically, but it's high enough to kill you. The power supply in this projects kicks out 200V, which is plenty, with startup spikes near 240V or more...
Don't believe it when they say "it's not the voltage, it's the amperage that kills you"--because it's both. Amps AND volts together dictate the danger level. If it were amps alone, then even a AA battery can supply many times what's needed to stop a human heart. The volts do the "pushing," and overcome the natural resistance of your skin. And there's plenty of current available to harm you in any tube audio amp...
Remember:
--Always drain the power supply filter caps before touching the circuitry.
--Always unplug the mains cord before working.
--Double-check (with a VOM) to be sure the filter caps are drained.
--DON'T mess with this stuff unless you have a decent understanding of the dangers.
--DON'T mess with this if you believe you know EVERYTHING about high voltage, and think that makes you immune to electrical shocks.
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I've been working on my version of this amp for some time now. It's so close to being done but I have this issue. See the video link. http://youtu.be/CWk6nhGLEV0 I'm all new to this (I'm actually a drummer, not a guitarist and a mechanical engineer, not electrical) but I have enjoyed learning and creating something really cool. Any help is greatly appreciated!
But to tame it at the power tubes like your probe, which could be acting like a conjunctive filter-- a cap (or a cap & resistor in series) parallel with the output transformer primary. That's basically a cap between the power tube plates and the B+ voltage. Google "Dr. Z conjunctive filter".
It's probably harder to find transformers for this project than to find typical tube transformers...I built this partly around the power transformer, but the output transformer is definitely an oddball one, too. That's why I documented it so well, to explain the design decisions.
The transformers will always be the most expensive part of a tube amp. If you're planning on using a tube rectifier, you'll need to use the equivalent of the Fender Deluxe power transformer (three secondaries--HV, 6.3V and 5V).
The hardest part about this project is still going to be the power and output trannies. Going down to the local thrift stores to try to see if i can find a suitable replacement.
The most common and obvious one would be a Fender Champ. You'll find all sorts of available transformers for a single 6V6GT...not to mention component layouts, if you check around.
When I answered earlier, I just assumed you were looking for the same topology as this project. You have much more freedom (and commercially available components) when using just one 6V6GT as the output tube...
Offhand, I'll guess that the MCS 3275 transformer is much lower voltage than one for tube amps--SS amplifers rarely use voltage higher than 48V (a typical Champ power transformer provides about 300V, plus the voltages for the tube filaments).
You'd have to test it, of course. That involves hooking up the primary to the AC mains, then testing the secondary with a volt meter. It's fairly dangerous, if you're not careful. And you can blow the transformer (or trip the breaker, if you're lucky) if you allow any of the secondary leads to short. Or hurt yourself bad.
In fact--everything that involves building or poking around in tube amps can be dangerous. Just want to stress that. If you're a younger person, you might want a competent adult around for support.
You can find an output transformer by searching for "single-ended 6V6 output transformer" or search for "single ended output transformer" and look for a primary impedance between 5.5K and 8K. You'll need to match your speakers to the secondary impedance of the transformer--or choose a transformer that matches your speakers (if you already have them). That's generally either 4 ohm, 8 ohm or 16 ohm.
I doubt you'll have much luck at RS. This stuff is officially obsolete technology, and isn't easy to find, retail. You'd be better off looking for old discarded TVs, stereos, record players and organs. They make great sources for "iron."
Resistor wattage depends where the resistors are used in the amp--in preamps, 1/2 is plenty for almost all amps (even 100 watters). But cathode bias resistors in the power amp section usually have to be 5 or 10 watts, even if the amplifier output is only 5 watts (more, if it's a high wattage amp). A single-ended "Class A" amplifier is fairly inefficient, and wastes more power than it actually delivers to the speaker...
How did you do that ??
The white boxes with numbers on the side, what are those and what purpose do they serve?
Thanks.
The white things are power resistors, and are part of the power supply. It's necessary to drop voltage for various stages in a tube amp, and it's almost always done via "brute force" (resistors).
Thanks.
JB
Swap out the tubes for known good ones? I've learned that lesson from bitter experience (sometimes my backup tubes weren't any good either, and I wasted weeks replacing stuff that was fine).
I really appreciate you help.
JB
Oh, and can describe the test I can run for this and the other resistors with a DMM?
You can easily test those resistors that can be isolated from the circuit by pulling the tubes--the cathode bias resistors. Most of the other will need to have one leg disconnected.
Old resistors can still test good when cold, but may drift more when they get hot....
If it were me, I'd check the voltages in the PS, and the tube plates. This is DANGEROUS! Deadly high voltage! Don't do it unless you're confident working with HV.
Don't forget to clean and re-tension all the tube sockets.
It comes to mind would a 6W6GT also be suited for this project. I think they also have a higher plate voltage and maximum power dissipation. I'm certain they are as available as a 6DG6GT as well.
cheers
(I also kind built this around the transformer--that had something to do with the power tube choice.)
Literally, the best sounding instrument I ever heard was an experimental Hammond Model that used BATTERIES to purify the electricity flowing into the instrument. This guy had taken apart a (I think it was a B3) Hammond Organ that had a huge speaker box and Tubes for amplification. I tried to find out why, exactly, but all I could get out of him was something about the electricity is cooler and the tubes lasted much longer. This chap was nearly 70 and could he ROCK that Organ! He would sit and listen to on record after another and play right along with then all! Uh! Record, the kind that you drop a needle on to listen to them. OH! And the turn table sat on a cement piling that passed through the floor into the ground and must have weighed close to 10 tons! He said that was the only way to make sure the needle never skipped! Oh! And this Organ ran 12 volts D/C exactly.
I like the nature of this website. But it shames me to notice there is not more tube enthusiasm !
I am working on a revision of your design with 6W6GTs and all Edcor transformers looks like its gonna be about $100 in transformers alone. And i respect the nature of your project completely. I am hoping to do a follow up instruction set on how add active bass and treble to your design as well as modify it for 6W6GTs if you have no objections ill start work on that soon.
I suck at making cabinets. So i am grateful for you added that.
Use or abuse the info in the project as you please. I stole ideas from other circuits, so have at it.
I look forward to seeing your amp...
I looked closely at the 6W6GT datasheet, and you'll never get 20 watts from a pair in parallel (or even push-pull), but rock on!
Ill note i have seen plate dissapation form 10 watts GE to around 14 for these tubes.. depending on manufacturer.
But your right i grossly over estimated the power output.
You should definitely learn about voltage and current flow before you attempt anything with tubes.
As an electrical engineer i would suggest trying to reverse engineer simple populated PCBs and create schematics to them try to understand how they work. Avoid surface mounted devices and more than 2 layer boards for the beginning.
If you want to use a very useful piece of software that has no tubes, but can get you started understanding schematics and laying out PCBs.
http://www.cadsoftusa.com/
its cross platform. OSX Linux and Windows.
PS if you don't understand what I'm talking about Google can answer faster than I can. Also a very powerful resource for electronics questions is stack exchanges electrical engineering forum.
Try some simple stuff first--like a guitar effect. There are lots of designs and discussions over at diystompboxes.org.
Congratulation for your proyect!!, i like me a lot. Before start I need you that I don´t speak well English I speak Spanish, so, perhaps you find a lot of mistakes in the comment :). I write for two comments, the first, I want share a program with you, its name is ‘TDSL Personal Edition 1.0.1 Duncan Amplification’, it´s a database of vacumm valves. look at!
The second comment, about technical questions , I´m beginner in electronic topics. So I don´t understand which is the capacitance unit (µF,mF,nF,pF,etc.) of red circles, neither resistance unit (kΩ,MΩ,etc) in blue line and finality about audio transformer, I sought its datasheet (http://www.edcorusa.com/products/522-gxse15-4-1_7k.aspx) and I don´t understand which is the correct wiring. So please help me with my questions. Thanks for your time (I image the time that you spent to understand me):)
My bad...the coupling caps are within the typical ranges for tube amps; I just assumed most people would savvy. That's sloppy on my part. So the capacitors circled in red are "uF" (microFarads).
The resistors in the blue boxes have no suffix--that's the actual value. So 180 = 180 ohms, and 150 = 150 ohms. The wattage is noted.
Looking at the Edcor site, I see the link I provided no longer works. Also, the transformers themselves have changed--no solder tabs, and now have end-bells. They are also a little more expensive. Here's a current link for the equivalent transformer.
http://edcorusa.com/products/522-gxse15-4-1_7k.aspx
The 10 watt version should also work fine (and is cheaper).
http://edcorusa.com/products/500-gxse10-4-1_7k.aspx
The hookups should be fairly obvious from the diagrams on each page... If not, let me know, and I'll see if I can help.
Note: I didn't include exact links before, simply because not everyone wants a 4 ohm output impedance for their amplifier (like if you have an 8 ohm cabinet)...
Be careful when cleaning tubes; you can rub off the markings...