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Joseph Mitchell
Joseph Mitchell

Building Valve Amplifiers __EXCLUSIVE__



In addition, audio testing, like racecar testing, is neither as simple nor as obvious as Consumer Reports would have us believe. Did you know that tube amplifiers can suffer from slew-limmited distortion? They can, and do you know how to test for it? Building Valve Amplifiers expalins how. A key point here is that audio electronics has its own subtleties and important details that do not appear on the radar of most other electronic undertakings. For example, as long as a digital clock keeps accurate time, it little matters if its power supply suffers from poor regulation, ground loops, or high noise.




Building Valve Amplifiers



In conclusion, I don't know of a better way to spend $30* and get so much useful information on building tube amplifiers. Morgan Jones has done us all a great favor by writing Building Valve Amplifiers. We should return the favor by buying it and defending it.


I imported the images for the transformers and valve bases from PDF data sheets into Inkscape, drew some of the other components and experimented with different arrangements until I was happy. I then shared my design with Alex Kitic via email, and he seemed to think the layout was OK, which was good news. I was now happy that I had a viable design at least for the audio stage of the amplifier. We would be using a pair of bench power supplies for testing, so the power supply could come later.


In future posts, I will be sharing the building of the prototype single amplifier, followed by the final version with two of these and a power supply. Finally, fitting this all into an attractive enclosure, with cabling and connectors etc. and, most importantly, how it sounds.


Ever wanted to build a highly dangerous, inefficient, yet awesomely retro piece of electronics? Well, I have. That's pretty much what a tube amp is. Vacuum tubes are old electronic components that act like transistors, controlling a lot of current with a little current. You usually hear about tubes being used in guitar amplifiers, because they distort in a way that suits guitar playing. However, tubes can also be used to amplify a stereo signal from another audio source such as a CD or MP3 player. Tube amps, unfortunately, aren't the most practical things in the world; they consume a great deal of power, get very hot, and are big. That being said, they look damn cool, and some people seem to think they sound pretty nice, too.


The audio circuit might seem a bit messy. I was soldering components to the legs of the tube sockets, there were wires criss-crossing, and so on. Thankfully, though, it works.This is a first-time kind of project, but it's also one that you can go back to again and again and improve and update, and I think I probably will. Those red capacitors there are supposed to be 0.33uF, but they're actually 0.47uF, which isn't really a problem, it just means I'll get more bass. They also happen to hold on to a big charge, and so you should be extra careful with them and remember to discharge them. These components are ones that are probably worth replacing with high-quality parts at some point in the future, since most people agree they are very important to the sound of the amp. (Oh yeah, and don't forget, you're building the audio circuit twice - this is a stereo amp, after all!)


Poindexter's Musical MachineAll About Circuits' Introduction to TubesVacuumtubes.net: How Vacuum Tubes Work Fun With Tubes is an amazing resource. (thanks satman!) There's always Wikipedia There are lots of good books too, such as Valve Amplifiers by Morgan Jones, which thoroughly covers all the fundamental tube concepts as well as amplifier design. Jones has a companion book called Building Valve Amplifiers which covers all of the physical design considerations that go into building a good tube amp, including component layout, enclosure design/construction, and performance testing and troubleshooting. The Power Vacuum Tubes Handbook is a great, detailed textbook on tubes.Note Poindexter has since updated his design, and was kind enough to provide the schematics, pictured below.


BACKGROUNDI'm new to valve amps, but am really excited about attempting this build. I have just purchased the valves. I also live in Melbourne Australia, which uses 240 Vac from the pole to the home, rather than 120 Vac as per US and Canada .QUESTION(S)What if any mods are required, to make the design 240 volt friendly? I'm hoping the answer is: None, you can just use a different tap in point on the power supply side of the transformers in the power supply circuit. If mods are required, are their instructions out their to assist, and able to be posted to me.....All feedback appreciated


Thank God for William Shockley that we don't have to play with infernal tubes for much today. Certainly not for audio amplification. Tube audio amplifiers belong in museums next to the stone knife and bear skin display!


As a myriad of total harmonic distortion specifications plainly show vacuum tube technology cannot match the performance of solid state devices. So even if manufacturers of tube amplifiers tried to emulate solid state sound, they could not. The technical reasons why tube amps remain popular today are too complicated to get into here. It mainly boils down to a mixture of ignorance, and nostalgia though. With a healthy helping of simply being difficult thrown in, for good measure, of course.


I would disagree pfred. Why a lot of people feel that tubes sound better has something to do not by THD in itself, but with the variety of THD. As you may or may not know, solid state amplifiers (SSA) mainly create uneven nth order distortion (e.g. 2263 hz, not full octaves). Tubes mainly create (and a lot more of it in total measured THD) eventh order harmonic distortion (full octaves). As we humans like full octaves better than uneven (hence why we don't like people who sing out of tune), tubes feel smoother.


There's plenty of tubes still being offered today, why do so many guitarists prefer them to solid state, cause Solid state sounds like poop in your desert ale-mode, compared to tubes. I know transistors are getting better tone wise, I like their longevity, and consistency but Tubes in a power amp, makes everything warm and smooth, do you prefer diet drink to naturally sweetened? One might be better for you but which has the endorphin effect that you prefer? if you have a design for a solid state power amp that blows every tube amp out of the water tonally clean and over driven, I'm listening :) I've searched for years. Clean tones are fine with solid state, over driven guitar tones (for lead guitar) just don't totally cut it with all transistors without a thin raspy harshness, and I build solid state pedals that many consider to sound very tube like, but still require a power tube at the end of the chain. I even have modded several hybrid Solid state/tube guitar amps to get more of this tubey vibe, but ultimately power tubes always come through with the tones musicians hear in their head, even the average listener can hear the difference in many play tests. The even order harmonics are very present in tubes, The odd order harmonics are very present in solid state, so when a solid state amp clips, it has a very harsh distortion, one way of getting around this is higher wattage/headroom amps that dont get to their clipping point with most use (more wattage than your going to use). A few have come close over the years, but the inefficiencies of a tube relates more to the human ear, then again some peoples hearing cannot appreciate the difference. I have looked endlessly for a all Solid State amp that did it for me, and I always end up going back to something with tubes in it, at least power tubes, as they filter out most of the odd harmonics, and have more even, not to mention us guitar players love the % of THD that tube output transformers produce, put that in your I-pod am smoke it!. Music Man had a great idea back in the 70's, combining the best of both worlds, but now components are available to further enhance the guitars tones, but even still, good power tubes are hard to beat, they compress just enough to not pierce your ear drums, but can, they are just more musical, if your not a musician, then you have no clue as to the sound and FEEL of tubes when playing an instrument, especially live, tubes have a life to them that solid state just cannot compare. Granted, there are some great sounding modeling amps available today, but even those sound better going through a tube power amp! Many Metal heads love solid state because of the transient attack and brighter edge it has, but many classic styles prefer the sound and dynamics of tubes, and so many companies build solid state gear as mentioned by another poster here, try to emulate tubes in their design not transistors... :D See, when driving cascaded stages in a preamp, then into a power amp, all stages that are tube based, add so much to the tone, and overdrive as it is perceived as great tone to the player and the feel and dynamic response is more forgiving with tubes, where certain registers on the guitar neck may produce unpleasing harsh results due to the nature of the frequencies of the electric guitar in general where a acoustic guitar will usually sound best through a solid state amp or PA system, as you dont want to color the acoustics of the guitar in most cases. The electric guitar is one instrument that if played clean it's one thing to use solid state and sound great, some of my favorite clean electric players use solid state, but the ones that use tubes or combinations of tubes, usually will implement a tube or more to achieve their signature tones. One very rare guitarist extraordinaire, Allan Holdsworth (God rest his soul!) got different but incredible tones using solid state and modeling devices with great success! Allan used both Tubes and Solid State over the years, but in the last days he was spotted using either Yamaha Magic Stomp pedals that had extensive programming capabilities to dial in a complicated tone as his, along with the Axe Fx II which is another amazing piece of gear, mostly the effects are out of this world, the amp modeling is decent, but the Kemper Profiler is said to be one if not the best Amp profiler (Modeler?) today, not to mention the Bias Grid and other new technologies that are doing very well. It is possible in time that they will come very closely matching the tubes sonic dynamic qualities us guitarist/musicians are listening for, if not already. But Digital still has a % of artifacts that tend to be audible to one who has an experienced ear. SO what I find that works for me is to combine Analog with digital, maybe use a good overdrive pedal that has the overdrive dynamics, run that into a quality modeler set to a fairly clean setting, with a mild breakup, then a warm power amp. There are some amp companies building hybrid power amps with a 12ax7 type input or preamp to warm up the dynamic response to a lesser degree, Koch is one of those, and they do sound very good! 041b061a72


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