37Views3Replies

Author Options:

I want to learn how to build a vacuum tube guitar amplifier Answered

I have a slight issue that I am sure a lot of you do too... I have a million interests, hobbies, and maybe even some borderline-diagnosable passions. My problem is, I am 40 years old already, and I do not have years left on Earth to become a full-system level electrical engineer, a full-stack software engineer, and a master carpenter... just to name a few. So, I am looking for the best resource that you guys can suggest for where to start so that I can learn how to build a tube amplifier along the lines of a Fender, Marshall, Vox AC30, et cetera. of course, I do not aspire to revolutionize, or even evolution-ize guitar amps, and I also do not aspire to build some esoteric masterpiece copy with three independent channels, each with a separate EQ, a foot-switch, and multiple ins/outs.

I just want to build a simple, 1-channel amplifier that has enough power to produce a very clean tone without distorting, but has a gain, and a master volume so that it can be "pushed" to produce a distorted sound. I do not care at all if it sounds "good." I just want to do it, and I do not want to have to spend 2 years going down a Nikola Tesla rabbit hole trying to learn every theory of physics, electronics, etc. I just want to learn how to construct the circuit(s) and not electrocute myself by being dumb. So, don't get me wrong... I want to learn the right way! Just looking for a good resource. Amazon.com has dozens of books with titles that all sound the same. Does anyone know of the quick-and-dirty-bible for this?

Discussions

0
None
Jack A Lopez

11 months ago

Uh, I dunno. This one looks nice:

http://www.circuitdiagramworld.com/amplifier_circu...

I found it by asking DuckDuckGo to do an image-search for, "vacuum tube guitar amplifier circuit diagram". Here:

https://duckduckgo.com/?q=vacuum+tube+guitar+ampli...

By the way, I personally have never built anything with vacuum tubes, but you know, how hard could it be?

Regarding what you were saying about self electrocution, I recommend not touching anything inside the circuit linked above when it is plugged in, because, 300 volts DC is not something you want to stick your fingers (or other body parts) into.

What would it take to be extra prudent? Maybe, after unplugging it, use your voltmeter to sense the voltage on the main filter capacitor, for to check that it does not still have 300 volts on it?

Also, you did not mention what the mains electricity in your country looks like. I mean, what voltage? Usually it is a choice between 110-120 VAC, and 230-240 VAC.

The author of the page I linked above seems to have 230 VAC mains power, and if it turns out you live in a country where the wall outlets supply 120 VAC, well that's not a big deal if you understand the second diagram on that page, the one for the power supply, labeled, "Tube amplifier power supply"

I know you said you didn't want to learn anything, but I think it would be worthwhile to learn how these old-school power supplies work, if you did not grok this already. I mean the kind like the one in that diagram, consisting of a transformer, plus rectifier stage, plus big filter capacitor.

Actually the Wikipedia page for, "Rectifier",

https://en.wikipedia.org/wiki/Rectifier#Rectifier_...

gives a good overview of this kind of power supply works.

Also I just noticed. There is a Wikipedia page for, "Valve audio amplifier",

https://en.wikipedia.org/wiki/Valve_audio_amplifie...

and, just at a glance, it looks like there might be some good leads in that one too.

0
None
Jack A LopezJack A Lopez

Answer 11 months ago

By the way, on closer inspection, I noticed the circuit I pointed you to previously,

http://www.circuitdiagramworld.com/amplifier_circu...

has some errors in it.

In particular I noticed some problems with the power supply circuit. Like the 100 ohm resistor placed in series with the main filter capacitor.

I mean, if I do the math for power dissipation in that resistor; i.e. P = V^2/R, I get

P = (300 V)^2/(100 ohm) = (90 000)/(100) = 900 watts!

So probably the deal there, is that is a typo. I think someone forgot a "K", a factor of 1000.

A value of 100 Kohm, and thus power dissipation of 0.9 W, makes more sense.

I know you said you didn't want to learn anything, but, Ohm's law,

https://en.wikipedia.org/wiki/Ohm%27s_law#Circuit_...

and that simple formula for power dissipation. It's kind of important if you want to do anything with electronics.

Also in that power supply diagram, the little neon indicator lamp should have a resistor in series with it. How big? Maybe something in the range of 50K to 100K?

Yeah. Little mistakes. It's disconcerting. Like maybe the author is sloppy.

You know Van Halen had that rule about no brown M&Ms, for a reason. Basically just as an indicator to see if they were dealing with someone who paid attention to minute details.

http://www.thisisinsider.com/van-halen-brown-m-ms-...

0
None
Jack A LopezJack A Lopez

Answer 11 months ago

The other thing I failed to notice was the URLs watermarked on the images did not match the domain name of the site displaying these images. So it looks like I was actually pointing you to a the site of someone who serially rips of circuit idea from other sites.

I think the original is here:

http://www.electronicecircuits.com/electronic-circ...

All the question mark characters. "?", in the text of the page at circuitdiagramworld.com, are also probably indicators of a bad copy-and-paste job.

As a bonus, this new, original, page I have pointed to, has a comments section, so there's some chatter to read there. Including the story about the value for R1 in the power supply being a typo, missing a letter "k".

Anyway, I apologize for any confusion this might have caused.