I have a 4" speaker I would like to make a nice little TUBE amp out of. But...It's my first amp build. I don't know if tubes will be more difficult than solid state. I'm looking for volume and overdrive as the controls, but tone and reverb would be nice too (I think that'd be too hard though). Anyone got any circuits? and a place to buy tubes?

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Tube Depot is a good place to start. Tube amps are challenging, but do-able. Just remember that the voltages inside the circuit can reach or exceed 450 volts...one wrong move and it's over...as in DEAD.

If you want to start small, look at Doberman Amplifiers (AX81 project) or look into the Noisy Cricket tube amp.

 

Otherwise, the Fender 5E1 and 5F1 (champs) are straight forward circuits.

 

Happy soldering...

Do you have to plug into the wall for tubes? But thanks, I'll definitly check out those circuits.

Decades ago, tube radios that would be found in homes were powered by large batteries. Guitar amps are altogether a whole different beast.

I am not aware of any guitar tube amps that would not use 117v or 230 volt ac power to operate. There are usually 2 power transformers...one changes the wall outlet (i.e. house power) from ac to dc...then that electrical current flows through the various components (capacitors, resistors, tubes, fets, and such to shape the "sound" of the amp) and then to the output transformer, then to the speaker(s).

 

So "yes", I believe you must have access to wall outlet to operate tube amp.

The battery killer with tubes is the amount of power it takes to run the filaments.

As an example, a typical preamp or input stage tube commonly needs 6.3 vac @ 0.6A or 12.6 vac @ 0.3 A for it's filament or 'heater' . That's about 3.5 W. A 2 or 3 tube amp needs roughly 2-3x more. The high voltage side (plate/anode/grid/screen, etc) might need (another rough arbitrary example) 150-300 VDC for input stage tubes at 5-10 mA each. That's a few more watts typically. This rules out a single 9V battery or maybe even several.

 

The 450 and up VDC scenarios are usually larger power tubes or the rectifier tube supplying power to the other stages. When an amp has a minimal number of transformers, typically 2, as mentioned, one is for the power conversion from the wall to the levels needed, and another, the output transformer, to convert the high output impedance tube output stages have to the typically low impedance of a speaker voice coil.

 

There are some 'starved plate' tube electronics (might be preamps rather than power amps) that run a very low voltage for the plate/anode/grid, but you cannot starve the filament...they rely on the proper amount of filament power to get hot enough to work.

 

Also check out the Audio Asylum and DIY Audio websites. There are some 1-5 W tube amps that can be done pretty inexpensively with surplus transformers, but they DO need transformers. Small toroidally-wound power transformers

have been used as audio output transformers, but they're not as prevalent in surplus sources in the US as in Europe, so they cost a fair amount.

  

It's possible with a lot of hassle & hacking (and safety) knowledge, to recycle a DC-AC power inverter to supply usable voltages to run a tube amp from a still-hefty battery source, but I think it would someone's personal goal to prove it can be done and not a very practical one. (Sorry, no promises when).

 

 

Alright, I think I'll stick to solid state because I want something easily portable. are there any solid state circuits that have nice overdrive because that's mainly what I'm after.

Take a look at www.runoffgroove.com

There are a few excellent amp circuit diagrams there that will fit your needs.

It is possible to build a basic tube amp that will run on battery power but you need to be aware of the limitations. It's probably not a good idea unless you have a bit of experience building simpler projects.

As Murray has correctly pointed out the big problem with tubes is that, in general, they require high voltages and suck up power. However there are low voltage / low power tubes (which I believe were originally used in applications such as car radios and other portable devices). Some people have designed and built small guitar amps using these types of components. Check out the following:

Beavis Audio has a design called the Tube Cricket, which uses a solid state LM386 power stage with a tube pre-amp stage:- http://www.beavisaudio.com/projects/TubeCricket/

There is a parts kit available from OLC:- http://www.olcircuits.com/olc_tubecricket.html

I considered building one of these a while back and had some correspondence with OLC, including confirming that it would be feasible to adapt it for battery power. However regular cells would not have the power capacity - instead I was looking at a small sealed lead-acid battery. I think it's possible to get ones with a high enough mAh rating that are still small enough to fit inside the cigar boxes I'm using.

Another design is the Matsumin Valvecaster

Beavis Audio has some info on this at:- http://www.beavisaudio.com/projects/ValveCaster/

There is also a discussion thread on the DIY stompboxes forum here:-
http://www.diystompboxes.com/smfforum/index.php?topic=63479.0

Sophtamps (http://www.sophtamps.ca) also came out with a "tube + LM386" hybrid amp called the Ruby Tuby - essentially the Ruby amp circuit with tube front end.

However, if it's your first build then I'd suggest trying one of the simple solid-state amps based on the LM386 chip. The sound can be surprisingly good, even with the most basic circuits. If you want to get a bit more sophisticated then there are some neat little circuits that try to mimic valve sounds with FETs (field effect transistors). There's plenty of info at runoffgroove.com, Beavis Audio and other sites.

Bob Danielak's tube amp pages...

 

 

http://www.reocities.com/bobdanielak/projects.html

 

It's nice to see some practical amps that prove armchair advice wrong (often mine!). The cricket was kind of interesting. I had forgotten what to call those 70V line output transformers...I bought a few of those...have them somewhere...from an eBay seller in Pennsylvania, in large part because he had specific details of what tubes he used them with and at what current. I would not have assumed I could run single-ended tubes with such a transformer...but that's another unfinished project...

 

 

I checked out the matsumin valvecaster and It was a pedal, not an amp. I was thinking I could just hook up a speaker instead of the output since I would like to try it, but I don't think that would work. I also wanted to try the tube cricket but that unfortunately didn't have a schematic. So, which solid state circuits have you guys found to be the loudest that can run on a battery?(assuming you guys have built some of those)

Many online electronics stores have amp components and DIY amp kits for battery-powered applications. QKits is one I know of...they have a 7 watt mono amplifier kit that works for guitars. One thing to realize is the higher the power & the louder the output, the more juice that gets drained from the battery. One variation to consider and recommended to save battery life when the amp is being used in home...add a wall wart input to the circuit.

If you're not familiar w/ term wall wart...its an ac/dc adapter that changes house outlet power ( 117volts a/c to a lower voltage...maybe from 9-18volts d/c).

The 7 watt amp kit will operate within a range of 9-18volts dc...but don't assume that using wall wart w/ higher dc output is better..in fact, that specific unit sounds better when juiced w/ 12volts dc.

 

The circuit I build is only 1/2 watt, runs on a single 9 volt battery, uses minimal components, and can fit, as a head, into your pocket. As a "combo" style...with speaker, I use cube shaped cigar boxes that wont make good guitars.

 

 

Attachments:
I've been doing some researching and listening and I've decided to make a ruby. I think it sounds the best. Like I said though, I have (only?) a 4 inch speaker. how loud do you think the ruby can get?
actually, never mind on the loudness thing because I just thought of a solution: I can build in the option to run it off a 9 volt wall wart so it can then power a larger speaker through an output jack on the amp (but it still has a built in speaker, and a led to let you/me know it's on). anyone got any circuits for that?

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