We record music. I focus on tape recorders, such as reel to reel machines like the teac 40-4, and four track cassette recorders like the tascam 414 MkII. Microphone preamps, tube mic pres, Ribbon mics, Cassette tapes, Guitars and Vintage guitar amps, great sounding mics- these are things that I feel deserve attention in the world of digital audio and DAWs. Not obsolete, these recorders are more viable now than ever, and should be used! Vintage gear rules!
Make a Mini Guitar amplifier! This simple practice amp is easy to build and fun to play! Use it with your favorite speaker cab, or DIY your own. The best mini amp is the one you make!
This simple electronics project uses a LM386 amplifier chip with a real wood head and speaker cabinet. Mine uses recycled paper headphone speakers.
Begin by drawing the layout on a peice of paper. This will help you understand the parts involved and how you'll be attaching them together. This is especially helpful for polarity of things like electrolytic capacitors. Also think about how your chip socket relates to the rest of your parts and wiring.
After you have a good idea of how you will "layout" your project, transfer your drawing onto your perf board with magic marker on the top of the board.
Start building the amp by placing your empty chip socket into the perf board. Bend a few pins to keep it in place.
Next, add the 10 ohm resistor, 220uf capactitor and 100uf capacitor. Bend those pins to keep the parts in place. Add the .047 cap and the .01 cap and bend the pins.
Double check your schematic and layout. Is everything in the correct place? Capacitor polarity ok?
Good, now you can solder your parts in place.
Now you need to wire up your creation.
For power, you are going to make a voltage "Rail" and a ground "Bus"
Voltage Rail:
Using a peice of thin wire (i prefer solid core here) make the connection between where your red 9 volt battery plug wire:
1. attaches to the board
2. to pin 6 of the chip AND
3. to the "+" side of your 220uf capacitor.
The wire will probably look like an "L" and you should solder it at all 3 points.
Ground Bus:
Wire the ground bus by connecting socket pins 3 and 4 with solder or a tiny wire jumper.
1. Solder a bare wire from socket pin 3/4 to the end of the board where your .047 cap and your 100uf cap (negative -) terminate. This wire will probaly look like a large "L" or a large "T".
2. Run the wire neatly along a row of empty perf-holes since you will be adding more "ground wires" to the bus.
3. Add your battery connector if you haven't already. (+) to pin 6, (-) to ground bus.
Add your input jack, positive to the open side of the .01 film cap(which ultimately connects to socket pin 2. The ground wire goes to the perf board ground bus.
Add your output jack, Positive attaches to the (-) side of the 220uf electrolytic cap.
The ground wire attaches to the perf board ground bus.
If you want a Rheostat volume control, wire it in place of the output jack(middle leg), then wire the output jack to either open leg of the rheostat as shown in the video.
If you want a High gain amp, make a jumper from a small peice of wire and install it between socket pins 1 and 8. That will set gain from "20" to "200". The video shows the high gain setting.
Install this into your favorite cabinet, or altoids tin, or candy package, or....
This amp will drive virtually any speaker cabinet.
You can build a DI box from a spare mic input transformer to record your bass or guitar direct. Build your own Bass DI box that would make the Motor City proud! You'll be one step closer to nailing that "Motown Sound" with your bass, or guitar!
Updade: I currently have a few of these for sale on Reverb:
One great reason to build your own transformer DI box is to help interface your gear into your vintage or modern recording equipment. Recording the bass guitar direct is especially appealing for a multitude of reasons, mostly to do with how loud the instrument is with an amplifier.
Doing a quick search for impedance matching will bring up a myriad of definitions, terms, and equations to help our understanding of Ohms law. It's a lot of good reading. But you need not do all that reading to make your own great solution.
However, if you have some spare gear(and time!) you can build a DI that will quickly interface most Hi-Z instruments to a Lo-Z input, most likely a mic preamp. Another reason to build your own DI box, is that a transformer will give your instrument a great "Sound" that's very hard to replicate without one!
Now, you may be thinking that this problem was solved years ago with the invention of the "Instrument" button on your mixer or computer interface. Well, that's partially true. That's one way to get your instrument into the box(or your mixing console, for that matter). But, another great sounding way is to do what the audio engineers of the 1960s and 70's did which is use an impedance matching transformer. Simple. Effective.
For this project you'll need:
A suitable enclosure, preferably aluminum
An input transformer (primary side approx 600 ohms, Secondary approx 20k ohms)
A mono input jack
A male XLR jack (and wire if you are making a cable end as I did)
Optional Noval Tube socket (if you choose to make the transformer removeable, I assume you won't.)
Soldering Iron and Solder
You could make the box more or less complex or useful by adding an attenuator of sorts. However, it does add to the complexity of the circuit including a switch, potentiometer and resistors. It also requires more drilling, which is a pain.
The video above shows the input and output wiring in detail.
Basically, you're going to figure out the primary or secondary of each winding of your transformer. No multimeter readings are necessary, you can just check the taps (or pinout) of your favorite transformer and you'll have all the info you need.
My transformer is wound for 200:15K. Or, another way to use the transformer would be 15K:200
For this project, our "Primary" side is going to be the Hi-Z taps. So, if you're using a mic input transformer as I did that is technically the "Grid" winding. This is the side that will be hooked up to the 1/4" input jack. Generally this is two wires- Hot and ground.
Now, we need to hook up the "Secondary," Lo-Z side of our transformer. Again, if using a mic transformer this would be the "Mic" or "Line" winding. This will consist of connecting the "hot, cold, and ground" of the winding. This will be clearly marked on your transformer taps or transformer literature.
Once these connections are made, and your connectors are fitted to your chassis, you're done! Give it a test and record your dream motown tones!
