Underground Bands: Get more Watts for less money
A year ago I made a USB guitar amplifier for my then 3 years old son. Later it became a cheap 400 Watts guitar amplifier that can be used in concerts and rehearsals. I will tell the history behind it because I think more small bands can benefit from it and have the chance to scream their attitude as loud as they should with less money. The project is simple and modular and it is easy to modify and increase or decrease its size and wattage.
(under revision, portuguese version here)
Version Zero
The name is “Marginall”. It is a joke with a Brazilian word “Marginal”, a pejorative way to call someone “poor gangster”, somebody marginalized in terms of society. Because yes, it was made to be cheap, accessible for marginalized bands.
It was simple, a Beats’ headphone box, a cheap 5 Watts amplifier (USD 2.98), two diodes connected in opposing directions (the easiest way to get some distortion), a handmade pre-ampli using a TL-072 CI (USD 0.07), and a 5 Watts 8 Ohms generic speaker.
I had to learn new things about electronics and I bugged some people (thanks Marcos Sobrinho, Gabriel Kaffka, Alexandre Ribeiro da Silva and Robinson Nakamura).
After that I was able to use proper voltage for a LED, to choose correct ohms for speakers, to use 5 volts USB, to create a simple pre-amplifier, to ground things correctly, and most important for this article: To learn the stages of a guitar amplifier.
The transformation stage, were you get a power source and adapts to the circuit. This is obviously dangerous. It does not appears in the picture above. The transformer I use was a mobile charger, it gets 110 volts from the wall and gives a 5 volts USB port. Transformers has something to do with the audio signal, poor transformers can lead to noises in the signal.
The pre-amplification stage, where you get a “low volume” signal and pre-amplifies it enough to modify it later, or just send it clean to the amplification stage. Remember most electric guitars are not plugged in any power source and their signal are weak. Usually the equalization is made here too.
The modification/distortion stage, where you get the pre-amplified signal and make some fun, like distortions, overdrivers, reverberations, etc. This stage is optional.
In the picture above the two diodes create a clipping effect. As Gleicon Moraes told me, the diodes are in the wrong place, before the pre-amplification stage, not after.
The amplification stage, where you get the now prepared signal and pull it to the speakers. This stage requires attention BECAUSE IT CAN BE DANGEROUS, it is not as obvious as plugging something in the 110V wall plug. Once you amplify the signal, it can burn things, give electric shocks, etc.
Guitar amplifiers are “modular”, good ones have multiple dedicated pre-amplifiers and you can bypass stages. That modularity made me start this project.
Version One
Luiz Henrique Gomes is the singer of the great “blackened grind core” band Lapso. I was showing him my son’s new amplifier when he asked me:
— Could you make me a big one of this?
My first reaction was:
— Of course not, you are an artist, things can not go wrong while you are playing. And I can kill somebody or myself by electric shock… I don’t know, it will not gonna work, and it can be an expensive experiment.
Then I got off to have lunch with his words in my head.
I realized I had to do anything! I could just put well done pieces together for each stage if I could make them match!
The first piece in my research was the amplifier.
The amplifier
I asked for help to my guitarist and audiophile friend Gleicon Moraes. He played in some underground bands, he liked handmade stuff, he had some knowledge about electronics. I asked him what could go wrong if I use a car system amplifier as the amplification stage.
He advised me to check the amplifier audio frequencies, and that it would never sound like a great amplifier to play at home or to record in a studio. He also enforced the reliability required for a concert.
I consider car systems reliable, because they operate in extreme conditions: under carpets, close to heat sources, under the sun. And they have built-in protection circuits against short-circuits, speakers misusage and overheat.
Since the project was modular I could take some risk. If some piece didn’t work well, we could just replace it with a better one. Luiz Henrique Gomes was anxious and willing to try anything. The reason behind his rush was his new project: a new space for underground bands. It is a mix of a pub, a tattoo shop, with a small stage for concerts in the Golden Line Tattoo.
Back to our project, I found a good estimation of the guitar frequency range in the internet, it is around 50 hertz and 5000 hertz. My honest guess was: if I can listen to any song in my car I would listen to my guitar.
I read some car amplifiers manuals. Most can reproduce, or say it can, frequencies from 20Hz to 30000Hz.
The next challenge was the speakers impedance. Car systems usually output signals at 4 ohms and 2 ohms. Usually they give double “power” in watts when using 2 ohms.
Most have 4 input and 4 output channels, 2 for the left signal and 2 for the right signal.
Some of then have something called “bridged mode”. It means its circuit is able to “sum” two channels, giving the double of impedance and power. For example, if it gives you 100 Watts at 2 ohms per channel, you can get 200 Watts at 4ohms using 2 channels in bridged mode.
Note: Never ever try to sum two output channels by only wiring them together, it can damage the circuit and the speakers.
4 ohms is perfect for two 8 ohms speakers in parallel. I will talk about this later.
Our first amplifier was a Hurricane mini H 400.4D. It provides 2 bridged 200 Watts at 4 ohms for R$ 150,00 (USD 50.00 at that time).
The guitar signal is “mono”, one signal, no left and right.
We had one signal, two output channels.
Splitting a signal is never a good idea, specially for the output. When you split your laptop’s sound to two headphones it changes the final impedance and it can force your laptop amplifier. Honestly I have never seen any problem related to it in laptops, but still not a good idea.
In the input I don’t know what can happen, but most of car amplifiers comes with two “Y” cables. If you have only 2 source signals (left and right) you can plug the “Y” cables in the all four channels. It means no matter if it is right or wrong the amplifier circuit takes care of it.
The car amplifier has no on/off switch. It has a control wire, called REM. When you put a 12 volts current on this wire the amplifier turns on. For our project, I just connected it to power supply. If the power supply was on, the amplifier was on too.
The Speakers
Guitar speakers are expensive. I tried to understand why guitar speakers were different than regular speakers. I sill not sure why, but I observed that the guitar speakers have lower wattage compared to car speakers of the same size. It is common to see 12 inches 200 watts speakers for guitars, and 1100 watts for same 12 inches in car systems speakers. I also observed that the impedance was higher for guitar speakers, usually 8 ohms, sometimes 16 ohms. Car speakers impedance are 2 or 4 ohms.
The next step was to understand the difference between Woofer and Sub Woofer. The correct for guitars is Woofer, even for bass guitars the answer is Woofers (different Woofers, but still Woofers).
I found a cheap and good woofer, low wattage and high impedance speaker: “Woofer 12 inches JBL Selenium 12PX — 150 Watts RMS 8 ohms”. (something similar at Amazon for USD 35.44).
Note: The JBL woofers are great for acoustic guitars and voice. You can add tweeters to make it even better. The math will be harder though.
Remember the amplifier output is 4 ohms and the speakers 8 ohms. It means I could use four speakers.
The way you wire the speakers results in different impedances. In parallel they divide, in series they sum. Two 8 ohms speakers in parallel results in a 4 ohms circuit. This topic at Seymour Duncan forum explains it better.
Parallel means to connect the positive wire of the channel in the positive pole of each speaker, and the same for the negative pole.
Two 150 Watts speakers results in 300 Watts. In a 200 Watts bridged channel I was playing safe, trying to not damage the speakers. I’m still not sure if this thought is correct, but it did work :)
Audio Cables
I let you decide, take a look: “USD 500.00 Monster Cable vs Coat Hanger”
“Of course, a coat hanger doesn’t have a Monster Cable lifetime warranty, so if your coat hanger breaks, you’ll have to go out and buy another coat hanger”
The Power Supply
Next step was to give juice for the system. The amplifier manual says it operates at 22 amperes, and 12 volts (the same voltage of any car battery). It is strange that those amplifiers have 12 amperes fuses, don’t ask me why :)
Some car amplifiers operates at 12,8 and 13,6 volts, it gives extra Watts to the system but requires additional power supplies. I would not use that much power anyway, I ignored it.
After a lot of math I came with a total of 60 amperes, it would be enough to the amplifier, the pre-amplifier and some coolers I never installed.
Because the price difference for a 60 and a 30 amperes I asked about it to some car systems specialists. They told me 20 amperes were more than enough for those amplifiers.
I could not trust myself, because I was not sure of what I was doing, so Luiz bought an expensive (USD 30.00) 50 amperes power supply like this one below. Note that it has a cooler on it, cool, one less thing to take care about.
The Pre-amplifier
For our project I had to find a pre-amplifier with volume controls, the easiest part of the project.
Any pedal with a volume knob would work. The first thing that came to my mind was an equalizer pedal. It has all features you find in a regular guitar amplifier.
At first, we decided to plug the pedal in the power supply. The pedal is 9V and the power supply 12V. For the sake of simplicity Luiz just bought a pedal power supply and a power cord with a on/off switch, easier than put a on/off switch somewhere else.
A Luiz’ bandmate, André, gave us a cheap amplifier emulator pedal. Not ideal, but would work.
The “casket”
We had no wooden knowledge and tools, so I asked my brothers Ricardo and Luiz to make me a 4 x 12" (four speakers of twelve inches) cabinet and a 4 x 10" I would use latter if the Version One worked alright. My brothers work in a small factory, they made me a wooden box painted in black.
Putting all pieces together
Before we started buying everything I made a diagram in a paper to check if it made sense.
We wanted to make it looks cool. A lot of strange ideas came to our minds to build our amplifier “head”. At first we tried to put the pieces in an old drawer, then in an old network switch. In the end we fixed everything in a barbecue cutting board :)
With all the “ingredients” in hands we made a little test, with only one speaker using only one amplifier channel. We wanted to see if nothing would burn.
We could not believe ! No noises, good sound, it was promising !!!
Testing
We invited Lapso’s guitarist André, the same one that gave us the pedal, to test the amplifier. We wanted somebody that could operate an electric guitar and make sure we had a great evaluation process. He looks satisfied in the picture :)
The first concert
The first concert happened at Golden Line Tattoo, in the line-up: Dash ArtPunk, Weirduo Hardcore and Lapso Blackened Death Grind Core.
I was nervous, Luiz was too. We could not stop looking at our Marginall.
At some point the lights reflected by the cymbals made us think something was wrong. Just paranoid.
One monitor speaker got burned. We jumped to the Marginall and turned it off. But it was not “him”. Marginall was screaming the voice of the end of the world \m/
I recorded the first chords played live with a Marginall, the Dash’s performance:
Few months later Luiz told me the Dash’s singer André was assassinated :( R.I.P André.
Version Two — Flex
I still had my empty 4 x 10" cabinet.
Since Version One was successful I had a good chance to try something different.
I was learning how to play bass guitar at that time and I loved it. The cabinet was smaller and I could bring it to my home. So why not make a hybrid bass and guitar amplifier for myself?
I had no idea what a bass speaker was, but I found at MercadoLivre, something like a Brazilian Ebay, a handmade speaker called “ELD Power” supposed to be replacement of Celestion speakers.
I bought 2 speakers for guitar, and 2 for bass guitar. I don’t remember the speakers’ wattage, but I do remember the bass speakers could handle more Watts.
The price was good and similar to the JBL, and it was made for guitars. Take a look at this ELD Power’s speaker test video.
For personal use I thought it was ok to play guitar or bass in the same cabinet. I was not willing to play both at same time.
But we did… We started using it at the office, playing with our co-workers.
I bought a different car system amplifier, a Hurricane HA 4.160. I used 1 bridged channel for the bass speakers (total of 320W) and a single 100W channel for the guitar speakers.
What to do with the spare 100W channel ?
I made a switch using a Tic Tac candy case and pedal cables. Those cables connected directly to the speakers. It gave me plenty of configuration possibilites (that doesn’t mean are useful):
- to play guitar at 100 Watts in two guitar speakers
- to play bass guitar at 100 Watts in two bass guitar speakers
- to play bass guitar at 320 Watts in two bass guitar speakers
- to play guitar at 100 Watts and bass guitar at 100 Watts, together
- to play guitar at 100 Watts and bass guitar at 320 Watts, together
- to play guitar in all speakers, using two 100 Watts channels
- to play a guitar in all speakers, 100 Watts for the guitar speakers and 320 Watts for the bass guitar speakers
Some car amplifiers have a LPF and a HPF switches. LPF = Low Pass Filter, and HPF is High Pass Filter. It means you can cut off high or low frequencies in the channels. I did not test it yet, but in theory I can play bass guitar in all speakers cutting off the low frequencies in one channel to not damage the guitar speakers, perhaps the best configurations for slaps.
There is also a "gain" potentiometer for each two channels, it controls the amount of input volume. And another two potentiometers to control in which frequency you want to cut the LPF and HPF filters. It helps to tune the sound. I ended up with two more possibilities:
- to play a bass in all speakers using two 100 Watts channels, the guitar speakers' channel in HPF mode on.
- to play a bass in all speakers, 100 Watts for the guitar speakers and 320 Watts for the bass guitar speakers, the guitar speakers' channel in HPF mode on.
Note: Remember the amplified signal is not safe as the guitar signal, you must be sure the wire gauge is correct.
Another difference from the Version One: the power supply.
Now I knew I wouldn’t have to buy a big one. I bought a 30 amperes 12 volts. I never played at full power, it cab be a problem though.
And now Marginall got wheels and speaker protection “grills”!
For the pre-amplifier I found a Mesa Boogie V-Twin clone called “Doctor Drive”. It had valves !! Cool !! I payed USD 100.00 for a second-hand at MercadoLivre.
For the bass, I bought a Hartke Bass Attack pre-amplifier pedal, second-hand too. How could it not be fun ?
Take a look at the amused brennovich testing it for me:
Some fun with Luiz Henrique Gomes, André, Marcos Wada and Thiago Paixão. Me playing bass guitar and André playing guitar at the same time in the Version Two:
The Version Two has a “bug”: To play bass you must open the back of the cabinet! I will fix it someday by drilling few holes.
Version One Upgrade
Two days ago I went back to the Golden Line Tattoo, more than a year from the last time. It was the avant-première of Lapso’s first video clip.
The event called “Last Day of Humanity Fest” had five bands in the line-up (flyer shown in the beginning of this text). All of them played the Marginall Version One.
I noted Luiz made an upgrade, he liked the Doctor Drive idea and bought a second-hand one too.
I was there, with my friends, worrying about the Marginall and if it could handle the whole event.
The first band, Obscvred, played.
The second band, Discurso de Pobre (Speech of the Poor) decide to not use any pedal, only Marginall. They performed a great thrash crossover music.
The third band, Dead Cops did the same, plugged the guitar directly to the Marginall and performed a dense grindcore.
When the fourth band, Qerbero, came to play, Luiz asked me to help them tune the Marginall.
I was there helping the guy, when he turned to me and said: fucking nice sound!
Oh shit, it did worked motherfucker!!! It took me a year and around 50 performances to understand it did the job!!! I was finally in peace with this project!!!
Next day I talked to Figaro who encouraged me to write this all :)
If you want to share your project, get some help, give some help, collaborate somehow with the underground scene, open an issue here: https://github.com/lorieri/marginall/issues
If you want to build your own Marginal, check it: https://lorieri.github.io/marginall/how-to-en.html
Thank you all the people below that helped me test the Marginall: