Archive

Posts Tagged ‘guitar amp’

Noisy Cricket mini-amp – Part 3

September 9, 2015 Leave a comment

Just a quick follow-up on the “Noisy Cricket mini-amp” project. As I mentioned in an earlier post this and many other interesting projects that one could find on the Beavis Audio site are now gone. I was about to post the PDF documents for three versions of this build when I noticed a reference to the Internet Archive and a cached version of the Beavis Audio site.

http://web.archive.org/web/20111015004206/http://www.beavisaudio.com/

I encourage anyone interested in audio, guitar amps, pedals, etc. to have a look at this archive. There’s a whole lot of useful and entertaining projects to play with. If you just want to browse to this project you can find the archive at the following link.

The Noisy Cricket – http://web.archive.org/web/20111004012623/http://beavisaudio.com/projects/NoisyCricket

Cheers and best luck with your multimeter….

 

Categories: Electronics Tags: ,

The Noisy Cricket Guitar Mini-amp – Part 2

September 8, 2015 2 comments

Over the long Labor Day weekend, I was able to get in a little shop time along with getting some chores done. As a change of pace, I decided to finish up my “weekend project” I started a year and a half ago. Although I hadn’t taken recent inventory, I was pretty sure I had all the components I needed to finish the build and this proved to be true. Take a look at my post of June 23, 2014, “The Noisy Cricket Guitar Mini-amp” for more information on the project. Unfortunately, the Beavis Audio website where I obtained much of my materials is not longer online. I was going to have to make do with the images and printed copies that I had on hand.

Where to Start?

Previously I had started by soldering components to the Radio Shack small projects proto-board. At this point I sorted through my large stash of purchased components and picked out what I thought I was going to need to continue the build. Let’s see, two 1/4″ guitar jacks, a DC power jack, three potentiometers, two LED’s and two switches all needed to mount in the plastic project box. I was a bit overwhelmed so I began by laying out what needed to fit in the box and begin drilling holes to receive the bits. I would say the project case was awesome but I wasn’t too happy with the grooves on the walls inside the case. It would appear these could accept vertical dividers (or circuit boards) but they prevented my components from mounting flush. I attempted to work around this by mounting components in between the ridges which limited my creativity with respect to layout. When something didn’t quite fit, I used a chisel to shave off plastic until it did! With most of the holes drilled I called it quits for the day. I was at least warming up….

The PCB

I picked up my work on the PCB board and quickly realized that I didn’t have very much left to solder. Methodically I reviewed what had already been done and worked my way around the board. I finally located a source for the MPF102  JFET transistor and removing one from the packet, bent the legs to fit and soldered it home. I also soldered in 3 or 4 capacitors that I didn’t have before. There really wasn’t a lot to do here, most of the work was going to be wiring in the external components. Note to self – If you build this again, use sockets for the LM386 and MPF102. That way if something goes amiss, you can easily pop in a replacement.

noisy_cricket

The Potentiometers

The design uses 3 pots, one each for volume, tone and overdrive which they call “grit”. Each of the three calls for a different value so the first thing I did was to label the case, V, T, and G to keep them straight during the build. Even though I’m supposed to be a guitar geek (student really) it occurred to me that I didn’t know how to wire these guys. I knew the theory, being two points with a resister in between and a wiper that moves to vary the resistance. Great, but which is pin 1, 2 and 3? The Internet and my multimeter proved to be invaluable. I came to the conclusion that pin 1 is the pin on the left with the pot turned fully counter-clockwise. These pots also had a prong that stuck out on that side. Placing my ohmmeter between pin 1 and pin2 and turning the pot clockwise, I observed the resistance increasing until the wiper was fully open displaying the full resistance as rated on the pot. Seems right, now I can wire according to the plan.

The Switches

Deceptively simple, even switches can confuse. Many have multiple lugs so again the multimeter proved quite useful in my quest to get things wired. My power on/off for example can be wired to be connected in either the on or the off switch setting. Something I managed to do during my troubleshooting times on the last day. The DPDT (double pole, double throw) switch was also new to me but using my meter and a lot of logic I was able to figure out how to wire and LED indicator to the overdrive switch. The DPDT is essentially two separate switches that both operate with a single actuator. Wow six terminals, again I am thankful for my multimeter. So one switch closes the overdrive circuit, the other switch provides POS voltage for the LED.

Note: I see the Sparkfun site has great tutorials for many of things I learned over the weekend. This one of switches in particular.

https://learn.sparkfun.com/tutorials/switch-basics/poles-and-throws-open-and-closed

The Power Source

Again I was thankful for the Internet while trying to figure out how to wire in the 2.5mm DC jack and battery. It turns out the jack has also three terminals. Obviously one of the terminals is for NEG (ground) and the other two somehow provide POS voltage either 9V if from the battery or 12V if supplied from a wall mounted transformer. So I knew the theory, power is supplied from the battery unless the external source is plugged in which case the battery is disconnected. I get that but for the life of me I couldn’t figure out how to make it work until I realized the external power needs to provide NEG on the tip and POS on the sleeve. All the power adapters I had looked at or had on hand all supplied positive power on the tip but reversing this was the only way I could make this work. As it turns out, the YouTube video I watched also did it this way so I figured I was on to something. Even after I had “figured it out” I still managed to misidentified the terminals and wired it all up wrong. My first clue was that the power LED didn’t light up. DOH!

The Test

Once I was able to get the power indicator light to glow, I figured I would see if the thing made any noise. I hooked up my guitar and…. nothing. Hummmmm. Let me turn some knobs and flip some switches. Finally when I flipped on the “grit” switch the noisy cricket made sound and it was definitely broken up as overdrive should be. Turning pots yielded a lot of snap, crackle, pop and hum. I was a bit deflated, time for some trouble shooting. I basically went over the entire board, looking for shorts and opens. Any solder joint that didn’t look sound, I reworked and tested. After some time (really not all that much time) I noticed a jumper that I had neglected to solder on the pcb. This jumper was underneath a resister and was something that I would have presumably done 18 months ago but had missed. The encouraging thing was the jumper linked the 386 to the transistor so it was definitely going to be important.

Like magic the amp sparkled to life with crystal clear sounds. DAMN!!! I went from deflated to well encouraged. Other than a some RF interference, everything seemed to be working. I played for a little while, turning knobs and testing. I could definitely overdrive the system using volume alone or turn volume down and use the “grit” setting. I was a happy camper.

Finishing Up

With this positive feedback, I decided to rework the “grit” switch to add in an LED indicator. For this I needed a different switch, which I was able locate buried in my stash. After figuring out how the DPDT switch worked I know only needed to find ground (NEG) and a POS source for the light. After looking over my options I decided to pull POS by wiring in to the power switch. It worked and just in time to mount all the components into the enclosure.

Assembly

I had already drilled holes for all the parts except for the second LED for the overdrive indicator. Measuring the hole size of the other LED I made short work prepping this one. As I began to stuff wire and components into the enclosure I began bolting up one by one until reached the LEDs. Oops, they have to be bolted from the rear BEFORE you hook up the wiring.

LED

No option but to snip them and solder them back after insertion. Now I do like this package because you get the LED, the panel mount holder and the needed resistor all ready for 12V service. I was now a soldering iron ninja so this didn’t take long and finally I had the project assembled.

noisy cricket - front noisy cricket - rear

Tweaking

It felt good to finally put this together and have an actual working example but there are a couple of final touches. First off, the internal wiring is definitely “spaghetti and meatballs”. I’m surprised there isn’t more RF hum than I’ve actually experienced. For this project, I’m not even sure how one would go about shielding but I will give it much more consideration on future builds.

noisy cricket - inside

A couple other last tasks include, securing the battery holder to the case and making rigging up a power adapter. I was thinking of just using hot glue to mount the battery holder. I have a surplus transformer that I think will work but I need to purchase a 2.5mm plug for it.

The neatest thing about this project was hearing it come to life and being able to button it up in the enclosure right before dinner time on my last day off. Priceless……

Thanks for dropping in— Sparky aka The Turtlecovebrewer

The Noisy Cricket Guitar Mini-amp

June 23, 2014 2 comments

As I may have previously mentioned, I’m discovering the real joy of electronics and discovering how they work. The basic facts I learned as a young-in were important but without learning how and when to put the components to use, the knowledge was unrewarding. It’s my own fault for not digging deeply enough into the topic but that was then and in today’s world we have so much wonderful (and free) information placed before us it is easy to learn. This revival begins with the simple desire to understand more fully how the electric guitar functions. Understanding pick-ups, volume and tone controls, microphones and amplification. It sounds like a life-time of study or at least a full retirement of study for me.

Soldering Iron/Station

As I often do I wrestled with picking my “first project” for trying out my new soldering iron. After much rumination and anguish, I decided to lay down my $100 on the Hakko FX888D, soldering iron. Review after review after recommendation compared this Hakko to the Weller WES51. Clearly for a “serious” hobbiest, these were the two irons of choice.

 

Hakko FX888D

 

Although the Weller iron had its following, the Hakko was mentioned over and over again as a solid buy. The Weller had an analog display whereas the Hakko was digital. There were debates both ways as to which was better. In the end, I went with the Hakko which included a free wire nipper (cutter). Woo hoo!

What to Build First?

My interest in electric guitars and “tone” lead me to learn more about audio circuits. As I was surfing the web, I ran across a pretty awesome site with the odd name, “Runoff  Groove“. I discovered all the wonderful work that has been done creating guitar effects pedals which has been placed in the Creative Commons for anyone to enjoy. I learned that guitar effects pedals exist to allow unique sounds to be sent/played through tube amplifiers which on the whole wouldn’t have many effects built in to them. The amp that I have is Fender Mustang I, solid state modeling amp with beaucoup effects already built-in to the amp. In a practical sense, I don’t really need any pedals at this point in my playing what I needed more was to learn about the effects that I already had available to use.  I was intrigued however by the many mini-amplifier designs I had run across. Using one or possibly two transistors to power a speaker and/or headphones. I figured I could use the mini-amp when traveling so in that sense, it would be both an educational and somewhat practical “toy” and also not terribly difficult to build.

I considered building the “Ruby” amp until I ran across the “Noisy Cricket” from Beavis Audio Research.

Ruby - mini-amp

The Ruby – mini-amplifier from Runoff Groove

Noisy Cricket - mini-amp

Noisy Cricket – mini-amp from Beavis Audio Research

The circuits are somewhat similar and both are based on the LM386  low voltage audio power amplifier chip. The Noisy Cricket project page came with a lot more information about actually building the device, pictures, parts lists and just a bit more documentation to get my feet wet for the first time. When I ran across the “Radio Shack Protoboard Build Guide” link, I was sold! This would be my first project and “instant gratification”. Rather than muddle for days over what parts to buy and where to buy them, I’ll stop by Radio Shack, and get started soldering. And that is exactly what I did, only they didn’t have all the parts that I needed so I still had to muddle over parts and the best place to purchase them.

RS mini-amp build

Radio Shack mini-amp project sheet (circuit build)

It felt good to finally tin the tip of my new soldering iron and solder up my first circuit board since I built my Heathkit H-8 in the 1980’s. I had the skills then, but I was very rusty now. After a while I began to calm down and my hands quit shaking so much and the welds got better. Hey, its new equipment and everyone has to begin their journey somewhere and so I started mine…..

Noisy Cricket mini-amp RS build

Start of the Noisy Cricket build, Radio Shack version.

I came prepared with magnification (reading cheaters) but I was shocked at how I needed it for every component and every weld. Man, how am I ever going to coup with surface mount components? Perhaps I never will…. On future builds, I’ll opt to use sockets for the LM386 and power transistor which in this case is the venerable MPF102. This would allow easy repair and some experimentation but really, if I fry the LM386 I know how to desolder and replace it so is the socket really necessary? And as far as experimentation goes, that is what the breadboard is used for so by they time one is building I should think the design would have been mostly locked in. There are many ways to get a job done so I have some experimenting in my future.

Next up…

Well the promise of instant gratification was a might exaggerated when I discovered that RS (in fact two stores) didn’t have one of the potentiometers nor the transistor that was required for the build. I was excited to get started though and gave me motivation to find a parts supplier and commit to an order. So I did, in fact I have two fairly substantial orders in for supplies. I finally ordered from Futurelec mainly because they seemed to have all (or most) of the parts that I was looking for and at good prices. Their website was navigable but I haven’t been super impressed with their customer service yet. It doesn’t appear that I can called them and I have no idea how to track my orders so I guess I’ll email them to see if everything is alright. Meanwhile, there are a few things I could work on with the project case, e.g. drilling holes for the pots and LED’s. I really think it best at this point however, to just wait for all the parts to arrive before I do much more with it. I purchased enough components to build additional units but I’ll be first interested in how this one turns out before deciding on what will follow. I think my next project might be a DIY iRig, or maybe a complete practice amp with speaker cabinet or perhaps ……

Categories: Electronics, Lutherie Tags: