Noisy Cricket lo-fi mini combo

[jugglindan]

Starting a new thread for this, since it's really a separate project to the foot drum. But inspired by needing something to plug the foot drum/stomp box into, I have decided to build a super cheap, lo-fi combo amp based on the Noisy Cricket circuit.

First up, I found this old and ugly Sanyo speaker, made a long time ago in a universe far far away. Or at least from before this sort of cheap home stereo gear was made from moulded plastic.


The 6" 5W speaker is perfect for now (a standard Noisy Cricket puts out 0.5W). If I want a better sound later I can swap to a car speaker, or even a 6" guitar speaker (but only if I can get one dirt cheap).

I did an initial test using an old headphone practice amp I built some years back. It sounded surprisingly sweet although the volume was very low. Even though the amp is based on the same chip (LM386), it is designed only for headphones and has a much lower output.


I am thinking of top-mounting the controls, input jack at bottom right, and DC jack at the back, with a fake control plate made out of metal that I can screw to the speaker enclosure. I am not sure what to do about the ugly box. I can embrace the brown and leave it as is (apart from a clean), I could paint, or cover in something else if I can find some vinyl on the cheap. Open to suggestions.

The circuit I am building has a switchable bass cap as well as a passive low-pass tone control. If that's not enough EQ I will adjust later. I don't think the cheap little speaker will deal with too much bass anyway.

DC

[JohnH]

I'm actually super into that box - it's the kinds of ugly that's so bad it's good

[jugglindan]

I'm actually super into that box - it's the kinds of ugly that's so bad it's good

I am leaning towards keeping it as is too. The knobs I got on the $5 broken Kustom 30W chassis are exactly the right sort of brown as well, so long as I can find chamfered shaft pots (all my current stash have knurled shafts).

DC

[McCreed]

I know you're looking to do this on the cheap, but if the amp intended for just the foot drum/stompbox, you could go with a 4"subwoofer/driver LIKE THIS

20 bucks and it would have more thump than that Sanyo will give you. My (budget) studio monitors have 4" drivers and they really kick.

[jugglindan]

Good idea. Which reminds me of something important. Out in the shed I have a crate of e-waste that I need to drop in at the recycling centre. One item in there is an old PC gaming subwoofer. I thought of using it but it only has SPDIF digital inputs. However I might be able to open up the case and liberate the driver itself.

Of course, if all that fails, I will just get one of the drivers you found for me. It's not that I can't afford to buy a speaker, it's more the challenge of building a mini amp from mostly reclaimed parts.

But the amp won't be just for the stompbox, so now I am wondering if could run the sub driver in parallel with the other speaker, or if I need to build a crossover. Or maybe I could just put in a switch to select bass or normal mode.

[jugglindan]

Forgot to mention the thing I learnt tonight: always score the copper side of a stripboard before snapping it to size. I ruined the trace on the edge of this one. I can still use the rest for other things, but I had to cut a new board for the amp.

[jugglindan]

Tore down the old gaming subwoofer just now. There are a few nice components I can salvage for projects, but unfortunately the driver is not so nice. It's using some sort of flexible foam/plastic around the edge of the cone to provide flex, but it has perished and the slightest touch makes it crumble. I hooked it for a test and it sounds, well, like a torn speaker. But not a nice fuzz, more like a flatulent frog. Definitely sticking with the original Sanyo speaker for now.

[jugglindan]

Board done. The two resistors end to end is where I soldered 2 values in series to replace a value I don't have. Apart from that, it was plain sailing. Didn't start the off-board wiring since that needs decisions about how to wire up the cabinet.

[Brendan]

Looks great - have been thinking about making a small practice amp and looking at the diyguitarpedals chime amp - my attempts previously with stripboard have been.... well.... awesome - if the success criteria is tuning in the local ABC - not so if the success criteria is a fuzz pedal.

[jugglindan]

Looks great - have been thinking about making a small practice amp and looking at the diyguitarpedals chime amp - my attempts previously with stripboard have been.... well.... awesome - if the success criteria is tuning in the local ABC - not so if the success criteria is a fuzz pedal.

Radio interference is a common problem, particularly in fuzzes. The op amp circuits are much less prone to it. I get non-specific noise (ie not a radio station) on breadboard circuits but haven't had a problem with stripboard at all. According to AnalogMike, a small capacitor from the signal input to ground can help filter out these very high frequencies.

The chime amp would be a good option if you want to avoid stripboard.

My next step on this build is to cut a hole in the enclosure top. I have some thin MDF that I will cut to size and paint to use as a control panel. The cabinet walls are too thick but I don't want to put everything on the back panel. If electrical interference becomes an issue I might have to do something creative with metal foil, glue, and tape to shield inside the box. I am hoping the low-gain, low power circuit wont be too prone to noise.