Low parts beeping or signal source

[bean]

I've got an MCU I'm going to be programming for bypass. I've already got all the bypass circuitry worked out and a small board to program it complete with a pushbutton momentary to test the operation when programmed.

What I want is a signal source that I can plug into the dry and wet bypass so that I can test the functionality after program. Ideally it would be something of two different pitches so I can identify them by ear. Doesn't really matter what it is, beep, chirp, etc. Just not incredibly annoying sounding.

From there I'll hook it all into a 386 amp (or something to mix the signal sources into a mono output) with a small desktop speaker and slap the whole thing on a cutting board to make it portable.

Anyway...does anyone have a suggestion for the signal source? Preferably something fairly low parts? Maybe an Atari Punk Console?

[BluffChill]

Would the 555 toy organ work? very few parts, and with a couple momentary switched will give you different tones.

http://www.555-timer-circuits.com/toy-organ.html

[EBK]

Smoke detectors beep and chirp.  Just saying.   
https://www.diystompboxes.com/smfforum/index.php?topic=120755.0

[Marcos - Munky]

I built my audio probe based on a very similar idea. Here's what I done (layout needs to be resized):



I connected a notebook speaker to "spk+" and "spk-" and a resistor lead (probe) to "amp_in". A guitar cable goes to "injetor out" and "gnd", with the other end going to the effect input. There you go, portable audio probe.

It generates just one pitch, but you can play with caps values to get other pitches. If you (or anybody else) want the eagle files, just let me know and I'll e-mail them.

[Rixen]

..function generator app for smartphone..
I have one on mine from Keuwlsoft that is two channel (different output on left and right headphone jack), sine, square, triangle, white noise, pink noise, amplitude sweep, frequency sweep, burst, modulation (AM and FM), memory function....

and it's free.

[PRR]

Among the "cheapest" (time and parts) audio sources is the one opamp multivibrator.

The good output is an annoying square. There is a near-Triangle on the timing cap which is far less obnoxious, but will not pull a heavy load.

In guitar world we can probably make it a light load, because the cap swing is large, our signals can be small, and our impedances are high.

While padding-out, throw in a hi-cut cap to take-down the >1KHz overtones for smoother sound.

Build two with different time-cap values.

I would aim more like 300Hz and 500Hz. High enough to carry on a small lab speaker, but not a lot higher so not too annoying. Not simple-integer ratio so you can't be confused by clipping.



Or two old iPods, one full of Polka and the other with Trance.

[italianguy63]

Or two old iPods, one full of Polka and the other with Trance.

Disturbing, and brilliant!  All at the same time.

MC

[MaxPower]

Rixen beat me to it, I was also going to suggest a signal/function generator app.

[bean]

Thanks for the suggestions, guys. I like the generator app idea and the multivibrator.

I did start drawing up my original idea of two Atari Punk Consoles to see what it looked like. After I got into it, I made it way more complicated than needed (of course). But, then I thought it would be cool as a standalone for some fun. Here's what I came up with:

The two APC have inserts for the bypass and effect mode, then mixed with a blend. From there, I put in an fx insert thinking adding a delay might be cool for just messing around (when not using it for the bypass testing). One path could be a guitar mixed with the APC, too, I guess.

Anyway, the idea is to use trimpots. Bourns makes the 3362 trimmers with these little shafts so you can turn them without a screwdriver. This whole thing is way more than I need but it looks fun. I might cook up the multivibrator idea, too.

[R.G.]

If you just want a signal source and have a phone, yep, the signal generator app.

If you just need a quick and dirty signal source, and don't want to expose your phone to the vagaries of electrical connection to lashups on the bench, there is always the quick and dirty test oscillator, the quick and less dirty oscillator, and the fake guitar oscillator at geofex.

The Q & D is s single transistor and is easy to whip up with few components.