i made a lofi pedal ( http://www.diystompboxes.com/smfforum/index.php?topic=40351.0 ) but it still doesn't sound good to me. for the sound of a transistorradio it's not enough to just cut away lots of frequencies. The sound of such a radio is also very compressed (the dynamic range of radio signal is very small) and it needs noise. i've allready managed to get radio signal but i also need noise wich isn't picked up by the thing but made by it, a very distinct "hey i'm on and cranked to max"-sound.

is there a way to achieve some noisy compression before the filter section? as simple as possible (simple circuits tend to be noisy circuits).

You mean with or without distortion?

Miguel

Quote from: bioroids on December 28, 2005, 09:17:47 AM
You mean with or without distortion?

Miguel

it doesn't have to be transparent or something like that but it can't just be a distortion circuit

a google search gave me this: http://machines.hyperreal.org/categories/DIY/info/compressor

would that be ok for what i'm describing?

Hey that circuit looks good and it seems simple. You may have to tweak it to hook it to your circuit (probably the 100ohm resistor and maybe adding a parallel/series resistor to the ldr) but I would give it a try.

Luck

Miguel

Nice lil' circuit.  You can even consider surrounding the LED & resistor in four Ge diodes to make it full-wave for best attack and reduced ripple, which doesn't increase circuit complexity by much.

Do a search for the Q&D Compressor II at AMZ. It´s simple and very versatile, and can do what you want (dirty compression).

maybe you could just put a diode in front of the transistor and use some bias current to 'kinda' turn it on? that would probably compress it in an ugly-ish way

I can hook you up with a noisy-assed 2N5133 if you want.  It WILL create its own noise, even without any input signal.  I keep my rejects in a plastic bin and can find you one that sounds like the ocean coming through a walkie-talkie.

Quote from: Marcos - Munky on December 28, 2005, 04:20:38 PM
Do a search for the Q&D Compressor II at AMZ. It´s simple and very versatile, and can do what you want (dirty compression).

i won't use it because the chips aren't available anymore and i have to build some more of these pedals (when i got it all figured out) for other people

I put the noise generator in my version of the low fi pedal.

See the Low Fidelity Telephone/Noise pedal at http://www.geofex.com/FX_images/lofi.gif


If you build it, there is a bug. The wiper of the panner pot needs to go to Vb, not ground.

i might want to use the noise section. but there is a cap with no value specified

The super-compressed sound on the radio comes in part from the seven-band compressors used at the transmitter.
Sorry if that's not much help!

Quotei might want to use the noise section. but there is a cap with no value specified

Wow. Must be a zero microfarad.

Try 0.1uF. If that's too much bass noise, try 0.01. If it's not enough bass, try 1uf.

thanks

Hi.
Xtra simple, extra ugly compressor.
Set up a simple 386 amplifier as a booster.  (Various threads will give hints about this)
At the ouput, chuck in a 100k trimpot in series with a 22uF cap to ground.  Then a big resistor (470k ??) in parallel with the cap.
Connect the junction of trimpot and cap to the gate of a mosfet that has its source at ground and drain at the input.

When the output is over 3V for long enough to charge the 22uF cap to 3V, the mosfet starts to conduct the signal to ground.

I've thought this thru from memory, so maybe I've forgotten something.  But a couple of years ago it worked really well as a heavy compressor ahead of a ring modulator I built.

cheers

i just tried that opamp circuit i found and it doesn't work well at all. it has a huge volumedrop and adds some distortion when i hit a chord. but it doesn't really compress. so it ain't good.

i have no mosfets lying around to try that last idea tough. only bf245 fets

Quote from: Connoisseur of Distortion on December 28, 2005, 06:04:35 PM
maybe you could just put a diode in front of the transistor and use some bias current to 'kinda' turn it on? that would probably compress it in an ugly-ish way

i don't really understand 

Quote from: birt on December 29, 2005, 09:29:17 AM
it has a huge volumedrop

May be the input impedance too low (100 ohms), how are you feeding this?
Also, does the led lights following the envelope of your palying, or it does nothing?

You can try several stages of Joe Davisson Diode Compresion trick, but it will distort too. I think the radio sound is pretty distorted anyway.

Luck

Miguel