Futz box... Some ideas for DIY-ing one...

There's a procedure often called-for in film post, known as 'Futzing' a signal. Lafont makes a box known as a 'futz box'... take a look. -I think that most of the time when you hear phone audio, or walkie-talkie chatter in a movie, it's been through a device like this.

Basically, the process of simulating telephone sound is rather more than the usual "roll off the top & bottom". There's more to it than just honk & squawk. -The front panel of the Lafont explains most of what is inside it.

There are other companies that do similar stuff in digital, like the Harrison version: take a look

Now... if I were to try and DIY something like the LaFont, I might like to add some of the aliasing to it as well (I remember noticing hearing this on international calls from time to time) -Anyone got any ideas for a circuit for some easy "LSB" aliasing-type effects?

Also, has anybody got any ideas for any other 'components' that I might like to put in the box, apart from an envelope-tracking clipper, filter, noise generator/gate, squelch etc...

Keith

compressor/expander with bad frequency response inbetween - NE570-type. Possibly adjustable bad amplitude or timing tracking.

Vocoder/de-vocoder for frequency band limiting like they use on the real telephone systems for channel space compression. If you switch bands on decoding, you will have a completely incomprehensible sound - but still a sound like the input. Most disturbing for speech...

IIRC saw some effect boxes that that I think messed up the bits after the A to D and then D to A them. I think it might be in the Alesis Philtre ModFX line. http://www.alesis.com/products/modfx/

Yes,

I second the NE570- it was actually designed for "communication channel" compression.

A good approximation of the aliasing noise could be made by using a PLL. If you use something like the CMOS 4046, you could "digitise" some of the signal using a schmitt inverter (use a six-pack of schmitt inverters, wire a resistor from in-to-out as a feedback path and you've got a lo-fi amplifier, followed by a standard schmitt inverter to create a digital-ready signal) By adjusting the feedback resistor you can then alter the level at which the schmitt gate is triggered. This "digitised" 1-bit signal then passes to the input of the phase-detector of the 4046, and the VCO will give out all kinds of rubbish! You can tune the VCO for different frequencies of artefacts, and mix it low into the original signal.

:thumb:

An 8-bit AD/DA system with variable clock rate and "disconnectable" or swappable data-lines is a more fancy way to go too...

Mark

Ah! -'Hashing" the 'sibilants is important as well.... good thinking... -I like Mark B's idea...

what about a simple analog sample and hold circuit with variclock
for aliasing efx?

steff

just eq the heck out of it. a pultec MEQ can give you some real nasalness if thats what you want.
or just use a megaphone like wumba jumba and be really uncool!
jeez, what ever happend to that pos band!
the flashed befor they hit the pan!

Acoustic solutions are out. I have a room in mind and leakage containment will be impossible. Things like the Cooper Time Cube are out of the question.

Also, things will need to be front-panel variable... look to the Lafont as an example of electronic-only solutions, but with variability. In film post-production, for a single scene the 'futz' device might be called upon to create police radios, a phone line and a megaphone, all in seperate passes, and all with differing 'signatures' in orter to prevent them starting to agglomerate into a 'mush'...

what about a simple analog sample and hold circuit with variclock

Click to expand...

I like it. Good thinking! -gets the aliasing, but saves the conversion process.

Keith

At some stage Neve mad a box for this sort of thing (it looks like 51 series console era) called a Teledistort. The studio I work at has one & it's really great... The front panel gives you control over a couple of filters and distortion. I don't know how good it is at simulating telephones, but it's really cool on drums and bass and has this distortion that goes all the way down rather than just making it kinda thin and fizzy... I'll have to look what's inside there one day :grin:

Justin

even more lo tech approach
mic the headphone output from the talkback mic

How about this, just add in a wah pedal circuit for the variable q filtering and a squelch.
Or this one:


Just make sure to shield everything so you don't get any real noise. :green:

$0.12 at Mouser

[quote author="buttachunk"]add this as the 2nd stage;

http://img.photobucket.com/albums/v251/buttachunk/bad.bmp

use germanium diodes in clippers like this, silicon is shit.
or use some germanium transistors connected as diodes /COLLECTOR+BASE/

And if you want real shit, use hard op amp clippers :-((((((((
xvlk

[quote author="xvlk"]....or use some germanium transistors connected as diodes /COLLECTOR+BASE/[/quote]
Or Mosfets :grin:

SSLTech
check your PMs...

here's a nice looking french futzer[/url]

Hmmf. -I have to have one of these in a few weeks time... I was thinking about DIY-ing one, but I think I'll jump all over that LaFont on eBay...

I can still make one of course... and I hope I can analyse teh laFont behaviour also...

Keith

> where to get the 1n5817 ??

Any 1A 20V Schottky Rectifier.

http://www.digikey.com/scripts/DkSearch/dksus.dll?PName?Name=1N5817RLOSCT-ND

Digi-Key Part Number 1N5817RLOSCT-ND
$0.32900
Manufacturer Part Number 1N5817RL
Quantity Available 3623

You need to buy 10 minimum, $3.29.

[quote author="SSLtech"]There's a procedure often called-for in film post, known as 'Futzing' a signal. Lafont makes a box known as a 'futz box'... take a look. -I think that most of the time when you hear phone audio, or walkie-talkie chatter in a movie, it's been through a device like this.[/quote]
Keith, do you know what is the list price of the LaFont LP-23? I couldn't find it anywhere...

regards, Jack

[quote author="AMZ-FX"]Keith, do you know what is the list price of the LaFont LP-23? I couldn't find it anywhere...[/quote]
I wrote to the US distributor a couple of days ago asking the price and have yet to get a response... not the best customer service in the world...

Yikes! I just checked and the one on Ebay went for $511...

regards, Jack