building a REAL bitcrusher/aliaser

[caress]

i'm interested to see if anyone has experimented at all with using an adc/dac to create a real bitcrusher/aliaser...?  i'm looking to start experimenting with this idea, but i'm stumped as to which adc/dac to start with.  there are so many including multiple inputs, channels, etc etc.  does anyone know of a simple integrated one or two channel adc/dac for use in a project like this?

check this out to see what i'm thinking about...http://www.theharvestman.org/2012.htm  --> see the video!  pretty amazing stuff.

[gez]

I haven't visited it in a while, but there might be some info about this in the DIGITAL area of this forum?

[caress]

i'll probably post this there or have it moved if there are few replies...but, i figured it would be less visible in the digital section.

[gez]

i'll probably post this there or have it moved if there are few replies...but, i figured it would be less visible in the digital section.

Yeah, it probably gets a little dusty in there from time-to-time! 

[para]

don't forget about this


http://experimentalistsanonymous.com/diy/Schematics/Fuzz%20and%20Fuzzy%20Noisemakers/Digital%20fuzz.bmp


futurelec carries the chips but they are kind of expensive. you might consider hitting TI.com and analog.com and signing up for samples and then dig around and see if there are any good simple single or dual channel models to work with. i have grabbed a few over the last year or two but i just don't have the time to work with them, so they sit. i'd love to hear about any progress you might have.

best,

steven

[Dragonfly]

http://electro-music.com/forum/topic-11369-25.html

http://electro-music.com/forum/post-90435.html#90435

[caress]

para - i forgot all about that one!  i'll have to check it out a bit more...but, if i'm reading it correctly then A-H corresponds to each bit.  hmmm...seems somewhat straightforward.  good to see you here!   

dragonfly - thanks for those links, although i was just checking out those exact threads earlier today!  i've built the bugbrand rate reducer and it's pretty awesome, but it's not really converting a>d>a like a real bitcrusher does.  i love the reduced bitrate sound in combination with sample rate reduction...reeeeeal lofi

i'm definitely going to try the digifuzz.  i have an order i need to make so i'll just add the chips on. 

also, sir h c has a version of this using an eeprom, but i'm not exactly sure what role that plays in the circuit...any ideas?

[para]

i've been here a long long time i just never have a reason to post. pretty active place

yeah if you go with old chips like that then you can switch them in and out but if you use a new one they are usually clock based 

maybe paul perry will stop by and explain his aliaser? i'm guessing PIC?


steven

[Paul Perry (Frostwave)]

The main question is this: micro or not?

If you want to avoid using a micro, it's not hard to get 8 bit A to D and D to A chips (although they are drying up). But it is difficult and/or expensive to go much further. For a severe effect, 8 bits is enough, though.

On the micro side, all the D/A & A/D chips are going to  be serial in & out. So that's going to help layout but on the downside, most of them are surface mount  If you can do PIC or ATMEL micro stuff, then obviously that's the way to go. But a discrete approach gives more scope for doing weird shit - in my opinion, anyway.

[caress]

i definitely plan on going discrete.  really, i don't have that much knowledge and i'm mostly interested in messing about.  we'll see if that gets me anywhere interesting...   8 bits and lower is exactly what i need.  it's not intended to be hifi!

[para]

hey Paul if i were to start getting into programming micros where would i start looking?


steven

[Paul Perry (Frostwave)]

hey Paul if i were to start getting into programming micros where would i start looking?

I have no idea. I looked for a programmer instead.
The keenest micro guys are the robot DIY fans.

[darron]

http://www.diystompboxes.com/smfforum/index.php?topic=41647.0

[caress]

i've been on that thread too!   

everyone's got layouts schems whatever for sample rate reducers, but no one has really gone the actual bitcrushing route beyond that one "digital fuzz" schem... i was able to find the dac but i'm having trouble getting the adc (which should be an adc0804, not 0808 like it says...)

[caress]

well, i found the adc and dac at futurlec for only about $6 for the pair.  not bad...hopefully i'll get to start this project asap so i can post some results...

[Sir H C]

You will also need a dual op-amp for the thing to work.  One for the input to gain up the guitar signal to work well with the voltage range the ADC wants to see, and one for the output as the DAC is a current output so you need a trans-impedance amplifier to convert that current into a voltage.  My circuit shows that, and you can ignore the EPROM and just use switches there and do the basic bit crusher.  Really cool is the clock speed control as you can get some super evil aliasing with the slowing of the clock.

[caress]

got all the chips super super cheap after some thrifty searching of multiple sites!     5 of each (including the eproms) for the same price as 1 of each...next weeeek
thanks a lot sir h c!

[Sir H C]

Enjoy, you need to use a good power supply for everything as batteries just don't have the kick for those old chips.  But there are a lot of really evil sounds in there.

Any questions pm or e-mail me (address can be given via PM).

[Processaurus]

Sometime I'd like to try a string of comparators setup so you can adjust the threshold of each, to get the different "bits" to come in by how hard you play.  Then resistively sum the comparators to get the output. The  alesis bitrman has a nice bit crush on there, but the threshold between the bits seems a bit far when you get down to the super distorted territory.

[Sir H C]

The problem with comparators is that you can not get much resolution beyond 4 bits (16 levels).  You start running into the offsets of the comparators and the like.  With 8 bit ADCs so cheap, they are easy to use, clock included, and you can do some pretty fun things with aliasing.