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 Forum index » DIY Hardware and Software » Circuit Bending
Bit-crushing reverb: The ART DR2A
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Christoffer



Joined: May 16, 2015
Posts: 16
Location: Denmark

PostPosted: Tue Apr 24, 2018 2:34 pm    Post subject:  Bit-crushing reverb: The ART DR2A
Subject description: Adding switches to the DAC of the DR2A to force individual bits to 0
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I got this idea after snooping around in my lovely ART DR2A 1985-vintage reverb. it has a dedicated dip 12-bit DAC that's unlatched - the AM6012.

It'd be interesting to add toggle switches to all the incoming data lines, toggling between normal and 0. if one started from the least significant bit, you'd basically 'round down' lowering resolution; hi-res sound with 4/8/..-bit reverb!

Here's a quick doodle of my planned implementation, see attached. I'm avoiding putting switches directly in-line with the DAC, as the long leads might mess up normal operation, one key feature being that this mod can be turned OFF completely, retaining the original sound.

I'm unclear as to exactly how the DAC works, on the datasheet it seems the 4 most significant bits are treated differently; different timing pulse, separate latch etc.

I'll try this when I get the time. I'm going to put it all on a board that plugs into the DAC socket, the DAC plugging into a socket on the new board, so i can undo my damage again.

Has anyone done anything similar? Anyone worked with this specific chip before?

thanks for your time,

Chris


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Christoffer



Joined: May 16, 2015
Posts: 16
Location: Denmark

PostPosted: Mon May 14, 2018 1:28 pm    Post subject: Reply with quote  Mark this post and the followings unread

So, this didn't attract as much attention as I'd hoped it would, but i think it deserves an epilog anyway;

I got a prototype wire-wrapped up and it did work as intended..ish. sound was terrible and response to each bit being flicked was at best erratic. the noise was unbearable, though, as i extended the entire DAC socket off-board to a wire-wrapped card. If this needs to be done, either have a DACrificial (hehe) AM6012 with pull-down resistors directly on the chip, and bend out/cut off the legs you don't want or design a small SMT chip carrier that keeps all distances VERY short.

Chris out

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Grumble



Joined: Nov 23, 2015
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PostPosted: Tue May 15, 2018 12:01 pm    Post subject: Reply with quote  Mark this post and the followings unread

By placing this and function between the address generator (processor?) you introduce a delay of about 10 to 15 nsec. Maybe too much?
Also be sure to place a capacitor of say 100nF between vcc and gnd as close to the 74LS08 as possible.

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