[sdiy] uLaw DACs in the modern era?

[Tom Wiltshire]

Yeah, recreate it is what I’m thinking. I don’t want to starting mining for unobtanium. A LUT+linear DAC is the obvious/simplest way for sure, but I was wondering about other more interesting (if probably less practical) possibilities like a non-standard resistor string or R/2R DAC (or combination thereof) or a exponential amplifier to convert a linear DACs step into a “expanded” range like a u-Law decoder.

Give it another fortnight and Alfa Rpar or Behringer will probably re-release the AM6070 anyway!! ;)
 

> On 19 May 2018, at 20:21, paula at synth.net wrote:
> 
> Tom,
> 
> Why go for a hard to find DAC? why not recreate it?
> 
> I "recreated" the uLaw using a 12 bit DAC and an 8 bit LUT. Then I was able to play back the LInn samples directly.. sounded pretty nice too IMHO. Ok, yes I should've used 13bits, but I didn't have any 14bit DACs to hand, but I did have 12 bit, so I went with that.
> 
> Paula
> 
> On 2018-05-19 11:08, Tom Wiltshire wrote:
>> Hi All,
>> Over the last couple of days I’ve been studying early drum machines,
>> mostly the Linn LM-1 and the Oberheim DMX.
>> Both of these machines use 8-bit memory, but manage a 12-bit dynamic
>> range by using a u-Law coding and outputting samples via the AM6070
>> u-Law DAC. Datasheet here if you’re interested:
>> http://synfo.nl/datasheets/AM6070.pdf
>> Does anything like this exist any longer? It seems to me that the
>> unusual DAC response is big part of the “thump” of these early
>> machines, since it has considerable distortion, but manages to spread
>> it to areas where it’s perceptually less noticeable (so higher level
>> signals have less detail than lower level signals).
>> Alternatively, would it be possible to build such a device? The
>> combination of a 4-bit value plus some gains and offsets doesn’t seem
>> impossible to manage, but I’d be interested to hear people’s ideas for
>> how you’d do it.
>> Thanks,
>> Tom
>> ==================
>>       Electric Druid
>> Synth & Stompbox DIY
>> ==================
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