ComputerVoltageSources

Has anyone experimented with doing a 4 channel recorder looper?

I need one for an experiment.

Any comments before I try to program one?

The BasicAtom Pro has fairly limited RAM - only 2k if
the documentation on their site is right. That's going
to severely restrict the sample rate and/or duration
of the loops. You might be able to add external
storage to augment the on-board RAM, but that gets
complicated due to limited digital I/O.

Eric

--- Grant Richter <grichter@...> wrote:

> Has anyone experimented with doing a 4 channel
> recorder looper?
> 
> I need one for an experiment.
> 
> Any comments before I try to program one?
> 
> 


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On 10/26/07, Eric Brombaugh <ebrombaugh@...> wrote:
>
>
> The BasicAtom Pro has fairly limited RAM - only 2k if
>  the documentation on their site is right. That's going
>  to severely restrict the sample rate and/or duration
>  of the loops. You might be able to add external
>  storage to augment the on-board RAM, but that gets
>  complicated due to limited digital I/O.
>
>  Eric
>

Which basic atom (pro) particulary has this limit?

Samppa

This one:

http://www.basicmicro.com/Product.aspx?productID=114&CategoryID=2

Eric

--- Samppa Tolvanen <samppa.tolvanen@...> wrote:

> On 10/26/07, Eric Brombaugh <ebrombaugh@...>
> wrote:
> >
> >
> > The BasicAtom Pro has fairly limited RAM - only 2k
> if
> >  the documentation on their site is right. That's
> going
> >  to severely restrict the sample rate and/or
> duration
> >  of the loops. You might be able to add external
> >  storage to augment the on-board RAM, but that
> gets
> >  complicated due to limited digital I/O.
> >
> >  Eric
> >
> 
> Which basic atom (pro) particulary has this limit?
> 
> Samppa
> 


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No experience with that, but you can add limited RAM using the I2C bus,
256x8 SOICs or DIPs are available, up to eight addressable.  If you can
tolerate the write cycles (1 million program/erase cycles) and speed, you
can also add EEPROM on I2C, up to 8 chips x 512Kbits.

John Loffink
The Microtonal Synthesis Web Site
http://www.microtonal-synthesis.com
The Wavemakers Synthesizer Web Site
http://www.wavemakers-synth.com

> -----Original Message-----
> From: ComputerVoltageSources@yahoogroups.com
> [mailto:ComputerVoltageSources@yahoogroups.com] On Behalf Of Grant Richter
> Sent: Friday, October 26, 2007 8:32 AM
> To: ComputerVoltageSources@yahoogroups.com
> Subject: [ComputerVoltageSources] 4 Channel CV recorder looper?
> 
> Has anyone experimented with doing a 4 channel recorder looper?
> 
> I need one for an experiment.
> 
> Any comments before I try to program one?
> 
>

Not exactly sure what you mean by a looper.  It depends upon whether 
your CV is continuously variable or steps between discrete values.

I did an arpeggiator where I would monitor the CV for a change since 
it was hard to detect a trigger (I since use edge interrupts).  With a 
real-time clock, you just timestamp the CV value change. Ram use is 
minimal since you just have a record of the changes.  Worked great.

I did something similar for a CV delay which can implement some really 
long delays.  Sample the CV transitions and clock them out at a 
variable delay later.

Dave

--- In ComputerVoltageSources@yahoogroups.com, "Grant Richter" 
<grichter@...> wrote:

>
> Has anyone experimented with doing a 4 channel recorder looper?
> 
> I need one for an experiment.
> 
> Any comments before I try to program one?
>

I always thought it would be fun to have a 4 channel looper that could loop the VCO CV, 
wave CV, filter CV and VCA CV. That way when you play a neat little lick, you could hit 
"loop" and then have you hands free to twiddle the knobs.

For Tangerine Dream kind of days (they did a lot of knob twiddling over sequences that 
sound real good).

The old ARP 1603 would do 4 bars of 4/4 (16) so only 16 to 32 actual notes need to be 
stored. I saw pictures of them using 1603s and 2600s at some point.

Just a thought.

--- In ComputerVoltageSources@yahoogroups.com, "djbrow54" <davebr@...> wrote:

>
> Not exactly sure what you mean by a looper.  It depends upon whether 
> your CV is continuously variable or steps between discrete values.
> 
> I did an arpeggiator where I would monitor the CV for a change since 
> it was hard to detect a trigger (I since use edge interrupts).  With a 
> real-time clock, you just timestamp the CV value change. Ram use is 
> minimal since you just have a record of the changes.  Worked great.
> 
> I did something similar for a CV delay which can implement some really 
> long delays.  Sample the CV transitions and clock them out at a 
> variable delay later.
> 
> Dave
> 
> --- In ComputerVoltageSources@yahoogroups.com, "Grant Richter" 
> <grichter@> wrote:
> >
> > Has anyone experimented with doing a 4 channel recorder looper?
> > 
> > I need one for an experiment.
> > 
> > Any comments before I try to program one?
> >
>

It wouldn't be that hard to do.  It's been 2.5 years since I wrote my 
trig-gate-cv delay but the basic concept is I have three 128 event 
buffers.  The first is used to timestamp an event (trigger high, 
trigger low, etc.). The second buffer is to record a trigger or gate 
transition (high or low). The third buffer is to record a CV value.  
When I detect a trigger, I timestamp it with a 'delay' factor and put 
the timestamp, trigger, gate, and CV in the buffer.  The buffer is 
circular and at 128 events long it never fills up.

Timer interrupts advance the timebase. When the timebase matches the 
next timestamp in the buffer, I output the event.  It would be pretty 
easy to modify the concept to continue to record until some other 
event (e.g. stop) and then simply playback the buffer. At the end of 
the buffer you'd simply reset the timebase. 

Note that this only works for discrete events such as a keyboard. It 
won't record a continuously changing CV such as with a pitchbend.

Four channels would be tough since you'd need 12 outputs.  A CVS with 
an optional digial I2C expander could do it, though.

Maybe someday when I'm bored I'll give it a try.

Dave


--- In ComputerVoltageSources@yahoogroups.com, "Grant Richter" 
<grichter@...> wrote:
>
> I always thought it would be fun to have a 4 channel looper that 
could loop the VCO CV, 
> wave CV, filter CV and VCA CV. That way when you play a neat little 
lick, you could hit 
> "loop" and then have you hands free to twiddle the knobs.
> 
> For Tangerine Dream kind of days (they did a lot of knob twiddling 
over sequences that 
> sound real good).
> 
> The old ARP 1603 would do 4 bars of 4/4 (16) so only 16 to 32 actual 
notes need to be 
> stored. I saw pictures of them using 1603s and 2600s at some point.
> 
> Just a thought.
> 
> --- In ComputerVoltageSources@yahoogroups.com, "djbrow54" <davebr@> 
wrote:
> >
> > Not exactly sure what you mean by a looper.  It depends upon 
whether 
> > your CV is continuously variable or steps between discrete values.
> > 
> > I did an arpeggiator where I would monitor the CV for a change 
since 
> > it was hard to detect a trigger (I since use edge interrupts).  
With a 
> > real-time clock, you just timestamp the CV value change. Ram use 
is 
> > minimal since you just have a record of the changes.  Worked 
great.
> > 
> > I did something similar for a CV delay which can implement some 
really 

> > long delays.  Sample the CV transitions and clock them out at a 
> > variable delay later.
> > 
> > Dave
> > 
> > --- In ComputerVoltageSources@yahoogroups.com, "Grant Richter" 
> > <grichter@> wrote:
> > >
> > > Has anyone experimented with doing a 4 channel recorder looper?
> > > 
> > > I need one for an experiment.
> > > 
> > > Any comments before I try to program one?
> > >
> >
>

At 11:25 PM 10/31/2007, you wrote:

>It wouldn't be that hard to do. It's been 2.5 years since I wrote my
>trig-gate-cv delay but the basic concept is I have three 128 event
>buffers. The first is used to timestamp an event (trigger high,
>trigger low, etc.). The second buffer is to record a trigger or gate
>transition (high or low). The third buffer is to record a CV value.
>When I detect a trigger, I timestamp it with a 'delay' factor and put
>the timestamp, trigger, gate, and CV in the buffer. The buffer is
>circular and at 128 events long it never fills up.
Check out the Modcan CV Recorder 57
It samples low frequency analogue input and stores the values to SRAM.
When the 512K x 8 ram is full it plays it back in a loop.
Loop start and end points can be set with panel controls and record 
/playback speed is also continuously variable.
I can store about 4.3 seconds of 4 channels at a sample rate of 20kHz.
A 12bit quad DAC is used for the output. Sampling is done using the 
dsPIC analogue inputs.
I pack 2 12bit values into three 8bit memory locations to extend ram.

Multiple samples strung together can be done by setting the loop 
start/end and it will only record between these limits.
All four channels can be recorded independently.
It was pretty easy to do as it is just a data logger but it does take 
a fair bit of expensive hardware.
64 pin dsPIC, Quad 12bitDAC, SRAM numerous rail to rail op-amps etc. 
and uses about 180mA of current.
It is the most awesome joystick movement recorder though.

Bruce