<div dir="ltr">And different GLIDE RATES?!</div><div class="gmail_extra"><br><div class="gmail_quote">On Sun, Apr 30, 2017 at 5:32 PM, W. James Meagher <span dir="ltr"><<a href="mailto:w.james.meagher@gmail.com" target="_blank">w.james.meagher@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">Ooooohhh . . . please report back! </div><div class="HOEnZb"><div class="h5"><div class="gmail_extra"><br><div class="gmail_quote">On Sun, Apr 30, 2017 at 7:25 PM, Adam Inglis <span dir="ltr"><<a href="mailto:21pointy@tpg.com.au" target="_blank">21pointy@tpg.com.au</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Actually, I just remembered, these synths can operate in midi mono mode, so theoretically you could acheive detune by applying slightly different amounts of pitchbend in each of the 6 midi channels. I’ll have to give this a try!<br>
<div class="m_-5808022248938816161HOEnZb"><div class="m_-5808022248938816161h5"><br>
> On 1 May 2017, at 10:12 AM, Adam Inglis <<a href="mailto:21pointy@tpg.com.au" target="_blank">21pointy@tpg.com.au</a>> wrote:<br>
><br>
> Thanks for sharing this Russell.<br>
> I’ve always felt the Alpha Juno sound to be a bit too clean and sterile! I have the rack version. Unison mode is a bit disappointing - it thickens the sound, but doesn’t make it particularly rich or lush. The onboard chorus does help a little with this.<br>
><br>
> From your description, it doesn’t sound like there would be a way of introducing some slop or detune between the 6 DCOs?<br>
><br>
>> On 1 May 2017, at 8:58 AM, Russell McClellan <<a href="mailto:russell.mcclellan@gmail.com" target="_blank">russell.mcclellan@gmail.com</a>> wrote:<br>
>><br>
>> After reading the very interesting conversation regarding the new<br>
>> novation peak synthesizer, I was made curious by something Richie Burnett<br>
>> mentioned in that thread regarding the Alpha Juno oscillators. This<br>
>> led to some further investigation on my part and some may be<br>
>> interested in hearing about the results.<br>
>><br>
>> I had always (incorrectly, it turns out) thought that the alpha juno<br>
>> oscillators followed the same basic topology of the Juno 6, 60, and<br>
>> 106 synths - which, for those unfamiliar, is a complicated<br>
>> digital/analog hybrid; basically an analog ramp wave hard-synced to a<br>
>> digitally generated pulse.<br>
>><br>
>> However, it turns out that the Alpha Juno has a completely different<br>
>> design, with much less of an analog component. There is a custom<br>
>> "DCO" chip which has 6 independent digital oscillators. Each<br>
>> oscillator takes the 12MHz master clock and divides it down by a power<br>
>> of two based on the note being played. For the highest notes the<br>
>> effective clock is 6MHz, and for the lowest notes this seems to be<br>
>> divided by 2048 to form an effective sample rate of 3kHz. On each<br>
>> divided clock, an increment is added to a 16 bit accumulator (I'm sure<br>
>> the accumulator is at least 13 bits, but I'm not sure of the exact<br>
>> number of bits). Then, the top 8 bits of the accumulator are sent to<br>
>> a digital waveshaper, and then to what looks like an R-2R based DAC<br>
>> on-chip. This signal is then sent straight to the fully-analog<br>
>> filter.<br>
>><br>
>> In general, the output is "pretty" clean - certainly there's no frequency<br>
>> drift since it's based on the crystal. There are aliasing artifacts,<br>
>> but since the sampling rate is always so high compared to the note<br>
>> they are usually fairly quiet (I noticed some audible aliasing on the<br>
>> lowest notes). Since the DAC is only 8-bits, quantization noise is<br>
>> also an issue.<br>
>><br>
>> Anyways, I was really stunned to learn that the alpha juno had so much<br>
>> digital horsepower, and a bit surprised that I haven't seen this<br>
>> oscillator design before. Does anyone know of any synths with a<br>
>> similar approach? (Other than the new novation, which seems to run at<br>
>> a fixed sampling-rate, but is otherwise similar)<br>
>><br>
>> I think it would be a fun project to create a similar oscillator using<br>
>> an FPGA and an R-2R dac - perhaps with some additional capabilities<br>
>> like inter-oscillator FM and a sine lookup table shaper.<br>
>><br>
>> Thanks to Richie for mentioning this in the other thread and for<br>
>> helping me off-list to investigate this.<br>
>><br>
>> Thanks for your time,<br>
>> -Russell<br>
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