<html><head><meta http-equiv="Content-Type" content="text/html charset=windows-1252"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">If you find another several dozen people who feel the same way, sure! ;)<div><br></div><div>Unless there's a lot of interest, I won't bother getting pre-programmed chips sorted out, but I've got no problem programming the odd one for anyone who asks nicely.<br><div><br></div><div>Tom</div><div><br></div><div><div><div><div>On 3 Apr 2017, at 16:43, Elain Klopke <<a href="mailto:functionofform@gmail.com">functionofform@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div dir="ltr">Hey Tom,<div><br></div><div>Does saying so here count as emailing you? Can we see these chips in your shop?</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Apr 3, 2017 at 10:37 AM, Tom Wiltshire <span dir="ltr"><<a href="mailto:tom@electricdruid.net" target="_blank">tom@electricdruid.net</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word">Thanks. It does have some high pass, but you might be right that more would be better. I've got it on the breadboard, so I'll give it a try.<div><br></div><div>It's an "adjust to taste" circuit really - you could do a lot of tweaking in terms of pop/crackle frequencies and tone.</div><div><br></div><div>Since I posted it here, I've written it up and put it online:</div><div><br></div><div><a href="http://electricdruid.net/adding-vintage-hiss-crackle-and-pop/" target="_blank">http://electricdruid.net/<wbr>adding-vintage-hiss-crackle-<wbr>and-pop/</a></div><span class="HOEnZb"><font color="#888888"><div><br></div><div>Tom</div></font></span><div><div class="h5"><br><div><div>On 3 Apr 2017, at 15:25, Amos <<a href="mailto:controlvoltage@gmail.com" target="_blank">controlvoltage@gmail.com</a>> wrote:</div><br class="m_2151845761886755534Apple-interchange-newline"><blockquote type="cite"><div dir="ltr">If I might offer a small aesthetic suggestion, I think the "crackle" channel might sound a lot better (er, more crackly) with a simple highpass filter on it. Very cool project. :)</div><div class="gmail_extra"><br><div class="gmail_quote">On Sun, Apr 2, 2017 at 12:25 PM, Tom Wiltshire <span dir="ltr"><<a href="mailto:tom@electricdruid.net" target="_blank">tom@electricdruid.net</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">I'm not sure how you'd synthesise the vinyl bump sound, but getting a periodic noise wouldn't be hard.<br>
<br>
If you used the same firmware in two H.C.P. chips and started them up at exactly the same moment, I suppose you might hear something, since they follow the same LFSR pattern. However, it would be easy to change the random seed in one of the chips at programming and then they'd follow completely different paths. The LFSR is 47-bit so doesn't repeat for 2^47 bits. It's running at 90KHz or so, and I calculate it a byte at a time, so that brings it down to 2^44, but it's still a vast number and a long repeat time - over 6 years. Set one at a different point in the pattern and they could well be 18 months apart.<br>
The other significant fact is that the chip uses the internal RC oscillator not any external crystal so even if they started in sync they won't stay that way for long. The two sets of sample outputs will be close to the same rate, but they'll drift in and out. That means there'll be no relationship between when the random crackles and pops occur on the two chips, even at the sub-millsecond level we're talking about.<br>
<span class="m_2151845761886755534HOEnZb"><font color="#888888"><br>
Tom<br>
</font></span><div class="m_2151845761886755534HOEnZb"><div class="m_2151845761886755534h5"><br>
<br>
On 2 Apr 2017, at 16:19, Mike HEQX <<a href="mailto:mike@heqx.com" target="_blank">mike@heqx.com</a>> wrote:<br>
<br>
> Tom,<br>
><br>
> That's a great idea, but my synths do this on their own LOL<br>
><br>
> If you wanted a cyclic bump like on vinyl what would you need to do? Could this thing drive a timer externally? If you had two of H.C.P working together would it create any type of convergence that might sound like something periodic?<br>
><br>
><br>
> Mike<br>
><br>
><br>
> On 4/1/2017 3:02 PM, Tom Wiltshire wrote:<br>
>> On 1 Apr 2017, at 18:53, Neil Johnson <<a href="mailto:neil.johnson71@gmail.com" target="_blank">neil.johnson71@gmail.com</a>> wrote:<br>
>><br>
>>> Hi Tom,<br>
>>><br>
>>>> Yeah, I was probably aiming for something about 30 years earlier than vinyl! But I know what you mean, that "old 78s" noise would be lovely. You could probably get closer with a bit of fine tuning of the circuit.<br>
>>>><br>
>>>> The mains hum…I dunno. I think it might be from recording the sample on the laptop with an unshielded cable. I should really have added a mains hum generator into the mix too, with a EU/US 50/60Hz selector!<br>
>>>><br>
>>>> And no, I definitely didn't think of using a dsPIC! A 16-bit processor to make the noise of old wax cylinders going round?! Are you crazy, man?!<br>
>>>> No, I used a simple *8* bit processor for a job like that!! I even stayed away from op-amps because that just seemed too modern for the job. Maybe a 741 would be allowable.<br>
>>>><br>
>>>> But you're dead right - it's one place the background hiss on the internal DAC might even be a benefit…<br>
>>> A few years ago a friend of mine (top-notch DSP engineer with an<br>
>>> interest in audio) developed a DSP system for recreating the sound of<br>
>>> 78s (I gather it was a homer project in between designing DSP code for<br>
>>> satellite comms). It had everything you could imagine - wow&flutter,<br>
>>> scratches, hiss, and so on. It was very convincing. Not sure where<br>
>>> it went, but suffice it to say that doing it right is a lot lot lot<br>
>>> harder than it seems...<br>
>>><br>
>>> Neil<br>
>> Hohoho! Yeah, I bet! You could definitely throw a pile of hardware/software at the problem.<br>
>><br>
>> I had several ideas for extending my basic version - lowpass filtering a noise output to give a wandering CV, and then sing that to control the volume of the other channels. Obviously this could be repeated several times for several channels…<br>
>> I also think that two channels is still sufficiently simple that your ear can differentiate them. If there were three or four or five, I think you'd get a noticeably richer effect.<br>
>> It might also be fun to build a version with knobs on. Each channel could have a"frequency/probability" control for the basic rate the events occur, a "decay" control for the envelope, and then "lowpass" and "high pass" filter knobs. Resonance would be a nice touch too. Several channels of that would enable you to mix up many flavours of noise.<br>
>><br>
>> There's a certain overlap with some other experiments I've done. One is a "granular oscillator" that I wrote as an alternative code load for Bruce Duncan's Modcan AHDBDSR envelope generator. That had raised-cosine-enveloped pitched grains, and you could alter the randomness of the pitch , start point, and the frequency of the grains in the grain cloud. It produced a range of textures from sputtery/spattery to rainy to sizzly.<br>
>> The other area that this borrows from is analog percussion synthesis. I borrowed Roland's VCA, but the basic idea of a blast of shaped noise with a tone filter is the guts of many a drum machine sound. This suggests other interesting directions, like trying alternative sources like the "Metal noise" combinations of CMOS oscillators used for cymbals, either XOR'd or not as the mood or your vintage inspiration take you.<br>
>><br>
>> So…yes, I can definitely understand how they might have spent quite a lot of time and DSP power on the problem!<br>
>><br>
>> Tom<br>
>><br>
>><br>
>><br>
>><br>
>><br>
>> ______________________________<wbr>_________________<br>
>> Synth-diy mailing list<br>
>> <a href="mailto:Synth-diy@synth-diy.org" target="_blank">Synth-diy@synth-diy.org</a><br>
>> <a href="http://synth-diy.org/mailman/listinfo/synth-diy" rel="noreferrer" target="_blank">http://synth-diy.org/mailman/l<wbr>istinfo/synth-diy</a><br>
><br>
<br>
<br>
______________________________<wbr>_________________<br>
Synth-diy mailing list<br>
<a href="mailto:Synth-diy@synth-diy.org" target="_blank">Synth-diy@synth-diy.org</a><br>
<a href="http://synth-diy.org/mailman/listinfo/synth-diy" rel="noreferrer" target="_blank">http://synth-diy.org/mailman/l<wbr>istinfo/synth-diy</a><br>
</div></div></blockquote></div><br></div>
</blockquote></div><br></div></div></div><br>______________________________<wbr>_________________<br>
Synth-diy mailing list<br>
<a href="mailto:Synth-diy@synth-diy.org">Synth-diy@synth-diy.org</a><br>
<a href="http://synth-diy.org/mailman/listinfo/synth-diy" rel="noreferrer" target="_blank">http://synth-diy.org/mailman/<wbr>listinfo/synth-diy</a><br>
<br></blockquote></div><br></div>
</blockquote></div><br></div></div></div></body></html>