KNOBS - VFE // Klein Bottle

[ula_sonicsmith]

Okay, but isn't this basically a really nicely featured PLL circuit? It seems like it's monophonic, which would suggest it's a PLL. That's what a PLL does. So is "ACO" just a marketing term?

Hi, let me address this right away

The ACO is NOT based on a PLL but rather a digitally-assisted analog FLL (frequency-locked loop). The circuit was awarded a patent this year and it will be published before the end of June so all the gory details will be known then. We have heard several claims that the ACO sounds "similar" to a PLL - perhaps that is true for very simple playing - but here are three main reasons why a PLL will never compete with the ACO:

1) To make PLL stable, the loop bandwidth (which is directly related to the tracking time) has to be maximum 1/10 the lowest reference frequency you will use. Let's say the lowest reference frequency is 25Hz. So the loop bandwidth can be 2.5Hz MAX. This means tracking time is on the order of 1/(2*pi*2.5) = 64ms and most likely longer. This is gonna be easy to hear, especially at high audio frequencies.
2) PLL depends on PHASE locking (hence PHASE-locked loop). This means when you have a large jump in reference frequency, you can get a huge accumulation of phase error and your PLL will SLEW. This means in most practical cases, the locking time is going to be WAY longer than the 64ms quoted above! If you tried to drive a PLL with alternating low and high frequencies, you would most certainly hear this. It can be used for pleasant musical effect but only if you want such an effect - and we have found that the majority of musicians who like our ACO-based solution love it precisely because it doesn't add any coloration or slewing or non-idealities to their playing, it duplicates EXACTLY their dynamics, gestures and agility.
3) The tracking range of our ACO is 25Hz to above 6kHz. You CAN design a PLL to track over such a wide range (with some variant of the 4046 chip for example), but if you do that chances are you'll have to make a lot of compromises in the design that will make the tracking time issues explained in (1) and (2) even worse.

Gabriel Marin's guitar playing in our NAMM 2017 booth is a good example of where our ACO exceeds the performance of what a PLL could do:
https://www.instagram.com/p/BPhDfmIjyDn/

We decided to publish this answer as a part of our FAQ too: http://sonicsmith.com/faq/#is-it-a-pll

Let me know if you have any more questions!

[cherler]

Well that's neat, any chance you'd ever sell the chips themselves?

[ula_sonicsmith]

Well that's neat, any chance you'd ever sell the chips themselves?

Selling the chips is always a possibility, it just has to make business sense for us.

[Jwar]

Well that's neat, any chance you'd ever sell the chips themselves?

Selling the chips is always a possibility, it just has to make business sense for us.

I wouldn't even know what to do with one. LOL!

I can say though after reading your answer, I'm back to being interested! I listed to that clip and holy shit! That thing tracks like I've never heard before without getting all muddy. That's insane.

This one and a few other higher end pedals are on my list.

[cherler]

Well that's neat, any chance you'd ever sell the chips themselves?

Selling the chips is always a possibility, it just has to make business sense for us.

Of course, and it sounds great where it is now, so no worries

[sonidero]

I'm late to the game but an Algal Bloom and some Shallow Water through dem Infinite Jets could prolly get me half way through my half life...

[yeatsvisitslincoln]

Okay, but isn't this basically a really nicely featured PLL circuit? It seems like it's monophonic, which would suggest it's a PLL. That's what a PLL does. So is "ACO" just a marketing term?

Hi, let me address this right away

The ACO is NOT based on a PLL but rather a digitally-assisted analog FLL (frequency-locked loop). The circuit was awarded a patent this year and it will be published before the end of June so all the gory details will be known then. We have heard several claims that the ACO sounds "similar" to a PLL - perhaps that is true for very simple playing - but here are three main reasons why a PLL will never compete with the ACO:

1) To make PLL stable, the loop bandwidth (which is directly related to the tracking time) has to be maximum 1/10 the lowest reference frequency you will use. Let's say the lowest reference frequency is 25Hz. So the loop bandwidth can be 2.5Hz MAX. This means tracking time is on the order of 1/(2*pi*2.5) = 64ms and most likely longer. This is gonna be easy to hear, especially at high audio frequencies.
2) PLL depends on PHASE locking (hence PHASE-locked loop). This means when you have a large jump in reference frequency, you can get a huge accumulation of phase error and your PLL will SLEW. This means in most practical cases, the locking time is going to be WAY longer than the 64ms quoted above! If you tried to drive a PLL with alternating low and high frequencies, you would most certainly hear this. It can be used for pleasant musical effect but only if you want such an effect - and we have found that the majority of musicians who like our ACO-based solution love it precisely because it doesn't add any coloration or slewing or non-idealities to their playing, it duplicates EXACTLY their dynamics, gestures and agility.
3) The tracking range of our ACO is 25Hz to above 6kHz. You CAN design a PLL to track over such a wide range (with some variant of the 4046 chip for example), but if you do that chances are you'll have to make a lot of compromises in the design that will make the tracking time issues explained in (1) and (2) even worse.

Gabriel Marin's guitar playing in our NAMM 2017 booth is a good example of where our ACO exceeds the performance of what a PLL could do:
https://www.instagram.com/p/BPhDfmIjyDn/

We decided to publish this answer as a part of our FAQ too: http://sonicsmith.com/faq/#is-it-a-pll

Let me know if you have any more questions!

Is a PLL not also by definition an FLL? You can't really be in phase if you don't have the right frequency. Pedantic... I know. Anyways, a PLL is also giving you at least two different signals through so that you can hear the phase difference, right? I'm assuming that there's no clean signal through on your pedal?

So on your FLL, can you say what you're using to track the frequency, then? Would it be possible to track over higher frequencies? (Obviously not for musical purposes at this point, but I can think of some other applications that would probably much more lucrative than a guitar pedal.)

Have you thought about making eurorack stuff? This kind of pitch tracking could be well received there.

Finally, is there anyway to make it polyphonic?

Thanks for getting on here and responding.

[cherler]

They do say digitally assisted so maybe there is some kind of FFT or FHT running in there.

[Jwar]

You guys have broken my goddamn brain with this nonsense. LOL. I don't even know what the fuck you're saying anymore.

[yeatsvisitslincoln]

You guys have broken my goddamn brain with this nonsense. LOL. I don't even know what the fuck you're saying anymore.

Since I'm sure you want an explanation...

FFT = Fast Fourier Transform, FHT = Fast Hartley Transform. Basically a nice quick way to calculate what frequencies are present in a signal. I'll let wikipedia do more talking if needed

[Derelict78]

Fuck, I got PLL gas again.
These last few pages pushed me into re reading all our glorious PLL threads and the GAS is stronger than ever.
I think I'm leaning towards the 4046-m.

[ula_sonicsmith]

Is a PLL not also by definition an FLL? You can't really be in phase if you don't have the right frequency. Pedantic... I know. Anyways, a PLL is also giving you at least two different signals through so that you can hear the phase difference, right? I'm assuming that there's no clean signal through on your pedal?

So on your FLL, can you say what you're using to track the frequency, then? Would it be possible to track over higher frequencies? (Obviously not for musical purposes at this point, but I can think of some other applications that would probably much more lucrative than a guitar pedal.)

Have you thought about making eurorack stuff? This kind of pitch tracking could be well received there.

Finally, is there anyway to make it polyphonic?

Thanks for getting on here and responding.

Good question! Yes, a PLL can also be considered an FLL because the output frequency is locked to the reference frequency. However, not all FLLs are PLLs. Our circuit, in particular, does not attempt to lock the phase of the output to the phase of the input because we believe this is not necessary for music applications, not to mention it causes difficulties in terms of stability and settling time as we already mentioned.

Our pedal does have a dry/wet mixer so you can mix the clean signal back in with the square/saw signal.

Our FLL is based on patented technology. The patent should be published within about two weeks so curious individuals will be able to read all the details. The technology has no upper limit on frequency so can be applicable to any clock generation situation. We are well aware of the various applications of clock generators in various fields.

We have received lots of requests to make Eurorack versions of our synths and you could say we are thinking seriously about it.

We've also thought about how to implement polyphony. Right now it would have to look something like hexaphonic pickups on a guitar going to six separate synths. We're planning to try this out although it's obviously not the solution for everyone.

[actual]

Eurorack would definitely be nice, so cosigned.
This might seem a bit irrelevant, but what are the dimensions of the the units? Can't seem to find em anywhere

[ula_sonicsmith]

Eurorack would definitely be nice, so cosigned.
This might seem a bit irrelevant, but what are the dimensions of the the units? Can't seem to find em anywhere

Yes, it seems that we completely forgot to put it on the website, so that's a very good point
ConVertor is 13cm x 13cm x 6cm
Squaver P1 is 19cm x 20cm x 6cm

[actual]

Thanks