Wish: More Pedals with Digital Audio I/O

[grafter.puzzler]

With the increasing popularity of digital pedals for live music production, the issue of latency is always a concern.

While many products today offer incredibly low latency that's virtually imperceptible, there is still the issue of chaining multiple digital products in signal path and compounding latency.

The Fractal VP4 is a new pedal product that is meant to integrate with both analog and digital gear as it offers not only analog audio I/O but digital via SPDIF. This avoids redundant A/D and D/A conversations and keeps latency to a minimum.

I think more products in the guitar pedal space should follow Fractal's lead here. For example, imagine a digital wireless unit with digital audio out. Assuming the product was high enough quality, that could be the first only place where you'd need A/D conversion and run digital out into all your other gear with digital I/O.

 

[EOengineer]

Agreed - it sucks to pay that latency tax.

 

[laxu]

The AD/DA conversion is not a major source of latency though. There's just pedals on the market with a bit shit latency for what they are.

For digital I/O you might need sample rate conversion or pedal makers agreeing on a standard sample rate. Which they won't.

 

[AFKAEjay(retired)]

In my mind: overcoming the challenge of syncing digital clocks may be a too big of a hurdle to overcome looking at the benifits digital connectivity brings.

 

[ragingplatypi]

I’d rather pay less money because latency has never been a thing I actually perceived post-2019.

 

[fret gunk]

I’d rather pay less money because latency has never been a thing I actually perceived post-2019.

 

[FractalAudio]

The AD/DA conversion is not a major source of latency though.

Yes, it is. For example, the latest ESS CODEC has about 70 samples of total latency. At 48 KHz sample rate this is nearly 1.5 ms.

If you use minimum-phase filtering in the CODEC you can reduce this but now your transients will "ring".

If you cascade several pedals together using analog I/O you'll have nearly 4.5 ms of converter latency (in addition to processing latency). If, however, you use digital I/O your maximum latency due to conversion will only be 1.5 ms.

 

[FractalAudio]

I should add that years ago I proposed a system with a "Analog Hub". You plugged your guitar into the hub which did the A/D and D/A conversion.

Pedals with digital I/O would then plug into the hub using SPDIF. The hub would also act as a switcher.

This idea ensured that there would only be one A/D and one D/A.

I couldn't get any of the pedal companies to get on-board. I envisioned a consortium of manufacturers with a "Digital Pedal Manufacturer's Group". This would also reduce the cost of the pedals because you could build digital-only pedals and save on the cost of the converters (which can be a significant portion of the total BOM).

 

[EOengineer]

TLDR - shit adds up.

 

[laxu]

Yes, it is. For example, the latest ESS CODEC has about 70 samples of total latency. At 48 KHz sample rate this is nearly 1.5 ms.

If you use minimum-phase filtering in the CODEC you can reduce this but now your transients will "ring".

If you cascade several pedals together using analog I/O you'll have nearly 4.5 ms of converter latency (in addition to processing latency). If, however, you use digital I/O your maximum latency due to conversion will only be 1.5 ms.

Is there a major difference between codecs in this regard? I think I've seen even you say that on Fractal gear the AD/DA conversion isn't a big deal in latency, but maybe in this discussion that's out of context and you mean "compared to all the digital processing".

 

[laxu]

I couldn't get any of the pedal companies to get on-board. I envisioned a consortium of manufacturers with a "Digital Pedal Manufacturer's Group". This would also reduce the cost of the pedals because you could build digital-only pedals and save on the cost of the converters (which can be a significant portion of the total BOM).

What kind of responses did you get? Were they simply not interested because they were afraid their userbase would not understand that you need a box like that for the pedals to work?

With the way things are, you can treat analog and digital pedals pretty much the same in terms of connections.

How would that sort of thing work when you might want to mix analog and digital pedals? E.g analog boost -> digital delay -> analog drive -> digital reverb or something?

 

[EOengineer]

The AD/DA conversion is not a major source of latency though. There's just pedals on the market with a bit shit latency for what they are.

For digital I/O you might need sample rate conversion or pedal makers agreeing on a standard sample rate. Which they won't.

I was speaking more to the cumulative effect of a chain of devices. Not a problem everyone has of course, but some of these monster pedalboards I see have like 5-6 digital pedals on them.

With analog dry-through becoming more common the latency thing might be less of a concern though. I still prefer to reduce the number of conversion stages if I can though.

 

[laxu]

I was speaking more to the cumulative effect of a chain of devices. Not a problem everyone has of course, but some of these monster pedalboards I see have like 5-6 digital pedals on them.

With analog dry-through becoming more common the latency thing might be less of a concern though. I still prefer to reduce the number of conversion stages if I can though.

At least with my 5 Strymons (3 non-ADT, 2 ADT) it's generally been a non-issue. Even with all of them on at the same time I just can't feel it. Afaik they are all ~1ms per pedal.

 

[EOengineer]

At least with my 5 Strymons (3 non-ADT, 2 ADT) it's generally been a non-issue. Even with all of them on at the same time I just can't feel it. Afaik they are all ~1ms per pedal.

Yeah I think that's probably a fairly typical case and most people wouldn't be impacted by that, especially if they are playing and monitoring through a traditional amp in the room.

Where I've run into issues is in a direct setup I use with the HXFX, Tonex Pedal, and then a couple other digital effects which hit a digital monitoring setup that adds 1-2 ms on its own. It doesn't take much for that to get to a point where it starts to feel a little disconnected. I wouldn't expect every digital pedal to provide digital IO, but it would be neat if the HXFX and Tonex could connect digitally.

 

[grafter.puzzler]

At least with my 5 Strymons (3 non-ADT, 2 ADT) it's generally been a non-issue. Even with all of them on at the same time I just can't feel it. Afaik they are all ~1ms per pedal.

Are these delay and reverb pedals? It’s a little different in that case because strymon makes use of analog dry-through. This makes sense for time based wet effects that go on top of a dry signal. For things like amp modeling and other gain/filter based effects, analog dry through doesn’t work

 

[grafter.puzzler]

I should add that years ago I proposed a system with a "Analog Hub". You plugged your guitar into the hub which did the A/D and D/A conversion.

Pedals with digital I/O would then plug into the hub using SPDIF. The hub would also act as a switcher.

This idea ensured that there would only be one A/D and one D/A.

I couldn't get any of the pedal companies to get on-board. I envisioned a consortium of manufacturers with a "Digital Pedal Manufacturer's Group". This would also reduce the cost of the pedals because you could build digital-only pedals and save on the cost of the converters (which can be a significant portion of the total BOM).

This is what I’m talking about! Just a general hub for A/D. I thought a wireless unit would work as a good hub

 

[laxu]

Yeah I think that's probably a fairly typical case and most people wouldn't be impacted by that, especially if they are playing and monitoring through a traditional amp in the room.

Where I've run into issues is in a direct setup I use with the HXFX, Tonex Pedal, and then a couple other digital effects which hit a digital monitoring setup that adds 1-2 ms on its own. It doesn't take much for that to get to a point where it starts to feel a little disconnected. I wouldn't expect every digital pedal to provide digital IO, but it would be neat if the HXFX and Tonex could connect digitally.

Yeah and if you use the fx loops on the HXFX those will add extra latency.

 

[laxu]

Are these delay and reverb pedals? It’s a little different in that case because strymon makes use of analog dry-through. This makes sense for time based wet effects that go on top of a dry signal. For things like amp modeling and other gain/filter based effects, analog dry through doesn’t work

Only the two ADT (analog dry-through) capable pedals. The rest would put me at just 3ms which is nothing.

Would be far worse if each had higher latency. E.g 2ms each would give you 6ms which is easy to feel.

 

[grafter.puzzler]

Only the two ADT (analog dry-through) capable pedals. The rest would put me at just 3ms which is nothing.

Would be far worse if each had higher latency. E.g 2ms each would give you 6ms which is easy to feel.

Oh whoops, I didn’t realize what ADT meant.

Still, there could be potentially other places where you accumulate latency. In ears, digital consoles, interfaces, etc. I think it’d be a good idea if music gear makers got on board with @FractalAudio ‘s idea of central hub for AD conversion

 

[[Nathan]]

I couldn't get any of the pedal companies to get on-board.

They cant even agree on top or side mounted inputs. The concept sounds amazing and would be super handy to the user, shame. Glad to see In/Out SPDIF on the VP4 and Stadium. Would be good to see it on all "quality" units moving forward (from all companies), not just top tier flagships.