# Interface latency: USB vs Thunderbolt ?



## Oneirokritikos (Feb 13, 2019)

Hey all,

For those who have tried both, is a Thunderbolt interface worth the extra cost for latency gains?
I have a Macbook Air from 2013, so USB3 and Thunderbolt 1 only, and am thinking of getting an interface. I am usually pretty sensitive to latency. Are recent TB3 interfaces even compatible with TB1? If not, I was eyeing an Audient ID4 or Focusrite 2i2.
Thanks for your advice!


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## Jeff (Feb 13, 2019)

Yes, a Thunderbolt interface (with a wel written driver) will have lower latency.


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## Descent (Feb 13, 2019)

Yes...anything is better than USB


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## Oneirokritikos (Feb 13, 2019)

Yes, I understand that TB has lower latency, but is the price difference worth it in your experience?


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## Descent (Feb 14, 2019)

Yep


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## Ed Fry (Feb 14, 2019)

The difference between Thunderbolt and modern USB interfaces is very slight and the change is not really to affect latency in a broad sense. The 2i2 2nd gen will almost definitely be absolutely fine for your needs.

The point of having the lower latency is to run higher buffer sizes to accomodate for more plugins and stability. 

As humans it is proven that below 10ms we're not really going to notice much difference between settnigs The latency between yourself and an amp whilst at rehearsal (lets say roughly 2-3m) is going to be 8.7ms between the speaker and your ear. 

Thunderbolt 3 has no latency benefit over Thunderbolt 1/2, just like USB 3.0 has no improvement in latency over USB 2.0. The difference is in bandwidth as opposed to speed of transfer.

Here are some comparisons between USB and Thunderbolt latency between our (Focusrite) Clarett TBT and Scarlett/Clarett USB interfaces.


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## Oneirokritikos (Feb 14, 2019)

Thank you Ed, very enlightening !


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## Winspear (Feb 14, 2019)

Indeed, it's more than fine and there are other things to consider. No way USB can be a problem for such a low number of channels. 
Audient would be a fantastic choice


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## vejichan (Feb 15, 2019)

Is the scarlet solo 2nd gen the same sound as the 2i2 2nd gen? no sound/quality differences?



Ed Fry said:


> The difference between Thunderbolt and modern USB interfaces is very slight and the change is not really to affect latency in a broad sense. The 2i2 2nd gen will almost definitely be absolutely fine for your needs.
> 
> The point of having the lower latency is to run higher buffer sizes to accomodate for more plugins and stability.
> 
> ...


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## Drew (Feb 15, 2019)

Ed Fry said:


> Thunderbolt 3 has no latency benefit over Thunderbolt 1/2, just like USB 3.0 has no improvement in latency over USB 2.0. The difference is in bandwidth as opposed to speed of transfer.


Yeah, I'm not an expert exactly, but especially on USB I undeerstand this is the major limitation, the amount of channels at a time you can send in either direction without having issues. If you're monitoring in stereo and only recording a couple tracks at a time, virtually anything will work - if you're monitoring four separate submixes while piping in 16 tracks of 24-bit 88.2khz audio, then you're going to need some serious bandwidth. 

But for most home studio applications USB3.0 should be able to keep up.


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## Elric (Feb 15, 2019)

While USB, theoretically, is capable of very low latency you will find that thunderbolt interfaces tend to be way lower latency in real life. This may very well be because thunderbolt hardware tends to be higher end and the manufacturer has put more R&D money into the overall package, or it is perhaps easier to create a low latency driver for a TBolt interface, or maybe there is some other reason I'm not familiar with that is limited USB interfaces from realizing all of their bandwidth potential; but honestly, if you want low latency Thunderbolt is the king regardless of theory.

I have a Presonus Quantum 2 (Thunderbolt 2) and that interface is so fast the computer's speed is the only weak link. I can go down to like 5.3ms round trip but if the computer was even faster it could go even lower. A guy that build dedicated DAWs on TGP said he was able to get it down into the 2ms range which is the same level of latency you are going to hit with dedicated processors like Helix and AxeFx.

The real question probably is, how much latency can you tolerate? There are lots of USB interfaces out there that perform well enough that latency is not a major issue for most people. I wanted real-time guitar processing so I was willing to spend a little more for the lowest latency possible. Not everyone needs that. 

USBC and Thunderbolt 3 may play out differently over the long term but this is sort of the current situation.


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## spudmunkey (Feb 15, 2019)

Elric said:


> USBC and Thunderbolt 3 may play out differently over the long term but this is sort of the current situation.



To be clear, I think you're confusing terms (or perhaps you know and just trying to simplify, but I think it's to a fault).

USB-C is merely the connector shape standard. Similar to how "m.2 SSD" doesn't give you enough information (as it could be either the same SATA as the 2.5" SSD drives, or it could be the much faster NVME), USB-C doesn't tell you what it's actually carrying....and it can even include Thunderbolt 3. Or DisplayPort. Or PCI-E. But again, that's also simplifying and ignores a couple of caveats.


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## Oneirokritikos (Feb 16, 2019)

Speaking of connector shapes, I know there are TB3 to TB2 adapters, but are there TB3->TB2 or TB2->TB1 solutions existing?


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## Andromalia (Feb 18, 2019)

I recoreded a shitton of things through USB and never really got that latency thing. Just make sure you can plug your monitors on the interface itself. That's true from cheap entry level focusrites up to the axe fx III.


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## Oneirokritikos (Feb 18, 2019)

I realized that I’m getting wildly different latency responses depending on what amp sim I use - with Mercuriall’s Reaxis, I have to go up to 256 samples to avoid cracks, but with Logic’s amps, i can get down to 32 easily... is this caused by my crappy interface (Apogee Jam 1st gen) or by my Mac’s CPU?


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## Metropolis (Feb 18, 2019)

Oneirokritikos said:


> I realized that I’m getting wildly different latency responses depending on what amp sim I use - with Mercuriall’s Reaxis, I have to go up to 256 samples to avoid cracks, but with Logic’s amps, i can get down to 32 easily... is this caused by my crappy interface (Apogee Jam 1st gen) or by my Mac’s CPU?



I can get to 64 samples with X4 oversampling using multiple instances of ReAxis, interface is Audient iD4 and W10 computer with i5-4570. That could be also depending on your DAW's settings if there is something specific in Logic which can be affected how VST's behave... or audiointerface's drivers don't behave how they should or aren't just capable. I've seen lot of complaints about how those kind of very small mobile interfaces work in certain situations.


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## will_shred (Feb 19, 2019)

I have a related question, @Ed Fry said that people won't notice the difference, but when I set up monitoring when i'm recording someone, I have heard several times that the latency is distracting to them. I've been using my setup for so long that I don't notice the latency, but enough people do that its become an issue. Would switching to thunderbolt make a difference in my case?


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