Possible to use two asio interfaces concurrently?


So, guitar effects on the computer require super small buffer to keep latency low. But this is too short for compute hungry keyboard oriented synths. If it were possible to use two interfaces at once, then there could be a fast one for guitar and a slower one for keyboard.

I’m not making a feature request, but I am interested in how people have solved this problem.


Hi Kirk

I use a Focusrite 18i8 and can run several guitars, and synths at the same time with unnoticeable latency. My buffers are at 512. Everything works great. If you are going to use a guitar, or their effects, you will need a decent audio interface for sure. No need for 2 audio drivers. Same driver for everything.



I’m using focusrite Scarlett 18i-something-or-other… msi laptop with 6 core i7, 16g memory. My interface isn’t new, but should be reasonable. Setting buffers at 512 is unacceptable for guitar.

I’ve also noticed that some plugins really hammer C3 hard (falcon for some patches)… maybe there’s something else going on that’s screwing up the performance. Definitely tweaked it to fun flat out… hmm.


Are you using the Focusrite driver?


Hi Kirk,

I have less powerful laptop (i7 4 core 2.9 GHz) and run 128 samples and cover guitar and all key VST plugins with the one setting. But it sounds like you are shooting for 64 samples for the Guitar plugs and that’s a stretch for my system on the hungrier keyboard plugins. The solution IMO is a second laptop for the Guitar stuff with it’s own interface but I realize that is not a great solution. ASIO is picky and so Cantabile would have to be suspended to change the engine sample rate so there is no quick switch way I know of.



Of course. Reasonable question. I think it’s running at 44khz… could jack it up I suppose.


Like Dave, I am running on a much lessor laptop than you (and Dave). Two gigs ago, I was performing with a Bass, Acoustic Guitar, and Electric Guitar, running thru Focusrite, into C3, and mixing amp sims, fx, and Piano/Organ VSTs out without a hitch. I do not use “cpu hungry” synths live. Many discussions on this forum about not using the resource hogs:

I feel there is more going on there than just buffer settings. Try using the resource monitor inside C3 to detect what plugs are killing your system, and use lessor ones.

BTW…What guitar fx are you using?

Are you using a latency monitor?


I have no problem running my complete keyboard and guitar arsenal on my laptops with either RME Babyface or Zoom UAC-2 at 128 samples buffer. Feels good enough for my guitar playing…



It is possible to mix several audio interfaces into a single driver which can be used by Cantabile (that will be ASIO in this case).

They are even multiple solutions for this, including:

  • your hardware supports multi-interface drivers (usually two to four interfaces from the same manufacturer)
  • you can merge WDM drivers into a unique ASIO driver with ASIO4ALL
  • use a dedicated merging product such as Voicemeeter

In some cases, you may encounter clock synchronization challenges and, most of all, I’m not sure that you will be able to set different buffers as those solutions merge into one unified driver.

You mentioned you did not make a feature request but some DAW’s Audio Engine include the possibility to merge several WDM-KS streams (e.g. Sonar). Cantabile does not support WDM-KS but maybe that could be another option in the future ? :slight_smile:

So in your very specific case, it’s probably better to follow the advices from @dave_dore, @Corky and @Torsten and try to streamline on a unique interface first.


Yes. There are a host of multi-client audio interfaces. I used to run through the audio interface of my Soundcraft UI24R which was a multi client audio interface, running Ableton and C3 simultaneously. Now I run a Uphoria 1820 for Ableton and my Steinberg integrated audio interface in my Montage for C3. I can use two separate audio interfaces with separate buffer size for each individual program respectively. For example, C3 via Montage at a 128 buffer and Ableton via the Uphoria 1820 with a buffer size of 512. However…

Remember that USB uses the system CPU (as opposed to Firewire, for example). Therefore, it is not realistic to figure any additional processing power according to the CPU. Meaning, you will get clicks and pops overall that wouldn’t happen otherwise when running both, with one at a lower buffer size. Clicks and pops may not develop until a few songs into your show, nevertheless. How do I know? Well…personal experience. It was devastating.


I think the issue is, as was mentioned above, “cpu hogitis”… Falcon is the worst offender. however once I set the buffer size small enough to work nicely with guitar, there are quite a few synths that start to cause problems . The weird thing is that overall CPU loading is very low, even though Cantabile is running out of time in the timeslice. It would seem to me that if I’m outstripping the buffer, at least one core should be really humming but it is not.

I’ll also try it in another DAW to see if I have similar behavior there or if this is specific to C3.

I could also upgrade my interface to a USB3 or USB-C interface (once I can afford it) to get more raw bandwidth to/from the interface… though I doubt that’s the problem since that doesn’t change the fundamental timing, just the bandwidth to/from the box. I’m generally not running more than 6 audio streams ( 4 in, 2 out) so there should be plenty of bandwidth in general. I suppose when it gets tight, transmit time could be an issue.


What’s a latency monitor? I can run the C3 profiler and watch C3 data and see when it gets in trouble, if that’s what you mean.


Hey Kirk

Latency monitor is an app to run on your PC. It checks to see if a system running Windows is suitable for processing real-time audio and other tasks.
LatencyMon analyzes the possible causes of buffer underruns by measuring kernel timer latencies and reporting DPC and ISR execution times as well as hard page faults.
It will provide a comprehensible report and find the kernel modules and processes responsible for causing audio latencies which result in drop outs. It also provides the functionality of an ISR monitor, DPC monitor and a hard pagefault monitor.

I use the free version (home version)

There are other programs available, but this is the one I use.

BTW…I own nearly every amp sim available. One of my favorites is Bias. If I add just a few resident fx pedals or modules, my CPU spikes, which causes drop outs, distorted noise, and pops n crackles. Needless to say, I rarely get to use Bias. I moved on to CPU friendly sims until I purchase a more powerful computer with more bells and whistles.

Setting buffers at 512 is unacceptable for guitar.

Works just fine for me with my specific computer. It took a lot of experimenting, but that setting has been golden for guitars and keys the last 4 years. You have to experiment…I still do.


Checking out LatencyMon and this seems like a very good tool for figuring out if there are reasons other than simple lack of horsepower that are causing issues. I will do a careful study when I get time.

In the mean time, I think I’m going to go with outboard guitar gear for now and use C3 to drive patch changes, etc.

Thanks for the help.


To put this in perspective: a buffer of 512 samples means about 23 ms of round-trip latency just for the buffering - depending on the efficiency of your drivers, you may need to add a bit to that (let’s assume zero-latency plugins as well).

Given the time sound needs to travel on a stage, this roughly translates to having your amp 9-10 meters away from you (roughly 30-33 feet for the non-metrics) - of course you’ll have to add the distance to your next monitor speaker, unless you’re playing in-ear.

Wouldn’t be my favorite setup - feels a bit “slow”, unless you are used to playing church organ… But I guess you can get used to it.

Personally, I feel fine with 128 samples - translates to 2 meters (6.5 ft) distance to the amp - I definitely wouldn’t get closer to a screaming Marshall than that :wink:

Looks like a healthy distance on stage:

and I don’t believe Joe B. complains about latency…




I definitely had some latency issues when I first started with guitar sims. It must be the Focusrite driver, because there is no noticeable latency on either of my laptops when connected to the Focusrite. The 512 setting in C3 shows 11.2 ms, but I can get it down to 9ms, and there is no noticeable difference. I would surely know the difference after all the hours I struggled with latency early on. :persevere: I am not suggesting this for anyone, but it has cleared up a few latency problems for a few people in the past. Go figure.
BTW…Bonamassa doesn’t deal with latency, because he IS the latency! Kinda like the Chuck Norris thing. :grinning:


512 samples at 48 kHz is 11.4 ms; at 44.1 kHz, it should be about 11.6 ms - not sure where 11.2 comes from… But that’s only one way - for guitars, you’ll have to double the buffers - one for input, one for output, so that’s how I got to the 23 ms of latency for the round trip.

So that’s the minimum delay between picking a note and hearing the result at 512 samples. How a specific person reacts to that delay is a completely different story - it’s all about what you are used to and how sensitive your ear is to delays. If you’re Angus Young and usually play 10 meters away from your wall of cabinets, it’s no issue at all :wink:

Not sure how you “get it down to 9 ms” - do you mean by reducing buffer size?


Not sure if that’s a positive thing - being the latency. I have several people in mind whose role in life seems to be delaying meaningful signals :rofl::rofl::rofl: