KPA into focusrite 18i20, spdif clock set to spdif, sample size makes no difference.
When reamping with spdif, a delay is introduced, see image (the reamped tone is the middle track). "Constant latency" on KPA makes no difference.
I suppose i can use Reapers "Output manual offset" feature to get the tracks roughly aligned, but it doesn't feel very precise.
How can i fix this?
...and potentially the delay introduces phasing with the original signal. Yep. Constant Latency helps to keep this consistent but does not change the "overall delay" which comes from the latency introduced by the overall roundtrip of the signal out of the DAW into the Kemper and back into the DAW.
Two ways I solve it:
I don't understand why this is happening. This "pre offset" error began when Kemper introduced USB reamping. SPDIF and Analog reamping was working correctly before that USB update. After that USB update, I was running about 200ms ahead, so I had to do some re-routing in Reaper to correct it.
So far, I've done these two tutorials (Non-SPDIF). I will do one for SPDIF whenever I get an interface with that option. But you may find something useful in one of these for the time being.
It's been a while since I have reamped so I'm glad I wrote this stuff down. Make sure you read thru the comments since I had updated some stuff after the USB Update.
This "pre offset" error began when Kemper introduced USB reamping. SPDIF and Analog reamping was working correctly before that USB update.
Huh?
I've always had the offset when I have been reamping (from almost ten years ago)
"Constant latency" on KPA makes no difference.
I suppose i can use Reapers "Output manual offset" feature to get the tracks roughly aligned, but it doesn't feel very precise.
"Constant latency" is not supposed to fix the delay (your signal is sent through digital processing, which will always come with some latency) but it does make it easier to fix it.
Without it, the Kemper tries to minimize latency, which is good for live playing, but also means that latency depends on the effects used, and thus differs from rig to rig. With "Constant latency" on, the delay is always the same (I seem to remember it was 4.9 milliseconds), regardless of the current effects settings. That way, once you've figured out the correct offset, you can set it and forget it.
If you want to be very precise, use "Constant latency" and calculate the offset as follows (please correct me if I'm wrong here):
Your project's sampling frequency in kHz * 4.9 msFor instance, at 44.1 kHz:
44.100 kHz * 4.9 ms = 216 samplesOf course, your audio interface may introduce a bit of extra latency. I don't know Reaper very well, but many DAWs have a way to figure this out and compensate for it across the board.
In any case, once you've figured out a good offset value, it should remain the same as long as you stick with "Constant latency".
Huh?
I've always had the offset when I have been reamping (from almost ten years ago)
Mine lined up perfect until that update. ¯\_(ツ)_/¯.
Thanks - this was my current understanding exactly.
Ah OK. In that case, I would say that when you've found an offset that works, I wouldn't worry about absolute precision too much. Once you get in the ballpark of compensating for that 4.9 ms delay, you're out of the audible range of latency and a couple of samples earlier or later won't make a difference.
In most cases, the DI signal would only be reamped once, and would be muted afterwards, right? So you wouldn't run the risk of two copies derived from the same signal being out of phase to each other. If you are reamping the same DI twice (for a dual amp sound), just make sure to use "Constant latency" and offset them both by the same number of samples.
Mine lined up perfect until that update. ¯\_(ツ)_/¯.
Same for me. I did not have the problem with S/PDIF reamping before USB reamping was introduced. Latency was never even a thought: it just worked.
And USB reamping has never worked correctly for me: the results always have a ton of unusable noise, even with all latest updates applied.
I've started to wonder if there's an issue with my Kemper, or maybe the hardware is too old or something (despite that supposedly not mattering). I've recently had the need to do some reamping and am having a rough time figuring out how to reduce/eliminate the latency. I'm getting better results using the return input and analog out than I am for S/PDIF, but the latency is still too annoying to be useful.
I've started looking into the fiddly solutions, with using the DAW (Logic Pro latest on an M2 chip) to nudge tracks, but that's untenable when trying to audition profiles.
I've pretty much given up on reamping. I still record the DI signal with the guitar for a "Just in case" scenario, but find it just as easy and faster to retrack the guitar with another profile selection. I might return to reamping again if I get it to behave like it did before all this latency mess.
I've pretty much given up on reamping. I still record the DI signal with the guitar for a "Just in case" scenario, but find it just as easy and faster to retrack the guitar with another profile selection. I might return to reamping again if I get it to behave like it did before all this latency mess.
I rarely use reamping anyway but like you record a DI as a safety just in case.
However, as your workflow has relied on reamping so heavily in the past I presume you would prefer to have it working properly again. Have you logged a support request about this? Based on you tutorials to help others, you would seem to be well placed to work through the issues with support to help find and resolve the root of the problem.
I rarely use reamping anyway but like you record a DI as a safety just in case.
However, as your workflow has relied on reamping so heavily in the past I presume you would prefer to have it working properly again. Have you logged a support request about this? Based on you tutorials to help others, you would seem to be well placed to work through the issues with support to help find and resolve the root of the problem.
If I get any down time I probably will. I hate fixing something to get broke again. 
If I get any down time I probably will. I hate fixing something to get broke again.
Go on. Take one for the team. Make the world a better place 😁
Having this resolved would certainly be a delight. I’ve been recording band rehearsals for months, capturing Stack and DI tracks with the idea that, when time allows, I can use reamping to audition other profiles in context with the rest of the band. I just figured it would work like it used to. I sat down to do just that, with some new Tone Junkies liquid profiles, only to find that it’s “broken”.
In Logic, I used to setup the reamping and a recording loop for a section of a song, hit record and manually switch to different profiles (using Rig Manager) at the end of each loop, thus getting a new take for each profile. Then I’d use Logic’s comping tool to switch between takes to listen more carefully to how each profile sounds in the context of the song. Worked great.
Having this resolved would certainly be a delight. I’ve been recording band rehearsals for months, capturing Stack and DI tracks with the idea that, when time allows, I can use reamping to audition other profiles in context with the rest of the band. I just figured it would work like it used to. I sat down to do just that, with some new Tone Junkies liquid profiles, only to find that it’s “broken”.
In Logic, I used to setup the reamping and a recording loop for a section of a song, hit record and manually switch to different profiles (using Rig Manager) at the end of each loop, thus getting a new take for each profile. Then I’d use Logic’s comping tool to switch between takes to listen more carefully to how each profile sounds in the context of the song. Worked great.
Nice workflow idea 👍
