The lag/latency depends of the buffer settings in the OS - like any other audio I/O device. this is true for the Expert Sleeper cards ES-9/ ES-3 at least (2ms - 30 ms latency depending on various settings).
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I guessed that this could be due to settings, so the audio DC-coupled audio interface solution is not necessarily the faster one, as I guessed. Maybe I should have asked in this forum before I bought the gear, duh. I’ll get an ES-3 like you, a Polyend Poly or a Mutant Brain sometime in the future I guess. Any preference here? I don’t need many gate/trigger-channels, but more freely assignable CV-outs per channel.
Depends … I’m happy with the old ES-3, it connects using ADAT to a Behringer UMX1820 here. But i haven’t looked - maybe ADAT Lightpipe is finally dead now.
The must fun i think is to DIY a microcontroller with a good DAC, at least 16 bit, and some MUXes + sample and hold for analog outputs. With cvOSCcv, you can have a bunch of analog outputs for little money. (one can look in the schematic for a moog slimphatty to see how DAC/MUX/S&H can be done.)
Awesome! Didn’t know about this option, nice little rabbit hole. Going to peek into it.
By regaining trust in Expert Sleepers concerning lag, I looked up their product line again and found that the FH-2 should be the perfect solution for me and also helps shrinking my setup. I just found one on ebay in the U.K. for 265€ incl. shipping. Retailing 335€ in shops here in Germany. Thanks for the info about the lag. I can use my audio interface again for audio, too XD. Although these DIY projects are interesting, the ES FH-2 looks like a quick and solid solution for me now.
Just found a nice thread about the topic:
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I use an ES-8 (with ES-6 and ES-3 attached via light pipe) as an interface.
After a variety of approaches, this year I finally feel like I solved my sync issues with external gear using the same method that @ LarsBjerregaard suggests in there (wish I’d found that discussion before, full of good ideas!).
I find that, at 48khz samplerate (the highest that the ES-6 and ES-3 seem to easily support, unfortunately), at Block Size: 256, I need to do a 22 millisecond delay to have my internal clock in sync with the external clock.
After that everything’s great. Very nice to have everything in sync. I think, after trying lots of other less effective methods, this one works perfectly.
Oh, I run that clock signal out into an external Marbles, which syncs to it nicely, and also allows me to do different clock multiples or divisions externally if I want.
For additional ins and outs, I have a Presonus Quantum that I use, and turned them into an Aggregate Device in MacOS with the ES-8.
Here you can see the aggregate device, and the Expert Sleepers modules I’ve used to calibrate five each of the ES-8 inputs and outputs.
That’s my little breakout panel for the Quantum to the left of the expert sleepers devices.
All in all, it’s a bit of overkill, and sometimes the aggregate device gives me a headache that requires closing and opening VCV and toggling power on the ES-8 a few times, but it works so well that, other than that, I basically never need to redo all the work whenever I want to get a bunch of signals in and out of the computer.
And if I need to get extra low latency, for like, guitar input or something, I can use the quantum on its own at whatever samplerate I want.
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Nice breakout panel and all! Thanks for the screenshots. I like the Expert Sleepers module plugins in VCV.
When using my audio interface PreSonus Studio1824c in VCV Rack only I could dial down the buffer size and use the interface for both audio input from a Eurorack module (PLONK in this case) as well as trigger and pitch control it from one of its outputs with hardly any noticeable lag at all from keypress to ear. Problems showed up when I tried running VCV Rack as a plugin in FL Studio. Normally FLStudio uses the ASIO driver from PreSonus and VCV rack just communicates with the DAW it is hosted in. Now I needed to get signals out of the ‘nested’ VCV Rack and back in. Seems to me they don’t seem to like sharing the same driver of the audio interface or something. VCV Rack crashes sometimes and with it FL Studio 21, or I cant get audio in and out and the pulse of the ping is also heard in the speaker because it’s been routed by the DAW also and sent to OUT 1-2 … So I tried using the PreSonus interface only in VCV Rack for sending CV to a EuroRack module. The DAW in which VCV Rack was running as a VST plugin was using another audio device to receive the audio in the DAW, a MOTU M4 which is about as fast as the PreSonus one. Unfortunately, this solution had a lag of somewhere around 25ms - I wish it was shorter. I hope the FH-2 from Expert Sleepers will be faster, and also since it being a midi and not an audio device, I also expect less issues like the one I had with running VCV Rack in a DAW ( DAW and VCV Rack needing full access to the same audio interface - vs - CV being controlled through midi channels via ES FH-2, separated from audio ). I also tried running FL Studio as a plugin in a host module in VCV Rack which seemed to work ok, but I prefer the other way around.
I’ll let you know if the ES FH-2 is any faster once it’s in the mail.
I have had no noticible issues with my es-8 in 18 months of owning it. I send pitches and they seem calibrated fine without the use of the silent way plugin and needing to send audio back in and all that.
How about lag and did you run VCV rack also as a VST-plugin in a DAW, while sharing the ES-8 between VCV-Rack2 plugin and DAW?
no daw, just vcv stand alone.
what i’ve done as a test is a sequence in vcv. Pitch + gate go to Plaits and also to audio 16, connected to ES-8 and then patched to physical plaits.
Both plaits play the same sequence at the same time.
The ES-8 is definitely not hardware calibrated so you might just be exceptionally lucky that all? the outs on yours are accurate enough for pitch work without using the silent way modules. Or maybe you have terrible ears haha 
Huh, now I’m curious if I got lucky or if my ears suck. Either way, it’s close enough for me 
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Nice black panel on your Plaits!
I normally route my external gear back into VCV and use Hot Tuna to check the validity of my cv out. You might find it doesn’t track quite perfectly across the whole range of octaves. But if it does, that’s cool!
I did a thorough measurement for calibration of my ES-3 MK3 when I got it. It’s not terrible, but I agree, It does need some calculation on rack to get it spot on. My memory played a trick on me, when I wrote that they’re calibrated.
Anyhow, I did the measurements using a multimeter and google sheets LINEST() calculated the 4th order polynomial correction formula for each output.
Here’s a sheet with the values for each of the 8 output channels. Maybe someone can use the method.
Disclaimer: I’m not brilliant with maths.
It does sound pretty close! Bear in mind that any offset in voltage will be different for each output/input, and different across the range.
The problem with doing that is that the inputs are not hardware calibrated either - so you are getting one calibration ‘error’ on the way out, and another on the way back in. The only real way to check the validity of the CV out is to check the voltage externally.
You’re right that the offset is not constant across the voltage range so it’s not easy to compensate for in Rack without using something like Silent Way or Tunathor, which is why they exist of course.
Or you can always just use an external quantiser to take care of it…
Yep that’s the way to do it (and your maths looks much better than mine haha). It’s interesting that on average the diversion seems to be greatest at around +/- 8 or 9 volts which are unlikely to be used for pitch - the voltages closer to zero are more accurate.
Bottom line is if it sounds good then it probably is good - but at the same time it’s worth knowing about this as you don’t want to make the best melody ever only to find out later that it was all recorded slightly out of tune.
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If people are wanting worry free tuning on eurorack VCOs I can heartily recommend acquiring one of these. You can pretty much set and forget tuning for up to 4 sources and it also offers semitone/octave switching on each. Works a treat on external sources like Behringer Model D too.
The only disappointment is you can’t use it to automatically tune anything that is plucky as it seems to rely on a fairly consistent tone to do its thing.
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The problem with doing that is that the inputs are not hardware calibrated either - so you are getting one calibration ‘error’ on the way out, and another on the way back in. The only real way to check the validity of the CV out is to check the voltage externally.
I meant checking the AC tuning of the external VCO, but agreed, DC out and DC in is just going to give you two unknowns.
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Update on my Eurorack integration inside VCV Rack 2 Pro, running inside a DAW - now working perfectly without any noticable lag: Since I already had a Presonus studio1824c, I added an Expert Sleepers FH-2 with one FHX-8CV expansion for full range CVs instead of another audio device that were on my list like the ES-3, ES-8 or ES-9. I had issues with midi and or audio routing in FLstudio. I downloaded test versions of Ableton and now finally in Bitwig, everything works like a charm. So I am running VCV Rack as a plugin using the FH-2 for CV and triggers. VCV Rack receives MIDI from Bitwig, sends data to the FH-2. The audio channels of the interface can be individually made available or unavailable to Bitwig. I reserved some inputs of the audio device so they are available now directly to the VCV Rack plugin. I guess I’ll switch DAWs now… Maybe a user error tho, idk … If I ever want more audio rate signals in and out, I will most likely get an ES-3 or ES-8. The ES-9 only has SPDIF, not ADAT afaik.
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Btw, if you want to use pitch bending or glide on real Eurorack modules controlled by VCV Rack, use the MTS-ESP modules from ODDSound instead of the stock MIDI to CV and CV to MIDI modules. The stock ones didn’t produce smooth glides while the ones from ODDsound did.
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