Sampling into inputs 1&2 vs 3&4

When sampling something into inputs 1&2 does it always go through the anti-aliasing filters even if you are sampling at 16bit 48khz or does it only go through the anti-aliasing filters if you are also sampling at 12bit 26khz?

I have asked a few people and no one seems to know the answer or they will even disagree with each other. Some say it does and using inputs 1&2 vs 3&4 changes the sound of samples even if both are set to16bit 48khz and another person says it doesn’t. I am thinking maybe there was a hardware or software revision and this changed?

So maybe Brad or a dev could settle this argument once and for all? Please :-).

the SP1200 anti-aliasing filters are enabled when and only when you record in 26kHz mode from LINE12/MIC/resample

there is still a difference between LINE12 vs LINE34 as only LINE12/MIC/internal resample pass through the gain stage amp and the gain trim pot


Awesome, thanks so much, just what I wanted to know!

There is most-definitely some type of Lowpass filter on inputs 1/2, when sampling at 16b/48k. The shape of it looks almost identical to the analog anti-alias filter on the original SP’s input to DAC.

To me, it sounds and looks like sampling at 26k goes through the original analog anti-alias filter from the SP’s schematic and a more modern digital anti-aliasing filter (possibly from the S2400’s sound engine chip) that prevents actual aliasing from happening. This is why the S2400 sounds dull compared to an SP, in my opinion.

If you switch between 1/2 and 3/4 with a hihat sound or some white noise, you can easily hear the difference in high end at 48k.

1 Like

i have never used anything other than 26k and 1+2 :rofl:

i don’t think of the input as lofi, just nice and weighty - i love the sound

maybe one day before death i get to 3+4 and 48k

1 Like

Great, so everyone is still not in agreement… Can Brad please clarify this ;-).

I will try with some white noise and see if I can tell a difference between inputs 1/2 and 3/4 I guess. The samples I tried before left me unsure lol.

I would tend to believe @av500 as he wrote the audio engine…


as above, av500 is the dude behind the engine and detailed the answer time ago…if anyone knows, :wink:

I think a diagram in the manual would help.
The sound of the S2400 still being one of its biggest sales point, I think it is something important to mention.
And it would help answer the question, as it is something that resurfaces from time to time :slight_smile:


Agreed! A diagram of the input signal path at least would be really awesome in the manual. I can understand why they wouldn’t want a straight up schematic but something slightly more simplified but informative would be cool!

1 Like

Best thing to do is just try the inputs and see what works best for whatever you’re sampling. Fortunately, we have so many options to run through.

I run my mono send from my mixer into a mult that sends the same signal to both inputs 1 and 3. That way I can easily switch between the inputs to decide. In my opinion, the gain stage amp dulls the high end a bit, which may be just what the user wants. I get the biggest sound overall (top & bottom) using inputs 3/4.

I’m pretty fortunate though, I’ve got SP’s that sound like SP’s. The S2400 smokes an SP in just about every way though.


well, of course there is an anti-aliasing filter when you record at 48kHz since that’s built into the actual AD converter. but it will limit the spectrum at ~22kHz, way above what anybody can hear. and or course what this filter won’t do is to fold back high frequency content around 13kHz as the original SP1200 did due to it’s “bad” anti-aliasing filter