Adjustable input level for SPDIF reamping

    Hi there,


    several users who do digital reamping via SPDIF reported that the SPDIF input signal lost a few db when being fed into the KPA. This is not a bug within the KPA but something that is related the bus routing of several DAWs and how they route signals to the outputs of audio interfaces.


    It would be nice to have a control in the input section called something like "SPDIF input sense", where you could adjust the input level to compensate for too weak or too hot signals.

    It happens, even if the routing is correct. There may be many causes for this, like the internal audio routings of an audio interface or a DAW software that preserves some bits as headroom.


    Also, you have to consider that the clean sense value determines the level of the dry guitar signal that is transported via SPDIF. With very hot passive pickups you would set clean sense to low settings, which will result in a softer dry signal. Even if you set everything to unity gain in you audio path, the returning SPDIF level might not have as much gain as if you would have played it directly with your guitar.


    So, as long as clean sense setting influences the dry recording level, a correction for the reamping level totally makes sense...

    +1 A manly suggestion... Spdif input sense. Like it. :thumbup:
    By the way, I've had some problems with the output levels of the Spdif not being very loud. Only ever seems to come halfway up my DAW level meters.
    Could do with being a few Dbs hotter - wonder if anyone else found this?

    Suhr Classic Pro, Fender deluxe Strat & Baja Tele, Gibson ES335, Ibanez S Prestige 2170FW, Eastman AR371CE, Variax JTV > KPA > Patch bay inc. Strymons (Mobius, Timeline, Blue Sky), H9 Max, TC Triple Delay, & POD HD500 > Adam A7Xs

    Quote from tylerhb

    It happens, even if the routing is correct. There may be many causes for this, like the internal audio routings of an audio interface or a DAW software that preserves some bits as headroom.


    Also, you have to consider that the clean sense value determines the level of the dry guitar signal that is transported via SPDIF. With very hot passive pickups you would set clean sense to low settings, which will result in a softer dry signal. Even if you set everything to unity gain in you audio path, the returning SPDIF level might not have as much gain as if you would have played it directly with your guitar.


    So, as long as clean sense setting influences the dry recording level, a correction for the reamping level totally makes sense...


    Still, isn't the level recorded the excact same level the Kemper want to see to sound the same? Unless something is attenuated in the DAW, I would think so. Routings in the DAW should not cause this, and no grown up DAW would attenuate to "preserve" bits....only thing I can think of is pan law. Why can't you just adjust in the DAW if needed?

    I would strongly vote for adjusting the volume in the DAW, before it is converted to SPDIF for an optimum S/N ratio.
    SPDIF is 24 bit, which is not too much when amplified by a high gain profile.
    The volume controls in the DAW are lossless as they work with floating point.

    Ok. I need to go into detail a little further. Imagine you set your whole audio path within the DAW and the audio interface mixer to 0 db unity gain. You would exactly get the right input level IF the recorded dry signal would be normalized to 0 db within the audio track of the DAW. However since the recording level of the dry track depends on the clean sense setting, you would need to either adjust the clean sense for every recording with a different guitar to just below the signal clipping point or you would need to normalize each recording or manually adjust the dry track faders. Since setting this for every recording is rather uncomfortable you would probably leave the clean sense and thus the recording level to a "safe" setting which will not clip but will also not use the optimal s/n ratio. So the whole story is about lazyness, not willing to adjust levels for each recording session. Using "safe" settings simply results in the loss of some signal level at the SPDIF input stage.


    In my own setup i use a digital mixer between the SPDIF out of my interface and the KPA digital in. This way it´s very easy to compensate by just pushing the signal to nearly 0 db for each reamping session by raising the fader level to over 0 db. Other users who do not have a mixer like this and just use an audio interface which cannot set the SPDIF out to over 0 db, only have the choice to raise the gain for that individual rig to compensate.


    So the idea was just to add a simple way for compensation which would only affect the reamping, and nothing else...


    It this still doesn´t display what i mean, i could make short video. Like i said, this is a rather small request which adds some comfort...

    I don't know if I got this right but if you talk about digital recording you "should" track your instruments around -15 dbfs as this equals a unity position in the analog world. tracking around 0 dbfs is way too hot and not really recommended but I don't know if I got your post right in the first place.


    If not then just ignore me ;)

    There is absolutely no need to normalize or get the level of the guitar up to 0 dBFS. None whatsoever. As soon as you're inside the Kemper (digital) the noise floor is set. No adjusting it up after that fact would alter it. The 24 bit pipeline (spdif) has some 144 dB's available, 6 dB's per bit. Imagine peaking out around -12 dBFS...you still have 136 dB. WAY more than what comes from your guitar and AD stage.

    Ok, this is getting hard... Just Forget about numbers and db for a few moments.


    - I have some guitars with very high output. So i set clean sense to very low values to be safe from distortion for clean rigs in any way, even i use guitars with lower output that would have required a higher clean sense. I wouldn´t change the clean sense every time i change a guitar.
    - Since the clean sense setting affects the level of the dry track that is recorded, some dry guitars will be recorded at rather low volume.
    - If you don not change anything about the dry track within the DAW the signal that arrives back at the KPA may be a little too soft.

    Ain't there a possibility to adjust the clean sense for every guitar and save it as a template, so when you switch guitars you just load the template for that type of guitar. I remember reading about something like this in the manual couple of days ago.

    Quote from KoMa

    Ain't there a possibility to adjust the clean sense for every guitar and save it as a template, so when you switch guitars you just load the template for that type of guitar. I remember reading about something like this in the manual couple of days ago.

    Of course, but it is rather uncomfortable to change those presets for every guitar. And in the workflow you sometimes just forget to change them back... So i just set it for the loudest pickup i have and leave it that way.


    Like i said, i personally could live without such a feature, because i compensate in my digital mixer. Just thought others might find it useful too...

    Quote from tylerhb

    Ok, this is getting hard... Just Forget about numbers and db for a few moments.


    - I have some guitars with very high output. So i set clean sense to very low values to be safe from distortion for clean rigs in any way, even i use guitars with lower output that would have required a higher clean sense. I wouldn´t change the clean sense every time i change a guitar.
    - Since the clean sense setting affects the level of the dry track that is recorded, some dry guitars will be recorded at rather low volume.
    - If you don not change anything about the dry track within the DAW the signal that arrives back at the KPA may be a little too soft.


    Arrive a little soft, in what way? Does it not hit the amp stage as hard as when playing? Less saturation? Or are you just concerned that it peaks far below 0 dBFS? If so, don't be ;)