Posts by drew2

I'm trying to control the Kemper Profiling Amp using MIDI out from Reaper. I know all the hardware is working because a standalone app for controlling the Kemper is working on my system. See Kemper Editor. I would like to change parameters over time in Reaper. This is possible using NRPN. From the Kemper Manual:

Quote

The Kemper Profiling Amplifier features more than 400 parameters. Of course, you can't address them all with a standard MIDI controller message, where only 128 parameters can be reached.

Therefore we support the NRPN (Non Registered Parameter Numbers) protocol additionally to the proprietary SYSEX protocol.
NRPN Definition NRPN allows addressing 16384 different parameters (that is 128 x 128) and even have a parameter resolution of 16384 values (14 bit) compared to 128 distinct values (7 bit) with regular controller messages.

NRPN messages consist of a set of four controllers being sent in a sequence. These four controllers are:
Decimal Hex
99 $63 MSB* of the parameter number ("address page")
98 $62 LSB* of the parameter number ("address number")
06 $06 MSB* of the parameter value
38 $26 LSB* of the parameter value
*MSB: most significant byte, the upper 7 bit of the 14 bit number
*LSB: least significant byte, the lower 7 bit of the 14 bit number

The MIDI specification demands that a manufacturer needs to decide if the devices understand 7 bit or 14 bit values. All NRPN controllers in the Kemper Profiling Amplifier are by definition 14 bit value controllers, so you'll need to send both MSB cc06 and cc38 in that order to apply a change. The actual value gets set after reception of cc38. The KPA keeps the address selection present. So, if a pair of cc98/cc99 Is being sent it does not need to be sent again for a further value change on the selected parameter.

To support generic, programmable floorboards/controllers that only support 7-bit values, KPA Firmware version 1.5.1 introduces cc119 ($77) to send 7 bit value changes instead of cc06 and cc38. In this case, the values are mapped internally to the correspondent 14-bit value (e.g. value 127 is internally 16383, 64 is internally 8192) properly.

Examples The parameter "Delay/Mix" is at NRPN #9475, so MSB ("address page") is 74 ($4A) and LSB ("address number") is 3 ($03).
To send a 14 bit high resolution value to 8192: $B0 $63 $4A $B0 $62 $03 $B0 $06 $40 $B0 $38 $00

To send a 7 bit low resolution value (64), so parameter is actually at 8192.*: $B0 $63 $4A $B0 $62 $03 $B0 $77 $40
* Supported in Firmware 1.5.1 or later
$B0 is the Midi Start Byte for controllers at Midi Channel 0. You may use "running status" transmissions.

The Kemper Profiling Amplifier will listen to the Midi Channel that is set as the Midi Global Channel in the System Menu. The standard setting is "OMNI", saying it responds to every channel1.

Parameter Types
There is two types of parameters in the Kemper Profiling Amplifier and their properties:
Continuous Parameters (like Gain, Volume,)  Are fractional numbers and will always cover the whole value range.  Will be smoothed upon reception of multiple continuous values. Thus, high resolution (14 bit) values are not necessary for a smooth parameter movement, only for accurate target values.

Switch or Section Parameters (like Type, On/Off)  Are integer numbers and will start counting from the least significant bit.  Values out of range will activate the highest value in the range, but should not be used due to future compatibility  Switches are "Off" at the value 0 (zero) and "On" at value 1 (one).  If a 14 bit value is being used to set a controller to "On", then the MSB byte is $00, the LSB byte is $01

Parameter List
Rig (Address Page 4)
0 Rig Tempo
1 Rig Volume
2 Rig Tempo Enable
Input(Address Page 9)
3 Intensity
4 Input Clean Sense
5 Input Distortion Sense
Amplifier (Address Page 10)
2 On/Off
4 Gain
6 Definition
7 Clarity
8 Power Sagging
9 Pick
10 Compressor
11 Tube Shape
12 Tube Bias
15 Direct Mix

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Given this information, I attempted to set up a midi track using the appropriate values in the correct sequence to change the Amplifier Gain. But it does not work. I set the MIDI output in Reaper to the midi out the device hooked to the Kemper. This configuration worked using the standalone app mentioned above. Here is what I have tried:

Google Drive Folder Containing Screenshot and MIDI File (Control left click the midi file to download, otherwise it will just say no preview is available.)

Ideally someone could create a MIDI file that changes the Amplifier Gain. Instructions on how to do so would also be very appreciated.

Thanks in advance for any guidance.

Edit: I'm using Firmware 2.1

I thought I perceived a difference between 1.54 and 1.6 after reading this thread. However, after proper ABX testing, I cannot reliable detect a difference. To everyone who claims to detect a difference in sound or feel, please attempt to compare the two with an ABX procedure.

Now there is certainly a difference in the frequency response between the two versions. This difference varies between .1 and 2 decibels depending on the frequency. But as I said, I cannot perceive this difference.