Ensoniq DP/4 – Version 1.15 Firmware Update OS Upgrade for DP4 DP-4 Effect Rack


Ensoniq DP/4 – Version 1.15 Firmware Update OS Upgrade for DP4 DP-4 Effect Rack

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Ensoniq DP/4 firmware OSupgrade v 1.15 – Final Revision

This is firmware revision 1.15 and is the latest official released operation system by Ensoniq Corp. This operation system update/upgrade requires two eprom chips as revealed in the article`s photos and the chips will be labeled to help you locate the correct chip socket. For more info, please check below.

Version 1.15 includes the following performance improvements and fixes for problems that have been discovered since the version 1.00 release.


  • VCF-DISTORTION – Changes were made to correct a problem which caused the envelope follower release time to work incorrectly over the 5-10 second range. This change affects the documentation in that the parameter limits are now actually In sec to 1 msec to 10sec instead of 50mSec to 10sec. The sound of existing presets is not affected and the displayed values will now be correct. Existing presets which were set in the range of 6 to 10 msec did not, and will not now sound correct.
  • FAST PITCHSHIFT,EQ-DDL-WITH LFO AND EQ-CHORUS-DDL-Polyphase interpolation was added to these algorithms to improve performance and reduce high frequency anomalies associated with LFO modulation.
  • PITCHSHIFTER , FASTPITCHSIDFI’ AND PITCHSHIFT2U – Modifications were made to the se algorithl1llf to eliminate a problem which caused excessive splicing at pitch ratios of zero and at non-zero LFO widths. These changes should reduce transport delay and eliminate clicking with extreme LFO widths.

General System:

  • FOOTSWITCH PRESET INC/DEC -A problem was corrected which could cause the system to get confused if the foot switch was used to increment the current preset “past” 99 or decrement the current preset “past” 00. In addition, the Show 100 Contig Preset switch limited the range of available presets for all preset types When it was set to NO. This limited range now applies only to Config presets as originally intended.
  • DOWNLOAD VERIFY DISABLE SWITCH – a new switch was added on l!new page available in System Diagnostic mode (accessed via “System-C”). The default state of this switch is”Disabled’and-in this state the redundant download verification is bypassed to speed up the download process. The switch can be set to “Enabled” if the user experiences any download problems or desires the extra level of checking.
  • SHOW 100 CONFIG PRESETS DEFAULT -The default state of the “Show100ContigPresets”switch has been changed to “Yes” in response to suggestions that users will find this more consistent with the overall design while learning about the system.
  • DCOFFSETWINDOW -The acceptable range,of DC offsets has been increased by a factor of two to eliminate production and field problems which resulted when inaudible minor DC Offset variations triggered the warning message display mechanism.
  • ES PHALT RELEASE – The halt lines of the four DSP chips are now released for a brief time during  system reset to allow the chips to run momentarily before the DRAM clearing procedure is initiated. This change is intended to reduce the incidence of Unexpected Event 75-78 messages.
  • DELAYTIMEIN2UDELAYPRESETS – Presets employing the 2Unit 3.3SecondDelay algorithm in Continuous mode will now install the correct delay time when they are saved or selected. In previous versions, an incorrect delay time was always installed even though the correct delay time was displayed.
    SWAP/COPY PROBLEM- This software release corrects a problem that occurred when the Swap/Copy Unit function was invoked and the two involved units each bad a different edit buffer status. The unit(s) wold temporarily be in a confused state until the Edit button was used to toggle the units in/out of their respective edit buffers.
  • PITCHSHIFTER-DDL-Several changes were made to improve the operation of this algorithm. The delay line regeneration will now operate correctly on both the left and right sides (as described in the manual). The regeneration was improved to allow higher values without distortion or loss of sound.


  • Presets employing the “PitchShift -DDL” algorithm were updated to correct previously out-of-range Regeneration parameter values that would be displayed as invalid data The following presets required adjustment: RAM lU-47, lU-49, 2U-29, 2U-49, 4U-48. DPI4