Promenade and the Prommer

The Prommer was originally intended as a stand-alone sound sampler and EPROM programmer. With the help of Promenade, you can use your computer along with the Prommer to do many new things.

Archiving sounds

You can preserve your EPROM sound data on computer files. By using the EPROM/Read EPROM Data menu option, you can copy the contents of the EPROM loaded in the prommer to local memory and view it in the waveform window. You can then use the File/Save menu option to save it to disk.

For example, let's say you want to save a copy of the bass drum sound in a DMX because you are planning to erase the EPROM and reuse it for a different sound. Here are the steps you would take, assuming the Prommer is already connected to your computer and set up correctly:

  1. Turn off the DMX and remove the bass voice card.
  2. Remove the EPROM from the voice card and insert it into the ZIF socket on the front of the Prommer.
  3. From the Options/EPROM Type menu, select 2732 or 2732A as the EPROM type, and select the "One EPROM, One Sound" organization option. The Audio or Data selection doesn't matter at this point, but it wouldn't hurt to select Audio.
  4. Select the EPROM/Read EPROM menu option. Promenade will send commands to the Prommer to set the EPROM type you just selected, adjust the size of Prommer memory block 1 to match the EPROM, and read the EPROM into block 1. Then, Promenade will read the data from the Prommer into its own local memory and update the waveform display.
  5. Now, you can select the File/Save menu option and select a new filename for the EPROM image. You will be warned if you choose a filename that is already in use.
  6. Be sure to backup your computer data before you erase the EPROM.

 
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Burning new sound EPROMs

You can make your own recordings using your computer, or download sound samples from the web and put them on EPROMs to use in your drum machine.

Here's an example of how you can program a downloaded sample onto an EPROM for use in the bass voice card used for the previous example.

  1. Let's say that you have two possible samples you'd like to try, but you're not yet sure which you want to use. The samples are sample1.wav and sample2.wav.
  2. If you haven't already, set the EPROM type and organization as described above in the first example. Be sure to pay close attention to the EPROM part number and select the correct type. Now, using the File/Open menu option, or by dragging and dropping the file from Windows Explorer, open sample1.wav.
  3. Click on the waveform display to audition the sound through the computer speakers.
  4. Now, open sample2.wav and do the same, to compare the sounds.
  5. OPTIONAL: If you have the line output of your Prommer connected to an amplifier and speakers, you can also audition the sound through the Prommer. This will give you a chance to hear how the conversion from Wave file to companded binary will sound. Use the Prommer/Send Prommer Data menu option to transfer the sample to the Prommer without starting the EPROM programming process. You can then use the PLAY button on the Prommer to listen to the sample.
  6. Once you have decided which sample you want to use and it is loaded in Promenade, load your blank EPROM into the ZIF socket on the Prommer and then click the Program button. The sample will be transferred to the Prommer and the programming process will begin.
  7. Watch the Prommer display. A countdown indicating progress will be displayed, and when it finishes, the Prommer display should read "OK".
  8. When programming is complete, click the Verify button and wait for the verify operation to complete. It is important to verify the data, as the MIDI data transfers between the Prommer and Promenade do not have error detection. The only way to tell if an error in the transfer has occurred is through the verify process. Note: For the same reason, you may occasionally get a false verify error, but if you re-verify the EPROM and it checks out OK the second time, you can be pretty sure that it is really OK.
  9. Now, you can remove the EPROM from the Prommer, install it in the voice card and put the voice card back in the DMX.
  10. If the sound doesn't sound the same as what you heard on the computer, there are a few possible reasons:
    • The sample playback rate is different. Try adjusting the tuning pot on the DMX voice card. Depending on the voice card, this might have a range of somewhere between 12kHz and 32kHz. If your original sample was recorded at 44.1kHz or higher, you may not be able to tune it into range. Try re-sampling the sound using your favorite sound editing software down to 22kHz or so.
    • The voice card may have an amplitude envelope that is affecting the sound.
    • The conversion from linear 16 bit to companded 8 bit will have affected the sound and some nuances may have been lost.

 
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Selecting a good sample

Making a sample suitable for a drum machine is not always easy. There are several things to keep in mind when selecting an existing sample or recording a new one.
  • Length of the sound vs. size of EPROM. The playback sample rate and EPROM size determine the length of the sound that can be placed on an EPROM for a given drum machine voice. For example, suppose we want to make a new sample for the DMX Snare voice card. The DMX snare has a higher than usual sample rate, usually around 33kHz. The EPROM on the snare voice card is a 2732, which has a capacity of 4096 samples. The time it takes to play back 4096 samples at 33,000 samples per second is 0.124 seconds (124 milliseconds). That's about 1/8 of a second. So, the new sample we choose for this voice should be very short. Any reverb or echo on the original sample would be wasted, so we want to find a nice dry sound with a short decay time.
    When choosing an existing sample (downloaded from the web, for example), choose one that is the same size as your EPROM, or shorter.
  • Attack, decay and amplitude. When editing a sound for use on a drum machine EPROM, there are a few things you can do to make it sound as good as possible. First, crop off any dead time before the initial attack of the sound. You shouldn't have more than a few samples of silence before the sound starts. Second, try to fade out the sound if it is going to be cut off abruptly otherwise. Some sound editor software has this capability. If not, you can transfer your sound to the Prommer and use its Envelope function, and then transfer it back to the computer. And last, make use of the "Auto-scale WAV Files" setting under the Options/Audio Settings menu. This will ensure you are using the maximum possible headroom without clipping the signal.
  • Choose a good sample rate. The best common sample rate for DX and DMX sounds is 22.05kHz (half of the standard 44.1kHz). This falls into the tuning range of most Oberheim voice hardware. You can always experiment with pitching sounds up and down to other levels, but in general, stick with this rate.

 
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Converting file formats

If you have downloaded a binary DMX sound file from the web and would like to edit it using a Windows WAV file editor, you can open it in Promenade and use the File/Save menu option save it as a .WAV file. The conversion takes place automatically.

Conversion from any of the three supported formats is just as easy.

Special option for loading WAV files: Under the Options/Audio Settings menu, you can select the option to "Auto Scale WAV Files". This option will calculate the maximum signal level over the full length of the original waveform and use this to set the level for conversion to obtain the minimum wasted headroom in the binary version of the sample. If this option is turned off, no level adjustment will take place, and a quiet sample will remain quiet and the audio quality may suffer due to a lower signal to noise ratio.

There are two other options for loading files.
The "Auto Zero First Two Bytes" option eliminates a problem with some DMX and DX voices where a faint high pitched whine can be heard if the first two bytes are not close to zero in value. When this option is selected and a file is loaded, if the first two bytes are not both less than 4, they will both be set to zero. This option only applies if the Audio option is selected under the Options/EPROM Type dialog.
The "Auto Detect BIN File Sample Rate" works on binary and Intel Hex files. (Wave files already have their sample rate encoded within the file). It uses a feature of samples originally recorded on the Prommer to set the Windows sample playback rate to match the original sample rate. When a file is loaded into Promenade, if the value of the first two bytes bytes of the file are 0, the playback rate will be set to 32kHz, if both are 1, the rate is 24kHz, 2 gives 16kHz and 3 sets the rate to 12kHz.
 
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Dealing with code EPROMs

Operating system firmware EPROMs can be handled by Promenade as well as audio sample EPROMs. There are a few special things to remember when loading or saving data EPROMs, where it is important to get exact copies without any modification of the data.
  1. Turn off the "Auto Zero First Two Bytes" option.
  2. Set the Data format option in the Options/EPROM Type dialog. This ensures that any empty EPROM space is left as erased (erased EPROM bytes are equal to FFh) in the case where a sparse Intel Hex file is loaded.
  3. Don't save data files in .WAV format. The resulting Wave file would just sound like a lot of noise, and the conversion process is not guaranteed to be reversible. Only use .HEX or .BIN file formats for saving and loading data files.
  4. Don't worry that the waveform display looks weird. It's data, not audio and is not supposed to look like a waveform. Blank parts will have a line at the top of the display, other parts will be all over the place.

 
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Programming 8-bit linear EPROMs

A few drum machines use a linear 8-bit data format (Simmons, for one). With a little extra effort, you can use Promenade and the Prommer to translate a regular companded binary file into this lower-resolution format.

Load the sound you want into Promenade as usual, selecting the appropriate EPROM type and other settings as you would for a DMX EPROM.

Instead of pressing the Program button when you are ready, use the Prommer/Send Data function to transfer the sample to the Prommer. Then, using the Prommer control panel, select the Program Linear command to translate the data as it is being programmed. The Promenade Verify function will not correctly verify a linear EPROM.
 
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Precautions and general advice

EPROMs can be damaged by exposure to static electricity and mishandling. Practice static-safe handling of EPROMs. Ideally you should only work on a grounded static mat while wearing an approved grounded wrist strap. Practically, few people actually do this, but you can still reduce the chances of equipment damage by following some simple guidelines.
  • Use grounded power plugs to connect the Prommer, your computer and drum machine to their power sources. Turn off but do not unplug the power cables when removing and replacing voice cards in the DMX.
  • Before touching any EPROM or circuit board, ground yourself by touching the grounded metal case of the Prommer or your drum machine.
  • If you are standing, do not move around or shuffle your feet without re-grounding yourself afterwards. If you are sitting, do not move your chair or shift in your seat.
  • Keep EPROMs in anti-static bags or anti-static foam when not in use. Do NOT use plain white styrofoam or plain plastic bags. Anti-static foam is black or pink and anti-static bags are pink or silver-colored.

Handle EPROMs carefully so you don't bend or break the pins. Remove them from standard IC sockets carefully, lifting a little bit at a time from each end until they come out easily. Use a small flat-blade screwdriver or right-angled probe hook to lever them out slowly. Once they are out of their sockets, inspect the pins carefully and straighten any that might have been bent. When you re-insert the EPROM in its socket, be careful that all pins go in the right place, that no pins get bent under and that the EPROM is oriented in the socket correctly. A small pair of smooth-jaw long nose pliers is very useful for straightening bent pins.

When using ZIF (Zero Insertion Force) sockets, there is a lever to operate that releases the EPROM pins before removal. Be sure to reset the lever to clamp down on the pins after reinserting the EPROM.

After programming and verification, label the newly programmed EPROM before removing it from the programming socket. You can use handwritten small paper labels (available at most office supply stores), or 1/2 inch wide plastic labels made by an electronic label maker. You will save yourself lots of trouble if you make this a habit.
 
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