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The Transformer is designed to be an all-in-one guitar amplification system using the PFC4 footswitch. However, there are plenty of other uses for those MIDI jacks on the back, and that's what we'll cover here. We'll start with the simpler stuff, and move on to the more complicated stuff later.
 

MIDI Channel on the Transformer

The Transformer's MIDI channel is 1 by default (after re-initialization). This means that any channel messages that are received on another channel are ignored, and any channel messages that are generated are sent on this channel. To change the channel, hold the STORE button down for at least a second, and (while holding) select channel 1-16 using the Preset Matrix selector.
 

MIDI Out as a MIDI Thru

Most likely, you'll be using the PFC4 to drive the MIDI In, since it adds so much to the usability of the amp. If you decide to link another Transformer up for stereo operation, you can have the second one be slaved to the first one's PFC4 by connecting a MIDI cable from the first's Out to the second's In. They will track program changes, EFX mode changes, TAP tempo, other preset edits, etc. Even if the audio link is from the first's effects send to the second's effects return, it's still useful to have the same presets in the second amp and link them since the Amp Model selection (which changes per preset) affects the voicing of the power amp.

The MIDI Out jack will echo virtually all commands that arrive at the MIDI In (with the exception of certain Sysex messages meant for the Transformer), so it can be used in the middle of a MIDI chain when driving a rig from another MIDI source, instead of using the PFC4. This is called a "soft" thru, which means it is dependent upon the software (processing power and MIDI buffer) of the unit. What's a hard thru? That's when there is a jack labeled "Thru" and not "Out" or "Out/Thru." It's usually accompanied by a separate MIDI In and Out, and it's usually in the middle. Most importantly, it's directly driven from the In jack, so it is not dependant on the software to do the echoing work. So if your other MIDI units are "3-jack" units, it may be wise to put the Transformer at the end of the chain, since a soft thru is never quite as bullet-proof as a hard thru. Not that we expect problems with ours, but a little insurance doesn't hurt!
 

Preset Synchronization with an External Effects Unit

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You may have a programmable effects unit with a MIDI In that you want to use in the Transformer's effects loop. If you want this unit to change presets when the Transformer does, connect a MIDI cable from the Transformer's MIDI Out to the MIDI In of the effects unit. Then the first 16 presets in the effects unit will be aligned with the 16 presets in the Transformer.

For this to work, the MIDI channel of the effects unit must either be set to OMNI, or match that of the Transformer.
 

Preset Backup

You can back your presets up to a computer, sequencer, or other type of MIDI librarian / recorder. You can also transfer them to another Transformer! Connect a MIDI cable from the Transformer's MIDI Out to the MIDI In of the recording device. Prepare the recording device or software program to receive data. (In the case of transferring to another Transformer, it just needs to be on.) We're now set to send the presets.

To initiate the transmission manually, hold the amp's TAP button and then press the MODULATION Select button. The six Amp Model LED rings (Pre Gain through Reverb) should go off for a second or two to verify the operation. When they come back on, the operation is done.

NOTE: The size of the System Exclusive preset dump is 1000 bytes.

To dump Globals:  hold TAP and press STORE
To dump a Single Preset:  hold TAP and press USER
 

Channel Messages

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The Transformer will accept (and echo) the following channel messages when they are sent on its MIDI Channel (values are shown in hexadecimal):

• Program Change - Cx nn where x = MIDI channel - 1, nn = 00-0F for presets A1 - D4
• Bank Select - Bx 20 nn where x = MIDI channel - 1, nn = 00 for factory, 01 for user
• Main Volume - Bx 07 nn where x = MIDI channel - 1, nn = 00-7F for mute to full

The Transformer will generate the following channel messages on its MIDI Channel:

• Program Change (as shown above) - whenever a preset change is initiated by front panel or PFC4.
• Bank Select (as shown above) - whenever the MATRIX bank is toggled from/to Factory to/from User.

The Transformer will echo these messages to the MIDI Out when received. None will be generated by the Transformer.
 

System Exclusive Messages

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We've equipped the Transformer with an extensive MIDI Sysex implementation. In addition to simple preset dumps and preset sharing via the Internet and such, this enables the amp to be programmed remotely by a computer program or hardware editor like the Peavey PC1600X.

All of the Transformer's Sysex messages start with a common header and end with an End of Sysex [EOX] byte. The table below shows the "unique" section (including the command and optional data) of each message that falls between the header and the EOX.

Here is the common part, along with descriptions of each byte's purpose:

F0 - Start of Sysex [SOX]
00
00
1B - Peavey Manufacturer ID = 00 00 1B
10 - Transformer Product ID
00 - Reserved for future use (keep fixed at zero)
CMD - Command byte that defines which Sysex message it is.
<data> - Optional data.
F7 - End of Sysex [EOX]

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Errata - 12/17/01

During development of Peavey's Windows editor/librarian program, I came across a few bugs in version 1.4 pertaining to patch editing via sysex. All had workarounds in my case, but I list them here for anyone designing 3rd party support. Version 1.5 and 2.0 has fixes for these..

Bug: When sending the Delay Time byte via sysex, the amp accepts the value but doesn't update the audible delay time.
Workaround: Anytime Delay Time is sent, I also send bit 6 of the Delay Separation byte (which is always zero, so it's a harmless message).

Bug: Partial addressing is not accepted by the amp if trying to send 7 bits (it only handles up to 6). One of those < vs. <= blunders (D'OH!).
Workaround: Delay Separation is the only likely candidate, and it only goes 0-25, so 5 or 6 bits will do the trick.

Bug: When programming the PFC4 Tap Function with a partial poke of the high nibble, the amp reloads the EFX mode status bits from the original recalled program. It's better to leave them be.
Workaround:I read the status bits first, then re-send them after I send the Tap Function. This undoes the change at the amp.

Bug: When changing the modulation effect to flanger via sysex, the two tweak values are not set correctly by the amp (which also sends these wrong values back to the PC.
Workaround: I send the correct values to the amp after the selection, and ignore the wrong values coming back from the amp.

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