Apple Logic Pro 8 TDM User Manual

Logic Pro 8 TDM Guide

In general, DAWs take one of two approaches to audio signal processing: the use of dedicated hardware DSPs (TDM systems), or the native processing capabilities of the computer CPU.

Logic Pro allows you to make use of both your TDM system DSPs and the computer’s native CPU processing resources. The link between the DSP world of your TDM system, and your computer’s native CPU processing resources is the ESB TDM.

The ESB TDM allows your computer’s CPU to process one audio engine (Direct TDM), and the DSP of the TDM hardware to process another (DAE). This is done by using two different mixers in Logic Pro: A TDM Mixer (using the DAE) and a native mixer (called the DTDM Mixer). The first one handles TDM plug-ins, while the other works with native plug-ins—in both Audio Unit and Logic formats.

Up to eight of the DTDM Mixer outputs can be routed in to the TDM Mixer. The output signals are received by the ESB TDM inputs—using TDM aux channel Input slots. This enables all Logic tracks, native and Audio Unit plug-ins—including software instruments—to be used in conjunction with your TDM system DSPs.

This guide will introduce you to all that you “need to know” to get your TDM hardware up and running with Logic Pro 8. It will also introduce you to the ESB TDM and EXS24 TDM.

The use of Logic Pro 8 functions is discussed in the

Logic Pro 8 User Manual.

Audio Hardware and Drivers

To use Logic Pro 8 with your TDM System, you will need at least Pro Tools HD 7.4 (on both Intel and PPC computers).

Selecting and Configuring a Device

Selecting, and activating, a particular audio hardware device is achieved directly in Logic Pro, via the Logic Pro > Preferences > Audio > Devices dialog. You can choose between the Core Audio, DAE, and Direct TDM tabs in the Devices pane.

Core Audio:

use Core Audio drivers. For full details on the Core Audio device settings, see the

Logic Pro 8 User Manual

DAE:

software used to access TDM hardware (including use of on-board DSP chips) in Logic Pro 8.

Direct TDM:

process the DTDM Mixer—which you can route into the (aux channel) inputs of the TDM Mixer, using the ESB TDM. This allows your computer’s CPU to perform native (instrument and effect) processing in Logic Pro, while using the DAE.

The Core Audio tab activates and adjusts audio hardware devices that

DAE is the abbreviated form of Digidesign Audio Engine. This is the driver

The native Direct TDM (DTDM) audio engine of Logic Pro is used to

DAE Settings

The DAE parameters can only be set after activating the DAE. To do so, check the Enabled box in the upper left corner of the DAE tab. You will then have access to the following parameters:

Global Bit Depth:

This parameter allows you to choose between 16 bit or 24 bit

playback and recording.

Note:

The DAE does not allow the use of 16 and 24 bit files simultaneously.

PT HD Type:

This parameter allows you to define the number of tracks for your Pro Tools HD system. Each entry in the pop-up menu allows you to define the required number of tracks, based on the number of Pro Tools HD DSPs that you want to use (and actually have) in your system.

TDM Setup Indicator:

The TDM Setup Indicator is a small status window that shows the current TDM process (inserting a TDM plug-in, for example). This parameter switches the display of this window on or off.

Pass Keyboard Events to Plug-ins:

Any key commands that are not used by a plug-in are passed on to Logic Pro. Under normal conditions, this ensures that functions like Start and Stop will continue to work. If this isn’t the case, use the options in this menu to specify that only certain key combinations will be passed to the plug-in. All other key presses will be received by Logic Pro.

Digidesign Hardware Setup Button:

Opens the Digidesign Hardware Setup window

that contains all important system settings for your hardware.

Note:

The Process Buffer Range and ReWire Behavior parameters at the bottom of the

Devices tab have no effect on the DAE!

Direct TDM Settings

To activate Direct TDM, check the Enabled box in the upper left corner of the Direct TDM tab.

Universal Track Mode

Universal Track Mode, when engaged, allows the playback of stereo and mono regions on a single track. Even-numbered audio channels are channels of the odd-numbered stereo audio channel to their left. Every audio channel has its own Format button. Dependent on whether a mono or stereo region is played back, the Pan knob will behave as either a Balance or Pan control. If you play back a mono region, and the Pan knob is set to the center position, both channels of the audio channel strip will output the same signal level.

not

regarded as the right

Note:

Universal Track Mode has limited routing capabilities, as it doesn’t allow separate

handling of the left and right audio channels.

The Non-Universal Track Mode is useful if you want (or need) to play different mono files for the left and right mono channels of a single audio channel strip, even when it is assigned as a stereo channel. A stereo/stereo plug-in inserted into this stereo channel receives different signals for the left and right channels.

About TDM

Logic Pro allows you to make use of the TDM functions supported by Pro Tools HD systems. TDM stands for Time Division Multiplexing—the time-interlaced transmission of multiple digital audio signals (or streams) through a single data bus. This bus system is physically isolated from the computer system bus, and runs between the individual TDM-capable PCI boards. Up to 512 digital audio channels, each with 24 bit resolution, can be transmitted on the TDM bus. These streams form the signal paths within a virtual mixer. These signal paths are necessary for the insertion of plug-ins, which are calculated on the DSP hardware, and routed into the individual channels, or are selected through auxiliary busses.

Note:

It should be noted that the TDM channel count is sample rate dependent, so if a rate of 88.2 or 96 kHz is used, the 512 channels available to a PT HD system will be halved to 256. At a sample rate of 192 kHz, this will again be halved to 128.

Differences to Native Processing

Basically, the use of Logic Pro with a TDM system is very similar to the use of Logic Pro with the native processing capabilities of your computer. Here is an overview of the main differences between the two systems:

In a TDM system, all audio processing is done by the DSP chips of the TDM hardware. This means that native Logic plug-ins can not be run on the TDM DSPs. TDM plug-ins, however, can be fully used and automated.

The TDM hardware determines the overall features of the system: number of tracks, number of TDM plug-ins that can be used simultaneously, number of in/outputs, and so on. Please refer to your ProTools system manuals for further information.

Stereo recordings require two tracks, and are recorded as two separate files. In the Arrange window, a stereo recording is handled as two linked regions, which use two tracks. In the Sample Editor, stereo recordings are displayed as a stereo file. All oddnumbered audio channels can be switched to stereo. Doing so will cause the following even-numbered audio channels to be “locked” to the preceding oddnumbered channels. The odd numbered channel controls both sides of the stereo recording.

The DAE does not support the QuickTime engine, so the Logic Pro movie facilities will not be available if you work exclusively with the DAE. Simply activate Core Audio or DTDM to use the movie facilities when working with the DAE.

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