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Subject Interface Amplifiers

The Subject Interface Module (SIM) is the control object for the SI2, SI4, and SI8 devices. It connects to a special DSP-M card in your RZ processor. The Subject Interface is configurable with stimulator cards (IZV), analog amplifier cards (PZA), or digital headstage interface cards (PZD). Because of the diversity in functionality of this device, each card type has its own "Sub-HAL" object within Synapse that is used to configure those cards. The acquisition and stimulation all happen within the Sub-HALs, which are all independent objects in the Processing Tree.

PZA Analog Amplifier & PZD Digital Headstage Interface

The PZA & PZD can split the available boards into sub-amps which are completely isolated from one another.

PZA & PZD Options

PZA Analog Options and PZD Digital Options.


Option Description
Use Sub Amps Divide the input channels into "logical amplifiers" that canrecord different types of signals, at different rates and referencing modes with independent grounds. All of the below configuration options apply only to the selected sub amp.
Boards Specify the number of boards to include in this sub-amp. Selectable values are limited by the Rig configuration.
Channels The channel count must be at least four and must be a multiple of 2. The corresponding physical banks on the SI are displayed to the right.
In Differential Reference Mode set the total electrode count here. The channels from the PZA sub-amp are mapped for you to remove duplicates on the output link.
Name ID Choose the name for this sub amp data source that will be visible to other gizmos.
Sampling Rate Set the Sampling Rate to match the desired frequency band of your incoming signals (or leave at 'System Rate' if you are unsure). By default, the sampling rate matches that of the RZ.
External Ground Connect this sub-amp ground to the external ground plug on the physical SIM device.
Caution: When using multiple sub-amps make sure they aren't all sharing the External Ground connection or else they won't be isolated!
DC Coupled Remove the 0.4 Hz high pass filter on the input signals and record DC potentials.
Reference Mode Select the mode from the drop-down menu.
Local - each bank of 16 uses its own reference (pin 5 on the DB26).
Shared - all channels in sub-amp share the same reference (pin 5 of first bank in sub-amp).
None - the ground connection is used as the reference.
Differential - each even channel acts as a reference for the odd channel before it. Note: the output channels will be mapped for you to remove duplicate channels.
Filtering Set the anti-aliasing low pass filter cutoff as a percentage of the sampling rate.
Set to base type If you are unsure, use Set to Base Type to configure the amp with default settings based on common signal types.
Option Description
Use Sub Amps Divide the input channels into "logical amplifiers" that canrecord different types of signals, at different rates and referencing modes with independent grounds. All of the below configuration options apply only to the selected sub amp.
Boards Specify the number of boards to include in this sub-amp. Selectable values are limited by the Rig configuration.
Channels The channel count must be at least four and must be a multiple of 2. The corresponding physical banks on the SI are displayed to the right.
Click the Refresh button to automatically detect the connected headstage count (your RZ hardware must be turned on and connected for this to work).
Name ID Choose the name for this sub amp data source that will be visible to other gizmos.
Fast Access Select this option to read the data as 16-bit to reduce cycle usage on the DSP. Required for acquiring 256 channels of digital headstage inputs.
Sampling Rate Set the Sampling Rate to match the desired frequency band of your incoming signals (or leave at 'System Rate' if you are unsure). By default, the sampling rate matches that of the RZ.
External Ground Connect this sub-amp ground to the external ground plug on the physical SIM device.
Caution: When using multiple sub-amps make sure they aren't all sharing the External Ground connection or else they won't be isolated!
AC Coupled Apply an additional 0.4 Hz high pass filter to the incoming signals.
Low Pass Filter Select a cutoff frequency for a lowpass filter that is implemented on the digital headstage. Set to 'Auto' to match it to the PZD sub-amp sampling rate. See table below.
Use DSP Filter check box Add an additional lowpass digital filter implemented on the RZ, set to the same frequency as the Low Pass Filter setting above, to remove high frequency digital noise from the incoming signal that was added by the digitizing chip.
High Pass Filter Select a cutoff frequency for a highpass filter that is implemented on the digital headstage.
Impedance Target Use to intelligently control the impedance checking circuit on the headstage based on your target impedance.

'Auto' low pass filter settings for different sub amp sampling rates

Sampling Rate LP Auto Filter
750 Hz 300 Hz
1.5 kHz 750 Hz
3 kHz 1.5 kHz
6 kHz 3 kHz
12 kHz 5 kHz
25 kHz 10 kHz

Technical Detail


See the SIM section of the System 3 Manual for more information about configuring and using the PZA amplifier and PZD interface.