Symphony 64 | ThunderBridge: Troubleshooting

“Bus Error” when using Symphony64 PCI card or Symphony64|ThunderBridge

Bus Error is a message that will appear in the Apogee Maestro 2 window under the System Status section. This is typically a communication issue between the connected device, and the Symphony64 or Symphony64|Thunderbridge.

This can be caused by several things:

  1. A common cause for this is that the port setting in Audio MIDI Setup (Applications>Utilities) is set to Ports 1-2, when only one port is actually being used.

  2. A bad PC32 cable (DigiLink)

  3. If using a Symphony I/O, the AIM setting could be incorrectly set to “USB Audio”, “Standalone”, or “Pro Tools HD”, instead of the “Symphony” setting.

  4. Connecting a single device to Port 2 (17-32), instead of Port 1 (1-32)

If only one device is connected and you are receiving the Bus Error message in the system status window in Maestro, please revert back to the Port 1 (32 channels) setting in Audio MIDI Setup. You may need to reboot your computer for the new setting to take place. Secondly, ensure by pressing and holding the right-hand encoder knob on the front panel of SymphonyIO, you are in fact in “Symphony” mode.


Level jumps when adjusting Symphony I/O’s front-panel output encoder knob

There was a known issue with some Symphony I/Os where the output level could jump by several dB when adjusting the output level with the front-panel output encoder knob.

This issue was resolved with Release 4.8 firmware and software


Click here to download the latest Symphony Release and follow the update instructions to ensure a successful firmware update.


Symphony 64 | ThunderBridge not recognizing Symphony I/O

Symptom: Symphony I/O does not show up in Maestro or properly function when connected to Symphony 64 | ThunderBridge

Solution: There are a number of logical and easily correctable causes for this.  Please examine the following steps:

  1. Confirm that you have both the latest firmware and software installed.
  2. Verify that the PC-32 cable is properly connected from the main port on the back of Symphony I/O to the first port on Symphony 64 | ThunderBridge.
  3. Confirm that the Symphony I/O is set to “Symphony” AIM mode.  To verify, push in and hold on the right-side front-panel encoder. This will bring you to the AIM selection menu. If its not already selected, scroll to Symphony and then push in on the right-side encoder to select and the unit will restart.
  4. Make sure you have selected the correct “Source” setting in Audio MIDI Setup.
    1. Open “Audio MIDI Setup” (Applications > Utilities > Audio MIDI Setup) and select Symphony64 on the left-side device column.
    2. Go to the “Source” drop-down menu in the main part of the Audio MIDI Setup window and set it for the appropriate port selection. If you’re using only 1 Symphony I/O, set it for “PCI Card 1, Port 1 (Chs 1-32)”. If you’re using 2 SymI/O’s, set it for “PCI Card 1, Port 1-2 (Chs 1-64)”. After changing Source selection, quit Audio MIDI Setup and restart the computer.

When using Apogee interface with Cubase, Sonarworks, output volume level goes to max.

Symptom: When opening a session or selecting Apogee as the audio device, the output goes to full volume every time.


  • In Cubase, go to Devices > Device Setup > Control Panel > Core Audio Device Settings. Under Options, verify that set device attenuation to 0 dB is unchecked.

NOTE: In Cubase 10 and up, this setting is in Studio Setup > Control Panel

  • In Sonarworks, go to Systemwide settings and deselect the “Adjust output device gain checkbox.

How is this possible? All modern Apogee interfaces have input gain and output volume that are digitally controlled rather than an analog potentiometer that must be physically turned. The advantages of digital control are many:

  • Improved Sound Quality (turning the gain doesn’t cause a “scratchy” sound, and enables the advantages of our Step-Gain preamp technology)
  • Settings can be saved to presets that can be recalled later.
  • You can also control the output volume directly from the Mac’s Keyboard, Touchbar, or Volume icon in the Task Bar.

Cubase:  In Cubase this is called “Device Attenuation.”  The intent of this setting is to attenuate, or lower your volume, so you don’t get blasted.  When selecting any audio device with this setting turned on Cubase sets the device’s output volume to 0, since most simple sound cards have 0 as the lowest value.  Since your Apogee is rating the Outputs in digital decibels, where 0dBFS is the highest value, this setting will have the unfortunate opposite result, maxing out the volume.  Be sure to disable this setting to prevent getting blasted.

Sonarworks Reference 4:  This is a sound calibration software that many customers may have and forget is even running.  It has a setting to Auto adjust output device gain, or volume.

Please remember, many other softwares not listed here have these types of settings so be sure to check all the softwares on your computer!

Updating Symphony I/O firmware

This article applies to the Original Symphony I/O only, not the MkII.

Note: The updater program is only compatible with OS X 10.6.8 – 10.10. This means you need a Mac running one of these operating systems in order to update your Symphony I/O’s firmware. Once the firmware update is complete, you can plug the Symphony I/O into a newer version of macOS and it will fully function. It is only the updater that needs the older OS.

If you do not have access to such a Mac through a friend, local business, or library and you are in the US or Canada, contact Apogee Support to arrange for the unit to be shipped to Apogee for the update. You are only responsible for getting it to Apogee however you choose, and Apogee will update the unit and ship it back to you for free via standard Ground shipping services. (If you are not in the US or Canada, contact the Apogee Distributor for your region. Be aware additional charges for service may apply if purchased in a different region.)

Before you begin the update process, trash ANY older Symphony installer packages you may have on your computer (desktop, downloads folder, etc.) Old installers can mistakenly trigger ‘firmware mismatch’ warnings.

  1. Download the latest Symphony installer package from our website:
    • Fill out the registration form. For Product, select “Symphony I/O”.
    • For Operating System, select the version on which you will run the fully updated Symphony I/O.
  2. Once you have the DMG file downloaded, open it and inside are many files.
  3. Locate the file “Symphony System” and run it. Follow the prompts to a restart of your computer.
  4. When the computer is back up, open the same DMG file but this time located the “Symphony Software Installer.pkg” and run it. Follow the prompts to another restart of your computer.
    • If on macOS 10.13 High Sierra or newer, make sure you allow the Apogee extension to run or it will not be recognized properly: Read More
  5. Plug in the Symphony I/O via USB to your Mac.
    • If your Mac has USB 3.0, you should first try it with a USB hub (an Apple keyboard with USB ports is the best hub to use if you have one) to do the firmware update… the firmware update will not work on most USB 3.0 ports, so a hub will bring it down to USB 2.0. Note- USB Audio should work fine on USB 3.0 ports.
  6. Power up the Symphony I/O.
  7. Locate the file for “SymphonyIO Firmware” and open it.
    • If the firmware needs an update, copy this newest to a USB memory stick and transfer to a Mac running OS X between 10.6.8-10.10, and connect the Symphony I/O via USB to that Mac to perform the update.
  8. Note any settings you may have made for your Symphony I/O in the Maestro software, as these settings can get reset after an update.
  9. Open the “SymphonyIO Firmware” and update the firmware. Make sure the firmware successfully updates before proceeding to the next step.
    • If the firmware updater gets stuck or doesn’t work, quit the firmware updater app, power off the Symphony I/O, power the Symphony I/O back on and try the update again.
    • You may need to try different USB ports.
    • If the updater says it ‘failed’, click ‘try again’ and run the update again.
    • If you have multiple Symphony I/Os, make sure to update EACH of them by selecting each unit in the drop-down menu of the firmware updater (Symphony I/O 1, Symphony I/O 2, etc.)
    • Once the update finishes, quit the updater and then relaunch it to confirm that the firmware is up to date for each unit.

Once you’ve confirmed that your Symphony I/O’s firmware is up to date, ensure it is in the correct Audio Interface Mode (AIM):

  • Push in and hold down the right-side front-panel encoder knob until you get to the audio mode menu.
  • Let off the knob and then turn it to scroll through the different modes.
  • One the desired mode is selected, push in on the knob again to restart the unit in that mode.
  • Here is a video demonstrating how to change interface modes: Video

If you’re using Symphony I/O with Symphony64 PCIe or Symphony64 Thunderbridge:

Launch Audio MIDI Setup (Applications> Utilities> Audio MIDI Setup). We recommend using Audio MIDI Setup instead of System Preferences Sound.

Make sure that ‘Symphony64′ (PCIe or Thunderbridge) is selected in the left-side column. In the ‘Source’ menu on the right, choose the appropriate port selection depending on how many Symphony I/Os you have. If you have 1 unit, choose ‘Port 1: 32ch’… if you have 2 units, choose ‘Ports 1-2: 64Chs’. Quit Audio MIDI Setup and restart the computer.  Wait until the unit/units sync and stop clicking before launching Maestro. This can take a couple minutes if you’re using 2 Symphony I/Os.



Symphony I/O Release 5 System Requirements

Symphony I/O Release 5 Requirements


 Click here to download Symphony I/O Release 5

Symphony Audio Interface Mode

Requirements to connect Symphony I/O to Apogee Symphony 64 or Mobile PCI cards:

  • Apogee Symphony 64 Thunderbridge or Symphony 64 PCIe card (sold separately)
  • OS X 10.8.5, 10.9.5, and 10.10 and higher (64-bit and 32-bit kernel modes)
  • 2GB memory required, 4 GB recommended


Pro Tools HD Audio Interface Mode

A Symphony I/O based Pro Tools system consists of two independent computer connections: audio (to a Pro Tools HD PCI card) and software control (via USB to an Intel Mac running Maestro 2). In the case where PCI cards are installed in a PowerPC Mac or Windows computer, it’s possible to run Maestro from a separate Intel Mac, such as Mac Mini or MacBook.


Running Symphony I/O in Pro Tools HD mode on a PowerPC Mac requires an older firmware version. You can request this older firmware by emailing: Only the 8×8, 16 Analog In/Digital Out, and 16 Digital In/Analog Out modules are compatible with versions of Pro Tools HD older than version 9. The 16×16 Analog In/Out and 2×6 modules are only compatible with Pro Tools HD versions 9 and above.


Requirements to connect Symphony I/O to Avid Pro Tools PCI Cards:

  • Avid Pro Tools HDX, HD Native or HD Core/Accel/Process card installed in a computer in accordance with the Pro Tools HD Compatibility Grids, available at
  • Pro Tools 8.1 (requires older Symphony I/O firmware), 9.0 or greater, 10.0 or greater, 11.0 or greater

Requirements to run Apogee Maestro software, to control Symphony I/O via USB:

  • OS X 10.8.5, 10.9.5, and 10.10 and higher (64-bit and 32-bit kernel modes)
  • Apple Intel Mac

USB Audio Interface Mode


Requirements to connect Symphony I/O as a USB audio interface:

  • OS X 10.8.5, 10.9.5, and 10.10 and higher (64-bit and 32-bit kernel modes)
  • Apple Intel Mac – 2GB memory required, 4 GB recommended


Standalone Audio Interface Mode

In Standalone audio interface mode, all audio connections are made using the standard analog and digital i/o found on the I/O Module(s). For software control, connects Symphony I/O’s USB port to a Mac.


Requirements to run Apogee Maestro software, to control Symphony I/O via USB:

  • OS X 10.8.5, 10.9.5, and 10.10 and higher (64-bit and 32-bit kernel modes)
  • Apple Intel Mac

Symphony I/O Firmware and Software Installer Release 5


Download Release 5 here.


16x and Rosetta series users, please consult the Legacy Interface Release Notes.


Who should update?

Users running or upgrading to OSX 10.10 Yosemite
New Users setting up their Symphony system for the first time
Users on 10.8.5 or 10.9.5 who would like the new Features and bug fixes
NOTE: Symphony Users who are currently running 10.8.4 or lower and don’t plan to update their OSX should not update to Release 5
New Features
Compatibility with Mac OS X Yosemite and Mavericks (10.10 and 10.9)
with continued support back to OSX 10.8.5
Up to 3 Selectable Speaker Sets can be toggled and controlled from Maestro
Command-click lets you enable multiple speaker sets at the same time
Dim functionality for Main Outputs and Headphone outputs
Sum To Mono functionality for Main Outputs and Headphone outputs
Various bug fixes


Before you update

  • Please note critical Maestro settings such as Trim levels before performing a firmware update.Parameters will be reset after installing new software.
  • Unplug headphones and mute speaker volume before updating firmware.


To update


After updating – After updating, verify the following settings;

  • Audio Interface Mode – press and hold the right hand encoder to verify that Symphony I/O is set to the desired audio interface mode.
  • If using the Symphony 64 card, verify that the Symphony Source setting (found in the Maestro 2 > System Setup tab and Audio MIDI Setup) is set to the appropriate Symphony 64 Port setting:

! ! If interfaces are connected only to Port 1, set Source to Port 1: 32ch.
! ! If interfaces are connected to both Ports 1-2, set Source to Port 1-2: 64ch.

  • Check that Output settings such as Speaker setting and level and headphone level and mute are set as expected.




How do I set my software’s I/O buffer?

The I/O Buffer setting found in most audio software is one of the most crucial, but often ignored, settings in a Mac-based recording system. When choosing a buffer setting, a compromise between the latency through the application and the amount of computer processor power accessible to the application must be made.Latency– the slight delay between the moment you play a note and hear it in your headphones after conversion and processing.

A lower buffer setting results in lower latency but less available processing power. If the application can’t access enough processor power, processor overruns may occur, resulting in audible clicks and pops or error messages that interrupt playback and recording. A higher buffer setting, on the other hand, results in greater amount of accessible processor power (i.e. less chance of overruns) but increases the latency. Determining the best setting requires some trial-and-error in order to find the best compromise.

Keep in mind that as tracks and plug-ins are added to a software session, processor requirements increase. Thus, the buffer setting that works during the early stages of a session might result in processor overruns during later stages. The best strategy is to set the buffer to a lower setting during recording and accept certain limitations on plug-in usage, and then raise the buffer during mixing to utilize the computer’s full processor power when latency isn’t an issue. With the processing power of today’s Macs, you may find that adjustment of the buffer isn’t necessary, and you can leave it at a setting for low latency and still access a sufficient amount of processing power when adding tracks and plug-ins. If you do encounter clicks, pops or software errors, don’t hesitate to experiment with the buffer setting. Please consult the section on Working with GarageBand, Logic and Mainstage to determine how to se the I/O buffer setting is found in your audio application.

When recording, the input is delayed in my headphones

Decrease the I/O buffer size in your audio application. See “How do I set my software’s I/O buffer?” for more information.