Since the release of the Sound Devices 633, we’ve noticed a number of questions that customers are consistently asking. I’ve addressed the top 20 FAQs below. If you have any further questions, please contact a member of our sales staff or e-mail me directly.
1) Where in the signal path are the A/D and D/A converters placed?
A/D conversion occurs immediately after the hardware limiters on channels 1-3 and right after the input on 4-6. The signal remains in the digital realm until it hits the D/A converter directly before the outputs.
2) What are the details of the unit’s high-pass filters and limiters?
The 633’s unique high-pass filter circuit occurs before any amplification of the signal, resulting in higher headroom for the remaining audio. Each channel’s HPF can be adjusted in 10 Hz increments from 80 to 240 Hz. The roll-off has a compound slope that varies depending on where it’s set.
The 633 has two types of onboard limiters, analog and digital. The analog input limiters affect only signal passing through the mic preamps on channels 1-3. These limiters are pre-fader with a fixed threshold of +16dBu, 20:1 ratio, 1 mS attack and 500 mS release. The analog input limiters are always on, protecting the A/D converter from overages.
There are post-fader digital limiters on each input, the L/R mix bus, and the Aux 1/2 output bus. These limiters can be globally switched on/off via the software menu. They have a 20:1 ratio with 1 mS attack and 500 mS release. You can select either a hard knee or soft knee reduction curve. The default threshold is +16dBu, but they can be adjusted from +4dBu to +18dBu.
3) Can inputs 4, 5, and 6 be panned within software menu?
Yes, but inputs 4, 5, and 6 can only be centered or hard panned. However, if you have the recorder set to capture ISO tracks, they can always be panned freely in post.
4) Does the 633 support Channel Linking? And which channels can be linked?
Channels 1-2 and 5-6 can be linked as stereo pairs or M/S pairs. This also links their respective limiters together to preserve imaging during gain reduction. The channels will retain separate trim and HPF controls, while their fader level and stereo balance will be linked to the dials of either channel 1 or 5.
5) Does the 633 have a 32-bit floating point DSP?
6) Can the 633 simultaneously record WAV and MP3 files?
The 633’s default setting is to record all 10 tracks (6 ISOs, L/R, Aux 1/2) to a polyphonic wav file that is mirrored on both media cards. You can easily set one of the cards to record either a stereo MP3 of the L/R bus or the Aux 1/2 bus.
Other options include recording polyphonic WAVs of just the 6 ISO tracks, just the L/R bus, or just the Aux 1/2 bus. You can also set it to record mono WAV files of all 10 tracks or just the 6 ISOs.
Simultaneous MP3 recording cannot be done when the 633 is recording at sample rates above 48 kHz.
7) Additional concessions at 88.2, 96, or 192 kHz sampling rates:
The maximum pre-roll time reduces from 6 seconds to 3 seconds in 88.2 or 96 kHz, and further to 1 second in 192 kHz.
In 88.2 and 96 kHz, the limiters and high-pass filters function as normal. However, in 192 kHz, all digital limiters are disabled, leaving only the 3 analog input limiters in effect. The high-pass filters can either be set at 50 Hz or disengaged.
7a) CORRECTION: High Sample Rate Recording
The Sound Devices 633 has a maximum recommended recording count of 8 tracks at 88.2 / 96 kHz and 6 tracks at 192 kHz. This count can be made up of any of the 633’s recordable tracks (ISOs 1-6, L/R mix, Aux 1/2), however, it is not a hard and fast track limit. If you try to record more than the recommended track count, a system warning will appear, but you can press OK and move on.
Be aware that depending on the quality and speed of your recording media, you may experience problems defying the recommended track count. But if you have top quality media, it can be done without issue.
8) How does the timecode circuitry compare to that of the 664?
It is identical.
9) Does the 633 have Word Clock I/O?
10) Does the 633 support Multi-Unit Linking?
11) What is its total battery life?
With AA batteries and two Sony L-type cells installed, the 633 can be in use for 30+ hours.
12) When the 633 is plugged into an external DC power supply, will it charge the Sony L-type cells?
13) Does the 633 have Mix Assist?
14) Does the 633 offer T power?
15) Will Sound Devices be releasing a CL3 Attachment for the 633?
As of now, no.
16) How do you connect an external keyboard?
The 633 comes with a USB B-to-A adapter, allowing you to plug any standard USB keyboard into the USB connector on the unit’s right panel.
17) Do you need to unplug the external keyboard to change media cards?
Yes. The media door cannot be opened with a USB cable plugged in.
18) Will the 633’s LCD be visible in bright conditions?
The 633 has a daylight mode that changes the LCD’s color scheme to be more visible in direct sunlight.
19) Is the 633 moisture resistant?
Yes, the 633 has a splash-proof front panel and sealed connections allowing you to safely record in a drizzle.
20) What is the size and weight difference between the 633 and similar units?
20a) (Updated 12/11/2013)
This quick video compares the 633’s footprint with other popular
One of our readers pointed out an oddity in the dimension specs we gave in the comparison video. I had used the manufacturer specs and even managed to copy and convert them correctly, so why the discrepancy?
I broke out my trusty tape measure and discovered that Zaxcom measures the chassis of their recorders, but not any protruding connectors. Sound Devices measures everything, which I think is a better way to go.
Here are the W x D x H dimensions, as painstakingly hand-measured by me:
Sound Devices 664: 12.88 x 7.75 x 2.31″ (32.72 x 19.69 x 5.87 cm)
mfr weight spec: 4.75 lbs (2.15 kg)
Zaxcom Nomad: 10.63 x 7.63 x 2.13″ (27 x 19.38 x 5.41 cm)
mfr weight spec: 3.8 lbs (1.72 kg)
Sound Devices 633: 9.25 x 5.63 x 2.13″ (23.5 x 14.3 x 5.41 cm)
mfr weight spec: 2.56 lbs (1.16 kg)
Zaxcom Maxx: 8.56 x 6.13 x 2″ (21.74 x 15.57 x 5.08 cm)
mfr weight spec: 2.5 lbs (1.13 kg)
I hope this article has answered some of your questions. Again, we’re here to help, so don’t hesitate to contact Trew Audio with any further queries. And don’t forget to follow us on Facebook and Twitter!
– Chris Frasco