Empirical Audio Off-Ramp 4 USB format converter Specifications

Sidebar 1: Specifications

Description: USB-AES/EBU, -S/PDIF, or -I2S data format converter for use with PCs and Macs (driver software included). Drivers available for Windows 7/Vista, Windows XP/2003, Mac OS X 10.6 (Snow Leopard), Mac OS X 10.5 (Leopard), Mac OS X 10.4 (Tiger). Input: USB 2.0–compliant. Operates in asynchronous isochronous mode. Output: S/PDIF electrical on RCA jack, AES/EBU on XLR jack, I2S on RJ-45 jack. Sample rates supported: 32, 44.1, 48, 88.2, 96, 176.4, 192kHz. Input/output bit depth: 16 or 24. Power supply: 12V DC wall wart. Options: Monolith lithium-ion battery power supply, one or two higher-quality clock modules, Hynes voltage regulator on USB module, Canare 75 ohm BNC jack or NextGen connector.
Dimensions: Off-Ramp 4: 4.25" (108mm) W by 2.5" (65mm) H inc. feet by 7.25" (185mm) D inc. RCA jack. Monolith battery supply: 6.75" (172mm) W by 2.5" (65mm) H inc. feet by 6.6" (168mm) D. Approximate weights: 1 lb (0.5kg), Off-Ramp; 3 lbs (1.4kg), battery supply.
Finish: Black-anodized aluminum.
Serial Number Of Unit Reviewed: None found.
Price: $799. Options: Canare 75 ohm BNC output jack, $20; 5V I2S output capability, $50; Dual Turboclock, $700; Hynes regulator, $300; Monolith LI battery, $1199. Approximate number of dealers: Sold direct. Manufacturer: Empirical Audio, 13852 Bishops Cap, Black Butte Ranch, OR 97759. Tel: (541) 595-1001. Web: www.empiricalaudio.com.

Empirical Audio
13852 Bishops Cap
Black Butte Ranch, OR 97759
(541) 595-1001

VandyMan's picture



Very interesting review. I look forward to seeing a comparison to the Alpha USB. I thought it was too expensive for a USB converter ($1600), but it looks like a potential bargin compared to the Offramp 4. 

thestewman's picture


Did I miss something in your article ?

"Up to this point I'd been using a generic USB cable with the Off-Ramp. I now substituted the expensive AudioQuest Coffee cable ($295/1.5m). If I heard a difference, it was very small, but if I had to swear on J. Gordon Holt's unwritten autobiography, I'd say that the AQ continued in the same direction the improvement I'd heard with the battery supply."

 "I spent the rest of that day trying to measure the differences between these two USB cables. It proved as frustrating as a snipe hunt, though I did find a very slight difference in jitter between the AudioQuest and generic cables with the Transporter: The generic USB cable was better."


The Transporter does not have a USB input. 

John Atkinson's picture

The comparisons were between the premium and generic USB cables feeding the Off-Ramp 4, which in turn fed the Transporter via AES/EBU.

John Atkinson

Editor, Stereophile

Johnny2Bad's picture

RE: " ... my 2006 G4 Mac mini runs OS X 10.5 (Leopard), the final version compatible with its obsolete G4 processor— ..."

Unlike the majority of current day Mac users, I am one of those people who bought a 68000 Mac running System 6.0.8 and have used Macs daily since that day in 1990. This means three incompatible CPU families (24 and 32-bit Motorola 680x0 series; 32 and 64-bit Motorola and IBM PowerPC series, and 64-bit Intel x86 series).

During that time I also worked extensively with WindowsOS and Linux / UNIX systems, including authoring documentation for a prominent Linux distro ( note that the typical Linux contributor would rather eat glass than write documentation).

Furthermore, I've been using the audio authoring and playback performance capabilities of these machines to the fullest as the current technologies allowed, and using the computer as a primary audio playback device in a High Fidelity Audio System for the last 20 years.

I can assure you that the Motorola/IBM G4 and IBM G5 CPU's and the associated MacOS Operating System code, third party software and Apple/3rd party hardware is not only adequate for the task, it in many aspects is superior to the Intel x86 hardware that supersedes it. It is only in the last 2 or 3 years that the x86 Macs can claim to catch up in Audio processing power to what G4 Macs could do in 2001.

I never experienced dropouts, not even once, while using G4-based Macs in real-time authoring or playback of up to 8 simultaneous 24/96 channels; it was a huge shock to discover dropouts on recorded audio files, after the musicians had gone home, of course, when reviewing with my first 2 GHz dual core Intel CPU-based Mac that, on paper, "ate for breakfast" the lowly 867Mhz G4 it replaced.

Naturally that led to further investigation on my part, and I can assure you the G4's are extremely competent audio performers (and video; you can play back12 Quicktime videos simultaneously, and actively manipulate any one video ... including scrubbing ... without a dropout on a G4 ... you might be able to simultaneously play back maybe 3 videos, don't attempt scrubbing, on the Intel x86 that first replaced it. There is much that was lost when moving from a PPC's RISC architecture to the x86's CISC when it comes to real-time data handling.

Obsolescent ... maybe. Obsolete ... hardly.