Manufacturer's Comment

Empirical Audio is very grateful for the Overdrive SE DAC review from Steven Plaskin and Audiostream. Steven did an outstanding job of capturing both the features and the sound quality attributes of the Overdrive SE DAC, the Final Drive and the Short-Block.

We recommend connecting the Overdrive using balanced cables directly to amps, however because the output is not transformer-coupled, some expensive preamps with low output impedance can sound a bit better. For best results, we recommend using the Final Drives with the Overdrive SE and going balanced direct to amps.

The release of Mavericks OS for Mac unfortunately threw a monkey-wrench into many vendors products that utilize the firmware and drivers from M2Tech for USB, including the Overdrive. M2Tech has not been forthcoming with a solution, however our customers have identified a fix for this which was developed by a third party and all of them are currently using this fix successfully. I'm not sure if Steven tried it, but the Snow Leopard driver also works with Lion and Mountain Lion OS's.

Thanks again for a great review—Steve Nugent, Empirical Audio


tubefan9's picture

I like Steven's reviews because I feel like they come from the heart.

Steven Plaskin's picture
tubefan9, The compliment is appreciated. Thanks, Steve
ketcham's picture


Did you ever place the final drive between your Ayre preamp and amp monoblocks? What was your impression? I found when I bypassed my $12,000 preamp the effect was like removing thick wool blankets that were wrapped around my speakers three times. This was not subtle. A passive preamp at a fraction of the cost has significant benefit.

Steven Plaskin's picture
I did try the Final Drive between my preamp and amp with no noticeable improvement in sound. As I stated in the review, I really liked the Final Drive. Just how all of this plays out will depend on your preamp-amp and setup. But going to the Overdrive-Final Drive-and my amps did not result in a substantial improvement compared to the Overdrive-Ayre Preamp and Ayre amps.
scully280's picture

After adding a Empirical Overdrive to my system several years ago I was initially quite happy with every aspect, until I tried to use my FM tuner. Wideband noise from a new, unknown source had made most FM listening useless. Disconnecting the Overdrive power, however, cleared up the interference. I took the Overdrive to work, where we have an Electromagnetic Compatibility test chamber and ran the standard FCC test for consumer products. The Overdrive failed the radiated emissions test miserably. Fortunately the application of a clip-on ferrite bead to the USB cable allows the Overdrive to pass the test, and it does significantly reduce the FM band interference in my system, but doesn't eliminate it completely completely. I was disappointed by this oversight and possible violation of regulations, and I was wondering if you have noticed any EMI compatibility issues with the equipment you have reviewed?

Steven Plaskin's picture
I'm sorry to hear this about the Overdrive SE. My setup and amplification does not appear to be sensitive to RFI / EMI; at least not in my limited reviewing experiences. My Ayre KX-R preamp, I hope to update it to the Twenty Model eventually, is pretty resistant to most extraneous RFI / EMI. Empirical Audio should respond to this issue.
scully280's picture

I've made a an error with the name of the device i have, it's an earlier Off-Ramp 4 not an OverDrive. I have never tested or heard an Overdrive and I can't comment on any aspect of it's performance. My experience with the older Off Ramp made me wonder how a current Empirical product behaved. I regret that my error with the name of the two products may have caused some confusion.

To put the technical issue in perspective, the frequencies involved are all over 30MHz, and the levels are around 40 micro-volts, so only wide-open components will allow the signals to get into their circuits, and I suspect most non-radio audio gear isn't wide open and will reject the interference. So it's quite possible most audiophiles will not experience any direct interference except with FM tuners. As to the regulatory issues this is something Empirical Audio may want to contemplate.

Regardless of all this, I continue to use my Off Ramp with the added ferrite bead as my primary DAC driver!

Empirical's picture

The EMI compatibility problem you experienced was likely due to the cable and computer you were using and the size of the ground-loop created with attached power cords. The computer is actually the primary emitter here and the Off-Ramp mainly the receiver. The emissions were due to the ground-loop with the computer, so putting a ferrite on the cable will solve it, however this will also effect the rise-time and therefore increase the jitter possibly impacting audio quality. A better solution is to add the Short-Block USB cable filter, which primarily minimizes HF in that ground-loop (common-mode noise) without impacting the differential signal lines, actually reducing jitter. We have found that different computers USB interfaces create different levels of common-mode noise on the USB cable, some worse than others.

When you performed the emissions testing, did you also have a coax cable and DAC attached to the system?

Were you using the OR4 wall-wart or a third-party power supply for the Off-Ramp? We offer a new wall-wart used on the OR5 and the Dynamo linear supply to improve on the OR4 wall wart.

All of the Off-Ramp products also have very fast risetimes on the S/PDIF coax outputs in order to deliver low jitter signal to the DAC. It is critically important that you use a well shielded coax cable that is very close to 75 ohms characteristic impedance in order to avoid emissions from that source. We offer an excellent cable for this called the BNC-BNC coax with RCA adapters for $250. There is also a new mod available for the Off-Ramp for $150 that changes the S/PDIF output transformer to a better one, improving the signal integrity of the S/PDIF output and reducing jitter even more. All of these will improve SQ and reduce emissions.

Steve N.
Empirical Audio

scully280's picture

Indeed the ferrite is on the USB cable. I don't recall the exact details of the test because it was done informally over a year ago, and the test technician who did most of the work has left the company. But we did the test with a different computer than I have at home. One is an apple mac mini the other was a Dell laptop, i believe. But I would be happy to personally repeat the tests that your own test lab did when you had your FCC and CE certifications completed. I suspect that the setup details are in the report that your test lab sent you.

Empirical's picture

I'm sorry that you had this problem. I wish you would have contacted my directly when it happened. The problem with retesting is that my products have so many options that its really impractical and very expensive to test every single configuration. Different power supplies, DACs and computers add a lot of additional configurations to the mix also. I must test only one configuration and hope that the other configurations are okay. In addition, I often make improvements to my products mid-stream, and I typically do not retest for these. I try to keep the costs down so that I am not forced to charge even more for my products.

It would be helpful for me to know if your OR4 has the USB Hynes reg or the Turboclock and whether you are using the standard wall-wart that came with it.

I'll tell you what, since you had this problem, I can offer you a Short-Block for free. This is what I would rather you use anyway. Just shoot me an email. I'm building another batch in the next 2 weeks.

Steve N.

scully280's picture

I was going to let this drop, but I’m a bit insulted by the last reply. Here’s where we are; I found what I think might be an FCC EMI violation in an earlier product. This is high stakes; large fines and large seizures of equipment have resulted from single violations. Gambling that a version of a product passes is a big risk, but Mr. Nugent has told us that’s a risk he takes. This is something the company I work for, and many other companies can’t tolerate because they have found that even the best engineers can’t always be right on the first pass and the potential legal liability is too great. We test in our own lab until we know that our equipment will pass the FFC as well as the much more inclusive CE regulations, then we go to an outside test lab with all the accessories that will be sold with the product and test multiple setups.

So here’s the part that really bothers me. What is the offer for a free upgrade all about? Is the freebie to make this potential big liability go away, in which case I’m really cheesed off? Because, Steve, you gotta know I’m not your usual audiophile customer. I’m an electrical engineer who knows his way around this stuff, is more interested in results than trade jargon, and I have a lab at my disposal to verify results. Even if this is just honest customer relations do you think I would really be happy with an upgrade? At this point that happens only if you can show me data that tells me the upgrade really solves the problem, and now I think I want that data from an independent lab. Anyhow I’m happy with my solution, and when I get around to it I may add another ferrite.

So here’s my bottom line for this review. How does the reader know when you bring the DAC under discussion home that it will play nicely with your AM or FM radio, with your cellphone, your Bluetooth keyboard, or your television? Or how about with your laptop, or your wireless network? By trusting Steve? If that works for you, fine, but I would have to see data quoted from an independent test report.

And that’s all I’ve got to say.