Core Power Technologies USBe Perfect by Greg Voth


Gregvoth.jpgPreamps with built-in high-quality internal DAC’s are lovely things. My current favorite is the PS Audio Stellar Gain Cell DAC preamp with its internal asynchronous USB DAC, capable of 24/384 kHz (max) PCM, as well as DSD64 and DSD128 via DoP. You would think such a combination future-proofed, as I’ve described it in recent reviews, but there’s a disconnect.

In November 2019, I found a used 2015 i7 iMac (a top-tier model) – with a USB 3.0. But, while the 2015 iMac fit nearly all of my upgrade requirements, I forgot about the ever-reducing maximum length requirement of USB cable as the USB bus has been steadily improved over time. It wasn’t until I tried connecting this iMac to the PS Audio Stellar Gain Cell DAC that I hit the wall… the iMac wouldn’t talk to the Gain Cell DAC.

Optical cables are readily available in long lengths and work in this application, though the resolution is limited to 96 kHz max, hence my desire to get its USB working. My digital sources sit on my work desk (again), requiring 26 feet of cables, an easy job with Toslink cables. The maximum length of USB cable allowed under USB 2.0 was 5 meters. Not only was I able to better that limit with 20-feet of cable length by using the higher quality cable. I experienced no dropouts nor noticeable errors under my old Mac Pro’s USB 2.0 bus. The maximum cable length under USB 3.0 has been further reduced to approximately 8 feet and, under USB-C, even further. 

The Man With the Perfect Plan

Recently. I found myself catching up with Mark Schifter, whom I met in-person while reviewing the Emerald Physics EP 4.7 speakers for this publication a good while back. We’ve stayed in touch since, and I look forward to his products that appear from time to time at my door for review. Schifter was excited about his recent and upcoming projects for Walter Liederman, the owner of Emerald Physics, Underwood HiFi and recently, of Schifter’s former company, Core Power Technologies, and we made plans for a few items to come my way for review. 

As we chatted about all things audio, I mentioned my USB issue, as I have with anyone who might offer input that might resolve my quest to return stable USB to the rig at the same distance. Schifter mentioned his USBe Perfect product, thinking it might offer the solution. To quote the underwood Hi-Fi site, “The USBe Perfect is a powered Reference USB interconnect solution. It is quite unique as it is not just a de-jittering device. It has a DC-to-DC converter and is a full USB regenerator. It makes a new super clean and quiet USB signal and then it [de-jitters] that signal. It will turn your computer into a high-end music server. It even makes good music streamers and servers better.” 

USBe Perfect_1.png


USBe Perfect Solution, Take One

Schifter sent me a USBe Perfect ($299 introductory price) and his Discovery LSA DPH-1Digital Preamp DAC for review (reviewed here). After spending a couple of pre-holiday weeks listening to the DPH-1 on New Year’s Day, I began experimenting with the USBe Perfect, hoping that the change in the year might offer a change in USB connectivity. With the USBe Perfect said to integrate seamlessly for both USB 2.0 and USB 3.0 protocols and, with power regeneration built-in, it shows great promise, and at its introductory price, it’s not a heavy lift to try out.

Tektonad.gifThe Perfect Solution is a small USB 3.0 dongle of sorts, similar in size to a very thick thumb drive, at 2″ long (including its male USB A plug), 1″ wide, and about 7/8″ deep. Its width can prevent using a neighboring USB port, but there’s always a way around such things. I stalled the device at my iMac, into the USB 3.0 dock, and unearthed my 20-foot length of Transparent Performance USB, connecting it between the USBe Perfect and the PS Audio Gain Cell DAC. As I went about selecting the drivers in System Preferences and Amarra Hi-Fi, I found that the Gain Cell DAC’s driver was coming up in each list… an excellent sign! I turned on the Gain Cell DAC, plugged my Sennheiser HD650’s into the Gain Cell DAC’s convenient front quarter-inch headphone jack, and selected the USB input with the remote. I heard music. It sounded great! What a relief.

My excitement got the better of me. When I attempted to add my additional 6-foot length of Transparent Performance USB to the 20-foot length, the music stopped, and the iMac locked up. I thought the Gain Cell DAC might have to return to PS Audio for a check-up but, continuing to troubleshoot the issue; I tried the two cable lengths and USBe Perfect with my older Mac Book Pro. Everything worked perfectly under the MBP’s USB 2.0 bus, properly sending the audio signal to the Discovery LSA DPH-1Digital Preamp DAC.

With the iMac no longer seeing the Gain Cell DAC’s driver under USB 3.0, I thought it likely the Sound Preferences had been corrupted, causing the iMac OS to lock up. I trashed some prefs, restarted, and found that the PS Audio USB Audio 2.0 driver was once again visible and selectable under the Output tab. Before turning the Gain Cell DAC on, I plugged in the USBe Perfect at the iMac and connected my single 20-foot length of Transparent Performance USB between the USBe Perfect and the Gain Cell DAC. When I turned on the Gain Cell, I got music thru headphones plugged into the headphone jack.

USBe Perfect, Take 2 

Origin250.jpgWith the iMac lock up resolved and the Gain Cell DAC’s driver again appeared in sound preference panels, I was now able to give the USBe Perfect a listen to see if there’s any other goodness under its hood. Under optical, while damn convenient, listening was limited to 24 bit-96 kHz. USB allows the play of far higher resolution music files and, thanks to the Gain Cell DAC’s USB side, I can play files up to 24 bits with a 384 kHz sampling rate. The USBe Perfect’s differential outputs provide selectable de-emphasis (programmed for 1 to 3 meters) to compensate for the increased error rates & distortion that USB 3.0 signals experience. This setting is not user-adjustable and is set upon purchase by the folks at Underwood HiFi. Though my sample was selected to the standard “short length” setting (1-3 meters), its voltage correction ability was powerful enough to allow me two-meters more length OVER the max length under USB 2.0 and 6 meters over the max length under USB 3.0!

In my case, the USBe Perfect liked being left alone and not plug and played, and that’s the way I’ve left it – it’s been quite stable. I leave my iMac on for days at a time; I’ve just needed a couple of restarts to maintain connectivity.

Finally, on to Listening

Unspeakable.jpgAfter this lengthy explanation of my USB cable length issue, I’m finally able to address how it sounds. Here goes: A play of Bill Frisell’s “1968” from his 2004 “Unspeakable” release (Nonesuch Records, Inc.) revealed added clarity to transients and what appeared to be extended and improved bass performance. The sound came from a quieter, blacker background, which yielded more life and vitality. “La Vie en rose” from the bonus edition of Melody Gardot’s “The Absence” (Decca 2012) had a musicality not recalled from prior listens – the strings possessed a liquidity that enveloped me. Gardot’s voice was soft and smooth like honey, and the instrumentation traveled to the ear with greater speed and definition, better rendered on a stage of excellent depth, though still quite intimate.

The Masquerade Is Over, a live track from the Jarrett, Peacock, and DeJohnette trio’s “After The Fall” (ECM 2018), was delightful, with its intimate piano, deep, thoughtful bass lines, and playful percussion. The dynamic range in my system seemed to be extended as the musicians emerged from denser black. Dynamics were enhanced, and the music was possessed with added musicality and interest.

abercrombie.jpgJohn Abercrombie’s final album with his quartet, “Up And Coming” (ECM 2018), was up next and, though there have been posthumous releases since, there was something very special about buying this CD on the day I heard of his passing, what seemed, at the time, to be John’s final musical statement. This music is beautiful in its simplicity – it takes a well-seasoned player to sit back and allow the music to flow around you from others without feeling the need to intrude. It’s clear, self-assured, and reverent of the musical moment, also relaxed and thoughtful, allowing its languishing pace to speak volumes. From the iMac, through the USBe Perfect and out across the room to the main rig, the play of this life’s finale was just lovely. Each note hung lighter in the air, with less Jitter apparent, holding added dimension. Each instrument’s character was reproduced with seemingly greater resolution, with each phrase rounder and better resolved than previously heard.


The Wrap

While researching this review, I ran across a post by a “flat-earther,” who proclaimed the USBe Perfect “snake oil” without even giving it a listen in person. That silliness could not be farther from the truth. The USBe Perfect makes digital audio sound better and helps resolve the USB 3.0 cable length issue. The USBe Perfect is an accessory l consider an absolute necessity.

As of 03-12-21, the USBe Perfect’s $299.00 INTRO SALE price is still in effect (delivered worldwide). In my case, the USBe Perfect was, in fact, the “perfect” solution to my long-standing USB length predicament… the fact that it ALSO improved my rig’s sound quality through USB, well, that’s nothing short of gold!  I find it fascinating that the solution to my long-lived USB cable length issue came from a friend.



greg voth           


Specifications: USBe Perfect

Pricing (as quoted from the Underwood HiFi site):

 $499.00 without a USB cable (One is required, yours or one of ours)

 $599.00 with one $199.00 1m Silver USB cable          

 $799.00 with one 1m $499.00 Diamond USB cable  

As of 02–05-21, its INTRO SALE, at $299.00 (delivered worldwide) appears still on.

This Underwood Hi Fi’s current deal is a USBe Perfect with a $200.00 Silver series USB cable for $399.00 (SAVE $200) OR USBe Perfect with a $500.00 Diamond series USB cable for $499.00 (SAVE $500). All the deals listed here include shipping anywhere in the world.



Underwood HiFi





• Power Regeneration BUILT-IN

• Integrates seamlessly for both USB 2.0 and USB 3.0 Protocols

• Vastly lowers Jitter

• The USBe Perfect is designed to minimize signal degradation effects such as crosstalk and inter-symbol interference (ISI) that limit the interconnect distance between two devices.

• The input stage of each channel offers selectable equalization (optimization) settings that can be programmed to match loss in the channel. We have optimized this for USB Cables of 1 to 3 meters.

• The differential outputs provide selectable de-emphasis (again programmed for 1 to 3 meters) to compensate for the increased error rates & distortion that USB 3.0 signals experience.

• The level of de-emphasis depends on the length of interconnect and its characteristics. Longer lengths are easily handled.

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