The Ultrafide audio U500DC Power Amplifier - Review

The initial look and feel of the amplifier

Lifting the amplifier out of the box, its weight is deceiving for its size, it's quite a hefty thing and gives you a very nice sense of quality. Although it's not a 50lb valve behemoth, weighing in at a very reasonable 14.6kgs (32lb), it's certainly not something you'd want to drop on your toes. Starting with the feet, its 4 round feet are solid aluminium with a rubber insert, giving it a low-slung look.

The 4mm aluminium one-piece chassis top cover is made from 4mm aluminium and is secured by 8 screws on the underside. Its rounded side edges are very nicely done with the Ultrafide logo nicely embossed into the top. Finished with a high-quality black coating, there's nothing about this amp which wouldn't make you question its build quality. It's solid.

Connecting up

The connection panel on the rear of the U500DC is also made from 4mm aluminium and is nicely thought out in regards to layout. With the power inlet and power switch to the left of the unit. It's nicely reachable when it's on a rack of some kind. 

The power switch is a supply switch that is generally left on to allow the unit to remain on standby when the power button on the front of the unit is switched off.

• Ultrafide U500DC
• 2 channels of 500W @ 4 Ohms | 250W @ 8 Ohms
• Fully DC Coupled input to output
• Push-Pull Class A input driver stage
• Brand New “ground up” “Ultra Sigma” class D output topology
• Bi-Wire compliant
• Timbre setting switch, Pure & A/B modes
• XLR & RCA connections
• 3db adjustable gain (via internal jumpers)

• Goldfrapp - Tales of Us
• Goldfrapp - Head First
• Shpongle - Ineffable Mysteries from Shpongleland
• The Chemical Brothers - We Are The Night
• The Chemical Brothers - No Geography
• The Velvet Underground - The Velvet Underground & Nico - Abbey Road half-speed remaster
• Killing Eve Season Two
• The Beatles - Love
• Paul Simon - Graceland - Remaster
• My Bloody Valentine - Loveless - Remaster
• Cavern of Anti-Matter - Void Beats - Invocation Trex
• Jimi Hendrix - Are You Experienced - UHQR pressing

The U500DC in the Tannoyista System

The loudspeakers used in this review are a pair of Lockwood Major monitors loaded with the 15" Tannoy Monitor Gold drivers. The Monitors date from the 1960s and were the original ones used at Trident Studios and were used by The Beatles, The Stones, Lou Reed, David Bowie to name but a few.

More information can be found here: The Original Trident Studios Lockwood Loudspeakers - Review

How does it sound?

Three of my favourite albums to give the equipment a good workout to are by Shpongle, Cavern of Anti-Matter (COAM) and The Chemical Brothers. 

So, this time it was time to drop some COAM - Void Beats, Invocation Trex. 

This is when I heard the extent of how fun bass can be. From the start of the first track, a thumping kick drum filled the room. Wow... I don't think I've ever heard the Tannoys sound so alive and enthusiastic. As the record progressed, the emphasis on timing and how the U500DC keeps things in focus was analysed. 

I always try to set out to find that straggling piece of thread that you can slowly pull to reveal any errors in how it handles multiple layers of instruments and vocals. Keeping the intended soundstage together in its concise framework is something many amps need to improve upon. With the U500DC, I couldn't find fault. 

The more music I listened to the more my confidence grew. There was no fear of any unravelling, therefore, no thread to pull.

I then listened to such as Paul Simons's Graceland, the production of that album came through so naturally. Easy and rhythmic, the U500DC presents it as it is, an astonishing and meaningful work of art. The amount of transient detail was quite astonishing. 

Then with The Beatles Love album, much of the same, another exceptional soundstage with swirling psychedelic sections really stops you in your tracks.

Now finding that my second cup of tea had now gone cold, the other outstanding experience with the U500DC was the album, We Are The Night by The Chemical Brothers. Now, this album has tripped up some of my previous amplifiers in places. 

And not only that but in some places, it never seemed to quite sound right with a Valve amplifier, even the copper amp sporting the mighty KT-150 valves. 

Somehow valves and this album (in places) just didn't grip the groove hard enough. It needs obedience, speed and flow. So with the U500DC, the opening track put a large smile on my face. The amount of detail and intensity came flooding through with grip and ferocious intent. 

And as the album progressed, it was clear to see that the U500DC really understood the complexity of the music. 

It's clear that Ultrafide has brought many years of knowledge and technology know-how into the U500DC. And they've made this amplifier extremely flexible to boot. 

Stepping back, this amplifier has a natural and highly realistic presentation with clarity that doesn't overemphasise and has a huge soundstage. That is, like being in a live environment, its presentation simply flows. 

The high frequencies portray no splashy confusion, imbalance or sibilance, and the mid-range has body and fluidity. The bass is tight and keeps its extension clean and organic with no notable misdirection. Everything I throw at this amplifier works like a charm.

Inside the Ultrafide U500DC amplifier

Inside is all neatly planned out using very high-quality internal components. The construction is also very solid, with the huge 500VA custom wound transformer. This amplifier is a fully DC design I/O using pure copper tracks. It also uses an overall DC servo on its input which eliminates any errors.

Devoid of any slew rate limitations, this amplifier also has no interstage capacitors and uses the 'Ultra Sigma' technology with a Push-Pull, Class A input driver stage.

The great thing about this is that if you need maximum output for more demanding systems, the gain can be increased via an internal link to give 3db more gain. This also removes the soft clipping circuits.

The U500DC is a pure dual mono design using x4 35A 600v rectifiers and 27,000uf capacitor banks enabling output from 5 - 5000w. Not that you would use 5000w, but its headroom is vast. And it's quite evident as it has no swing deterioration, performing with total ease.

But, Tannoys don't need anything like 250wpc I hear you say. Well, over time, it's become very clear to me that more watts aren't a problem with the Tannoys when you find the right design. Finding an amp to match with Tannoys can be a big undertaking to get right. 

With valve or SS, Class A/AB/D... it can sometimes be more restrictive if you go by what's generally a recommended suiting.

That is, in my opinion, a lowish power push-pull valve amp of around 30-100wpc is a safe bet with these speakers. But regarding dynamics and sound and getting the very best out of said speakers, could that safe bet be sometimes too safe? 

The amount of power my Tannoys use would be extremely low, even at very high volumes. So, for me, the design of how it delivers the power is more important, regardless of how much power it has in reserve.

For another listening experience, although quite brief, I had a friend bring his Harbeth Super HL5 plus speakers over to try. Although it was a brief visit as he couldn't stick around for long. I had a few hours with the Harbeths and they surprised me no end. 

Okay, they're not 15" Tannoys and it would be futile to even try to compare the two as they're totally different beasties, but the U500DC really made them work and the expression through the music was really impressive.

I used to own the same speakers, albeit not the 'plus' version, and they were great with Chord Electronics kit but not with the various valve amplifiers I tried. 

The best valve amplifier I tried with the Harbeths was a vintage Woodside Radford STA25 but in my opinion, they generally seemed to enjoy well-designed solid-state amplification rather than Valve. 

The U500DC and Harbeth combination was quite astonishing, lovely and powerful. Again, the midrange shone through as lush and wholesome bringing that realism and texture to the sound. On my friend's return, he didn't need to sit down to hear how great it sounded and was very impressed.

 In regards to the sound. It's beautifully articulate, neutral and with no straggling or annoying traits that would distract you or take you away from the music and its intended expression.

Using XLR or RCA connections

This clever little switch slightly alters the input circuits. Switching it to Vintage, allows the amplifier to operate in a more traditional class A/B sounding mode. I started the tests with the switch in the Pure setting, and after each session, I flicked over to the Vintage setting using the same material. My findings were subtle, but nevertheless, the effect was audible. 

Reading the literature from Ultrafide in regard to this switch, they also came to pretty much the same conclusion. In fact, a 50/50 split was found in their tests. I found that in Pure mode, the sound had a very subtle amount of added air and expression than in Vintage mode. 

In my opinion, the Vintage mode however seemed to suit older analogue recordings. Music from Paul Simon The Beatles and Jimi Hendrix all benefited slightly from having the switch set to Vintage. For me... I'd be happy to keep the switch in Pure mode 90% of the time. 

But of course, we're all different and perceive things differently in our music and our systems. The Timbre switch is a very nice addition to the amplifier, it adds that extra flexibility and it's certainly useful for the fine-tuning of a system and for different tastes in music.

The U500DC is a digital amplifier but it has the heart and soul of a very high-end analogue, class A or AB amplifier. From Dance to Hendrix, the purity of its performance gives it the ability to bring drama and life to the sound. Let's face it, this is how class D should be done.

Conclusion

Before I started this review I had a chance to audition a selection of loan amplifiers as production on the U500DC was delayed slightly (due to worldwide reasons we can all understand). Some were valve, Class A and D and were mostly Hi-Fi but some were from the professional arena too. 

Firstly, the Air-Tight ATM-1, a very nice Radford STA25, newly re-conditioned by Radford Revival, Luxman L550AXII, the Nuprime AMG STA, ART SDA1 pro amp, Neurochome 286 as well as a few other pro amps.

The best of the lot was probably the Luxman (which was integrated), but because it was on loan from a friend, I only had a week with it. Second, in line was the Radford and trailing in 3rd place was the Neurochrome. 

And although I didn't have much time with the Nuprime AMG STA digital amplifier, I found almost immediately that it simply wasn't a good match. The Nuprime, like the Luxman, had a gratifying grip with the Tannoys and the bass was also great, but unlike the Luxman, the high frequencies were more harsh and clinical and, well... obviously digital.

So listening to the Ultrafide U500DC it was safe to say that it beat everything else into a cocked hat and I'm more than impressed on all counts, to say the least. 

It has everything you'd want from an amplifier and more. This isn't one of those flimsy rattle boxes so many manufacturers produce. Using high-quality materials with plenty of thickness, the chassis and build quality are as solid as concrete. 

The styling aesthetic brings a serious tone, bringing that feeling of, yeah... this means business. And with that same token, it's none intrusive, slick and a very professionally thought-out design is indisputably satisfying. 

The internals is also very well thought out too using top-notch components and materials. No annoying over-bright LED lights, no garish features or whirring fans.

In regards to the sound. It's beautifully articulate, neutral and with no straggling or annoying traits that would distract you or take you away from the music and its intended expression. 

Impressive and detailed, the U500DC has a powerhouse of juice to keep you coming back for more. The reproduction of textures and that dynamic authority is a beautiful thing to experience and it does it incredibly well. 

It presents the complexities of even the most demanding material and leaves nothing behind. Even with 'not so great' recordings, it gives it straight. The magic of its layered and dynamic sound stage is exact and precise and keeps everything in control, prioritising the handling of huge swings with tonal ease. 

And the use of the Timbre switch is also a very nice feature. I can see it being used in either setting to suit different systems and tastes. 

The U500DC is a digital amplifier but it has the heart and soul of a very high-end analogue, class A or AB amplifier. From Dance to Hendrix, the purity of its performance gives it the ability to bring drama and life to the sound. Let's face it, this is how class D should be done. 

When you have an amplifier performing and flowing with no perceived error, and when you have a sound stage doing everything right, you know you have something very special. 

No matter what kind of speakers or setup you have, whether you enjoy valve or solid state, dance, rock or classical, I can highly recommend that this amplifier is on your list of contenders.

The sound of the studio is now at home.

What else is coming from Ultrafide?

Ultrafide are currently in production of the forthcoming U4PRE. A matching preamplifier for the U500DC. This sounds very exciting and would love to match it.

• Audio Channels (quantity) 2
• Audio Inputs 4 2 RCA (Single Ended)
• 2 XLR (Balanced)

NOTE: both input types are always active; thus 2 sources can be summed if desired

• Input Impedance 10k RCA and XLR
• Input RFI Filtering Capacitance 550pF RCA and XLR
• Audio Outputs 4 pairs Binding Post

NOTE: double channel connectors allow separate Tweeter and Woofer cables if desired

• Output Impedance 25mR
• Maximum Voltage 70V
• Maximum Current 30A (pulsed testing)
• Voltage Gain 26dB (x20) 29dB (x26)
• Current Gain 50,000 94dB
• Sensitivity 2.2 Volts
• Dynamic Range 115dB Un-Weighted 22-22kHz
• Inter-stage Coupling DC Coupled
• Frequency Response 5 to 20kHz +-0.3dB
• Distortion 0.003% at 5W 0.008% at 200W
• Rise/Fall Time 10uS
• Stability Unconditional
• RMS Power into 4R 500W 600W at high gain setting
• RMS Power into 6R 333W 400W at high gain setting
• RMS Power into 8R 250W 300W at high gain setting
• RMS Power into 12R 166W 200W at high gain setting

NOTE: Amplifier is stable into 2 ohm loads but with no increased power.**

• Power Supply Connector 10A Furutech C13 IEC
• Fuse 10A
• Nominal Power Supply Voltage 230Vac (50Hz) or 120Vac (60Hz)
• Power Voltage Selector Internal
• Power Isolation Switch On Rear Panel
• Standby Switch On Front Panel
• Remote Standby Connector on Rear Panel
• Power Consumption operational 200W average 1,000W max
• Power Consumption Idle 15W
• Power Consumption Standby 1W
• Current Consumption 230v – 1A nominal (5A max) 120v – 2A nominal (10A max)
• Power Indicator Green for Out of Standby
• Fault Indicator Red Led illuminates if clipping or protection is active
• Product size / weight (packed) 590(L) x 405(W) x 152(H)mm 14.65kg (GROSS)
• Product size / weight (unpacked) 382(L) x 325(W) x 97(H)mm 13.05kg (NET)

**NOTE** Driving loads with a nominal impedance below 4R is not recommended as it may cause overheating but driving speakers with 2-ohm impedance dips that only occur at specific frequencies will not cause any problems. 

The Ultrafide U500DC remains stable into any load including a dead short however shutdown protection will occur if the output current exceeds 35A which is very likely at impedances below 2-ohms.