I can never quite tell if Cypher Labs practices soft launches or things just creep up on me with their product line but towards the end of 2015 David and his team got all tubey and launched the portable tube amp, the Trio, and now this, a mid-range desktop tube amp called the Sustain84.

I have no clue why Brian Setzer themed audio came to mind. It has a rockabilly ring to the name I guess but at $1200 and sporting a form factor I have seen quite a few times at the budget end of things I was indeed very intrigued as to what David has done with this much-loved format to chime in at $1000 plus.

This is no Little Dot, by the way, guys, it is way above that level, but it is, in the end, a tube amp so some things you should expect are there – rolling, heat, that “tube” sound plus a few more things you might not expect from a tube amp.

Build Quality

This is no Class B or D push and pull type budget amp. The Sustain84 is a Class A desktop AC powered 2 channel tube amp built specifically for headphones use (though, as you read on, it performs admirably with some IEMs).

It weighs in 2.5kg and the main chassis is machined aluminum in black making it a very sturdy but compact desktop tube amp. I would not classify this as portable or transportable but it does take me back to the days of having only a single tube amp, the Little Dot MK2 and a set of Grado SR80s as my main source of 2.1 audio.

Given the similar dimensions so it does indeed make a fine laptop table companion with the right DAC or source. In short, it’s not that big and it is tough enough to take a knock or two.

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Front & Rear Panels

It is a pretty minimalist affair both front and rear with the branding on the bottom left just below and sturdy switch for low and high gain. To the middle of the front panel you have a quarter jack input and then to the far right you have a beveled grip alps type volume pot which has a smooth and balanced performance right throughout.

It is actually very reminiscent of both the look and feel of the Theorem 720 pot and side by side both pots look similar though with the Theorem 720 the pot acts as both volume control and power on and off.

With the Sustain84 power on and off is handled in a more traditional desktop on/off translucent red power switch at the back directly connecting to the switching AC power supply and right beside the AC jack in a central layout.

To the far left as you look at the back you have a set of single-ended RCA inputs to handle the line source input and this can be from anything from a dedicated desktop DAC to a more humble line out to RCA single-ended cable powered by say a FiiO X3ii.

What performance and resolution you want from whatever source is really up to you the Sustain84 as a pure amp will handle anything you throw at it via these single-ended RCA inputs.

Set up

Most of this review was done with the ALO Audio Continental Dual Mono as the primary DAC for a solid set of tube goodness right throughout and with a more solid-state flavor using the NuPrime DAC-10 as well as a portable source from the excellent FiiO X7.

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Inside

True to form Cypher Labs tinkered with the insides and then some. Everything from the ‘get-go’ is set up to handle both power-hungry cans and more sensitive IEM confidently and as such noise floors and general buzz typical of budget push-pull tube amps were specifically targeted to be minimal if non-existent in the Sustain84’s performance.

Cypher Labs have used Z11 Output Transformers (sourced from Japan) as well as Nichicon Electrolytic Capacitors and Cardas RCA input connectors. In case you are wondering where the Z11 are housed, that is the reason for the encased boxes on top of the main chassis behind the tubes.

Output

The Z11 output transformers are not cheap either with some outlets offering them at $120 up to $300 for Z11 grade for a pair. These silicon steel transformers offer a very good price to performance ratio, typically quite powerful with no obvious sound quality weaknesses across the board. Yes, indeed transformers can and do offer differing sound qualities into the mix and not just the tubes.

Nichicon has been in the capacitor business for around 50 years and are seen as the safe choice and a good alternative to Black gate caps which for me are the top caps around but sadly no longer being made.

Cardas needs no introduction either for most audiophiles and I highly recommend to finish the unit off with some nice matching Cardas RCA caps from Music Direct at $50 a pop. If you believe in the audiophile chatter caps have been mentioned to improve resistance to RF interference from the opened inputs. More logically it closes out a gaping hole in some style to prevent dust and bugs from getting in.

The Tubes

It’s about the tubes at the end of the day and the Sustain84 packs 2 NOS ECL84 tubes as standard lending to the moniker “84” in the name of the amp itself. These tubes are New Old Stock 9 pin miniature triode pentode constructs and are of course roll-able (6DX8 tubes).

Given the original purpose of these tubes were for TV sets back in the 50’s there has been some who would shy away from using these for audio purposes. However, the little ECL84’s do pack a significant grunt. These high Mu triodes and can easily handle decent wattage for demanding headphones. In some design setups they have been competently setup to driver speakers nevermind just headphones.

The Sustain84 also comes with a pair of circular aluminum black tube guards with the aim of further preventing external RF or magnetic interference during playback as well as providing handy barrier against inadvertent knocks and possibly bending the pins in the process beyond repair.

Sound Impressions

Tonality

Tonally the Sustain84 is a relatively quick-paced and clean sounding class A tube amp and with an impressively black background right throughout suffering none of those tell-tale signs of cheap tube amp designs such buzz, hum, and low-end distortion. There is a hint of warmth right across the spectrum which should come as no surprise. It has a nice full sounding and very smooth mid-section with an excellent vocal delivery that is full of detail; for me the stand out aspect of the Sustain84’s signature.

I am personally glad that the stock sound out of the box is not molasses thick or too rich to sound ponderous and limiting to all but a few genres. Leave that to the cheap push and pull budget tube amps. The Sustain84 is a more flexible beast in that respect. Not only do you have power and efficiency side by side but you have a smooth tonal flavor that is relatively natural-sounding, musical and at home with quite a few styles.

Bass

Though full sounding and possessing great texture and detail the bass performance of the Sustain84 is more relaxed and polite than punchy or aggressive. I actually find this to be a plus point for my own personal tastes as the Sustain84 sounds much more coherent and balanced with this type of bass signature.

The balance between attack and decay is above average for tube performance and in some ways reminds me of the stock response of the Studio 6 tubes in terms of tonality and tempo though the Studio 6 has the better sub-bass definition and weight compared to the Sustain84’s slightly heightened mid-bass.

The Sustain84 is quick enough to sound at home with the likes of Benny Benassi without too much over mid-bass emphasis and only a minor roll off in sub bass extension. There is very little, if any, bloat or bloom in the Sustain84 bass response and distortion levels are very low indeed.

It is also has a nice hint of warmth to it to stop it sounding overly dry or sterile. It won’t compete with the outright aggression and punchy dynamics of the Schiit Mjolnir but it lacks that edgy slightly tiring impact that the Mjolnir/Gungnir can sometimes produce with the bass response.

Mids

The mid-range on the Sustain84 is excellent, very smooth sounding indeed with a very pleasing timbre and a slightly forward vocal emphasis. Vocal presence has excellent control, nothing too soft or veiled and with zero unnecessary sibilance even with edgy cans like the AKG K812.

Being a big vocal fan this is one of the traits in any source, amp or headphone that I zero in first and the Sustain84 nails it. Vocal powerhouse performances from Blue October’s Justin Furstenfeld to Ann Brun are all confidently delivered with only slight variations depending on the source you throw into the mix.

Solid-state portable sources such as the FiiO X7 have a slightly cleaner and harder feel to the vocals whereas the ALO Audio CDM produces a fuller-sounding vocal performance with a richer and more textured response out of the Sustain84. I am still a fan of the CDM Wolfson’s more musical tonality over the slightly more clinical ESS9018 in the X7, especially when it comes to mid-range performance on their respective line outs.

Treble

The treble on the Sustain84 is detailed, clear and articulate but much like the bass performance, it is in no way overly strident and forceful. Instead, you have a slightly smoother top end that helps take the edge of quite a number of headphones known for their overly sparkling top end or peaky performance.

It will not change their inherent tonality but it does produce a more pleasing and less fatiguing treble experience than quite a number of solid-state counterparts such as the Mjolnir or the Tisbury Audio Challenge One amp I tested last year.

The Sustain84’s treble performance makes this amp a less picky component for headphone matching as a result. The K812, though by no means a river of treacle, sounded much smoother and the typical peak in the stock HD800 didn’t have the same level of bite I get from cooler more analytical amps.

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Staging & Dynamics

With a touch of roll-off at the top and bottom, the Sustain84 doesn’t have the deepest staging quality but it lacks for in height it more than makes up for in width with excellent spacing, instrumental separation, and above-average imaging.

Headphones such as the HD800 are a great pairing in terms of maximizing a lot of the qualities of this width with the HD800’s already out of your head soundstage experience. With a slightly forward mid-range though vocal staging does take center stage and the experience is more of a 1-3 row stage recital or dance hall than an arena rock workout.

Impact, grunt, and aggression are not the hallmarks of the Sustain84 but it isn’t lacking in power, just ever so slightly less emphasis on in your face dynamics. The micro side is excellent for a tube amp with tiny details shining though and very clear and clean response on the more delicate touches in a lot of the audio we threw at it.

As such, I found the transient response of the Sustain84 to be very good indeed and far beyond regular mid-level tubes amps and slaying those budget Asian tube variants. Thankfully the decay is not so quick to make it sound overly dry, there is just enough wetness in the decay to keep that really nice smooth signature for easy listening.

Matchability

Given that smooth and natural flowing tonal profile with a behaved but coherent bass performance I actually found the Sustain84 to be pretty much matchable to just about every mid-fi and dynamic flagship headphone out there.

The K812 and the HD800 performed very well indeed with the K812’s slightly screechy treble performance toned down a little. The tricky to drive K501 sounded effortless with some of the best mids out there performing true to form and a bass delivery that never sounded overly lean or underpowered.

Planars were no problem either to the Sustain84 with both the HE-560 and the LCD-2 rev 2 adequately powered. Even the mighty HE1k didn’t sound terribly diminished on the Sustain84 compared to the ALO Audio Studio 6 which costs almost 4 times the price though soundstage wise it was just a little bit less 3-dimensional sounding than the big 6.

Sensitivity

I was particularly impressed also with the Sustain84’s performance with more efficient IEM’s with an excellent low noise performance and a very impressive black background even on highly sensitive customs such as the A12 from 64Audio. There was a touch of imbalance from a slight right side predominance at very low levels but nothing surprising given that it’s an analog pot and something inherent in most pots of this nature.

Low gain pot play is a bit more limited though than dynamic and planar headphones with the A12 hitting comfortable levels at around 7am on the dial so it’s not quite as sensitive as say the Picollo portable amp but as a desktop tube amp it’s a very welcome bonus indeed. It also happens to sound very sweet and easy-going indeed with the A12 tonally, even with the more neutral FiiO X7 source line out.

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Final Thoughts

Sometime in the middle of 2015 I went all out and grabbed the 4k ALO Audio Studio 6 tube amp. It satisfied my “what if” curiosity when the HE1000 planar headphone landed on my desk as well as a lust to bring some tube tonality back into my otherwise very solid-state setup.

If I had the Sustain84 beside it before I bought it I might have hesitated slightly given that it is a quarter of the price given that as a desktop tube amp the performance with the vast majority of my headphones is relatively closer than the price suggests it should be.

The Sustain84 also has a superior sensitivity performance with IEM’s and very low impedance headphones such as the T5P than the Studio 6, which for those looking for one desktop tube amp to play them all might just outweigh the benefits of getting a top of the line tube amp.

Preferences

That being said those looking for aggressive dynamics, a heavy-hitting bass line or supreme headroom with soaring treble performances might be better suited to a more solid-state amp as the Sustain84’s big strength is in a smooth flowing mid-range and a beautiful vocal presence. It is an amp for those who simply want detail and excellence without the aggression and for those who want a musical performance for lengthy listening periods.

Cypher Labs have put a lot of thought into what they wanted out of the Sustain84 as a tube amp and very sensibly they have steered away from an out and out fat-sounding tube performance out of the box. Yes, you can roll these tubes and produce some variable sounds signatures but as it stands the ability to power planars cleanly and yet stoop down and deliver low noise levels with highly sensitive IEM’s with minimal distortion is just right.

Technical Specifications

  • Tube: ECL84 (6DX8 tubes may be substituted by the customer)
  • Input: RCA Jacks
  • Impedance: 10K ohms
  • Sensitivity: 700mV
  • Output: 6.3mm
  • Impedance: 8 to 600 (Japan Z11-EI48 Output Transformers)
  • Output voltage: 14Vp-p
  • Headphone power: [email protected] ohms; [email protected] ohms; [email protected] ohms; [email protected]
  • Low gain 2db, High gain +17db
  • Frequency Response: 30-30Khz (+-1db)
  • Auto-switching AC Voltage: 100-250V AC
  • Power Consumption: 20W
  • Standard IEC input with fuse protection (2A Fuse)
  • Weight: 2.5kg
  • Dimensions: 225mm (w) x 116mm (d) x 113mm (h)
Slide here to add your score on the gear!12 Votes
8.7
8.7
Score
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11 Responses

  1. daj74

    Would you also recommend using 6F4P tubes with the Sustain84? There seems to be lots of them available. They are supposed to be the Soviet equivalent to the 6DX8 and ECL84.

    Reply
    • headfonics

      I need to research those ones but if they fit and are the right price i could try and grab a matching pair.

      Reply
      • daj74

        The price on the 6F4P tubes is actually quite cheap. I ended up ordering pack of 8 tubes for $9.50 U.S. plus $8 U.S. shipping to Canada. These are Russian military gold grid grade tubes. I don’t know how good they would be with audio though. I will contact Cypher Labs before trying them and probably just save them as a backup if I can’t get any ECL84/6DX8. There just seems to be an abundance of the 6F4P tubes and the ECL84/6DX8 equivalent seem harder to find on eBay.
        I also ordered a set of 4 6DX8/ECL84 NOS Zenith Gt. Britain tubes for $46 U.S plus $10 U.S. shipping which are considerably more expensive, but if I can get around 1 year out of a pair of tubes then I would be happy.

  2. daj74

    Excellent and very well written review Marcus!
    My Sustain84 came in yesterday and I am absolutely loving it. Out of the box I did find it a bit congested with my Hugo>S84>Nighthawks, but it really seemed to open up after around 4-5 hours. Maybe the tubes needed to settle a bit? I now even prefer it to my Liquid Carbon (which I find very impressive as well), and I find the sound signature quiet similar between the two amps. I find the S84 lush and musical with great vocals and well articulated bass. I could easily listen to either amp for hours on end.
    On low gain it drives my HE-500 with ease as well, with better dynamics than the Hugo alone especially for classical songs like Hans Zimmers Gladiator “The Battle”
    I agree that it is also great with IEM’s as there is no hum or hiss with my JHA Angie.

    Reply
    • headfonics

      Thank you so much for the positive comments. Very much appreciated.

      Yup the IEM performance is what seals it for me as a great all round amp along with that very sweet midrange.

      As for the tubes, I need to get some more and will likely do so in the coming months so I cant say yet on anything other than the stock tubes but they perform far better than I expected.

      Reply
    • headfonics

      Thanks for the feedback, always happy to help :)

      I actually used the CDM as my DAC to the Sustain84 and whilst the amp is unbelievably sweet sounding from the CDM its slightly under-powered compared to the Sustain84. I also found the Sustain84 to be the slightly cleaner sounding of the two. Mind you the CDM has a fantastic tube sound also and in some ways sounds more tube like than the Sustain84 not to mention its much smaller with a battery inside for transportability.

      Reply

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