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March 2020
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Superior Audio Equipment Review

Soulution 511 Stereo Amplifier
An iron fist in a velvet glove.
Review By Phil Gold


Soulution 511 Stereo Amplifier Review


  I've written before about Soulution Audio, the high-end Swiss manufacturer. Their entry-level amp, the 330 Integrated Amp, was the subject of my 2018 review and I admit to being astonished at its capabilities. My conclusion ran “when the recording is of the highest caliber, the 330 is sensationally good over virtually every dimension of sound that I can think of, and I give it my fullest recommendation for an integrated amplifier. I have never been sadder to have to pack up a review component".

Soulution has an integrated amp in its Series 5, the 530 Integrated Amplifier, reviewed here LINK LINKLINK by my colleague Wojciech Pacuła. At first glance, the Soulution 511 Stereo Amp looks like a 530 Integrated Amplifier without the preamp section, but it arrived on the market much later, making its debut at CES 2017.


Soulution's Architecture for Power Amps
Adapted from my 330 review.
All current power amps from Soulution involve switched-mode power supplies. Unlike the traditional transformer-based linear power supplies used in most competing amps, these are regulated to deliver a stable voltage under any load. Here there are four 600VA power supplies with a massive 500,000 µFarad of storage capacitance in the power supply. Soulution's first amps used massive linear power supplies but they later found major sonic benefits from switching to switched-mode power supplies, and this also helps to make the chassis smaller and lighter than competing models.

Soulution's secret sauce is the ultra-wide bandwidth and high speed of its circuitry – two or three orders of magnitude faster than in other amps. This is not an add on to the circuitry but the very basis on which it is designed, using fast switching transistors, ultra-short signal paths and the design of the switched power supply. This high speed is not an end in itself, although it naturally provides many benefits in terms of transient performance and so on. The reason is so that very high levels of local negative feedback can be applied in each stage of the amplifier without the usual adverse side effects of that feedback. Cyrill Hammer attributes those adverse side effects to the slow nature of traditional feedback circuits. If it is to be truly effective, the correction should come virtually instantaneously since the signal can change very rapidly. This is a very different path than that taken by the competition. I will not argue the theoretical merits of this approach, but I will tell you that I am very impressed with the results, and so have been all who have helped me audition the 511 Stereo Amplifier and the 330 Integrated Amplifier before it.

The third aspect of design applies to the signal path. Soulution found that the choice of connectors and cable make a big impact on the sound, and their solution is to remove all connectors and cables from that path. Instead, the boards are connected directly to the inputs and outputs. In the 511 Stereo Amp, copper bars and massive copper traces on the boards are used internally instead of wires and connectors.


I took a look at the specs to see how the two power amp sections compare between the 530 Integrated Amp and the 511 Stereo Amp. Nothing to see here and Soulution's Cyrill Hammer confirmed that the power amp circuitry is shared between the two amps. Why then does the newer 511 Stereo Amp deserve its own review in these pages?

Well, there are in fact some differences. First and most obvious from the outside is that there is no cooling fan in the 511 Stereo Amp. Soulution's engineers found that by reducing the idle current the amplifier sounds better, and generates much less heat, so the fan was no longer necessary. The height of the amp has also been reduced, from 13.8" to 10.6", because the top layer of circuitry that supports the preamp functionality is no longer needed. The power supply is now more refined - nine separate power supplies in the 530 Integrated Amplifier versus 10 in the 511 Stereo Amp. But the biggest change is in the physical topology of the internal circuits. The building blocks of the 511 Stereo Amplifier (amplifier modules, switched-mode power supplies, auxiliary power supplies, and speaker terminals) are now arranged to minimize the number of interfaces between them and these connections are now massive copper bars screwed directly to those building blocks.


Soulution 511 Stereo Amplifier Review


These bars replace longer cables, providing a significant reduction in the output impedance of both the power supply and of the amplifier modules because the pathways are both shorter and wider.   Soulution claims that these changes elevate the performance of the 511 Stereo Amp closer towards the Series 7 amplifiers. The copper bars are a feature of the 511 Stereo Amplifier and the 501 Monoblock Amplifier but do not appear in the entry-level 311 Stereo Amplifier, 330 Integrated Amplifier or of course the 530 Integrated Amplifier.

I've had the 511 Stereo Amplifier within my home for at least twelve months and have used it with a wide range of equipment. This includes both my reference system, and from other components in for review. As with the Soulution 311 Stereo Amplifier I could not hear a whisper of hiss or a trace of hum from the speakers with the CD transport on pause, even at the maximum volume level. That's very impressive.

The 511 Stereo Amp shares a lot of its performance traits with the 330 Integrated Amp and the 311 Stereo Amp both of which I have tested extensively but is considerably more musical. You still get that magnificent presence, a fabulously wide frequency response, very fast reflexes, tremendous detail, and low distortion. But it feels more relaxed and throws a bigger image with both greater depth and height. I find I'm spending a lot more time listening to music and enjoying many older recordings I had previously avoided due to their thinner sound. Coupled with a top-notch source, wide-open speakers and fine wires, I'm drawn into the music.

Rather than A/B individual tracks, I find myself listening to complete musical works. In fact, I've taken to playing complete box sets I would only sample before. Right now, I'm on disk 15 of a David Oistrakh collection which I started just last week. My only concession to multitasking is Solitaire or Sudoku on my phone.

The 511 Stereo Amp exerts such an evenhanded influence, favoring no particular type of music, or rather favoring all types of music, that I don't notice particular aspects of reproduction. But I will your draw attention to the bass since the ability to fully drive difficult loads with such ease is rare indeed. The bass here is just as clear as the treble, and remarkably, just as fast. No bloat, no softening, no overhang. Just the notes, fully articulated.

The biggest difference in my experience between live music and its reproduction in the home is neither the level of detail nor the tonal quality. It's the dynamic compression we experience at home that lets the side down. Live music, especially classical music, is often shocking in its dynamic scaling. Every stage of reproduction, from the phono cartridge or DAC to the loudspeaker, will act to compress the dynamics to a certain extent. Sometimes this is by design and sounds better than the alternative – overload distortion at peak sound levels. In selecting reference components, a key requirement of mine is the least possible compression. That's why I've chosen the YG Hailey 2.2 speakers, the EMM Labs DV2 DAC, and Nordost Valhalla 2 cables.


Soulution 511 Stereo Amplifier Review


In each case, these components are extremely linear throughout their wide operating range. The Soulution 511 Stereo Amp clearly belongs in this same elite category. Put them all together and you get a system that scales all the way from the quietest pianissimo to the powerful climaxes of Mahler's Third Symphony. I could not detect the slightest evidence of compression. Transients remained clean throughout, orchestral color and detail easily appreciated at all volume levels, with each instrument clear in the mix. In this way, music comes to life, and this is why I can't interrupt its flow.

Notice I'm not talking about the beauty of the sound. A lot of sound isn't beautiful, and I do not appreciate systems that sugar coat everything. If you're a serious audiophile, then I'm sure you've experienced that at some point. A good system should produce beauty when the performers express it, and only then. The 511 Stereo Amp is true to the source in that respect.

To my mind, there are no reservations here on audio quality. Some may worry about the limited power output figure of 150 Watts per channel into 8 Ohms. But this thing will give you 300 Watts per channel into 4 Ohms and 600 into 2 Ohms. Its massive power supply capacitance of over 500,000 μFarad will allow an impulse power rating of over 3000 Watts per channel and a peak current of over 60 Amperes. This is way more than other nominally 150 Wpc amps. But for those who are driving the most inefficient speakers to crazy high levels, you can always buy two 511s, operating each as a monoblock. This will give you 600 Watts into 8 Ohms all the way up to 2400 Watts into 2 Ohms!

I will not list all the albums I played, and where it did well and where less well. On all objective criteria I have used in the past, this amp passes with flying colors and is as close to perfect as I've heard.  So, what's the point? My ears, very used to finding fault, could not find anything to criticize this time. Power, articulation, detail, imaging, attack, decay, color, dynamics – they are all there in spades, and on everything I've thrown at it.


Soulution 511 Stereo Amplifier Review


For all these fine qualities, I still have some suggestions for improving the amp. I'd like to see a two- or three-position sensitivity switch, for those preamps that provide unusually low or unusually high maximum output. And I'd like to see something more useful than the limited status text. The biggest omission is an unbalanced input, which is strange seeing that the balanced inputs are converted to unbalanced internally – this is not a fully balanced design. But as to the price – I'm not going to complain about that. It is fully commensurate with the performance level on offer. If I find something that sounds this good or better for fewer dollars, then I'll start complaining. Everything I've heard in this class has been more expensive.


Exploding A Myth
A lot of very knowledgeable people in this industry have told me there is nothing more important than system synergy. When trying to put together a really high-performance system, you can't mix and match components willy-nilly. This pair of speakers need this particular power amp. Those expensive cables won't work well with that preamp. While these synergies or a lack of compatibility may indeed be the case, I feel this thinking is wrong on two counts. First, the listening room itself is a more important factor than system synergy but is rarely given the attention it deserves. Second, if two components don't work well together, then in my opinion, something is wrong (or at least not quite right) with at least one of them. In my opinion, a great amp should be able to drive any speaker load. If it can't then it's not really a good amp. I have spent my life staying away from components that are fussy about their partners. And I don't like the idea of pairing two components that compensate for each other's weaknesses.

I would like to see components that support a wide variety of partnering components and not a narrow subset. I would like to see even the most basic components do a great job with the midrange, and as you pay more money, the bandwidth, transparency and maximum output levels should increase, while distortion drops. I would like manufacturers to be very open about how compatible their products are with components out there, and I'd like to see difficult loads and fussy electronics gradually eliminated until all available components can work with all others. The Soulution 511 is an example of an amplifier designed to drive almost any load with ease.


A good number of friends have come by to listen to the system. I've told them what's different in the way this amp is designed, but like me, they soon forget about the amp and the rest of the system. What interests them is the music itself. It's a joy to be able to pull any recording they like off a shelf, or pull out a disc of their own, and hear it in all its glory. Yes, a system of this caliber allows you to forget the system and experience the music. You pay a lot of money for that privilege, but with this fine amplifier slotted into the reference system for the very first time, I'm not looking to change anything. I like it just the way it is.


Soulution 511 Stereo Amplifier Review


If you read reviews of exotic hi-fi like I read reviews of Ferraris and McLarens, then there is no more to be said. But if you are in the market for a very high-performance amplifier, I can certainly commend the Soulution 511 Stereo Amp and its baby brother the Soulution 311 Stereo Amp for your shortlist. The 311 Stereo Amp is the better value of the two at just over half the price, keeping most of the goodness.

Their 330 Integrated Amp is the very best value for money within the Soulution range, and while not the most full-featured or impressive looking integrated around, it sounds great. In addition, it saves you a power cord, a set of interconnects, a shelf on your rack, plus gives you more than a glimpse of what their 511 Stereo Amplifier has to offer. Without a doubt, Soulution's 511 Stereo Amplifier does have enough extra-musical refinement and headroom to make the choice an easy one, money apart. It's special!




Sub-bass (10Hz - 60Hz)

Mid-bass (80Hz - 200Hz)

Midrange (200Hz - 3,000Hz)

High Frequencies (3,000Hz On Up)



Inner Resolution

Soundscape Width Front

Soundscape Width Rear
Soundscape Depth Behind Speakers

Soundscape Extension Into Room


Fit And Finish

Self Noise

Value For The Money



Type: Solid-state stereo amplifier
Soulution Audio 511 Stereo Amplifier
Power Output: 150 Watts @at 8 Ohms, 300 Watts at 4 Ohms, and 600 Watts at 2 Ohms
Maximum Output: > 60 Amperes
Channel Separation: > 120dB
Frequency Response: 0Hz to 800kHz (-3dB)
THD: < 0.001% at 50W into 4 Ohms
IM Distortion: < 0.005 % SMPTE, < 0.0006 CCIR
Signal To Noise Ratio: > 108dB at 5 Watts at 1 kHz
Damping Factor: > 10,000
LINK (Remote Turn On): Two 3.5mm phono jacks
Analog Inputs: Balanced XLR
Input Impedance: 2000 Ohms
Gain: +26dB
Dimensions: 17.4" x 10.3" x 17.6" (W x H x D)
Weight: 66 lbs.
Price: $32,000



Company Information
Soulution Audio
Spemot AG
Industriestrasse 70
CH-4657 Dulliken

Voice: +41 62 285 3040
E-mail: info@soulution-audio.com
Website: www.Soulution-Audio.com















































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