This is a review summary written by Terry Ellis June 2023

For the full review please see my YouTube video linked here .

For many audiophiles the allure of the rich warm sound of tubes, or valves, is appealing. However, in a lot of cases it might also determine what speakers you need to use rather than choose to use because of amplifier power limitations. So, when I was approached with the opportunity to review the Synthesis Roma 510 AC (quite the mouthful), a tube integrated amplifier with a claimed 80 watts of power for pretty reasonable money, it appealed to me as I thought this could be a tube amplifier very suitable for a wide range of speakers, and therefore a wide range of audiophiles. For various reasons, which I will go into later, this has turned out to be one of the easiest reviews I have ever done.

The Company

Synthesis are an Italian HiFi manufacturer who I wasn’t previously aware of. However, looking at the company website they have been in business over thirty years. It also seems that big power tube amplifiers are a thing of theirs, with their flagship tube monoblock offering 500 watts of tube power. Everything Synthesis makes is carefully hand-crafted within the company. The extensive use of lacquered wood, in a range of finishes, is adopted from their earliest projects and characterises their design, making their products immediately recognisable to audiophiles who know of their brand.

Build and Features

The 510 AC is from the Roma line, which is Synthesis’ entry level line. It costs £3,599 and so it is certainly not an entry level price. In view of this my expectations were high. The all-black finish with the cage on is a very attractive, stealth-like design. The cage can, of course, be removed but is screwed in place. The stealth-like design continues when you power on as you are not overwhelmed with bright LEDs, there is just one, indicating which input is being used. I like that approach. Even the volume control is stealth-like, and the big circular indent indicator could be seen from my listening position twelve or so feet away even in dim light, something I definitely appreciated.

It is important to point out that the Synthesis is an 80 watt per channel amplifier at 6 ohms. I wished they just provided the power rating at 8 ohms because that’s more common. However, looking at the specifications the amp has a 6 ohm output and so the power rating at 6 ohms is probably the most accurate, and justified, in this instance. It is a push-pull pentode integrated amplifier using 12AX7 tubes for input, 12BH7 for driver tubes and KT88 for the power tubes, the PSVanne KT88 tubes included are, from my research, UK spec versions and to replace a set of would cost you around £200 for four. While not small change this is not expensive in the current tube world and thats important as you are likely to need to replace the tubes at some point down the line.

One thing that Synthesis mention about this amp is the use of high-grade iron silicon output transformers for better sound quality, but this is not a heavy amplifier by tube amplifier standards at only 25kg.  Being a tube amp means it will run hotter than a lot of modern solid-state amps, but surprisingly not so hot as to warm my room up by any real noticeable amount but, as ever, ventilation is important.

One thing I have found maybe a little odd is the distinct lack of any information for biasing the power tubes, no mention on the website, no instructions in the manual, and so I asked about this. Biasing tubes is not something Synthesis expects the customers to do on their own.  It is possible to bias the tubes but not necessarily easily like with other designs, Synthesis encourage their customers to speak to their dealer / distributor about this at the time for assistance.  This was they ensure everything is done correctly but it does mean tube rolling is not going to be an easy thing to do here and that is a shame to me and its something that appeals to me.  Instead Synthesis are going for simplicity, a more plug and play approach in the main and that may have more appeal.  However this is only relevant for the power tubes, the input and drive tubes can of course be changed.

The simplicity continues with this being just an integrated amplifier with no DAC, no phono stage, and no headphone amplifier built in. I was pleased about that; and the simplistic nature extends further on the rear as there are only 5 single ended inputs, no balanced, which is a shame, but I kind of expected this with a tube amplifier. Then there is just one set of speaker cable terminals, or taps, at 6 ohms, and so simplicity is big here, which meant that within minutes I had music playing with nothing else to think or worry about, I could just get on with the listening and straight into my review.

Listening

I have owned the Mission 770 speakers for about a year now and I have been keen to listen to them with a tube amplifier as I know their design makes them quite tube amplifier friendly. The closest I previously came can be seen here in my review of the superb and similar priced Audiozen Embrace hybrid tube pre, solid state designed power amplifier which I really liked with the Missions, but the Synthesis is offering something very different to the Audiozen and I appreciated it for very different reasons.

The Synthesis 510s sound is very easy to talk about because its character is obvious. It is bold, warm, lush, super smooth and so quite typically ‘tubey’ sounding but not so much for it to be too soft, there is a good amount of liveliness and it’s quite a ballsy and punchy sounding amplifier too so it is more in the middle of the sound spectrum between ultra soft and romantic at one end and ultra analytical at the other, although a bit more to the warmer side, which is kind of what we expect from a KT88 based tube amplifier.

For me, the 510s super-power is its musical flow, it smoothly and gracefully flows like a calm sea. This is because the edges of the music are very rounded off and so transients are more softly delivered and there are some distinct pros and cons to this.

The big pro to this is musical flow I mention, is where notes just roll on in a lovely, satisfying manner, one into the next one and so on. This is very pleasant to listen to and I think this has the benefit of making this amplifier very undemanding. It is not fussy of the source or music quality. Everything you listen to sounds bold, warm and pleasing and so that could be very appealing to you, depending on what you have now and where your looking to go with your system’s sound.  The Synthesis is rich and bold in the vocals, rich, bold, solid, and surefooted in the bass and then rather softer and ultra smooth in the treble. To me it’s a curated sound aimed at being very pleasing across a very wide variety of music and maybe less than perfect speakers, HiFi systems and rooms.

The downside to this approach is with clarity, you cannot have edges to music this soft and then have them be very well defined and carved out in stone across the overall soundstage, with a lot of sound stage space. The soundstage is good, don’t get me wrong, left to right is pleasant but not the best I have had in my room, and the same front to back, with the front being better than the back. This may be because the sound of this amplifier has a very obvious glossy bloom to it, and this is where I think reviewers bring out the descriptions of “sounding chocolatey”. Maybe thats a phrase you can take meaning from but, to me, it’s a pleasing bloom on the sound, and of course this is unlikely to be for everyone as it won’t be resolving or cutting clear enough, however if you have some harsher sounding speakers, or just some that are top heavy in your room, it could be ideal.

At this price point around £3,600 there is a lot of competition. I have another KT88 based tube integrated amplifier here, the Galion TS120 Special Edition, which is the tube integrated amplifier that YouTube reviewer Thomas and Stereo is the man behind. Listening to both these amplifiers was really interesting because both use KT88s as power tubes, but they sound totally different. Straight away you can hear where the Galion is looking to go one better in certain key areas over the Synthesis, it is clearly aiming to give you a sound with much more specificity, more high frequency detail information, more vocal clarity and pop, with a tighter, more focused less bloomed, overall sound. Interestingly, the Galion is several amplifiers in one, but all its different sound modes had this similar characteristic compared to the Synthesis, with more or less small degrees of difference, depending on the mode.

For the Galion, the result is a more see-through-the-speakers-on-to-the-music kind of sound, with sound stage elements and the vocals being positioned more obviously beyond the speakers plane and far more carved out better defined edges and so with more overall clarity. In this regard the Galion reminds me more of a modern solid state amplifier with the Synthesis sounding far more vintage.  Its important to stress that the Galion still needs a lot of run in time so no final assessment has been made.

In a frequency plotting sense the Galion is designed with a V curve shaped delivery with more energy in treble and bass than the mid band to create the sense of sound stage depth I think and the energy especially in the higher frequencies works really well for lower listening volumes.  I think the Synthesis is better turned up a little bit as its darker presentation has more pop with a bit more volume. It is still very bold and rich at lower volumes which makes it a very pleasing amp to listen to at more background levels across a wide range of music, great if you’re a radio listener, or a maybe a listener to Roon radio or just have a very eclectic music taste.

I could go on talking about the specific differences, but the big one for me here is that the Synthesis is offering more of a typical or traditional tube sound thats warm, very smooth and less fussy and you could say its technically not as good as the Galions more audiophile sound, but you might prefer the Synthesis in your system for its big warm lovely flowing always easy-going nature. However you might also find its sound a little suffocating of the specifics of the music, which is what the chocolatey bloom does, in a very pleasant manner.

I think the Synthesis is very much worth auditioning, especially if you are craving a classic ‘tubey’ warm sound for speakers with a more normal demand and without fuss, a more simple plug and play amplifier and there is nothing wrong with wanting that.

Conclusion

I have enjoyed my time with the Synthesis amplifier, how can you not enjoy your time with an amplifier that is this pleasing to listen to.  I also have appreciated how easy this review has been in terms of the Synthesis being a very simple product to setup use and enjoy.  That is probably its biggest strength and also my main complaint, I do wish it was made it easy and possible to tube roll the power tubes, because tweaking has massive appeal to me I cant help but wonder about the effects.  I also think given the competition from the likes of Prima Luna and the Galion amplifier mentioned in this review, both offer auto bias or bias adjustment in their amplifiers for this kind money so I do think it’s something that some will find missing here and therefore find the Synthesis not for them as a result.  However I fully appreciate not every one will be interested in this and some will prefer to not to have to think about it and of course that’s totally fine too.

I have given the Synthesis Roma 510AC with an Essential Audition award as I know some audiophiles will find its musical flow too good to turn down.

An Essential Audition Award is granted in recognition of a products high performance but with a certain uniqueness that makes auditioning even more essential.

For the full Specification of the Synthesis Roma 510AC 
See the website here