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Bellari RP562

Stereo Tube Sonic Exciter By Paul White
Published July 1997

Paul White tests one of the few low‑cost tube enhancers on the market, from a new name in excitement.

Back in the early '80s, exciters were — well... exciting, but now everyone builds the things and, though there are subtle differences, few stand out from the pack as being truly different. Bellari's claim to individuality is the use of tube circuitry and an all class‑A signal path. Rather than using conventional harmonic regeneration, they've used an approach that seems closer to BBE's, where the various harmonics of the sound are restored to their original time relationships after the phase‑mangling that goes on in a typical audio chain. The tubes are there just to add a little compression and coloration.

In order to access as wide a market as possible, the designers have also included a sub‑bass output, which makes the Sonic Exciter useable in home‑theatre and PA applications as well as in studio work. The brief manual describes some of the techniques used to restore the correct phase relationships, and these include all‑pass filtering, frequency‑compensated gain adjustment (EQ?), and frequency‑compensated domain delay — which seems to be another way of saying that some parts of the frequency spectrum are delayed slightly with respect to others. Using all class‑A circuitry means that any distortion components will be mainly second‑harmonic, and this tends to sound more musical than odd‑harmonic distortion.

The hardware is conventional, with the exception of the two tiny, circular moving‑coil level meters, and the fact that the main left/right audio connections are duplicated on both unbalanced jacks and balanced XLRs. The power cable is fixed, which avoids the irritation of an EC lead becoming dislodged in the back of a busy rack, and there's a further jack output to feed a mono sub‑woofer.

Bellari have done a lot of work on restyling their products, but I'm not convinced that they've quite got it right yet. The gold anodised panel is nice enough, but the rather cheap‑looking plastic knobs seem out of place on a piece of pro audio gear.

Inside Story

Before proceeding further, I just had to take off the lid and have a look around. What I found was a pair of 12AX7/ECC83 dual‑triode valves, run at a proper high‑tension voltage, plus a few IC‑based circuits, most of which looked like filters of one kind or another. I must admit that I'd expected the circuitry to be a little more complicated, but the constructional standard is OK and the accessibility of parts for servicing is good.

All the controls are ganged for stereo operation, and the first two controls relate to the sub‑bass output — something that few studio users will have an application for, though it could be interesting to compress the sub‑bass output, then add it back into the mix for more low‑end energy. One control sets the upper frequency limit of the sub‑bass output, between 35Hz and 200Hz; the other sets the sub‑bass level. The controls that deliver the excitement are labelled Bottom and Definition, but there's no drive control to set up and no way to adjust the frequency range that's excited. The lack of a drive control is a good thing — it makes setting up easier — but not being able to vary the part of the spectrum that's being excited could be seen as slightly limiting.

Transient details are lifted out of the mix and the overall clarity and transparency of the material improve, as does the apparent separation between instruments.

Bottom is, as you might imagine, a bass control of sorts, and it is centre detented, though the manual implies that the flat position is with the pointer at about 11 o'clock. The book then goes on to talk about spectral spread in the first half‑turn of the control but, as far as I can tell, turning the knob left of centre reduces the amount of bass, while turning it clockwise increases it. An Active button with status LED lets you know when the process is in circuit, and the Definition control adds brightness as it's turned up from its minimum position. Interestingly, when the unit is switched into circuit with the Definition control set to minimum there still seems to be a very slight excitement effect, possibly due to the valves in the signal path.

(Rack) Mounting Excitement

To test this unit, I tried it on a couple of CDs that I felt were slightly on the dull side, and I also used it to beef up a drum submix, something it did extremely well. The Bottom control seems to be little more than EQ, but it's well designed and adds the requisite weight to the low end, providing you use it sparingly. Definition does just what it says on the tin, and the effect is reasonably smooth, sounding more like a BBE than a typical harmonic exciter; again, though, it has to be used sparingly if you're processing a whole mix. Transient details are lifted out of the mix and the overall clarity and transparency of the material improve, as does the apparent separation between instruments.

When it came to processing the drum mix, I needed a modern sound that would cut through, so I used far more processing than I would dream of using on a full mix, but it worked beautifully by sharpening up the snare drum, adding edge to the hi‑hats, and giving the bass drum more attack. The mid‑range seems completely unaffected by the process so the overall timbre of the sound isn't changed too radically, which can be a good thing; on the other side of the coin, you can't address mid‑range problems when they do show up as you can with something like SPL's Vitalizer. Being ruthlessly honest, I don't think I managed to do anything that I couldn't have done almost as well using one of the better solid‑state exciters — but then again, the RP562 is a good deal cheaper than many solid‑state models!


The pricing on this processor is very competitive, and the unit does everything you'd expect an exciter to do, and does it rather more smoothly than many of its competitors. The use of valves also seems to add a little something to the tone, as evidenced by the slight timbral sparkle you hear when the unit is switched in, even with the Definition control turned right down.

The Bottom control behaves more like a regular EQ, but it operates at the right point to prop up ailing bass and kick‑drum sounds, and the sub‑bass output, although unbalanced, is fine for feeding a sub‑bass amp and speaker system in a small PA or home theatre. Another major point is ease of use — the Bottom and Definition knobs can be used in exactly the same way as a 2‑band equaliser, and everything is done by ear rather than by watching meters or LEDs. Given its sub‑£300 price, the RP562 is a strong contender in what's becoming an increasingly crowded market place.


  • Attractive price for a valve processor.
  • Easy to use.
  • Smooth, forgiving sound.


  • Only really offers effective control of high frequencies


I have to admit to being surprised at the low cost of this unit; though it is fairly limited in what it can do, it does it extremely well.