Roll Music Systems Bellari RP520 by Rob Coates
Bellari, a U.S. company based in Utah has been making inexpensive tube based mic preamps for a number of years. The cosmetics have changed slightly on the various units through the years but the basic design and function remains the same. The latest version, the RP520 sports newer style knobs and VU meters, as opposed to the previous version which had rather cheap looking and feeling knobs, and LEDs instead of VUs. Other than that, it's the same unit as the previous version.
Lets talk about the positives first. Bellari preamps are a full fledged, "true" tube design. By "true" tube design, I mean the input is transformer coupled and the tube is running at a full 240 volts. These preamps were made in the good ol USA and one of the things that users really like and that has been discussed quite a bit on the web is the ability to modify them easily. In fact, the Bellari preamps were made to be easily modded. The stock Chinese tubes can be swapped for something better of course, but that's not all. The op amps on the Bellari units are socketed, meaning they are also easily exchanged for higher quality ones. Cosmetically, the RP520 looks nice and it's very easy and intuitive to operate.
Now the negatives: the build quality on the Bellari units is in general pretty poor. I've owned quite a bit of made in China gear that was built much better. One example: I once bought a single channel version of this preamp that's now discontinued. It came with the top on backwards, so that the slots for air ventillation of the tube were not where they were supposed to be! Another unit I demoed was microphonic. Not just the tube, the WHOLE UNIT! When gain and output was turned up to a normal level, tapping on or just brushing the front with my hand would be amplified like the whole thing was a guitar pick up! The input transformers on the Bellari units are pretty cheap and easily overload with even a moderately hot input signal. They don't sound pretty when driven to this point. As far as the overall sound, it's very vintage and one can get pretty good even order harmonics going. Clarity and definition however, are not it's forte and I suspect this has something to do with the fact that the input impedance of the RP520 is a mere 600 ohms. You can't use this preamp with a ribbon mic because of the low input impedance. Overall, the RP520 looks good on paper, but is pretty limited in it's usefulness.