Tube Processor Review

Grant Fidelity B-283 Tube Processor
A Review by Hans E. Sahlen

As a 12-string bassist regularly looking for ways to improve my equipment, I recently came across an impressive yet inexpensive way of improving the way my bass amp sounds.

There are some of us bassists who use solid state amplification as we may not want to deal with the expense, power or heavy size of many tube bass amplifiers. In the case of tube amps like the 100-watt Bassov Blues Boy, it may simply not be possible to find one - especially in Canada. The price and availability of 12-string bass equipment here can be prohibitive, especially for those of us with family obligations.

I purchased a Behringer BX3000T bass head a number of years ago because of its low price and light weight. Although it does the job admirably, I’ve always known that the tube is king when it comes to tonality. A number of 12-string bassists have talked at length on this subject. Solid state does have its advantages but having a tube sound option is something I have always wanted.

Imagine my surprise when I was introduced to the Grant Fidelity B-283 Tube Processor from It was originally designed for use with a DVD, CD, tape loop or preamplifier and stereo amp for in-home systems. I have discovered, after suggestion from Grant Fidelity, that the B-283 performs admirably with an instrument amp as well, in this case my bass rig. With a stereo system the B-283 adds depth, presence and detail and also adds warmth and realism to sterile digital music and solid state amplification. This transfers very well to bass - especially a 12-string bass!

The B-283 is relatively small, has two 6J1 vacuum tubes (about the size of a 12AX7), comes with a stock 18AWG removable power cable and quality gold plated RCA inputs / outputs. The power supply has some weight to it, indicative of the quality build. It is a solid and attractive unit which is easy to use and maintain. It has a black metal case with thick Lucite front panel with cool blue light. There is a "no-thump" power switch built in. Good-o!

For use in my bass amp system I used two RCA to female ¼" plug Y-cords, one for the input and one for the output. The cost for each of these is in the $5.00 range at your local music or electronics store. I run the B-283 between my rack tuner and bass amp using these adaptors along with ¼" cables and it sits on the back of the actual bass rack.


Input Power: 110V 60Hz
Vacuum Tubes: 6J1 x 2
Frequency Response: 5 Hz – 50 kHz (-1db)
Signal to Noise Ratio: >75 db
Distortion: <0.15% @ 1 kHz
Input Sensitivity: 500 mV
Crosstalk Separation: >75 db
Weight: 3.5 kg = 7.70 lbs
Size: 250 mm W x 185 mm H X 210 mm D
Color: Black Only

Before using the unit onstage I tested it out on a small 50-watt practice amp. Since there is that "no-thump” switch it was easy to go between the processor on-line and off. While playing, I had it turned off, then on with very noticeable results. Without the B-283 the sound had that flatter feeling that a solid state amp provides. When I had the B-283 turned on while playing, the sound became more round and much fuller as the tubes kicked in. When I use the B-283 the sound tends to “leap” forward and the “sound stage” talked about in stereo magazines is more in evidence - bigger.

Onstage I found that I could decrease my volume somewhat and still receive a very full overall presence in my sound due to increased tonal clarity as there is approximately a 3db uplift when using the B-283. Our guitarist (who will also be getting a unit for his amp) and other band members made several comments about my newfound improved sound quality. I had a friend in the audience that made the same comment. Although this is not a fix-all for whatever ails you, the processor does broaden your tonal stance within a band setting, although like anything else it has to be tweaked through use of tone controls, EQ's etc. to personal taste as with any amplifier, instrument or pedal.

In the Keeley Compressor pedal Review on this site by Philip Snyder he states, “Your tone is a very special thing… it’s your musical identity. Everything you put between your fingers and your speakers affects it.” This B-283 tube processor naturally brightens and helps shape your sound to be more ambient and alive almost as if you were using a true tube amplifier. It positively affects the sound, my “musical ID”! I like it!

I found the effect more evident in the sound when I was using balanced midrange and top end tones in the mix, although they don’t have to be shrieking! The two 6J1s are not bass 6550 tubes and as such are not designed to add huge depth to the bottom end. The 6J1 tubes retail for around $8.00 CDN each so the overall maintenance cost is minimal. It is more designed to add the roundness and detail that comes with an overall balanced sound and the B-283 does it very well.

At a modest $299.00 CDN this is a true bargain for the solid state amplifier-using guitar, bass or 12-string bass player. I found that with the Grant Fidelity B-283 there is much to gain sound wise for such a small investment!


For more information about the B-283 Tube Processor check it out on the Grant Fidelity website: