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.construction...
to find out more about Blues90s (and their ancestors) check out these pages...
Blues 90 pickups are based on Gibson P90 single coil pickups - continuing the same soap-bar appearance, but with a substantially modified interior. Blues 90s have -
 | Alnico 5 magnets for pole pieces - rather than the steel or ceramic magnets (depending on which "authority" you are reading) used in many forms of P90 pickup (Alnico is a magnetic material made typically with Aluminium, Nickel and Cobolt - hence the name. Alnico 5 is a specific grade.) | ||
| windings of 42 gauge, enameled, copper wire (with reportedly fewer windings than P90s) | ||
| non-adjustable pole pieces which are all the same height - ie non-staggered and without individual screws
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| As far as I can tell, the same pickup design is used in both the neck and bridge positions - although I have noticed recently that my neck pickup has R (for Rhythm?) marked on the base-plate and the bridge pickup is marked with a T (for Treble?). Does anyone out there have certain information about this? Update - see Pickup orientation below | ||
| The pickups seem to be wax potted - traces of wax can be found on the pickup bobbins. Wax potting helps reduce pickup microphony (responding to audio signals, as opposed to changes in the magnetic field), which in turn reduces squeal (as opposed to more desirable forms of feedback - which occurs via string/body resonance). | ||
| The pickups are mounted direct to the body via two gold-plated screws between pole-pieces 2 & 3 and 4 & 5. These screws allow the height of the pickups to be adjusted - the pickups are supported on springs threaded on to the mounting screws. The mounting screws fit into threaded metal bushes that are set into the body. | ||
| The dummy-coil appears to be a Blues 90 pickup without the magnetic cores - which makes sense from an electronic point of view! | ||
| Pickup orientation - the bridge pickup has its north magnetic pole upwards/towards the strings, and the neck pickup has its south magnetic pole upwards/towards the strings. This helps cancel hum when the pickups are selected together. |
the dummy coil |  |
check pickup detail by clicking the thumbnail below...
| neck pickup with "bits" | neck pickup - underside | "naked" bridge p/u | bridge pickup - underside | the front pickup rout | both pickup routs |
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If you want to read about the history of P90 pickups go here...
Below is the text of a page from the Gibson website which I have edited a bit to get rid of obvious mistakes - read on...
"The main feature of the BluesHawk is that you can obtain a good single-coil, fast attack-type sound with hum-cancelling capability," Riboloff said, "With the hum-cancelling mechanism in place, it also makes the pickups more efficient and makes them more powerful."
The secret of Riboloff "Blues-90" pickup system is a dummy coil, placed away from the strings to cancel hum without interfering with the working pickups. He explained how the hum-cancelling mechanism works.
"The 'dummy' pickup is basically another pickup, but it doesn't have the magnetic core in it," Riboloff said. "It cancels out opposing sides of the A/C signal and provides a path for the other side of the signal to travel through to prevent the hum." - the blueshawk thinks this is a pretty inarticulate explanation of what is admittedly a difficult thing to explain. Riboloff notes that the idea of a dummy coil is not new, but his use of the technology is. "Dummy coils have been used in the past, but I've never seen it used in the manner that I used it in," he said. "It's wired into the circuit in a unique fashion to where it knows to get out of its own way when it's not needed."
"The user doesn't have to worry about turning it on or off; it automatically happens when he selects his pickups normal with the normal three-way pickup selector. When you are in the middle position, for example, the two normal pickups cancel each other out and the dummy coil is automatically inoperative. The pickups are 360 degrees out of phase with each other, which makes them actually in phase but opposite polarity. One pickup is picking up the top side of the sine wave and the other pickup is picking up the bottom half." - the blueshawk says - this is the same principle at work in humbucking pickups.
With magnets rather than screws for pickup poles, the Blues-90 pickup is obviously different from Gibson's traditional P-90 soap bar, but the differences go far deeper, Riboloff explained. "On a Blues-90, the core of the pickup is the actual magnet mode whereas on a P-90 pickup, the core is steel with the magnet placed beneath it, he said. "This, in effect, will give the Blues-90s a narrower, more precise magnetic path to pick the strings up with. The result is a faster attack. On a P-90, the steel tends to warm up the sound more and gives you a fatter sound. I was going for more of a brighter tone with a faster attack than a P-90. Also, to increase the high end of the pickup and get more of a traditional single coil sound, the coil of the Blues-90 pickup has fewer turns of the coil wire."
Riboloff went a step further by implementing a "Varitone" circuit similar to the one Gibson introduced in 1959 on the ES-345. By filtering out specific frequencies in it's five active settings, the Varitone gives the BluesHawk enough sounds to satisfy a session player. The end result is a fresh new sound. "It fills a whole new niche because it's not quite a "Fenderish" type instrument," Riboloff said. "It doesn't sound like a Les Paul either."
