Serial No. 0096
Jester Oahu JU-28 amps were hand-made by Jester Enterprises from 1998 to 2000 and are based on old Valco/Supro amp designs. This particular amp has 2 x 6v6GTs, 2 x 12ax7s and a 5Y3 tube rectifier. It has an Eminence 50W 10-inch ceramic speaker.
It is a class A push-pull design rated at 16.5 watts output.
The amp has 2 channels with 2 inputs each. It has an extension speaker out and a line-out with a level adjustment pot accessible under the chassis.
The amp's circuitry is very much like that of the 5E3 Fender Tweed Deluxe circuit. In the Gibson amp line, the closest equivalent are the Gibson GA-6 Lancer and Gibson GA-14 Titan amps. It has 2 VOLUME controls, one for each channel and a common TONE control.
The amp is hand-wired and the transformers are hand-built. The amp is beautiful inside and out. Oliver Archut, the amp maker used aircraft-grade thick aluminum chassis and the nuts and bolts used to attach the transformers to the chassis also appear like they were used in an airplane.
The lead dress and the grounding is very well executed and an amp tech would have no problems maintaining this amp.
The amp is quiet with no input and sounds excellent when played. A similar amp, an Oahu JU26 (also 6v6s power tubes, but in head unit form) can be seen and heard on "youtube". Search for keyword: oahu ju26
The cabinet is made of pine and nice plywood materials (no fiberboard here) and appears to be sturdy and thick. The gray/white tolex has a very nice deep texture and appears to be waterproof and easy to clean if that becomes necessary.
The amp has a 220V original power transformer so I am able to plug the amp directly to house power outlet without the need of a step-down transformer. Considering that only about 300 of these were made and ~50% were produced for Japan (100V) , Germany and Switzerland market (220V) and the other ~50% for the US market (110V), it is fortunate indeed to get a 220V model for use in the Philippines. This unit was obviously made for the German/Swiss market (220V power supply).
One customer who ordered units from Jester is Keith Richards (10 units in '96 and 20 units more in '06). Looking closely, the amp can be seen in some of the newer youtube videos of the Rolling Stones.
The majority of the 300 or so Oahu amps units made use EL84 power tubes according to the Jester site. This maybe why Jester did not bother printing labels for their 6V6 amps. The amp label inside this amp show EL84 power tubes though it actually use 6V6s.
I consider having this unit with 6V6s a definite plus as this is the only amp I have that uses this type of power tube. I have bigger EL84 and 6L6 powered amps and welcome the tonal variety this amp offers.
Gut Shots:
The 50's Valco Oahu Amp Inspiration
2 comments:
Do you have drawings for this one?
hi marwooj,
thanks for dropping by! i traced the schematic for this amp which i plan to post in future. i still need to verify some cap values in my drawing. the circuit is derived from the Valco 510-24 or Supro 1624 / Supro 6424. The schematics are available from the interwebs. Delete the tremolo circuit and one set of tone control from those circuits and you got the basic Jester Oahu Ju-28schematic. The power tubes in the Ju-28 are 6V6GTs instead of the 6973s in the above circuits. hope this helps...
Post a Comment