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BIRTH OF A NEW AX84 HIGH OCTANE TUBE
AMPLIFIER
(click on any photo for
A larger picture)
This page details the construction of an AX84 High Octane style amplifier:
www.ax84.com
Features
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Hi-Gain 12ax7 Preamp
-
6BQ5/EL84/SV83 Power Tube in Class-A Single
Ended Configuration provides a surprisingly loud 5 watts or so of output power
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Cathode-follower driven Bass, Mid and Treble
tone controls allow you to shape your sound. Alter the values of the components
in the tone stack to tailor your sound.
Many thanks to
Ramiro Silva for his excellent construction web page with plans, photos, the
works. Ramiro is a gifted amp builder with extraordinary attention to detail.
See his amps website here:
www.silvatone.bravepages.com
CONSTRUCTION: WIRING THE CHASSIS PART I
TRANSFORMERS & HEATERS
February 21, 2006 (5
Hours)
Cumulative build time, 19 hours
After polishing the
chassis to a brilliant shine, it was time to start final construction. This page
details installation of the transformers, mounting to the turret board and tube
sockets, and wiring the heaters. How did this take me 5 hours? Well, I guess
twisting the wire and making sure everything was perfect takes time. Also, great
music and ample breaks for snacks helps.
Step one was to install the
transformers and tube sockets. I used rubber grommets for the transformer
wires as they pass through the chassis. The white ceramic sockets and gold
mounting rings look good on the gloss white paint.
NOTE: Although it has been
removed for these photos, I always keep a thick towel under the chassis to
prevent scratching the finish during construction. |
Next time I'll put a shield
on the inside of the chassis to protect it from overspray! Note that only
three screws are installed in the power transformer. That is because I still
need to run a wire to that screw from the turret board to ground the buss bar.
I've sanded off the overspray around the hole to ensure good ground contact. I also sanded
around one of the output transformer mounting holes to make sure it was well
grounded. |
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I used Hillman 1/4" x .140 x
1/4" Nylon Spacers as standoffs for the turret board. These were about 50
cents at Lowes. |
These spacers don't leave
much clearance between the board and the chassis. We used the dental mirror
to make sure there were no problems under the board after mounting. Having
the right tools certainly makes the job easier. |
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I purchased some twisted
Teflon wire on eBay, but the twist was quite loose. To get a nice tight
twist, I attached one end to an electric drill, and the other to my filing
cabinet. Let the wire shorten as it tightens to get a nice, tight twist (see
large photo).
NOTE: This photo illustrates
three types of heater wiring for three different tube types. |
Heater wiring detail for
12AX7 9-pin (noval) socket. For 6.3VDC heaters pins 4 and 5 are connected to
the white wire and to each other, with pin 9 receiving the black wire.
NOTE: DO NOT WIRE THE EL84
SOCKET THIS WAY! Connect white to pin 4 and black to pin 5, and do NOT
connect the pins to each other. On the octal socket connect white to pin 7
and black to pin 2. |
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It may be overkill, but I
used hemostats as heat shields when I wired the PT leads to the diodes.
Again, having the right tools sure makes things easy. |
Finished Part I. The
transformers, turret board, tube sockets, and heaters are all mounted and wired.
Next comes adding the switches and finishing this beautiful beast. |
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OCCI HARD AT WORK ON QUALITY
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