INSTRUCTION SHEET
• Contains one Yellow Jacket converter model
YJ7591
.
• Converts most audio amplifiers with 7591s to EL84s
without mod i fi ca tion or rebiasing.
•
Converts from Class AB to Class A operation!
• Slight power reduction from the 7591.
• Safe for all common amplifiers and trans form ers.
• One Year Limited Warranty on converters.
• “The next best thing to getting yourself a new amp.”
- Guitar World Magazine
• “Increase amplifier flexibility”
- Guitar Player Mag a zine
Thank You!
Thank you for buying our Yellow Jacket con vert er! It will
provide you with years of service, as sum ing that you re-
place the tubes when they are worn, and will also give
you a much greater variety of sounds from your am pli fi ers
than you have ever ex pe ri enced before.
How to Install Yellow Jackets:
How to Install Yellow Jackets:
1. With your amplifier cold and turned off, remove the
7591 tube from its socket. (Use a towel to pro tect your
hands if the tubes are hot.)
2. Place the Yellow Jacket converter in the tube sock et,
screw the ground wire under the tube sock et mount ing
screw (to provide an adequate ground con nec tion), and
in stall an EL84 tube into the Yel low Jacket. Make sure that
all pins are prop er ly aligned and do not force any thing.
It should all go smooth ly if the tube pins are prop er ly
aligned.
3. Turn the amp on, let it warm up, and play. Your amp is
now run ning in Class A mode with an EL84 output tube.
You do not have to adjust the bias of your amplifier as the
Yel low Jackets themselves create their own cath ode bias
circuit, ig nor ing the bias setting in your amp. This also
means that when you put your old tubes back into the
am pli fi er, your bias will be set just as you left it.
®
™
Yellow Jacket
Tube Converter
YJ7591
Handbuilt in the U.S.A.
THD Electronics, Ltd.
3510 6th Avenue W
Seattle, WA 98119-1513
Phone: 206.781.5500
Fax: 206.781.5508
www.thdelectronics.com
Other Thoughts Regarding Yellow Jackets:
Other Thoughts Regarding Yellow Jackets:
This mod el of the Yel low Jacket converter, the YJ7591, is a
spe cial ized, cur rent-lim it ing/volt age-con di tion ing adapt or
for use in most am pli fi ers which use 7591 out put tubes.
YJ7591 series Yellow Jackets are NOT to be used in am-
pli fi ers de signed to take tubes other than the 7591. Use
in am pli fi ers de signed to take 6V6, 6L6, EL34 or 6550
am pli fi ers will result in failure of the Yellow Jacket and no
out put.
If you are not sure if this Yellow Jacket will work in your
amp, please feel free to con tact us at the factory either by
phone or by e-mail. We will be happy to ad vise you on
your in di vid u al sit u a tion
Amplifiers which vary the bias voltage to create a trem o lo
effect will not have any tremolo effect when using Yel low
Jackets. This includes the Fender’s Brown Deluxe Amp
(6G3), Princeton, Tremolux (5G9, 6G9), and Vibrolux (5F11,
6G11) to name a few.
If your amp uses 6V6 output tubes, you need the YJ20
Yel low Jacket. If your amp uses 6L6, 6550 or EL34 fam i ly
tubes, you should use the YJS Yellow Jacket. The correct
unit can be ob tained from the factory or from your local
dealer, or this unit can be ex changed for the one you need.
Please con tact the factory.
Thank you once again for buying our products. With out
cus tom ers like you, we would have noth ing to do all
day.
- All the folks at THD Electronics, Ltd.
