Duncan 84-50 Tube User manual

84-50 TUBE AMPLIFIER
SEYMOUR DUNCAN
OWNER'S MANUAL
5427 Hollister Ave.
Santa Barbara, CA. 93111
Ph. 805.964.9610
Fax [phone]

CAUTION
To prevent electrical shock, do not operate this unit in wet or
moist areas. There are no user serviceable parts inside.
(See, "Maintenance"' and "Tube Chart" sections for user
maintenance procedures.)
The 80-50 Tube Guitar Amplifier
Power Output: 50 watts @ 5% THD with 1khz input.
Power Circuit: (4) EL-84 vacuum tubes.
Input Impedance: I meg O
Overall Gain @ full output.
Low gain channel -59dB
High gain channel -88dB all (boosts disengaged)
Power Amp Signal to Noise Ratio: 9OdB typ. referred to full output
Boosts:
Boost #1 -+6 dB @ 1khz
Boost #2 -+8 dB @ 1kflz
Crunch Boost -+8 dB @ 6kHz
Speaker Options: Seymour Duncan King Tone Classic 12" (50 Watt)
Seymour Duncan King Tone Classic 10" (50 Watt) X 2
Voltage Requirements:
I 00v -Japan
120v -U.S., Canada
220v -Europe
240v –UK
Weight: lxl2" -44 lbs. 2xlO" -49 lbs. head -30 lbs.
Dimensions: Combos -22.625" x 17.5" x 9.5"
Head -22.625" x 9"x 9"

Congratulations on your purchase of the Seymour Duncan Research 84-50 Tube
guitar amplifier. The 84-50 is the product of an intense research and
development effort. Our object was to provide guitarists with an affordable,
all-tube amplifier, which sounded great.
The 84-50 is based on classic principles of tube guitar amplifier design. An
all-tube preamp drives a quartet of EL-84 power tubes, which provide the
sweetest, most musical tone possible. The rectangular cabinet shape enhances
the spacious "breathing" quality of the sound. Features such as on-board reverb
and a buffered effects loop make the84-50 a simple, functional rig, which can
adapt to any musical situation.
Read this manual carefully to familiarize you with the features and operation of
the 84-50. Your new amp will provide years of trouble free performance, great
tone and musical fun.

PERFORMANCE APPLICATIONS AND GUIDELINES
The name of the 84-50 Tube amp reflects its design -the amp uses a quartet of
EL-84 type tubes to produce 50 watts of power.
The EL-84 tube was chosen specifically for its rich, sweet tone qualities, especially when
pushed to distortion. This tube was widely used in many early amplifiers, but it is most
famous for its use in the Vox AC-30. This was the amp used on the early Stones,
Beatles and Yardbirds records. The EL-84 has a wonderful musical character -it sings, it
growls, and it has great dynamic response. The harder you play, the more it distorts and
sustains. Back off on your attack and it "idles", cleaning up the sound. In short, EL-84's
are a ton of fun!
The first thing you'll probably notice about your amp is that it's very loud for its size. We
wanted to make an amp for the working guitarist -something that could cut it in most
club and casual gig situations. The 84-50 has more than enough kick to keep up with a
loud drummer and bass player. In fact, when we were testing prototypes in clubs
around town, the 84-50 had no trouble holding its own on a stage full of 100-watt amps.
Using the 84-50live is simple. Just use your ears to dial in the EQ settings you need,
depending on the type of pickups in your guitar, the demands of the job, etc. Switch
channels to find a balance between clean and overdrive settings. A typical lead/rhythm
sound setting might be:
EQ/TONE CONTROLS
Even though both channels share the same tone controls, the 84-50 Tube
amp has been carefully voiced for a smooth natural transition between channels. By
switching back and forth a few times and adjusting the gain controls of each channel,
it will be easy to get the proper tone and volume balance between clean and
distortion sounds.
GAIN BOOSTS
The 84-50 has two gain boosts and a Crunch Boost, which are activated, by push-pull
pots on the front panel. Pulling out the overdrive control of Channel One actives a subtle
6 dB boost in both channels. Pulling out the OD control on Channel Two activates a

stronger, 8 dB boosts in Channel Two only. In general, these boosts are designed to get
more bottom end, punch and sustain when using the amplifier at low volumes. As the
volumeincreases, the need for added low frequency response decreases. Using the
boosts at high volume levels may produce unwanted "mushiness" in the sound.
CRUNCH BOOST
This is activated by pulling out the Channel Two volume pot. This adds 8 dB of boost at
6kHz for added definition and bite to your dirty sound.
TONE TIP
Your 84-50 Tube will get the richest, most dynamic tone when the power amp section is
working hard; i.e. when the master volume control is up around 4 or 5. With the preamp
volume around 6-7and the master at 4-5, the 84-50 Tube will produce a punchy "clean"
distortion -plenty of sustain and harmonics, but without too much "fuzz" cluttering up the
sound. For maximum overdrive and distortion, run the preamp volume at 10.
REVERB
Reverb adds a spacious quality to your tone. The reverb control affects both channels.
Set for the amount of reverb you need.
EFFECTS LOOP
The effects loop allows you to place your effects into the signal path after the preamp,
for smoother, quieter operation. To use the effects loop, run a cable from the "send" jack
to the input of your effect device. Then come out of the effect to the "return" of the effect
loop.
REMOTE ACCESS OF CHANNEL SWITCHING AND GAIN BOOST
FUNCTIONS
Channel Switching and Gain Boost functions can be accessed in three ways:
1. Manually from the front panel of the 84-50. 2. Via the optional Quadra Tone
4-Function Programmable Footswitch. 3. By using the optional Adapter Cable with a
MIDI switching device. Note: You can also use any standard 1/4" plug footswitch
("short to ground") to switch channels, but you will not be able to access the Gain
Boost functions.
USING THE 84-50 WITH THE QUADRATONE
FOOTSWITCH
The optional Quadra Tone Programmable Footswitch will give you quick and easy
stage access to four different sounds at the touch of a button.

IMPORTANT: In order for the Quadra tone Footswitch to have full control over the
various functions, make sure the amp is in the green (clean) channel and all Boosts
and Crunch are off (pushed in) on the front panel. Then simply plug the Programmable
Footswitch into the "4 Function" DIN jack on the front of your 84-50.
DIP switches inside the footswitch allow you to create the ~ soundsmost useful to you.
The footswitch comes pre-programmed as follows:
#1 Button -Green Channel = "Fendery" clean with good presence & depth.
#2 Button -Red Channel = Tight, punchy, dirty rhythm-Fat, bluesy lead.
#3 Button -Red Channel with Boost 2 = Hi Gain lead, smooth, rich in harmonics and
lots of sustain.
#4 Button -Red Channel with Boost 1, Boost 2 and Crunch
USING THE 84-50 WITH A MIDI SET-UP
With the addition of a Duncan adapter cable (Model # 128017) and a programmable
MIDI switching device such as the Scholz MIDI Octopus, you can place functions of the
84-50 under MIDI control:

Sample Settings
Note: This combination uses the red channel only. GainBoost2 and Crunch Boost are
pulled to achieve "Scorching Lead." To achieve remote switching between these sounds,
a Quadra Tone programmable footswitch must be used.

Note your favorite 84-50 Tube Tones:

84-50 Tube Amp Rear Panel
1. Primary fuse
-for 100V & 120V operation, use a 2A/250V slo-blo
-for 220V & 240V operation, use a 1A/250V slo-blo
2. AC cord
3. 4 ohm speaker output
4. 8 ohm speaker output.
Tube Chart
Note on Tubes:
For the three 12AX7's in the preamp, we use a Chinese 12AX7 in the input position for
low noise and microphonics, a Yugoslavian one in the second position for its good
overdrive characteristics, and another Chinese one in the third position for the driver.
For the power amp, we use a quartet of EL-84’s, which go through the most extensive
matching process of any tubes available. They are matched for both bias and
transconductance, and into very tight bias groupings. This superior matching process
delivers more power and dynamic range. And if one of your EL-84's shorts out, you can
purchase just one tube from us, with the same rating as the set you have. You'll get the
samematched-tube performance without having to pay for an entire set. Also, when it

comes time for you to replace the whole set, if you get a quartet from us with the same
rating as the set you have, you won't have to re-bias the amp.
MAINTENANCE
Most maintenance procedures for your ampwill involve the tubes. Refer any other
necessary work or adjustments to a qualified technician. THERE ARE NO USER
SERVICEABLE PARTS INSIDE. If your amp requires ser-vice, contact the
Seymour Duncan factory for the name of your nearest Authorized Service Center.
PLEASE NOTE: WE CANNOT ACCEPT UNITS SHIPPED TO THE FACTORY
WITHOUT A RETURN AUTHORIZATION NUMBER.
The 12AX7 preamp tubes should last up to 2-3 years, depending on the amount of
use. Symptoms, which indicate failing pre-amp tubes, include:
-Any intermittent noise (sputtering, ringing, etc.) that seems to come
and go as the amp warms up.
-Excessive white noise or hiss.
-Inability to get a clean sound, even a low volume levels.
The EL-84 tubes in the power section of the amp could last up to 2 years,depending on
volume levels and hours of use. High volume playing 3-4 hours a day, 5-6 days a week
could wear out a set of output tubes in a little as 6 months. Symptoms, which indicate
worn power tubes, include:
-Loss of power, punch; amp sounds "mushy" when pushed.
-Excessive hum.
If the outer plates of a tube begin to glow brightly, this tube has shorted. Turn off the
amp and replace the tubes, preferably with a matched set. It's OK in an emergency to
replace only one output tube, but all four output tubes should be replaced ASAP with a
matched set. These are tubes, which have been tested and matched according to their
power and performance characteristics (ex. RAM labs tubes, Groove Tubes, etc.). A
matched set of power tubes will significantly lower audible hum and increase power
output (possibly as much as 10-20 watts). This will offer more clarity on the clean
channel and a tighter low-end response for a punchier overdrive sound. Also, when
replacing the output tubes on your amp, it is good to have the amp's bias control
adjusted to achieve the optimum performance from a set of tubes. ALWAYS REFER
THE AMP TO A QUALIFIED TECHNICIAN FOR BIAS ADJUSTMENT.
Always store your amp in a dry area. Storage in damp areas will cause corrosion of
internal electrical contacts (switches, pots, jacks, etc.) and will in time degrade the
performance of the amp. Amps used in damp environments should be periodically
cleaned by a qualified technician. Symptoms which may indicate corrosion include:
-Potentiometer rotational noise (volume or tone controls sound "scratchy"
when turning). Use of a commercially available tuner spray will work in
mostcases.
-Intermittent or noisy jacks.
-Intermittent tube noise that is affected by slightly wiggling the tube in its
socket.
To maintain the tolex covering on your amp, use "armor-all" type cleaner.

TROUBLESHOOTING
The following chart should help isolate some common problems you may encounter with
your amplifier. Some are obvious problems you can remedy yourself, but remember,
THERE ARE NO USER SERVICABLE PARTS INSIDE THE AMP. If you cannot identify
the cause of the problem using the chart, or if it indicates your amplifier to be defective
and in need of repair, return the unit to an authorized Seymour Duncan Service Center,
or call [phone] for a Return Authorization number. No units will be accepted by
Seymour Duncan without an RA number.
Symptom Cause Remedy
Amplifier does not come on
when power switch is "on" 1. Power not connected 1. Ensure power cord is plugged in.
2. Blown amp fuse 2. Check amp fuse; replace
with appropriate value fuse-
1A/250 V for 220V & 240V
operation
2A/250V for 100V & 120V
operation
3. No source voltage 3. Verify power source with
something you know works.
4. Defective on/off power
switch 4. Return unit to authorized service center.
No sound coming from
speakers; no audible hum
from amplifier, but LED's are
on.
1. Master volume and/or
overdrive control set too low
1. Increase control settings
2. Speaker output jack not
connected
2. Connect speaker to 4 ohm
or 8 ohm output.
3. Defective speaker or cable 3. Verify if speakers operate
properly by using another
amp.
4. Volume controls on
instrument down 4. Increase instrument settings
Distorted sound from one or
both channels at low
volumes
1. Overdrive control set too
high 1. Reduce control level.
2. Worn tubes 2. See maintenance and
tube chart section
No Reverb 1. Reverb control set too low 1. Increase control level
2. Reverb output wires not
connected to send/return
inputs or connected
backwards
2. Ensure reverb output
wires properly connected.
3. Defective spring
3. Refer to authorized
service center

service center
4. Defective send/return
circuits
4. Refer to authorized
service center
Amp does not switch
channels 1. Defective footswitch 1 Replace footswitch.
2. Defective manual channel
switching switch
2 Refer to authorized service
center.
3. Defective internal channel
switching circuit 3. Refer to authorized service center
SEYMOUR DUNCAN LIMITED WARRANTY
FOR YOUR RECORDS: SERIAL NUMBER___________________________________
DATE OF PURCHASE____________________ DEALER________________________
KEEP YOUR BILL OF SALE IN A SAFE PLACE.
Please read carefully:
Seymour Duncan amplifiers (hereinafter referred to as the Product) are warrantied
against defects in workmanship and materials, excluding tubes covered separately, for
a period of one year from date of purchase BY the original purchaser. Tubes are
warrantied for 90 days from date of purchase. This warranty is transferable.
Defective parts will be repaired or replaced without charge if the product is returned to
the Seymour Duncan factory, at the address below or to a Seymour Duncan Authorized
Service Center. In the event a product is to be returned to the Seymour Duncan Factory
for repairs, A RE7URN AUTHORIZATION MUST BE OBTAINED PRIOR TO
SHIPPING BY CALLING OR WRITING THE COMPANY FOR THERA NUMBER.
When returning make certain to include a copy of the bill of sale and a dehe problem.
Any product shipped must be returned in the ORIGINAL
SHIPPING CONTAINER WITH ORIGINAL PACKING MATERIAL and freight prepaid.
Transportation charges involved in warranty service are the sole responsibility of the
purchaser.
This warranty does not apply to damage caused by misuse, mishandling, negligence in
use or maintenance or storage, and is voided if repairs or adjustments are made after
purchase by anyone other than the Seymour Duncan factory or a Seymour Duncan
Authorized Service Center. Seymour Duncan reserves the right to be the sole judge as
to the misuse or abuse of the product.
The company assumes no liability for incidental or consequential damages which may
result from the failure of this product. Any warranties implied by law are limited to the
duration of this express limited warranty.
Some states do not allow limitations on how long an implied warranty lasts or the
exclusion or limitation on incidental or consequential damages, so the above
limitations may not apply to you. This warranty gives you specific legal rights, and you
may also have other rights, which vary from state to state.
Please return the enclosed warranty card so that we can give you the best warranty service possible.